Real-world examples
Named cases you can use in an answer, each under the syllabus point it illustrates and linked to the lesson it comes from.
1 Foundation
1.1.1A perspective is how a particular situation is viewed and understood by an individual. It is based on a mix of personal and collective assumptions, values and beliefs.
McDonald's Suisse purchasing and Swiss beef
McDonald's Suisse reported 190 restaurants, 8,400 staff and over 85% of its CHF 250 million purchasing spent in Switzerland in 2025. Meanwhile Proviande data showed Swiss beef imports rose 22.6% and the Swiss share of beef supply fell from 81.8% to 77.4%: farmers, franchisees and welfare campaigners read the same figures in opposite ways.
Shows that people with identical evidence reach different positions because their assumptions and values differ, not because they lack facts.
1.1.2Perspectives are informed and justified by sociocultural norms, scientific understandings, laws, religion, economic conditions, local and global events, and lived experience, among other factors.
McDonald's dismantling, Millau, France
In August 1999, Confédération paysanne activists dismantled a McDonald's under construction in Millau, Aveyron, France, in protest at a trade dispute over hormone-treated beef and US tariffs on Roquefort. The action made the company a symbol of the European anti-globalisation movement.
Demonstrates how global events (trade disputes) and economic conditions for local farmers shape and justify a perspective strong enough to drive direct action.
1.1.4The values that underpin our perspectives can be seen in our communication and actions with the wider community. The values held by organizations can be seen through advertisements, media, policies and actions.
McLibel trial, England
In the McLibel case (1994–1997), McDonald's sued two campaigners in England over a critical leaflet. It became the longest trial in English legal history, and in 2005 the European Court of Human Rights ruled that the campaigners had been denied a fair trial.
Shows that an organisation's actions under pressure can reveal values (protecting its brand) that differ from those stated in its advertising.
1.1.6Worldviews are the lenses shared by groups of people through which they perceive, make sense of and act within their environment. They shape people’s values and perspectives through culture, philosophy, ideology, religion and politics.
Cultural burning and Amazonian agroforestry, Australia
Aboriginal Australians' traditional fire (cultural burning) management and indigenous Amazonian agroforestry view humans as part of nature with a responsibility to maintain ecological balance rather than to control resources.
Shows how culture and belief systems shape an environmental worldview in which humans are interdependent with, not separate from, nature.
Australia Environmental worldviews
1.1.8Environmental perspectives (worldviews) can be classified into the broad categories of technocentric, anthropocentric and ecocentric.
Geoengineering schemes: sulfur injection and ocean fertilisation
Proposed stratospheric sulfur-aerosol injection and ocean iron fertilisation are geoengineering schemes intended to cool the planet and boost carbon absorption through large-scale technological intervention in the climate system.
Shows a technocentric worldview built on confidence that human ingenuity and engineering can solve environmental problems.
Whanganui River legal personhood, New Zealand
New Zealand granted legal personhood to the Whanganui River in 2017, giving the river its own legal rights and guardians, a policy that treats ecosystem health as intrinsically valuable rather than a resource for human use.
Demonstrates an ecocentric worldview by prioritising the rights of nature over economic growth or human expansion.
1.1.9Perspectives and the beliefs that underpin them change over time in all societies. They can be influenced by government or non-governmental organization (NGO) campaigns or through social and demographic change.
Swiss smoking prevalence trends
Swiss smoking (Swiss Health Survey, ~22,000 respondents): prevalence rose from 30% in 1992 to 33% in 1997, fell to 28% by 2007, plateaued at 27% through 2017 despite the 2010 passive smoking law and the 2011 SmokeFree government campaign, then dropped to 24% in 2022. An education gap also opened, with 20% of tertiary-educated people smoking compared with 25% of those without post-compulsory qualifications.
Shows that government laws and campaigns line up with changes in behaviour only loosely, and that campaigns may reach some social groups more than others.
Swiss tobacco advertising initiative
Public health organisations launched Switzerland's popular initiative on tobacco advertising, and the government opposed it. Voters passed it on 13 February 2022 with 56.6% of the vote, and it led to the Tobacco Products Act (in force October 2024).
Demonstrates an NGO campaign shifting public perspectives enough to override government opposition and turn changed values into law.
1.1.10The development of the environmental movement has been influenced by individuals, literature, the media, major environmental disasters, international agreements, new technologies and scientific discoveries.
Blue Planet II 'Blue Planet effect'
David Attenborough's Blue Planet II (BBC, 2017) showed ocean plastic to a mass audience, including an albatross feeding plastic to its chick. The surge in public concern that followed became known as the 'Blue Planet effect', although its size is disputed because some plastic policies were already under way.
Demonstrates media influence on public concern, and shows a critical point: it is hard to prove cause and effect when policy change had already started.
COP 27 loss and damage fund, Sharm el-Sheikh
COP 27 at Sharm el-Sheikh, Egypt (November 2022) agreed to create a loss and damage fund for countries suffering climate impacts they did not cause, after developing countries had been refused for about thirty years. However, it did not strengthen the COP 21 Paris emissions commitments and left open who would pay into the fund.
Demonstrates how an international agreement can change what the movement is able to argue for, even though non-binding intergovernmental deals cannot force compliance.
Earthrise photograph and environmental movement
Bill Anders' Earthrise photograph, taken from Apollo 8 on Christmas Eve 1968, showed the whole Earth as small and finite with a thin atmosphere. It was carried worldwide by the media and fed into the first Earth Day (22 April 1970) and the 1972 Stockholm Conference, although it came six years after Silent Spring (1962).
Shows how the media can shape a movement by changing how people feel about the planet, and that this influence has to be qualified because it amplified a movement that already existed rather than starting it.
Fukushima Daiichi nuclear disaster
The Fukushima Daiichi nuclear disaster (11 March 2011): a magnitude 9.0 earthquake shut the reactors down safely, but a 15–17 m tsunami about 50 minutes later overtopped the 5.7 m sea wall and disabled 12 of 13 backup generators, causing loss of cooling and hydrogen explosions. Around 164,000 people were displaced, and Germany shut eight reactors and accelerated its phase-out, Italy rejected a nuclear restart by referendum and Switzerland banned new reactors (a ban it is now reversing).
Shows how a major environmental disaster strengthened anti-nuclear sentiment and changed national energy policies, while the Swiss reversal shows the influence was uneven and temporary.
1.2.4Flows are processes that may be either transfers or transformations.
Biosphere 2 oxygen decline, Arizona
Inside Biosphere 2 the crew lost about seven tonnes of oxygen, with levels falling from 21% to 14.2%, because excess soil compost was decomposed by microbes that consumed O₂ and released CO₂, which was then chemically transformed as it reacted into the concrete of the structure.
Shows a transformation (change of form) as decomposition converts organic carbon and O₂ into CO₂ which is then fixed into concrete, altering the system's atmospheric balance.
Biosphere 2, Oracle, Arizona, USA Systems and systems diagrams
1.2.5Systems can be open or closed.
Biosphere 2 closed system, Arizona
Biosphere 2, a three-acre sealed glass-and-steel structure in Arizona, housed eight people for two years (1991–1993) as a materially closed but energetically open system: no matter entered or left, but solar energy passed through, mirroring how Earth's biosphere operates.
Demonstrates the definition of a closed system as one that exchanges energy but not matter with its surroundings, at an engineered whole-system scale.
Biosphere 2 oxygen decline
Biosphere 2 in Oracle, Arizona, was a sealed 1.27 hectare glass structure where eight people lived from September 1991 to September 1993. It was materially closed but energetically open. Oxygen fell from about 20.9% to 14.2% over sixteen months because compost-rich soil sped up decomposition and the curing concrete absorbed the CO₂ released, so oxygen had to be pumped in.
Shows what a closed system means in practice: matter cannot cross the boundary while energy can, so any internal imbalance in the coupled oxygen and carbon cycles builds up instead of being exported.
Closed global hydrological cycle
The global hydrological cycle behaves as a closed system: solar energy enters and heat is radiated back to space, but the total mass of water stays essentially constant, simply cycling between oceans, atmosphere, ice caps and groundwater without meaningful exchange with space.
Contrasts a closed system (energy in/out, matter conserved) with an open drainage basin, clarifying the matter-versus-energy distinction at planetary scale.
Rhône basin water budget, Switzerland
The Rhône drainage basin above Geneva is an open system: water enters as precipitation and leaves as river discharge, evaporation and groundwater flow. Viewed globally, the same water sits inside a water cycle that is almost closed.
Demonstrates that whether a system is open or closed depends on where the boundary is drawn, not on what the system is made of.
Rhône basin, Switzerland The Earth as a system
1.2.6The Earth is a single integrated system encompassing the biosphere, the hydrosphere, the cryosphere, the geosphere, the atmosphere and the anthroposphere.
StudyGaia hypothesis (Lovelock and Margulis)
James Lovelock's Gaia hypothesis, developed further with Lynn Margulis, models the Earth as a single self-regulating system in which atmospheric composition and temperature are held within a range suited to life by feedback control mechanisms.
Shows the Earth treated as one integrated system, with the biosphere, atmosphere and other spheres coupled through feedback rather than working as separate systems.
1.2.7The concept of a system can be applied at a range of scales.
Rainforest bromeliad as a small system
A rainforest bromeliad holds a few litres of water in the cup between its leaves. Frogs breed in it, fallen insects decompose there and the plant absorbs the nutrients, so it forms a small system inside the larger rainforest system, which itself sits within global atmospheric circulation.
Demonstrates that storages, flows and boundaries apply at every scale, and that rainfall is an input to the bromeliad but only an internal flow at the global scale.
1.2.8Negative feedback loops occur when the output of a process inhibits or reverses the operation of the same process in such a way as to reduce change. They are stabilising as they counteract deviation.
Daisyworld model (Lovelock and Watson)
Lovelock and Watson's Daisyworld model shows black and white daisies self-regulating a planet's temperature: as the star warms, heat-absorbing black daisies decline and reflective white daisies spread, cooling the surface and holding global temperature near an optimum despite changing solar output.
Demonstrates how negative feedback from the biota maintains a planet in stable equilibrium, in contrast to a lifeless world.
Lynx and snowshoe hare cycle, Canada
The lynx and snowshoe hare population cycle in the boreal forests of Canada: when hares are abundant lynx numbers rise, increased predation crashes the hare population, lynx then starve and decline, allowing hares to recover. The result is regular oscillations around a long-term equilibrium.
Demonstrates how predator-prey negative feedback counteracts deviation to maintain a steady-state equilibrium over time.
Canada Feedback loops
1.2.9As an open system, an ecosystem will normally exist in a stable equilibrium, either in a steady-state equilibrium or in one developing over time (for example, succession), and will be maintained by stabilising negative feedback loops.
Grey wolf reintroduction, Yellowstone
The reintroduction of grey wolves to Yellowstone National Park in 1995 triggered a trophic cascade: wolves reduced elk browsing, allowing willows and aspen to recover, which stabilised riverbanks and changed river courses, shifting the ecosystem toward a new, more resilient equilibrium.
Shows how feedback following a species reintroduction can move a system into an alternative stable state.
Pre-industrial and modern carbon cycle
Before industrialisation, carbon inputs to the atmosphere (respiration, decomposition, volcanoes) roughly balanced outputs (photosynthesis, ocean uptake), and CO₂ stayed between 180 and 280 ppm. Now human emissions of about 11 GtC/year exceed natural sinks of about 6 GtC/year, and CO₂ has risen above 420 ppm.
Quantifies the contrast between a steady-state equilibrium and an open system whose inputs now exceed its outputs, so the atmospheric store keeps growing.
1.2.10Positive feedback loops occur when a disturbance leads to an amplification of that disturbance, destabilizing the system and driving it away from its equilibrium.
Arctic permafrost carbon feedback
Arctic permafrost holds about 1,400 GtC. Warming thaws it and releases stored methane and CO₂, which causes further warming and more thaw.
Demonstrates a self-amplifying positive feedback in the carbon cycle that moves the climate system away from equilibrium and could keep warming going even if emissions stop.
Arctic permafrost The Carbon Cycle: Systems, Energy and ChangeForest removal and erosion feedback
Forest removal and erosion: clearing forest exposes soil to erosion that strips organic matter and nutrients, leaving fewer plants to anchor the soil, which in turn accelerates further erosion. This is a harmful, self-amplifying positive feedback that degrades the ecosystem.
Demonstrates a destabilising positive feedback driving a system away from equilibrium toward a degraded new state.
Ice-albedo feedback, Arctic Ocean
The ice-albedo feedback: as Arctic sea ice melts, dark ocean replaces reflective white ice, lowering albedo so more solar radiation is absorbed, which warms the region and melts still more ice. This amplifying loop can drive the climate towards a tipping point.
Shows positive feedback causing exponential deviation from equilibrium that can push the system past a tipping point into a new state.
Arctic Ocean Feedback loops
1.2.11Positive feedback loops will tend to drive the system towards a tipping point.
Amazon rainforest dieback threshold
Amazon rainforest dieback: the Amazon generates much of its own rainfall through transpiration, so if deforestation passes a threshold, rainfall falls, the remaining forest dies back and releases stored carbon, and the system shifts to savanna, an alternative stable state that stores far less carbon.
Shows how a positive feedback (less forest, less rain, more dieback) drives an ecosystem past a tipping point into a regime shift to a new equilibrium.
Amazon rainforest, Brazil The Carbon Cycle: Systems, Energy and Change
1.2.13A model is a simplified representation of reality; it can be used to understand how a system works and to predict how it will respond to change.
Gaia hypothesis, Lovelock
James Lovelock's Gaia hypothesis, named in 1965 with novelist William Golding, models Earth as a self-regulating system in which ocean algae emit gases that seed reflective clouds (keeping Earth ~10°C cooler) and made ten predictions that later came true.
Shows how a systems model can be used to make testable predictions about the outcome of events, such as biologically mediated temperature regulation.
1.2.14Simplification of a model involves approximation and, therefore, loss of accuracy.
Crawford Lake golden spike proposal, Ontario
The Anthropocene Working Group proposed sediment from Crawford Lake, Ontario (a meromictic lake ~270 m across and 23 m deep, with undisturbed annual layers recording a ~1950 plutonium spike from hydrogen-bomb tests) as the 'golden spike', but the International Commission on Stratigraphy rejected it in 2023 as too brief (under 70 years) to model in geologic time.
Demonstrates that models of a system have limitations: stratigraphic tools built for deep time struggle to represent recent, rapid human impact.
1.2.17Diversity and the size of storages within systems can contribute to their resilience and affect their speed of response to change (time lags).
Pacific Northwest old-growth forest carbon store
Pacific Northwest old-growth forests store 400–1,200 tonnes of carbon per hectare, and this large nutrient and biomass store is released slowly during drought years, allowing trees to survive months without rainfall.
Quantifies how a large storage creates a delayed, buffered output that sustains system function through periods of low input.
Pacific Northwest, USA System resiliencePacific Ocean thermal mass and ENSO lag
The Pacific Ocean's massive thermal mass takes decades to centuries for deep water temperatures to change significantly, so El Niño/La Niña cycles reveal a large time lag between climate forcing and ocean response, unlike small lakes that shift temperature rapidly with weather.
Demonstrates how a large storage introduces a long time lag between inputs and outputs, buffering the system against rapid change.
Pacific Ocean System resilience
1.3.1Sustainability is a measure of the extent to which practices allow for the long-term viability of a system. It is generally used to refer to the responsible maintenance of socio-ecological systems such that there is no diminishment of conditions for future generations.
Irish Potato Famine
The Irish Potato Famine (1845–1852) struck because a single potato variety, the Lumper, was grown across Ireland, so late blight wiped out the entire crop and caused mass starvation, whereas Peru's cultivation of over 3,000 potato varieties buffers against any single disease.
Shows how low genetic diversity destroys resilience while high diversity maintains a stable relationship between food inputs and outputs.
Lake Erie cyanobacterial bloom, USA
The 2014 Lake Erie cyanobacterial bloom, driven largely by agricultural phosphorus and nitrogen runoff, produced the toxin microcystin that shut off drinking water for around 500,000 people in Toledo, Ohio for three days.
Demonstrates how an imbalance between nutrient inputs and a system's outputs pushes eutrophication past a tipping point, undermining sustainability.
1.3.8Common indicators of economic development, such as gross domestic product (GDP), neglect the value of natural systems and may lead to unsustainable development.
Green GDP concept
GDP excludes environmental costs such as pollution and unpaid work, prompting the Green GDP concept that subtracts the value of environmental degradation from GDP so that a country with heavily polluting factories records a lower Green GDP.
Shows how conventional economic indicators fail to capture the poorly understood links between Earth systems and economic activity, requiring adjusted metrics.
1.3.13The concept of ecological footprints can be used to measure sustainability. If these footprints are greater than the area or resources available to the population, this indicates unsustainability.
Almond water footprint, Central Valley
California's Central Valley almond groves are flood-irrigated several times each season, giving high water footprints of ~1 gallon per almond, ~5 gallons per walnut, ~14 per orange and up to 60 gallons per avocado, in a state where ~80% of US water use goes to agriculture.
Shows how the land and water required to supply a population's food is measurable and location-specific, a core component of the ecological footprint.
Central Valley, California, USA Measuring sustainabilityAmsterdam Doughnut Economics adoption
Amsterdam became the first city to downscale the Doughnut Economics model in 2020 (with Circle Economy), adopting it to guide its ambition of becoming a fully circular city by 2050 and to account for its overseas impacts, such as on garment workers in Bangladesh.
Shows a more-developed city acting to bring its consumption back within planetary boundaries, as required of high-income nations with the greatest obligation to transform.
BLT sandwich carbon footprint
A single BLT sandwich carries an embedded footprint of ~800 g CO₂ equivalent, dominated by the fertiliser for the bread and especially the four strips of bacon, so eating one daily for a year equals the emissions of driving a car from New York to Chicago.
Demonstrates how the resources and waste absorption behind everyday consumption accumulate, making an ecological footprint concrete at the individual scale.
Regenerate Costa Rica initiative
Costa Rica launched the 'Regenerate Costa Rica' initiative using the Doughnut Economics framework, aiming to become one of the world's first regenerative nations.
Shows a national-scale attempt to redesign the economy to operate within Earth-system capacity through regenerative and distributive design.
Costa Rica Models and their limits
1.3.14The carbon footprint measures the amount of greenhouse gases (GHGs) produced, measured in carbon dioxide equivalents (in tonnes). The water footprint measures water use (in cubic metres per year).
StatisticPer-capita CO2 emissions by country
Per-capita CO₂ production emissions vary starkly: the USA emits ~16.1 tonnes per person per year, China ~7.1 tonnes, the UK ~5.5 tonnes, the DR Congo only ~0.03 tonnes, and oil-and-gas-rich Qatar ~38.6 tonnes.
Quantifies how unevenly humanity draws down the atmosphere's carbon-absorbing capacity, showing that climate debt is driven overwhelmingly by wealthy, high-consumption nations.
1.3.15Biocapacity is the capacity of a given biologically productive area to generate an ongoing supply of renewable resources and to absorb its resulting wastes.
Ecological footprint and overshoot
The ecological footprint, measured in global hectares per person, reveals ecological overshoot when a region's footprint exceeds its available biocapacity, meaning resources are consumed faster than ecosystems can regenerate them.
Quantifies how Earth's finite biocapacity imposes measurable limits on resource use and flags unsustainable consumption.
1.3.17There are a range of frameworks and models that support our understanding of sustainability, each with uses and limitations.
Doughnut Economics model
Kate Raworth's Doughnut Economics model (first published 2012) frames a 'safe and just space for humanity' between a social foundation (based on the social SDGs) and an ecological ceiling (based on the nine planetary boundaries), redefining sustainability as thriving in balance rather than endless GDP growth.
Demonstrates an alternative interpretation of sustainability that integrates both social justice and ecological limits, contrasting with growth-based definitions.
Greater Geneva doughnut limitations
The Greater Geneva doughnut shows the limits of sustainability models: 6 of its 14 indicators had no data, its footprint figures relied on data from around 2011 that probably understate the real values, and by early 2024 it had drawn little interest from local businesses or residents.
Demonstrates that models simplify reality and depend on data and public uptake, which gives concrete evidence for evaluating their limitations.
Planetary Health Check, Potsdam
The 2025 Planetary Health Check by the Potsdam Institute's Planetary Boundary Science Lab reported that seven of the nine planetary boundaries have now been breached, with ocean acidification the latest as surface ocean pH has fallen ~0.1 units (a 30–40% rise in acidity) since the industrial era.
Provides a science-based interpretation of sustainability as staying within quantified Earth-system limits, and quantifies the extent of overshoot.
1.3.18The UN Sustainable Development Goals (SDGs) are a set of social and environmental goals and targets to guide action on sustainability and environmental justice.
UN Sustainable Development Goals halfway point
In 2015 UN member states adopted the 2030 Agenda's 17 Sustainable Development Goals with 169 targets; at the 2023 halfway point only 15% of targets were on track and over a third had stagnated or regressed, with more than 780 million people facing chronic hunger.
Demonstrates the SDG framework as a concrete global sustainability agenda while quantifying its limited progress against both social foundation and planetary-boundary targets.
2015–2023 Development, justice and the SDGs
1.3.19The planetary boundaries model describes the nine processes and systems that have regulated the stability and resilience of the Earth system in the Holocene epoch. The model also identifies the limits of human disturbance to those systems, and proposes that crossing those limits increases the risk of abrupt and irreversible changes to Earth systems.
IKEA and WWF acacia timber sourcing
IKEA, in partnership with WWF, sources acacia timber from FSC-certified plantations grown with smallholder farmers to allow forest regeneration and support local communities.
Illustrates operating within the land-system-change and biosphere-integrity boundaries by managing a renewable resource at its replacement rate.
1.3.20The doughnut economics model is a framework for creating a regenerative and distributive economy in order to meet the needs of all people within the means of the planet.
Greater Geneva doughnut model and charter
In 2022 University of Lausanne researchers drew a doughnut for Greater Geneva (about one million people across Switzerland and France) using 14 indicators with 2050 targets. It showed overshoot, such as a carbon footprint of 11 t CO₂e per person against a target of net zero, alongside shortfall, with more than 14.4% of people living in precarity. In January 2023 local politicians signed the Grand Genève en Transition charter, which sets 10 ecological and social objectives for 2050.
Shows the doughnut being scaled down from global to city-region level, measuring the ecological ceiling and social foundation together and leading to real policy commitments.
MUD Jeans leasing model, Amsterdam
MUD Jeans in Amsterdam leases jeans rather than selling them, returning worn pairs to be shredded and remanufactured into new denim in Prato, Italy; the EU circular-economy package projected 2 million new jobs and €600 billion in business savings.
Shows how the doughnut model's economic redesign can decouple prosperity from resource depletion while staying within planetary limits and meeting social needs.
Amsterdam, Netherlands Sustainability, its pillars and collapseSouth Africa 1996 Constitution and NEMA
South Africa's 1996 Constitution was the first in the world to explicitly recognise the right to a healthy environment as a basic human right, implemented via the National Environmental Management Act (NEMA), which mandates public participation and environmental impact assessments before development is approved.
Demonstrates how legal structures deliver social-foundation goals such as equity, health and political voice by empowering communities to hold polluters accountable.
1.3.21The circular economy is a model that promotes decoupling economic activity from the consumption of finite resources. It has three principles: eliminating waste and pollution, circulating products and materials, and regenerating nature.
Freitag circular economy bags, Zurich
Freitag, a company in Zurich, makes bags from used lorry tarpaulins, seat belts and bicycle inner tubes. It keeps products in use through free repair parts, rental, exchange and resale, and launched a single-plastic recyclable backpack in 2024. However, its tarpaulin bags still cannot be recycled as a whole at the end of their life.
Shows the circular economy principles of eliminating waste and circulating materials in practice, and also exposes the technical limits on closing the loop.
2 Ecology
2.1.2An individual organism is a member of a species.
Zebra and horse zebroid hybrid sterility
A zebra and a horse can interbreed to produce a zebroid, but the zebroid is sterile and cannot itself reproduce, so zebra and horse are not the same species under the fertile-offspring definition.
Demonstrates the biological species concept by showing that producing offspring is insufficient: fertility of the offspring is the decisive criterion for species membership.
2.1.3Classification of organisms allows for efficient identification and prediction of characteristics.
Linnaeus and binomial nomenclature (Systema Naturae)
Carl Linnaeus (Swedish botanist, b. 1707) devised binomial nomenclature and the taxa kingdom–phylum–class–order–family–genus–species in Systema Naturae, cataloguing roughly 7,700 plants and 4,400 animals using morphology-based homologous traits.
Shows how a standardised hierarchical classification system enables efficient identification and prediction of shared characteristics across the ~2 million known species.
Taxonomic classification of the domestic cat
The domestic cat is classified Animalia > Chordata > Mammalia > Carnivora > Felidae > Felis > catus, with each rank defined by predictive traits (vertebral column, lactation and three ear bones, retractable claws), giving the binomial Felis catus.
Demonstrates how following an organism down the taxonomic hierarchy allows prediction of characteristics and reveals it is more closely related to a cow than a chicken.
2.1.4Taxonomists use a variety of tools to identify an organism.
Genetic evidence in modern taxonomy (Archaea and Eukarya)
Modern taxonomists use genetic testing (e.g. RNA polymerase similarity showing Archaea are more closely related to Eukarya than to Bacteria) alongside Linnaeus's morphology-based methods, and this molecular evidence largely agrees with classifications based on structure and form.
Shows the variety of tools taxonomists deploy, contrasting traditional morphological keys with genetic analysis that resolved the three-domain system.
2.1.5A population is a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.
Humpback whale population segments
Humpback whales are divided into 14 distinct population segments worldwide, of which four are classified as endangered, illustrating spatially separated groups of the same species.
Demonstrates that a species can comprise multiple distinct populations defined by area and interbreeding.
2.1.8A niche describes the particular set of abiotic and biotic conditions and resources upon which an organism or a population depends.
Woodpecker and nuthatch foraging partition, European forests
In European deciduous forests the Great Spotted Woodpecker (Dendrocopos major) deep-excavates wood-boring beetle larvae from main trunks (2–10 cm depth, foraging upward), while the Eurasian Nuthatch (Sitta europaea) gleans the surface (0–2 cm) foraging headfirst downward and caches seeds, partitioning the same trees to reduce interspecific competition.
Shows how two species occupy distinct niches through different foraging depths, techniques and diets despite sharing habitat.
2.1.9Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease and competition, with ecological, behavioural and evolutionary consequences.
Grey and red squirrel competition, UK
In British deciduous forests, introduced grey squirrels outcompete native red squirrels, leading to competitive exclusion and local extinction of red squirrels, with niche partitioning only where coexistence occurs.
Shows interspecific competition producing competitive exclusion and evolutionary/behavioural consequences like niche differentiation.
United Kingdom PopulationsWhite-nose syndrome in North American bats
White-nose syndrome, a fungal disease (*Pseudogymnoascus destructans*), has caused population crashes of over 90% mortality in North American bat populations, driving some colonies to local extinction and disrupting ecosystem services such as insect control.
Demonstrates disease as a population interaction with dramatic density-dependent mortality and cascading ecological consequences.
North America Populations
2.1.10Carrying capacity is the maximum size of a population determined by competition for limited resources.
Reindeer overshoot and lichen loss, St. Matthew Island
On St. Matthew Island the reindeer population overshot carrying capacity because a 2–3 year time lag masked lichen depletion; overgrazing reduced future carrying capacity so slowly-regenerating lichen could never again support even a small herd.
Shows how competition for a single limiting resource (lichen) sets carrying capacity and how overshoot permanently degrades it.
St. Matthew Island, Alaska, USA Population Size
2.1.11Population size is regulated by density-dependent factors and negative feedback mechanisms.
Density-dependent starvation crash, St. Matthew Island
On St. Matthew Island the 1963–64 crash was driven by density-dependent starvation: at peak density (18.1 reindeer per km²) the depleted lichen could not feed the herd, causing mass die-off evidenced by bone marrow depletion and declining body weights.
Demonstrates a density-dependent factor (food scarcity intensifying with density) driving negative feedback on population size.
2.1.12Population growth can either be exponential or limited by carrying capacity.
Reindeer irruption and crash, St. Matthew Island
In 1944 the US Coast Guard introduced 29 reindeer to St. Matthew Island (332 km²) in the Bering Sea, Alaska; with abundant lichen and no predators the herd irrupted to about 6,000 by 1963, overgrazed the lichen mat from 100 mm to under 25 mm, then crashed to just 42 animals after the severe winter of 1963–64 and went extinct by the 1980s.
Demonstrates a J-curve exponential growth followed by overshoot and crash rather than an S-curve stabilising at carrying capacity.
2.1.15Population abundance can be estimated using random sampling, systematic sampling or transect sampling.
Daisy density transect from field gate
A transect laid at 1 m intervals away from a field gate showed daisy density per m² rising with distance from the gate, attributed to reduced trampling (a biotic factor) further from the entrance.
Demonstrates transect sampling revealing how abundance changes along an environmental gradient caused by a specific pressure.
2.1.16Random quadrat sampling can be used to estimate population size for non-mobile organisms.
Daisy population estimate by quadrat sampling
Dr Acton measured a field as ~620 m², used a random number generator to place a 1 m² quadrat at 10 coordinates, counted Bellis perennis (daisies) to find a mean of 7 per m², then multiplied by 620 to estimate a total population of 4,340 daisies.
Shows random quadrat sampling used to estimate the population size of a non-mobile organism by scaling mean density up to total area.
2.1.17Capture–mark–release–recapture and the Lincoln index can be used to estimate population size for mobile organisms.
Lincoln index ant colony study
In an ant colony study, researchers vacuumed and counted 300 surface foragers, marked them with fluorescent printer's ink diluted in ether, then 24 hours later recaptured 300 ants of which ~150 (50%) were marked, giving a Lincoln index estimate of (300×300)/150 ≈ 600 foragers.
Demonstrates capture-mark-release-recapture and the Lincoln index applied to a real mobile-organism population, showing both the marking method and the (M×N)/R calculation.
2.1.21Sustainability is a natural property of ecosystems.
StudyCentral California kelp persistence
A 2024 PLOS Climate study of California kelp (1910–2016) found central California, where ~3,000 southern sea otters survived, expanded its kelp canopy and withstood the same disease, heatwave and El Niño that collapsed northern California, with otter density the strongest predictor of kelp change.
Demonstrates that intact keystone predation and functional redundancy confer the resilience that sustains an ecosystem through disturbance.
2.1.22Human activity can lead to tipping points in ecosystem stability.
Northern California kelp collapse
Northern California's kelp forests lost over 95% of canopy across ~350 km of coast (2013–2025) after sea star wasting disease killed sunflower sea stars and the 2014–2016 'blob' marine heatwave and El Niño raised sea temperatures 2–3°C, letting purple urchins explode with no otters (extirpated in the 1800s fur trade) to check them.
Shows how loss of a keystone predator plus climatic stress pushed a resilient system past a tipping point into a near-irreversible urchin-barren state.
2.1.23Keystone species have a role in the sustainability of ecosystems.
Sea otter keystone role, Monterey Bay
Sea otters are a keystone species in California's bull kelp forests: a single otter eats ~25% of its body weight (up to 15 lb) daily in sea urchins, and this top-down control of urchin grazers allows kelp forests supporting over 1,000 species to persist rather than collapse into urchin barrens.
Demonstrates how a species of low abundance exerts disproportionately large control over ecosystem structure and biodiversity via a trophic cascade.
Monterey Bay, California, USA Communities and ecosystems
2.1.24The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold.
StatisticPlanetary boundaries, biosphere integrity
The planetary boundaries model shows biosphere integrity has crossed a critical threshold, with current extinction rates running at 100–1000 times the natural background rate.
Quantifies the degree to which the biosphere-integrity boundary has been transgressed in the planetary boundaries framework.
2.1.25To avoid critical tipping points, loss of biosphere integrity needs to be reversed.
River Otter Beaver Trial, Devon
The River Otter Beaver Trial in Devon, England found that reintroducing beavers raised plant species richness by 28% and bird species by 26%, and tripled fish populations in some areas, while Scottish beaver populations now support over 30 specialist wetland plant species.
Shows how restoring a keystone ecosystem engineer reverses biodiversity loss and rebuilds biosphere integrity across multiple niches.
River Otter, Devon, England Communities and ecosystems
2.1.26There are advantages of using a method of classification that illustrates evolutionary relationships in a clade.HL
Crocodile-bird archosaur clade, cladistics
Cladistic analysis places crocodiles closer to birds than to lizards or snakes, uniting them as archosaurs sharing four-chambered hearts, nest-building and vocalisation, and reveals the traditional class 'Reptilia' to be paraphyletic because it excludes birds.
Shows how clade-based classification uncovers true evolutionary relationships and corrects misleading paraphyletic groupings.
2.1.27There are difficulties in classifying organisms into the traditional hierarchy of taxa.HL
Giant panda thumb and polar-brown bear hybrids
The giant panda's 'thumb' looks like a human thumb but is actually a modified wrist (sesamoid) bone that evolved independently, and polar and brown bears interbreed to produce fertile 'pizzly'/'grolar' hybrids, showing gene flow across supposedly distinct species.
Illustrates how analogous traits and interbreeding make discrete traditional taxonomic boundaries difficult to define.
2.1.28The niche of a species can be defined as fundamental or realized.HL
Connell's barnacle study, Scotland
Joseph Connell's 1961 study on Scottish rocky shores showed that Chthamalus stellatus has a fundamental niche spanning the upper and middle intertidal zones, but is competitively excluded from the middle zone by Semibalanus balanoides, restricting its realised niche to the upper zone; when Connell experimentally removed Semibalanus, Chthamalus colonised the middle zone.
Demonstrates experimentally that a species' realised niche is narrower than its fundamental niche due to competitive exclusion.
2.1.30Knowledge of species’ classifications, niche requirements and life cycles help us to understand the extent of human impacts upon them.HL
Pied flycatcher and caterpillar timing, Netherlands
Pied flycatchers migrate to Dutch oak forests such as Arnhem and feed their chicks winter moth caterpillars. Oak bud burst there now comes about 10 days earlier and caterpillars hatch 15 days earlier, but the birds' timing has not shifted. Flycatcher populations have fallen by up to 90% in some areas.
Demonstrates that a migrant cued by day length at distant wintering grounds cannot track local temperature-driven food peaks, so its life cycle makes it especially vulnerable.
Arnhem, Netherlands Understanding the extent of human impactsPied flycatcher decline, Europe
Pied flycatchers (Ficedula hypoleuca) leave West African wintering grounds on a photoperiod cue that has not changed, yet spring caterpillar peaks in European breeding woodlands have shifted earlier with warming, so birds arrive too late for peak food, causing population declines across parts of Europe.
Demonstrates that species locked into fixed photoperiod cues cannot adjust migration timing to human-caused warming, exposing them to mismatch impacts.
Winter moth and great tit mismatch
At Hoge Veluwe (Netherlands) and Wytham Woods (UK), warming has pulled the winter moth caterpillar peak on oak forward faster than great tit (Parus major) laying dates. Between 1985 and 2005 the caterpillar peak advanced about 15 days but laying advanced only about 10, so chicks hatch after peak food. Models suggest extinction risk rises sharply once the mismatch exceeds 24 days.
Shows how knowing each species' temperature cue and life-cycle timing, plus the K-strategist great tit's single brood each year, explains why it is more exposed to climate change than the r-strategist caterpillar.
Winter moth and great tit mismatch, Netherlands
In the Netherlands, winter moth (Operophtera brumata) caterpillars evolved to hatch as oak buds burst, and great tits (Parus major) time breeding to peak caterpillar abundance; warming springs advance bud burst while great tit cues (day length) stay fixed, creating a phenological mismatch that reduces chick survival.
Shows how knowledge of synchronised life cycles reveals climate-change-driven phenological mismatch cascading through trophic levels.
2.2.1Ecosystems are sustained by supplies of energy and matter.
Bear Island food-web study, Norway
On Bear Island (Bjørnøya), Norway, at 74°N, Charles Elton conducted one of the first systematic food-web studies in 1921, mapping an Arctic community that links terrestrial, freshwater and marine subsystems, for example phytoplankton → zooplankton → Arctic cod → ringed seal → polar bear.
Shows how an ecosystem is sustained by energy and matter flowing through interconnected trophic relationships across sub-systems.
Coral reef energy and nutrient inputs, Great Barrier Reef
Coral reef ecosystems are sustained by dual inputs: solar energy captured by photosynthesising zooxanthellae living inside coral polyps, and matter delivered by ocean currents (dissolved nitrates, phosphates and minerals for skeleton formation), supporting biodiversity from plankton up to apex reef sharks. Blocking the light or halting the nutrient flow degrades the whole system.
Shows how continuous, separate supplies of both energy and matter are jointly required to sustain a real ecosystem.
Great Barrier Reef, Australia EnergyGiant kelp productivity, California kelp forest
The California kelp forest is sustained by giant kelp (Macrocystis pyrifera) with a net primary productivity of ~5,000 g dry mass m⁻² yr⁻¹, one of the highest on Earth, which feeds urchins, otters and detritus-based food chains alike.
Shows how a supply of energy captured by producers underpins an entire ecosystem and all its consumer pathways.
California kelp forest, USA Energy flows
2.2.6Cellular respiration releases energy from glucose by converting it into a chemical form that can easily be used in carrying out active processes within living cells.
Cheetah muscle cells and cellular respiration
A sprinting cheetah's muscle cells rapidly break down glucose via cellular respiration, converting stored chemical energy into ATP to power the active process of muscle contraction during the chase.
Shows respiration converting glucose into an immediately usable chemical form (ATP) to drive an active life process.
2.2.7Some of the chemical energy released during cellular respiration is transformed into heat.
Energy loss as heat in cellular respiration
In cellular respiration only about 38–40% of glucose's chemical energy is captured as usable ATP while the remaining ~60–62% is transformed into heat, which is why an exercising human gets hot and loses roughly 2,000–2,500 kcal of heat energy daily that must be replaced by eating.
Quantifies the fraction of respiratory energy converted irreversibly to heat and links it to daily food requirements.
Southern sea otter metabolism, California kelp forest
Southern sea otters (Enhydra lutris nereis) lack blubber and have a field metabolic rate of ~687 kJ kg⁻¹ day⁻¹ (2–3× that of similar-sized land mammals), consuming 25% of their body mass daily so that most assimilated energy is lost as heat maintaining body temperature in cold water, giving an ecological efficiency of only ~5% from urchins to otters.
Demonstrates how chemical energy from respiration is transformed into heat, and why endotherms in cold environments show especially low ecological efficiency.
California kelp forest, USA Energy flowsStudyStick-insect and cabbage-white respiration losses
The stick-insect and cabbage-white caterpillar (Pieris brassicae) experiments show consumers lose far more assimilated biomass to respiration than producers, because mobile animals expend energy on locomotion, foraging and (in homeotherms) maintaining body temperature.
Demonstrates that chemical energy released in respiration is transformed into heat, explaining high respiratory losses in consumers.
2.2.8The second law of thermodynamics states that energy transformations in ecosystems are inefficient.
African grassland food chain energy flow
In an African grassland food chain, grass captures ~10,000 kJ of solar energy, a zebra eating the grass obtains ~1,000 kJ (10%), and a lion eating the zebra obtains only ~100 kJ (10% again), with the rest lost as respiratory heat. This explains why vast grassland areas support only a few lions and why food chains rarely exceed four or five levels.
Demonstrates how repeated ~90% energy losses per transfer limit food-chain length and predator abundance.
California kelp forest energy flow
In the California giant kelp (Macrocystis pyrifera) forest food chain, energy flow falls from 50,000 kJ m⁻² yr⁻¹ in kelp to 4,000 kJ m⁻² yr⁻¹ in purple sea urchins (Strongylocentrotus purpuratus) to just 200 kJ m⁻² yr⁻¹ in southern sea otters (Enhydra lutris nereis), giving an overall efficiency of only 0.4% from producer to secondary consumer.
Quantifies the second law's inefficiency of energy transfer with real trophic-level energy values, showing losses well below and above the 10% approximation.
California kelp forest, USA Energy flowsEnergy flow through an oak woodland
An oak woodland receives 7,000,000 kJ/m²/yr of solar radiation but fixes only 42,000 kJ as GPP; of the 16,800 kJ NPP, just 1,680 kJ (10%) passes to herbivores and 168 kJ (10%) to primary carnivores, with ~89% of NPP passing to decomposers and most energy lost as heat.
Quantifies the inefficiency of energy transformations, giving ~10% trophic transfer efficiency and <1% photosynthetic efficiency.
North Atlantic inverted biomass pyramid
In a North Atlantic marine ecosystem the pyramid of biomass is inverted, with zooplankton (21.0 g m⁻²) exceeding phytoplankton (4.0 g m⁻²), because fast-reproducing phytoplankton are grazed almost as fast as they grow, yet the corresponding pyramid of energy remains upright.
Counter-example showing biomass pyramids can invert while energy pyramids cannot, reinforcing the second law's constraint on energy flow.
North Atlantic Ocean Biomass and food websStudyStick-insect privet feeding experiment
In a stick-insect feeding experiment, ten insects fed privet leaves assimilated 2.4 g (gross productivity) but gained only 0.3 g biomass, meaning 2.1 g (about 87.5%) was lost to cellular respiration.
Quantifies the inefficiency of energy transformation predicted by the second law, with most assimilated energy lost rather than stored as biomass.
2.2.11Carbon compounds and the energy they contain are passed from one organism to the next in a food chain. The stages in a food chain are called trophic levels.
British oak woodland food chain
In British temperate oak woodland, carbon compounds pass along the chain oak (Quercus robur) leaves → caterpillar → blue tit → sparrowhawk. A parallel detritus chain runs leaf litter → earthworm → blackbird → tawny owl.
Shows carbon compounds made by a producer passing through four named trophic levels, in both a grazing chain and a detritus chain.
2.2.12There are losses of energy and organic matter as food is transferred along a food chain.
Kelp–urchin–sea otter food chain, California
In California kelp forests, giant kelp (Macrocystis pyrifera) passes about 50,000 kJ m⁻² yr⁻¹ to purple sea urchins, which assimilate about 4,000 kJ m⁻² yr⁻¹ (8%). Southern sea otters then assimilate only about 200 kJ m⁻² yr⁻¹ (5%), so just 0.4% of the producer energy reaches the third trophic level.
Puts numbers on the energy lost at each transfer: not all food is eaten, egestion, excretion and respiratory heat loss, with values either side of the 10% approximation.
California, USA Energy flows
2.2.14The number of trophic levels in ecosystems is limited due to energy losses.
Southern sea otter metabolism, California kelp forest
Southern sea otters (Enhydra lutris nereis) have no blubber. Their field metabolic rate is about 687 kJ kg⁻¹ day⁻¹, 2–3 times that of similar-sized land mammals, and they eat about 25% of their body mass each day. Most of this energy is lost as heat, so very little is left to support a fourth trophic level such as orcas.
Shows that heat lost by a warm-blooded consumer leaves too little energy to support further trophic levels, which explains why food chains are short.
California, USA Energy flows
2.2.15Food webs show the complexity of trophic relationships in communities.
Elton's Bear Island food web, Arctic
In 1921 Charles Elton mapped the food web of Bear Island (Bjørnøya, 74°N), linking terrestrial, freshwater and marine subsystems. Generalists such as the Arctic fox and glaucous gull feed across several trophic levels, on bird eggs, ptarmigan, seal carcasses and Arctic cod.
Shows how a food web captures omnivory, links between subsystems and multiple feeding pathways that a simple linear food chain cannot represent.
2.2.17Ecological pyramids are used to represent relative numbers, biomass or energy of trophic levels in an ecosystem.
Inverted biomass pyramid, North Atlantic
Winter sampling in the North Atlantic recorded 21.0 g m⁻² of zooplankton but only 4.0 g m⁻² of phytoplankton, giving an inverted pyramid of biomass. Fast-reproducing phytoplankton are grazed almost as quickly as they are produced.
Counter-example showing that biomass pyramids are snapshots that can be inverted when producer turnover is high, unlike pyramids of energy.
North Atlantic Ocean Biomass and food webs
2.2.18Pollutants that are non-biodegradable, such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and mercury, cause changes to ecosystems through the processes of bioaccumulation and biomagnification.
Minamata Bay mercury disaster, Japan
The Minamata Bay disaster (Japan, discovered 1956): the Chisso Corporation discharged mercury-laden wastewater which bacteria converted to methylmercury; it biomagnified from 0.000003 ppm in seawater to ~200 ppm in fish-eating birds (a ~67-million-fold increase), causing over 1,500 deaths and thousands of cases of severe neurological damage in people who ate contaminated fish.
Demonstrates how a non-biodegradable, lipophilic pollutant (mercury) bioaccumulates in fatty tissue and biomagnifies up the food chain to devastate top predators including humans.
2.2.19Non-biodegradable pollutants are absorbed within microplastics, which increases their transmission in the food chain.
Great Pacific Garbage Patch, microplastics
The Great Pacific Garbage Patch, the largest of five oceanic gyres concentrating plastic debris, contains areas where microplastics outnumber plankton in surface samples; hydrophobic PCBs and DDT bind to their large surface areas, so filter feeders ingest plastic-borne pollutants at the base of the food chain.
Demonstrates how microplastics act as vectors concentrating non-biodegradable pollutants and transmitting them into food chains while disrupting energy transfer at low trophic levels.
Great Pacific Garbage Patch Pollutants, Bioaccumulation and Biomagnification
2.2.20Human activities, such as burning fossil fuels, deforestation, urbanization and agriculture, have impacts on flows of energy and transfers of matter in ecosystems.
Brazilian Amazon deforestation
Between 1988 and 2008, deforestation in the Brazilian Amazon ran at 10,000–30,000 km² per year (65–70% driven by cattle ranching), releasing carbon from a biome storing roughly 150–200 billion tonnes of carbon in its biomass.
Shows how deforestation removes producers, disrupts food webs and releases stored carbon, altering energy flows and matter transfer while creating a climate feedback loop.
Iowa corn and soybean monoculture, USA
Iowa (USA) has converted over 85% of its land to corn and soybean monoculture using ~30 million kg of nitrogen fertiliser annually, whose runoff feeds a Gulf of Mexico dead zone covering up to 22,000 km² each summer.
Demonstrates how agriculture simplifies food webs, removes matter via harvest, and links terrestrial nutrient loading to eutrophication and disrupted energy flow in a distant aquatic ecosystem.
2.2.23Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.HL
Deep-ocean hydrothermal vent ecosystems
At deep-ocean hydrothermal vents (2000–4000 m depth), first discovered in 1977, chemoautotrophic bacteria oxidise inorganic hydrogen sulphide to fix carbon, powering an entire ecosystem including giant tube worms (Riftia pachyptila) with no reliance on sunlight.
Shows primary productivity driven by an external chemical energy source rather than light, using inorganic carbon and chemosynthesis.
2.2.26Maximum sustainable yields (MSYs) are the net primary or net secondary productivity of a system.HL
Grand Banks cod collapse, Newfoundland
The Grand Banks cod fishery off Newfoundland, Canada collapsed in 1992 after annual catches (e.g. 0.8 million tonnes in 1970) repeatedly exceeded the maximum sustainable yield, crashing estimated cod biomass from 1.6 million tonnes in 1960 to under 0.1 million tonnes, triggering a moratorium that still restricts the fishery over 30 years later.
Demonstrates that harvesting Atlantic cod (Gadus morhua) above the net secondary productivity (MSY) depletes the stock and causes population collapse.
2.2.27Sustainable yields are higher for lower trophic levels.HL
Energy loss in a simplified agricultural food chain
In a simplified agricultural food chain, crop plants receiving 10,000 kJ pass 1,000 kJ to cattle and only 100 kJ to humans, so eating crops directly gives people ten times more energy than eating beef.
Quantifies why sustainable yields are higher at lower trophic levels, making plant-based diets more sustainable than meat-based ones.
2.2.28Ecological efficiency is the percentage of energy received by one trophic level that is passed on to the next level.HL
Kelp forest sea otter energy efficiency
In the kelp forest case study, ecological efficiency from producers to secondary consumers was only ~0.4%, and sea otters showed unusually low efficiency (~5%) because their high metabolic rate diverts much assimilated energy to heat.
Shows that real ecological efficiencies deviate widely from the 10% rule, with high-metabolism endotherms passing on very little energy.
2.3.1Biogeochemical cycles ensure chemical elements continue to be available to living organisms.
Carbon cycle fluxes and residence time
In the global carbon cycle photosynthesis removes about 120 GtC/year from the 800 GtC atmospheric store while respiration and decomposition return about 60 GtC/year, keeping carbon continuously available to organisms with an atmospheric residence time of only 3-5 years.
Quantifies the biogeochemical fluxes that recycle carbon and keep it available to living organisms.
2.3.7Fossil fuels are stores of carbon with unlimited residence times. They were formed when ecosystems acted as carbon sinks in past eras and become carbon sources when burned.
Fossil fuel carbon pool vs human release
The global fossil fuel pool holds about 10,000 GtC accumulated over hundreds of millions of years, yet humans are releasing roughly 9 GtC per year, converting stores with effectively unlimited residence times into a rapid carbon source.
Quantifies how ancient carbon sinks with near-infinite residence times become sources when burned, releasing millions of years of stored carbon in decades.
2.3.8Agricultural systems can act as carbon stores, sources and sinks, depending on the techniques used.
Wetland drainage turning soil into carbon source
Draining and repeatedly ploughing a wetland for arable land exposes its organic matter to oxygen, accelerating decomposition and oxidation so the soil switches from a carbon store to a source, whereas no-till farming, cover crops and crop rotation keep soils acting as stores or sinks.
Demonstrates how agricultural technique choice determines whether a soil system is a carbon store, sink or source.
2.3.9Carbon dioxide is absorbed into the oceans by dissolving and is released as a gas when it comes out of a solution.
Ocean carbon sink (net uptake)
Ocean-atmosphere exchange moves roughly 90 GtC in each direction annually, but the oceans currently take up a net ~2.5 GtC per year, acting as a carbon sink even though this is far less than the 9+ GtC/year humans emit.
Quantifies bidirectional dissolving and out-gassing of CO2 and shows the ocean's net uptake is limited relative to emissions.
2.3.10Increases in concentrations of dissolved carbon dioxide cause ocean acidification, harming marine animals.
Ocean acidification and Great Barrier Reef, Australia
Ocean surface pH has fallen from about 8.2 in pre-industrial times to roughly 8.1 today; because pH is logarithmic this represents a ~26% increase in acidity, reducing calcification in molluscs and corals such as the Great Barrier Reef, which is experiencing bleaching and reduced calcification rates.
Quantifies how rising dissolved CO2 lowers ocean pH and demonstrates the concrete harm to calcium-carbonate-forming marine animals.
Great Barrier Reef, Australia A Tour of the Carbon Cycle
2.3.11Measures are required to alleviate the effects of human activities on the carbon cycle.
Global carbon budget imbalance
IPCC-style carbon budget figures show anthropogenic emissions of 9.4 GtC/year from fossil fuels plus 1.6 GtC/year from land-use change, against natural sinks of only 3.4 GtC/year (land) and 2.5 GtC/year (ocean), leaving a net ~4 GtC/year accumulating in the atmosphere.
Quantifies why sources exceed sinks and justifies mitigation measures targeting emission reduction over sink enhancement.
2.3.14In past geological eras, organic matter from partially decomposed plants became fossilized in coal, and partially decomposed marine organisms became fossilized in oil and natural gas held in porous rocks.HL
Carboniferous coal formation
Coal formation peaked during the Carboniferous period (~360–300 million years ago), when vast swamp forests of ferns, horsetails and early trees near the equator died in waterlogged, anaerobic conditions and were buried and compressed over tens of millions of years.
Demonstrates that coal derives from partially decomposed plant matter fossilized under specific geological-era conditions, as required by the syllabus point.
Oil and gas formation (Jurassic–Cretaceous)
Oil and natural gas formed mainly during the Jurassic (201–145 mya) and Cretaceous (145–66 mya) periods, when warm climates, high CO₂ and extensive shallow seas produced enormous plankton productivity; dead marine algae and zooplankton sank, were buried, and were transformed by heat and pressure into oil and gas held in porous rocks.
Shows that oil and gas originate from marine organisms fossilized in porous rock during specific eras of high productivity, illustrating the syllabus point in detail.
2.3.16Methane has a residence time of about 10 years in the atmosphere and is eventually oxidized to carbon dioxide.HL
Methane residence time and warming potential
Methane has an atmospheric residence time of only about 10 years before being oxidized to CO₂, yet it has roughly 80× the warming potential of CO₂ over a 20-year period, meaning cuts to methane emissions can deliver rapid climate benefits.
Quantifies methane's short residence time and its oxidation fate, showing why potency and residence time must be considered together.
2.3.19Denitrification only happens in anaerobic conditions, such as soils that are waterlogged.HL
Flow Country sundews, Scotland
The Flow Country of Caithness and Sutherland, northern Scotland, is Europe's largest blanket bog (~4,000 km²) whose waterlogged, acidic, anaerobic peat soils cause denitrification and leaching to strip available nitrogen, so insectivorous sundews (Drosera rotundifolia) trap and digest insects to obtain nitrogen instead.
Demonstrates how anaerobic waterlogged soils drive denitrification/leaching and create nitrogen-poor conditions favouring insectivorous plants.
Flow Country, Scotland The Nitrogen Cycle: From Bacteria to Planetary Boundaries
2.3.20Plants cannot fix nitrogen so atmospheric dinitrogen is unavailable to them unless they form mutualistic associations with nitrogen-fixing bacteria.HL
Brazilian soybean inoculation
Brazil, the world's largest soybean producer, has farmers inoculate seeds with Bradyrhizobium japonicum so the legume–bacteria mutualism fixes atmospheric N₂ into ammonia, saving the sector billions of dollars annually in synthetic fertiliser costs (Embrapa).
Shows the agricultural significance and competitive advantage of the legume–Rhizobium mutualism as a route for plants to access unavailable atmospheric nitrogen.
2.3.22Human activities such as deforestation, agriculture, aquaculture and urbanization change the nitrogen cycle.HL
Corn Belt nitrate run-off, Gulf of Mexico
Synthetic nitrogen fertiliser on intensive maize in the US Corn Belt (Iowa, Illinois, Indiana) generates nitrate run-off carried down the Mississippi, feeding the Gulf of Mexico 'dead zone', a hypoxic area of roughly 15,000 km² and one of the world's largest cases of eutrophication.
Quantifies how agricultural nitrogen inputs alter the nitrogen cycle and produce large-scale downstream eutrophication.
Gulf of Mexico dead zone The Nitrogen Cycle: From Bacteria to Planetary Boundaries
2.3.23The Haber process is an industrial process that produces ammonia from nitrogen and hydrogen for use as fertilizer.HL
Haber-Bosch process
The Haber-Bosch process, developed by Fritz Haber in 1909 and scaled by Carl Bosch for BASF, produces ammonia from N₂ and H₂, now sustaining roughly half the world's food production while consuming about 1–2% of global energy, almost entirely from fossil fuels.
Shows both the advantage (feeding half the world) and disadvantage (fossil-fuel dependence and emissions) of industrial ammonia production for fertiliser.
2.3.24Increases in nitrates in the biosphere from human activities have led to the planetary boundary for the nitrogen cycle being crossed, making irreversible changes to Earth systems likely.HL
Baltic Sea nitrogen eutrophication
The Baltic Sea, bordered by nine countries, is one of the most eutrophied seas in the world because agricultural nitrogen run-off from all of them has caused severe oxygen depletion, illustrating the consequences of exceeding the proposed 62 Tg N yr⁻¹ nitrogen planetary boundary.
Demonstrates the transboundary eutrophication that results from crossing the nitrogen planetary boundary driven by fertiliser use.
2.3.25Global collaboration is needed to address the uncontrolled use of nitrogen in industrial and agricultural processes and bring the nitrogen cycle back within planetary boundaries.HL
Sri Lanka fertiliser import ban
Sri Lanka's 2021 abrupt ban on synthetic fertiliser imports, intended to force a switch to fully organic farming, collapsed rice and tea yields because there was no phased transition or alternative nitrogen source.
Counter-example showing that reducing inorganic fertiliser dependence requires careful, phased global collaboration rather than abrupt bans.
2.4.2A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur.
Convergent rainforest structure, Congo Basin and Amazon
Tropical rainforests in the Amazon Basin, the Congo Basin and Southeast Asia share recognisable structural features (tall canopy, dense undergrowth, high diversity) despite containing entirely different species, because similar climatic conditions produce convergent structures.
Shows the defining 'wherever they occur' idea that comparable climates produce parallel ecosystem features across continents.
Congo Basin Biomes: Characteristics, Distribution and Change
2.4.5The tricellular model of atmospheric circulation explains the behaviour of atmospheric systems and the distribution of precipitation and temperature at different latitudes. It also explains how these factors influence the structure and relative productivity of different terrestrial biomes.
Desert latitude, Sahara (Hadley cell)
The Sahara (≈25°N), Arabian (≈25°N) and Australian (≈25°S) deserts all sit at roughly 30° latitude because dry, cool air descends there as the poleward limb of the Hadley cell, creating a permanent zone of high pressure and arid, low-productivity conditions.
Demonstrates how the descending arm of the Hadley cell produces high-pressure arid biomes at a predictable latitude in both hemispheres.
Sahara Desert Climate, Atmospheric Circulation and Biome DistributionWestern Europe rainfall, UK (Ferrel cell)
Western Europe, including the UK (≈45°–60°N), experiences frequent rainfall and variable weather because it lies in the Ferrel cell where warm subtropical air rises over cold polar air at ≈60°, cooling and condensing to produce the moderate precipitation that supports temperate forest.
Shows how the rising air and polar front of the Ferrel cell generate the mid-latitude precipitation and variable weather characteristic of temperate biomes.
United Kingdom Climate, Atmospheric Circulation and Biome Distribution
2.4.6The oceans absorb solar radiation and ocean currents distribute the resulting heat around the world.
Humboldt Current, west coast of South America
The Humboldt Current brings cold water northward along the west coast of South America, cooling the adjacent coast and contributing to the aridity of the Atacama region.
Shows how a cold current transports polar water towards the equator and shapes the climate and biomes of nearby land masses.
Humboldt Current, west coast of South America Climate, Atmospheric Circulation and Biome DistributionLondon and Calgary winter temperatures
London (51°N) averages about 5°C in January while Calgary, Canada (51°N) averages about −7°C, because the Gulf Stream and its extension the North Atlantic Drift carry warm water from the Gulf of Mexico across the Atlantic, warming the westerly winds that reach western Europe.
Quantifies how a warm ocean current redistributes tropical heat to give two locations at the same latitude very different climates.
2.4.7Global warming is leading to changing climates and shifts in biomes.
Boreal forest contraction and expansion, Canada
Canada's boreal forest, part of the largest relatively untouched forest on Earth (1.9 billion hectares globally, supporting 3.7 million people), is contracting at its southern margin as milder winters and hotter summers cause drought stress, stomatal closure and mountain pine beetle outbreaks, while expanding at its northern margin into Arctic tundra.
Shows a biome being squeezed from both margins simultaneously, illustrating that biome shifts are not smooth migrations.
Boreal-tundra treeline, Dalton Highway, Alaska (2000s)
Along the Dalton Highway ~232 miles north of Fairbanks, Alaska, researchers study the boreal-tundra treeline, the largest ecosystem transition on Earth; Arctic warming is occurring ~6 times faster than at the equator, but although spruce may advance north the tundra extends to the Arctic Ocean and has nowhere to retreat.
Demonstrates poleward biome shift under global warming and why the tundra is squeezed with nowhere to migrate.
Dalton Highway, Alaska, USA Biomes: Characteristics, Distribution and Change
2.4.8There are three general patterns of climate types that are connected to biome types.HL
London and Calgary temperature contrast, UK and Canada
London (maritime temperate) has a January average of around 5°C while Calgary (continental temperate) at the same latitude averages around -10°C, showing how proximity to the ocean, not latitude, determines the temperate subdivision and biome potential.
Demonstrates the distinction between maritime and continental subdivisions of the temperate climate type at equal latitude.
Calgary, Canada Climate Types, ENSO and Tropical Cyclones
2.4.9The biome predicted by any given temperature and rainfall pattern may not develop in an area because of secondary influences or human interventions.HL
Atacama Desert rain shadow, Chile
The Atacama Desert in Chile receives under 15 mm of precipitation per year despite lying on the Pacific coast, because the rain shadow of the Andes and the cold Humboldt Current suppress moisture and rainfall.
Shows two secondary influences (rain shadow and cold ocean current) preventing the moister biome expected at a coastal location.
Atacama Desert, Chile Climate Types, ENSO and Tropical CyclonesNairobi altitude and lapse rate, Kenya
Nairobi, Kenya, sits at just 1°S latitude but at an altitude of 1,795 m, so the environmental lapse rate (~6.5°C per 1,000 m) cools it enough that it does not develop the tropical rainforest predicted by its equatorial latitude.
Demonstrates how a secondary influence (altitude) overrides the biome predicted by latitude-based temperature and rainfall.
Nairobi, Kenya Climate Types, ENSO and Tropical Cyclones
2.4.10The El Niño Southern Oscillation (ENSO) cycle is the fluctuation in wind and sea surface temperatures that characterizes conditions in the tropical Pacific Ocean. The two opposite and extreme states are El Niño and La Niña, with transitional and neutral states between the extremes.HL
Peru anchoveta collapse, El Niño
The catastrophic 1972-73 El Nino decimated Peru's anchoveta population, killed millions of seabirds and crashed Peru's export economy, illustrating the irregular and severe extremes of the ENSO cycle.
Shows the extreme El Nino state of the ENSO cycle and the unpredictability of event intensity over decades.
2.4.11El Niño is due to a weakening or reversal of the normal east–west (Walker) circulation, which increases surface stratification and decreases upwelling of cold, nutrient-rich water near the coast of north-western South America. La Niña is due to a strengthening of the Walker circulation and reversal of other effects of El Niño.HL
Peru anchoveta season cancelled, El Niño
During the 2023-24 El Nino, one of the five strongest on record with eastern Pacific SSTs ~2.0°C above average, Peru cancelled the June 2023 anchoveta fishing season because collapsed upwelling drove fish below 100 m, cutting fishmeal production 28% and raising global feed prices since Peru supplies ~20% of world fishmeal.
Quantifies how weakened Walker circulation suppresses upwelling off Peru and collapses marine productivity with global economic knock-on effects.
2.4.13Rises in ocean temperatures resulting from global warming are increasing the intensity and frequency of hurricanes and typhoons because warmer water and air have more energy.HL
Hurricane Milton intensification, Gulf of Mexico
Hurricane Milton (October 2024) intensified from tropical storm to Category 5 in ~24 hours over a Gulf of Mexico that Climate Central found 400-800 times more likely to be so warm due to climate change; World Weather Attribution concluded that without warming it would have made landfall as Category 2 rather than 3, with rainfall 20-30% higher.
Provides attribution-study evidence linking elevated ocean temperatures to rapid intensification and greater cyclone severity.
2.5.1Zonation refers to changes in community along an environmental gradient.
Sand dune zonation at Studland Bay, Dorset (England)
At Studland Bay, Dorset, walking inland from the shore produces clear sand dune zonation: marram grass peaks (~63% cover) around 20 m from the sea while heather only appears from 40 m and dominates (100% cover) at 60–70 m, as salt spray falls and soil depth and humus rise.
Shows community changing along a distance-from-sea environmental gradient, with species replacing one another as abiotic conditions shift.
Studland Bay, Dorset, England Zonation and Succession
2.5.2Transects can be used to measure biotic and abiotic factors along an environmental gradient in order to determine the variables that affect the distribution of species.
Studland Beach transect survey, Dorset
Students at Studland Beach laid three parallel transects at 90° to the sea, sampling 1 m² quadrats at 10 m intervals to record percentage cover of marram grass and heather alongside slope angle, revealing that the two species barely overlap and are separated along the gradient.
Demonstrates transect methodology (parallel replicates, regular quadrats, biotic and abiotic factors) used to determine variables affecting species distribution.
Studland Bay, Dorset, England Zonation and Succession
2.5.3Succession is the replacement of one community by another in an area over time due to changes in biotic and abiotic variables.
Studland Bay dune psammosere, Dorset (over 400+ years)
The Studland Bay dune psammosere progresses over ~400+ years from foredunes (sea rocket, pH 8.5) through mobile and fixed dunes to climax oak-ash woodland (>40% humus, pH 4.5), so walking the 2.5 km inland from the 16th-century oldest dunes is effectively walking forward through time.
Demonstrates succession as temporal replacement of communities, with the spatial dune sequence mirroring change over centuries.
Studland Bay, Dorset, England Zonation and SuccessionSurtsey primary succession, Iceland
Surtsey, a ~1 km² volcanic island off southern Iceland formed by eruptions in 1963–67, shows primary succession on bare rock (lithosere): first insects arrived in 1964, mosses and lichens as pioneers, the first willow shrub in 1999, and by 2008 it had 69 vascular plant species (versus 460 on mainland Iceland), with 2–5 new species arriving each year.
Quantifies primary succession from a documented start date, showing pioneer colonisation of newly formed substratum and slow community development due to isolation.
2.5.4Each seral community (sere) in a succession causes changes in environmental conditions that allow the next community to replace it through competition until a stable climax community is reached.
Studland Bay psammosere soil and sere feedback, Dorset
In the Studland Bay psammosere, marram grass traps sand and adds leaf-litter organic matter, raising humus and lowering soil pH from ~8.0 to 6.5, so that red fescue and heather eventually outcompete the marram, which itself requires sand burial to thrive: each sere engineers its own replacement.
Shows a seral community modifying abiotic conditions (pH, humus) so the next community can outcompete and replace it, the core mechanism of succession.
Studland Bay, Dorset, England Zonation and Succession
2.5.5Primary successions happen on newly formed substratum where there is no soil or pre-existing community, such as rock newly formed by volcanism, moraines revealed by retreating glaciers, wind-blown sand or waterborne silt.
Studland Bay dune psammosere, Dorset
At Studland Bay, Dorset, primary succession begins on wind-blown sand with no organic content. Salt-tolerant pioneers such as sea rocket and saltwort colonise the strandline (pH 8.5, no humus), then marram grass takes over, using waxy rolled leaves, deep roots and silica-strengthened cell walls to survive on mobile dunes.
Shows why sand dunes count as primary succession: newly deposited mineral substrate with no soil, colonised by hardy pioneers adapted to harsh abiotic conditions.
Studland Bay, Dorset, England Zonation and Succession
2.5.6Secondary successions happen on bare soil where there has been a pre-existing community, such as a field where agriculture has ceased or a forest after an intense firestorm.
Broadbalk Wilderness succession, Rothamsted
The Broadbalk Wilderness at Rothamsted Research, Hertfordshire, England, is one of the world's longest-running ecological experiments: a section of the Broadbalk wheat field abandoned in the 1880s underwent unmanaged secondary succession, progressing through annual weeds, perennial grasses, hawthorn and blackthorn scrub, and by the present day a closed-canopy mixed deciduous woodland of oak, ash and sycamore after roughly 140 years.
Demonstrates secondary succession on pre-existing soil with a seed bank following the cessation of agriculture, reaching woodland in about 100 years.
Rothamsted Research, Harpenden, Hertfordshire, England 1880s–present Secondary Succession, Changes During Succession and Resilience
2.5.7Energy flow, productivity, species diversity, soil depth and nutrient cycling change over time during succession.
Broadbalk Wilderness soil and food web, Rothamsted
At Broadbalk Wilderness the deepening leaf litter and steadily rising soil organic carbon since 1881, alongside the shift from short simple food chains to a branched woodland food web, provides direct long-term evidence that soil depth, nutrient cycling and energy-flow complexity increase during succession.
Quantifies how soil depth, nutrient cycling and energy flow change over time using a documented 140-year dataset.
Rothamsted Research, Harpenden, Hertfordshire, England since 1881 Secondary Succession, Changes During Succession and ResilienceSand-dune succession transect
Along a sand-dune succession transect, the strandline pioneer stage supports only 2–3 species while the dune heath supports dozens of plant species plus associated animals, and soil humus rises from near zero to over 40%, showing species diversity and soil depth both increase through the seres.
Quantifies the systematic rise in species diversity and soil organic matter across successional stages.
2.5.8An ecosystem's capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience.
Prairie to monoculture crops, Great Plains
The displacement of diverse North American prairie ecosystems with monoculture crops drastically reduces species diversity and the size of biomass and nutrient storages, simplifying food webs and lowering the ecosystem's resilience to disturbance.
Demonstrates how human activity reduces diversity and storage, thereby lowering resilience and moving a system closer to tipping points.
Great Plains, North America Secondary Succession, Changes During Succession and ResilienceTrampling at Studland Bay, Dorset
Sustained trampling on the sand dunes at Studland Bay, Dorset, destroys marram grass and exposes bare sand, resetting succession and creating a plagioclimax; because the pioneer community has low diversity and small biomass storage it is pushed toward a tipping point, unlike a resilient climax oak woodland.
Shows how low diversity and small storage reduce resilience, and how human interference (trampling) diverts succession to a plagioclimax.
Studland Bay, Dorset, England Secondary Succession, Changes During Succession and Resilience
2.5.9The type of community that develops in a succession is influenced by climatic factors, the properties of the local bedrock and soil, geomorphology, together with fire and weather-related events that can occur. There can also be top-down influences from primary consumers or higher trophic levels.HL
Flow Country blanket bog, Scotland
The Flow Country of Caithness and Sutherland, Scotland, is one of the world's largest blanket bogs (~4,000 km²) where flat topography, impermeable bedrock and high rainfall keep soils waterlogged; Sphagnum moss, cotton grass and sundews dominate instead of the forest predicted by latitude, because anaerobic conditions halt decomposition and tree establishment.
Shows how geomorphology and poor drainage arrest succession at a bog seral stage rather than forest.
Flow Country, Caithness and Sutherland, Scotland Factors Influencing Succession, Productivity and PlagioclimaxSerpentine soils, Troodos Mountains
The serpentine soils of the Troodos Mountains, Cyprus, form from ultra-basic oceanic crust that weathers to soils very high in nickel and chromium but low in calcium and potassium; instead of the Mediterranean woodland predicted by climate, only sparse endemic metallophyte plants grow, halting succession by soil chemistry.
Demonstrates how bedrock and extreme soil chemistry override climate to determine the community that develops.
Troodos Mountains, Cyprus Factors Influencing Succession, Productivity and Plagioclimax
2.5.12The concept of a climax community has been challenged, and there is uncertainty over what ecosystems would develop naturally were there no human influences.HL
Sea otters and urchin barrens, North Pacific
Where North Pacific sea otters keep sea urchins under control, dense kelp forests grow. Where the fur trade removed the otters, urchin numbers exploded and grazed the kelp down to rocky 'urchin barrens' with almost no macroalgae.
Demonstrates alternative stable states: the same environment can hold two very different communities depending on the presence of a single species, which challenges the idea of one fixed climax.
Wood-pasture hypothesis, post-glacial Europe
Frans Vera's wood-pasture hypothesis proposes that post-glacial Europe was a shifting mosaic of woodland, scrub and grassland maintained by large herbivores such as aurochs, wild horses and European bison, rather than the closed-canopy forest of the traditional monoclimax view; early Holocene pollen and open-habitat beetle fossils are cited as support, though the evidence remains contested.
Demonstrates how the single-climax concept is challenged and uncertainty over the 'natural' human-free ecosystem.
2.5.13Human activity can divert and change the progression of succession leading to a plagioclimax.HL
Grazed alpine pastures, Jura Mountains
The open montane grasslands of the Jura Mountains are kept open by centuries of cattle and goat grazing and seasonal transhumance. On abandoned alpages, scrub and young trees quickly move in as the land heads back towards mixed beech-fir forest.
Shows a plagioclimax kept in place by livestock grazing, with abandoned pastures giving direct evidence that succession restarts once human activity stops.
Jura Mountains, France/Switzerland Factors Influencing Succession, Productivity and PlagioclimaxScottish Highlands plagioclimax, Glen Affric
The open heather moorland of the Scottish Highlands is a plagioclimax: wolves and lynx were extirpated centuries ago, and combined with sheep grazing and deer-stalking management this prevented regeneration of the native Caledonian pine forest, until rewilding by Trees for Life in Glen Affric let Scots pine, birch and rowan recover.
Shows how removing top carnivores plus human grazing diverts succession into a maintained plagioclimax that recovers when pressure is removed.
Glen Affric, Scotland Factors Influencing Succession, Productivity and Plagioclimax
3 Biodiversity and conservation
3.1.1Biodiversity is the total diversity of living systems and it exists at several levels.
Swiss National Park, Engadin
The Swiss National Park in the Engadin (170 km², founded 1914) spans 1,400 m to 3,174 m, creating distinct habitats (coniferous forest 28%, alpine grassland 21% and high alpine rock/scree 51%) that support 36 mammal species, ~100 bird species and over 650 vascular plant species.
Demonstrates how a steep altitudinal gradient generates high habitat diversity, one of the three levels of biodiversity.
Tasmanian devil DFTD decline
The Tasmanian devil (Sarcophilus harrisii) has extremely low genetic diversity from historical population bottlenecks, leaving it vulnerable to devil facial tumour disease (DFTD); with immune systems unable to recognise the transmissible cancer as foreign due to similar MHC genes, the population has declined over 85% since 1996.
Shows genetic diversity as a distinct level of biodiversity and the consequences of its loss within a population.
3.1.2The components of diversity contribute to the resilience of ecological systems.
Quagga mussel filtering, Lake Geneva
In Lake Geneva each quagga mussel filters up to 2 litres of water per day, feeding on phytoplankton at the base of the food chain; the resulting phytoplankton decline cuts food for zooplankton and fish, threatening the livelihoods of roughly 120 professional fishers on the lake.
Shows how loss/replacement of species propagates up the food chain, affecting ecosystem functioning and human livelihoods.
Lake Geneva, Switzerland Human Impact on Biodiversity and Invasive Alien SpeciesQuagga mussel invasion, Lake Geneva
Quagga mussels (Dreissena rostriformis bugensis), native to the Ponto-Caspian Black Sea region, were found in Lake Geneva by 2016 and by 2024 made up 100% of mussel samples at densities over 35,000 per m², driving native snails, shrimps and mussels to local extinction through competitive exclusion for space and food on the lake bed.
Demonstrates competitive exclusion, one of the three biodiversity-reduction mechanisms, with quantified colonisation of a named local ecosystem.
Wild banana resistance to Panama disease TR4
Wild banana populations with high genetic diversity resist Panama disease TR4, which devastates genetically uniform commercial Cavendish plantations where every plant shares the same disease susceptibility.
Demonstrates how genetic diversity confers resilience while genetic uniformity leads to collapse under a single pathogen.
Wolf reintroduction to Yellowstone
The reintroduction of wolves to Yellowstone in the 1990s triggered a trophic cascade that restored ecosystem function, whereas the historical loss of wolves from European forests let deer populations explode, reducing tree regeneration and simplifying the ecosystem.
Shows how species diversity and a keystone predator maintain complex food webs and ecosystem resilience.
3.1.3Biodiversity arises from evolutionary processes.
Italian wall lizards on Pod Mrčaru
Italian wall lizards (Podarcis sicula) introduced to Pod Mrčaru, Croatia in 1971 evolved over ~36 years (~30 generations) a plant-based diet (up to 60% plant matter), larger heads with stronger bite force, and novel cecal valves in the gut compared to the source population on Pod Kopište.
Demonstrates evolution as cumulative, heritable change in a population's characteristics observable over a short timescale.
3.1.4Natural selection is the mechanism driving evolutionary change.
European robin winter selection
The European robin (Erithacus rubecula), a year-round woodland resident, faces harsh winters with reduced invertebrate food; individuals with higher metabolic efficiency and greater fat-storage capacity survive to breed in spring and pass these heritable traits on, increasing their frequency over generations.
Illustrates natural selection as a continuous mechanism acting on heritable variation through seasonal selection pressures.
3.1.5Evolution by natural selection involves variation, overproduction, competition for limited resources, and differences in adaptation that affect rates of survival and reproduction.
Great tit laying dates and caterpillar peak
European great tits (Parus major) that time their egg-laying to coincide with the ~2–3 week spring peak in canopy caterpillar abundance raise more surviving chicks, and populations have shifted laying dates earlier within a few decades in response to warming springs.
Shows heritable variation, competition and differential reproductive success producing measurable evolutionary change over just decades.
Pedunculate oak seed survival
A single pedunculate oak (Quercus robur) can produce over 70,000 acorns in a mast year, yet an ancient woodland may hold only a few hundred mature oaks: most seeds are lost to herbivory, competition and shading, while seedlings germinating in canopy gaps receive more light and are more likely to survive.
Quantifies overproduction and demonstrates competition for limited resources and differential survival driving natural selection.
3.1.6Speciation is the generation of new species through evolution.
Leaf warbler niche partitioning, Europe
Four similar leaf warblers, the chiffchaff (Phylloscopus collybita), willow warbler (P. trochilus), wood warbler (P. sibilatrix) and garden warbler (Sylvia borin), coexist in a single European woodland by partitioning niches through feeding height, food source and nest location, having diverged from common ancestors after Pleistocene isolation.
Shows how repeated speciation and adaptation from ancestral populations generates biodiversity and niche partitioning within one habitat.
Treecreeper speciation in Pleistocene refugia
The Eurasian treecreeper (Certhia familiaris) and short-toed treecreeper (Certhia brachydactyla) diverged when Pleistocene ice sheets (2.6 million–11,700 years ago) fragmented European woodland into isolated refugia in Iberia, Italy and the Balkans; adapting separately, the populations could no longer interbreed when woodlands reconnected.
Demonstrates allopatric speciation via geographic isolation, divergent selection and resulting reproductive isolation.
3.1.8Simpson's reciprocal index is used to provide a quantitative measure of species diversity, allowing different ecosystems to be compared and for change in a specific ecosystem over time to be monitored.
Ground beetle diversity, Scottish Highlands
On a rewilded estate in the Scottish Highlands, ground beetle (Carabidae) communities were compared using pitfall traps: after 15 years of rewilding (sheep removed, birch and Scots pine regenerating) Site 1 gave a Simpson's reciprocal index of D = 5.28, while the still-grazed Site 2, dominated by 45 Nebria brevicollis out of 60 individuals, gave only D = 1.74, despite both sites having identical richness (5 species) and total individuals (60).
Demonstrates how Simpson's reciprocal index quantifies diversity and detects change from a management intervention when richness alone stays constant, using a valid same-organism, same-ecosystem, same-method comparison.
Scottish Highlands, Scotland Species diversity
3.1.9Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity.
Puffin rally monitoring, Iceland
Dr Erpur Snær Hansen of the South Iceland Nature Research Centre conducts a twice-yearly 'puffin rally', travelling over 3,100 miles to about 700 marked burrows across 12 colonies with plumbing cameras; this government-linked systematic monitoring revealed Iceland's puffin decline since the early 2000s, linked to falling sand eel numbers and rising sea surface temperatures.
Demonstrates why systematic professional monitoring, alongside citizen science, provides the long-term trend data needed for effective conservation strategies.
Puffling Patrol, Heimaey (Iceland)
Iceland's Puffling Patrol on Heimaey in the Westman Islands is a citizen-science programme where local children and families collect, weigh, log and release disoriented Atlantic puffin chicks each August–September, feeding standardised data into GBIF (the Global Biodiversity Information Facility) for use by researchers.
Shows how citizen science following a standardised protocol gathers regional biodiversity knowledge that aggregates into global databases underpinning conservation management.
Heimaey, Westman Islands, Iceland Species diversity
3.1.10Mutation and sexual reproduction increase genetic diversity.HL
Eastern tree frog melanism, Chernobyl
Eastern tree frogs (Hyla orientalis) in Ukraine's Chernobyl Exclusion Zone are, per 2022 research, significantly darker than frogs in uncontaminated areas nearby; pre-existing melanin-producing alleles gave protection against elevated radiation after the 1986 disaster, so darker frogs were selected over ~14 generations.
Demonstrates how mutation first generates genetic variation (dark-pigment alleles) which natural selection then amplifies once the environment changes.
3.1.11Reproductive isolation can be achieved by geographical separation or, for populations living in the same area, by ecological or behavioural differences.HL
Apple maggot fly host races, North America
The apple maggot fly (Rhagoletis pomonella) began, from the mid-1800s in North America, laying eggs on introduced apples rather than native hawthorn; because flies mate on their host fruit and apples and hawthorn ripen at different times, the two 'host races' rarely interbreed and now differ in emergence timing and genetic markers.
Demonstrates behavioural (sympatric) reproductive isolation without a geographical barrier: 'speciation in progress' within a few hundred generations.
Bonobo and chimpanzee divergence, Congo River
Bonobos (Pan paniscus) and common chimpanzees (Pan troglodytes) diverged from one ancestral population ~1.5–2 million years ago when the Congo River became too deep and wide to cross; chimps north of the river evolved male-dominant, aggressive, tool-using societies while bonobos south of it (lacking gorilla competitors) became female-dominant and less aggressive.
Shows speciation by geographical separation, with a physical barrier splitting a gene pool and different selective pressures driving divergence.
Congo River Reproductive Isolation and Biodiversity Hotspots
3.1.12Biodiversity is spread unevenly across the planet, and certain areas contain a particularly large proportion of species, especially species that are rare and endangered.HL
Mediterranean Basin biodiversity hotspot
The Mediterranean Basin, one of 36 recognised biodiversity hotspots, holds over 25,000 plant species (~13,000 endemic) adapted to hot dry summers and mild wet winters (maquis and garrigue), yet millennia of agriculture, urbanisation, tourism and fire have destroyed most of its original habitat.
Demonstrates a non-tropical hotspot meeting both criteria (high endemism plus severe habitat loss), showing hotspots are not only tropical rainforests.
Mediterranean Basin Reproductive Isolation and Biodiversity HotspotsSocotra endemism and UNESCO listing
Socotra, an Indian Ocean island ~380 km south of Arabia isolated from Africa ~6 million years ago, has ~37% endemic plant species, including the dragon blood tree (Dracaena cinnabari) and the cucumber tree (Dendrosicyos socotranus), the only tree-form cucumber on Earth; it became a UNESCO World Heritage Site in 2008.
Shows how long island isolation concentrates rare endemic species, illustrating the uneven, vulnerable distribution of biodiversity.
3.1.13Human activities have impacted the selective forces acting on species within ecosystems, resulting in evolutionary change in these species.HL
Elephant poaching and tusklessness, Gorongosa
In Gorongosa National Park, Mozambique, ivory poaching during the civil war (1977–1992) killed ~90% of elephants (from ~2,500 to ~200); tuskless females rose from ~18.5% before the war to ~51% of survivors, and ~33% of the next generation, a genetic shift confirmed by Campbell-Staton et al. (Science, 2021).
Demonstrates how a human activity (poaching) unintentionally altered the selective force on a population, causing rapid, measurable, heritable evolutionary change: human-altered natural selection, not artificial selection.
Great tit phenological mismatch, Europe
European great tits (Parus major) have evolved earlier egg-laying dates as climate warming shifts the caterpillar peak earlier; populations that cannot keep pace suffer a phenological mismatch where chicks hatch after peak food, reducing breeding success.
Shows how climate change from burning fossil fuels alters the selective advantage of a trait (laying date), driving evolutionary change dependent on a population's genetic diversity.
Europe Humans and Selection
3.1.14Artificial selection reduces genetic diversity and, consequently, species resilience.HL
Cavendish banana and Tropical Race 4
The Cavendish banana, which dominates global trade, is propagated vegetatively as genetic clones with essentially zero genetic diversity and no resistance to the spreading fungus Tropical Race 4 (Fusarium oxysporum); it replaced the Gros Michel variety, itself wiped out by Panama disease in the 1950s for the same reason.
Demonstrates how artificial selection for uniformity eliminates genetic variation, leaving no material for selection to act upon and creating extreme vulnerability (loss of resilience) to disease.
1950s Humans and Selection
3.1.15Earth history extends over a period of 4.5 billion years. Processes that occur over an extended timescale have led to the evolution of life on Earth.HL
Marine fossils in the Jura, La Dôle, France
The limestone peaks of the Jura mountains near Ferney-Voltaire, such as La Dôle (1,677 m), contain marine fossils (ammonites, belemnites, corals, sea urchins) deposited on the floor of the warm shallow Tethys Sea around 150 million years ago during the Jurassic, before being uplifted 1.7 km by the collision of the African and Eurasian plates.
Shows how fossils and the geological record work together to reveal both the evolution of life and the movement of environments over deep time.
3.1.16Earth history is divided up into geological epochs according to the fossil record.HL
Cretaceous–Palaeogene (K–Pg) boundary
The Cretaceous–Palaeogene (K–Pg) boundary at 66 million years ago is marked worldwide in rocks by the sudden disappearance of non-avian dinosaurs and ammonites together with a chemical signal from a large meteorite impact, and is formally defined by the International Commission on Stratigraphy.
Demonstrates how an epoch/period boundary is read from a globally synchronous change in the fossil record rather than assigned arbitrarily.
3.1.17Mass extinctions are followed by rapid rates of speciation due to increased niche availability.HL
Ammonite radiation and extinction (Devonian–K–Pg)
Ammonites, shelled cephalopods related to modern squid, adaptively radiated into thousands of species after surviving three mass extinctions (Late Devonian, Permian–Triassic, Triassic–Jurassic) before going completely extinct at the K–Pg boundary 66 Ma, after which niches were filled by radiating bony fish.
Illustrates repeated rapid speciation into vacant niches following mass extinctions, plus eventual extinction, within a single well-documented lineage.
Great Dying extinction
The Permian–Triassic 'Great Dying' at ~252 Ma, caused by super-volcanic eruption and resulting climatic change, killed ~96% of species, the largest extinction in Earth's history, after which surviving lineages radiated into vacant niches.
Quantifies the scale of a mass extinction and its abiotic cause, and shows the vacated niches that drive subsequent adaptive radiation.
~252 Ma Deep Time and the Anthropocene
3.1.18The Anthropocene is a proposed geological epoch characterized by rapid environmental change and species extinction due to human activity.HL
Proposed Anthropocene golden spike, Crawford Lake
The 2024 proposal to formalise the Anthropocene used a 1950s start with the 1964 Carbon-14 peak as its golden spike, preserved in the annual varves of Crawford Lake, Ontario, but the Subcommission on Quaternary Stratigraphy voted against it in March 2024, leaving the Anthropocene a proposed epoch.
Demonstrates the golden-spike concept and the contested, unresolved status of the proposed Anthropocene epoch.
3.1.19Human impacts are having a planetary effect, which will be detectable in the geological record.HL
Plastiglomerate, Kamilo Beach, Hawaii
Plastiglomerate (fragments of plastic fused with natural rock, first documented on beaches in Hawaii) is a novel human-made mineral-like material with no pre-industrial precedent that will persist in the far-future rock record.
Provides a concrete example of novel minerals as a permanent planetary-scale human signal in the geological record.
Kamilo Beach, Hawaii, USA Deep Time and the Anthropocene
3.2.3Invasive alien species can reduce local biodiversity by competing for limited resources, predation and introduction of diseases or parasites.
Quagga mussels and climate change, Lake Geneva
In Lake Geneva quagga mussel filtering makes water clearer and lets light penetrate deeper, while climate change has stopped seasonal lake mixing since 2012, warming deep water and raising the risk of toxic blue-green algal blooms: a combined impact far greater than either stressor acting alone.
Quantifies the amplification effect where climate change and an invasive species interact to reduce resilience beyond the sum of their parts.
Quagga mussels at EPFL cooling pipes
In Lake Geneva quagga mussels clogged the deep-water cooling pipes of the Swiss Federal Technology Institute of Lausanne (EPFL), cutting heat-exchanger efficiency by a third, and prompting plans for a new closed-loop cooling system beginning in 2027 since eradication is impossible.
Shows why adaptation rather than eradication is the only management option once an invader is established, illustrating persistent multi-impact stress.
EPFL, Lausanne, Switzerland Human Impact on Biodiversity and Invasive Alien Species
3.2.6Investigate three different named species: a species that has become extinct due to human activity; a species that is critically endangered; and a species whose conservation status has been improved by intervention.
Steller's sea cow extinction, Commander Islands
Steller's sea cow (Hydrodamalis gigas), an 8–9 m sirenian discovered in 1741 around the Commander Islands, was hunted to extinction by Russian fur traders for meat and hide within just 27 years (by 1768), the first historical extinction of a marine mammal caused by humans. Its small remnant population (~1,500), tameness and shallow-water habitat made it defenceless.
Demonstrates a species driven extinct by human overharvesting, with cascading effects on kelp-forest food webs and no conservation attempted.
Vaquita decline from totoaba gillnet bycatch, Gulf of California
The vaquita (Phocoena sinus), the world's smallest porpoise, is Critically Endangered with fewer than 10 individuals remaining in the upper Gulf of California; its decline is driven not by hunting but by bycatch in illegal gillnets set for totoaba fish, whose swim bladders sell for thousands of dollars per kg, despite a 2005 refuge, a 2017 gillnet ban and support from WWF and Sea Shepherd.
Shows a critically endangered species whose decline continues despite well-funded intervention because economic incentives behind the threat remain unaddressed.
Upper Gulf of California, Mexico The IUCN Red List and the Tragedy of the Commons
3.2.7The tragedy of the commons describes possible outcomes of the shared unrestricted use of a resource, with implications for sustainability and the impacts on biodiversity.
Baltic Sea dead zone
The Baltic Sea, bordered by nine countries, now holds the world's largest human-caused dead zone at almost 70,000 km² (about 1.5 times the area of Denmark) after agricultural nitrogen and phosphorus runoff drove eutrophication; despite the Helsinki Convention (HELCOM) cutting nitrogen inputs ~20% and phosphorus ~40% since the 1980s peak, levels remain roughly double those of the early 1900s.
Shows the tragedy of the commons through contamination of a shared resource, where each nation gains from farming but shares the collective cost of biodiversity loss.
Grand Banks cod collapse, Newfoundland
The Grand Banks cod fishery off Newfoundland, once among the world's most productive, collapsed after 1950s industrialised trawling by multiple nations acting in self-interest under weak international regulation; Canada imposed a moratorium in 1992, costing over 35,000 jobs, and after 30+ years cod have still not recovered because shrimp and snow crab occupied the vacant niche.
Quantifies the tragedy of the commons through overharvesting of an unowned shared fishery leading to catastrophic, possibly irreversible, ecosystem collapse.
3.2.8Biodiversity hotspots are under threat from habitat destruction, which could lead to a significant loss of biological diversity, especially in tropical biomes.HL
Boma-Badingilo KBA wealth-biodiversity mismatch
The Boma-Badingilo KBA illustrates the wealth-biodiversity mismatch: South Sudan has per-capita GDP under US$500 and, after civil war (2013–2018), depends almost entirely on a single NGO (African Parks, 10-year agreement signed 2022), and the 2024 survey found hippos, elephants and warthogs had collapsed over 40 years due to bushmeat hunting where enforcement was absent.
Demonstrates how tropical biodiversity concentrated in low-income countries lacks the governance, funding and security capacity to prevent habitat and population loss.
3.2.9Key areas that should be prioritized for biodiversity conservation have been identified on the basis of the international importance of their species and habitats.HL
Aeolian wall lizard KBA, Aeolian Islands, Italy
The Aeolian Archipelago off Sicily (~115 km²) holds the entire global population of the Critically Endangered Aeolian wall lizard (Podarcis raffonei), roughly 2,000 individuals in an area of occupancy under two hectares, qualifying as a KBA under criterion A (threatened biodiversity) and B (geographically restricted biodiversity).
Shows that KBA prioritisation applies at tiny scale in a temperate high-income biome, based on international importance of a microendemic species rather than megafauna spectacle.
Aeolian Islands, Italy Hotspots, KBAs and the Conservation ConflictBoma-Badingilo-Gambella migration
The Boma-Badingilo-Gambella landscape (~122,000 km² across eastern South Sudan and western Ethiopia) hosts the largest land mammal migration on Earth: a 2024 African Parks aerial survey confirmed ~6 million migrating antelope, including ~5 million white-eared kob, and it qualifies as a KBA under criterion D (biological processes), C (ecological integrity) and A (threatened species such as the endemic Nile lechwe).
Demonstrates how a specific site is prioritised as globally important on the basis of a globally significant life-cycle stage (migration) meeting formal KBA criteria.
3.2.10In KBAs, there is conflict between exploitation, sustainable development and conservation.HL
Brazilian Cerrado vegetation loss
The Brazilian Cerrado, a biodiversity hotspot holding ~5% of global biodiversity, has lost over 55% of its native vegetation (~650,000 ha in 2024 alone) as soy occupies ~75% of cropland; Brazil's Forest Code requires retaining only 20–35% of native vegetation there (vs 80% in the Amazon), and the 2006 Soy Moratorium excluded the Cerrado, displacing ~16% of avoided Amazon deforestation into the savanna.
Quantifies the three-way conflict between profitable legal soy/cattle exploitation, water/climate-based sustainable development needs, and conservation of KBAs meeting criteria A and B.
Tropical Forest Forever Facility, Belém
At COP30 in Belém (November 2025), Brazil launched the Tropical Forest Forever Facility (TFFF), under which consumer countries pay tropical governments to keep forests standing with at least 20% going to indigenous and local communities; over US$6.7 billion had been pledged by the summit's end.
Shows an attempted resolution to the exploitation-versus-conservation conflict by realigning who pays, addressing the justice dimension of protecting hotspots in lower-income countries.
3.2.11Traditional indigenous approaches to land management can be seen as more sustainable but are facing challenges of population growth, economic development, climate change and a lack of governmental support and protection.HL
Sámi reindeer herding, Sápmi
Sámi reindeer herding across Sápmi (northern Norway, Sweden, Finland and Russia's Kola Peninsula) is an extensive, low-input system managed collectively through the siida, but faces external threats such as climate-driven 'rain-on-snow' events that ice over lichen pastures and internal threats such as motorisation (snowmobiles, GPS) and young people leaving for salaried urban work.
Demonstrates a named sustainable Indigenous practice and the syllabus distinction between threats from outside and from within.
3.2.12Environmental justice must be considered when undertaking conservation efforts to address biodiversity loss.HL
Fosen wind farm, Norway
At the Fosen wind farm in central Norway, the Norwegian Supreme Court ruled unanimously in 2021 that the Storheia and Roan licences were invalid because the turbines violated Sámi herders' cultural rights under Article 27 of the ICCPR, yet the turbines kept operating and only 2023–24 settlements left them standing in exchange for compensation: an example of 'green colonialism'.
Demonstrates the gap between legal rights and environmental justice when 'green' projects dispossess a biodiversity-rich Indigenous community.
Swiss National Park, Engadine
The Swiss National Park, founded in 1914 in the Engadine valley of Graubünden and classified under the strict IUCN category Ia, banned all traditional uses (grazing, hunting, fishing, mowing, wood-cutting) on land leased from local communes, making it a textbook European case of fortress conservation.
Shows conservation overriding traditional land use, illustrating the environmental-justice tension even without forced relocation of Indigenous people.
Swiss National Park, Engadine, Graubünden, Switzerland 1914 Indigenous Land, Justice and Biosphere Integrity
3.2.13The planetary boundary "loss of biosphere integrity" indicates that species extinctions have already crossed a critical threshold.HL
Planetary boundaries framework update
The planetary boundaries framework developed by Johan Rockström, Will Steffen and colleagues at the Stockholm Resilience Centre identifies nine Earth-system processes; its 2023 update placed 'loss of biosphere integrity' firmly in the high-risk zone, with extinction rates (its genetic-diversity component) estimated at tens to hundreds of times the natural background rate against a proposed safe boundary of ~10 extinctions per million species per year.
Quantifies how the biosphere-integrity boundary has been crossed and shows the distinction between its genetic-diversity and functional-integrity components.
Stockholm Resilience Centre, Stockholm, Sweden 2023 Indigenous Land, Justice and Biosphere Integrity
3.3.1Arguments for species and habitat preservation can be based on aesthetic, ecological, economic, ethical and social justifications.
Elephant pressure, Hwange National Park (dry season)
In Zimbabwe about 60,000 of the country's ~100,000 elephants pass through Hwange National Park in the dry season (roughly double the region's carrying capacity), where safari tourism is a major income source yet Fransica Sibanda's husband was trampled to death near their home: the same elephants bring economic value and a social and human cost.
Demonstrates how one species can simultaneously carry economic (ecotourism) and social (well-being, livelihoods) justifications that conflict in local context.
Hwange National Park, Zimbabwe Why and How We ConserveLast bull elephant, Badingilo National Park
In South Sudan the elephant population has fallen to about 5% of the ~133,500 estimated in the early 1970s; in Badingilo National Park the last bull elephant, so isolated it moved with a herd of giraffes, was killed by suspected poachers at the end of 2025, and one hunter said he killed an elephant out of hunger for $50 per tusk.
Shows how ecological (keystone role), ethical and social justifications collide with extreme poverty, undermining preservation arguments in practice.
3.3.2Species-based conservation tends to involve ex situ strategies, and habitat-based conservation tends to involve in situ strategies.
CITES Appendix I listing of African elephants
CITES listed African elephants under Appendix I in 1989, effectively banning international commercial ivory trade after catastrophic 1970s–80s declines; enforcement varies by country and southern African states like Zimbabwe and Botswana repeatedly push at CoP meetings to sell ivory stockpiles or downlist to Appendix II.
Illustrates ex situ, species-based conservation through international trade regulation and its dependence on national enforcement.
Seed bank, Conservatoire et Jardin botaniques de Genève
The Conservatoire et Jardin botaniques de Genève seed bank, established 1999 in Chambésy, is Switzerland's only wild-flora seed bank, holding over 600 species (~30% of Switzerland's threatened flora, 57% of Geneva canton's) dried to ~5% moisture and stored at -20°C for reintroduction projects.
Shows ex situ, species-based conservation preserving genetic material outside natural habitat as an insurance policy against wild extinction.
3.3.3Sometimes a mixed conservation approach is adopted, where both habitat and particular species are considered.
Giant panda conservation, Sichuan, China
The giant panda combines ex situ conservation at the Chengdu Research Base (founded 1987, ~240 ha, 9 million+ visitors in 2019) with the in situ Giant Panda National Park created in 2021 (27,134 km²), which reconnects habitats for ~1,900 wild pandas; as a flagship species (WWF logo since 1961) it provides an 'umbrella effect' protecting 8,000+ other species, though leopards, wolves and wild dogs in the region have declined.
Demonstrates a mixed approach using a flagship species to justify protecting intact habitat, including its trade-offs.
Giant Panda National Park, Sichuan, China Why and How We Conserve
3.3.4The Convention on Biological Diversity (CBD) is a UN treaty addressing both species-based and habitat-based conservation.
Convention on Biological Diversity
The Convention on Biological Diversity, established at the 1992 Rio Earth Summit and in force from 1994, is a legally binding UN treaty requiring national biodiversity strategies covering both species and habitat; its 2010 Nagoya Protocol ensures fair and equitable sharing of benefits from genetic resources with countries of origin.
Shows a UN treaty addressing both species-based and habitat-based conservation plus benefit-sharing, broader than trade-focused CITES.
3.3.5Habitat conservation strategies protect species by conservation of their natural environment. This may require protection of wild areas or active management.
La Grande Cariçaie wetland, Lake Neuchâtel
La Grande Cariçaie, Switzerland's largest lakeside wetland (>3,000 ha along 40 km of Lake Neuchâtel's south shore, ~800 plant and 10,000 animal species), was created accidentally by the First Jura Waters Correction (1868–1889) lowering the lake by 2.7 m; the Second Correction (1962–1973) then removed the seasonal flooding that kept it open, so since 1982 it requires rotational mechanical mowing on a 3–4 year cycle and Highland cattle grazing to stop alder, willow and buckthorn succeeding it to woodland.
Demonstrates active management to hold a habitat at a seral stage, and shows how surrounding engineering, farmland runoff and invasive Louisiana crayfish create the pressures conservation must balance.
Sanctuary Mountain Maungatautari, New Zealand
Sanctuary Mountain Maungatautari (3,400 ha, Waikato, New Zealand) is the world's largest fenced ecosanctuary, enclosed by a 47 km Xcluder pest-proof fence (2004–2006) with a curved anti-climb hood and buried mesh skirt; after aerial brodifacoum drops eradicated 14 mammal species, natives like kiwi, takahē, tuatara and (in 2023) four kākāpō were reintroduced, though mice could not be eradicated and some kākāpō climbed out over fallen trees.
Shows pest-exclusion fencing as an active management strategy in a country whose birds evolved without mammalian predators, illustrating both its power and its 'ecological island' limitations.
Sanctuary Mountain Maungatautari, Waikato, New Zealand 2004–2006 Habitat Conservation and Reserve Design
3.3.6Effective conservation of biodiversity in nature reserves and national parks depends on an understanding of the biology of target species and on the effect of the size and shape of conservation areas.
StudyProtected areas and food webs, Europe
A study of European protected areas by Lurgi (2025, Swansea University) found that reserves and national parks do increase species richness and support larger predators, but they do not consistently preserve ecological interactions such as food-chain length and food-web complexity, with remoteness, habitat diversity, human pressure and surrounding agricultural land all affecting how well food webs were maintained.
Provides evidence that reserve design factors (surrounding land use, edge effects, connectivity) determine effectiveness beyond mere species counts, adding critical depth to conservation-area evaluation.
Yasuní Biosphere Reserve, Ecuador
The Yasuní Biosphere Reserve in the Ecuadorian Amazon uses the UNESCO three-zone model: a ~10,000 km² national park core (protected 1979, biosphere reserve 1989), a buffer including the Tagaeri-Taromenane Intangible Zone for uncontacted peoples, and a transition zone of Kichwa and Waorani communities. It protects record biodiversity (~1,300 tree, 150 amphibian, 170 mammal species) despite sitting on 1.7 billion barrels of oil (~40% of Ecuador's reserves) drilled since 2016.
Demonstrates the core/buffer/transition zonation model applied to a globally significant biodiversity site and the human-impact conflict (oil extraction, 2023 anti-drilling referendum) it must manage.
3.3.7Natural processes in ecosystems can be regenerated by rewilding.
Beaver wetland on Chris Jones's farm, Cornwall
On Chris Jones's organic beef farm in Cornwall, Eurasian beavers (Castor fiber) reintroduced in 2017 expanded a pond by two-thirds and built leaky dams, and University of Cambridge scientists measured an 80% reduction in nitrates in water leaving the beaver wetland, alongside larger fish and returning otters and invertebrates.
Shows how reintroducing a keystone ecosystem engineer regenerates natural hydrological and water-quality processes even on a small farm in a populated landscape.
Hinewai Reserve gorse nurse crop
At Hinewai Reserve (~1,250 ha) on Banks Peninsula, New Zealand, botanist Hugh Wilson from 1987 stopped fighting invasive gorse (Ulex europaeus) on former sheep pasture, using it as a nitrogen-rich nurse crop under which native broadleaf forest regenerated with no replanting, herbicide or intervention.
Demonstrates rewilding through minimisation of human influence and cessation of agriculture, showing natural succession can regenerate forest when active management ceases.
Hinewai Reserve, Banks Peninsula, New Zealand 1987 onwards Rewilding, Regeneration and Conservation Choices
3.3.8Conservation and regeneration measures can be used to reverse the decline in biodiversity to ensure a safe operating space for humanity within the biodiversity planetary boundary.
Eurasian beaver reintroduction, Switzerland
The Eurasian beaver, hunted to extinction in Switzerland by ~1820, was reintroduced from 1956 by naturalist Maurice Blanchet and artist Robert Hainard using French beavers, so that several thousand now live across Switzerland including in the Rhône, Arve and Versoix rivers in canton Geneva.
Shows a successful long-term national regeneration measure re-establishing a locally extinct keystone species, with the 70-year head start over the UK highlighting the role of success factors.
UK beaver release licensing, Purbeck Heath
After being hunted to extinction in Britain ~400 years ago, the Eurasian beaver's return culminated in the UK government's 2025 decision to licence wild releases (first at Purbeck Heath, Dorset), requiring each release to have a beaver management plan with mitigations, linked to the international 30 by 30 target to protect 30% of land and water by 2030.
Illustrates how national legislation and international targets combine as regeneration measures to reverse biodiversity decline within the planetary boundary.
3.3.9Environmental perspectives and value systems can impact the choice of conservation strategies selected by a society.
Maungatautari ecosanctuary, New Zealand
Maungatautari ecosanctuary in New Zealand uses high-tech pest-exclusion fencing (a technocentric strategy) to protect a wild forest that is then largely left to run itself (an ecocentric goal), showing a single project spanning the EVS spectrum.
Shows how a real conservation project blends technocentric intervention with ecocentric non-intervention, reflecting mixed underlying values.
Maungatautari, New Zealand Rewilding, Regeneration and Conservation ChoicesUK beaver debate and stakeholder views
In the UK beaver debate, ecocentric voices like Derek Gow argued beavers intrinsically belong in British rivers, anthropocentric water companies backed them for cheaper flood and pollution control, while some dairy farmers and landowners lobbied against releases over flooded fields and felled trees, resolved by a technocentric licensing system with chicken-wire tree guards and German-style trap-and-relocate schemes.
Demonstrates how ecocentric, anthropocentric and technocentric value systems produce conflicting conservation preferences over a single species, resolved through compromise.
United Kingdom Rewilding, Regeneration and Conservation Choices
3.3.10Success in conserving and restoring biodiversity by international, governmental and non-governmental organizations depends on their use of media, speed of response, diplomatic constraints, financial resources and political influence.HL
Bern Convention wolf downgrade, Europe
The 1979 Bern Convention (Council of Europe, 49 member states) listed the wolf as 'strictly protected', but only in December 2024 did its Standing Committee, acting on an EU proposal and needing a two-thirds majority, vote to downgrade the wolf to merely 'protected', effective March 2025, with the Czech Republic, Monaco and the UK opting out; Switzerland's own bid for the downgrade in 2022 had failed.
Shows how an IGO's political influence is constrained by diplomatic negotiation and slow speed of response: change took years while wolf numbers shifted rapidly on the ground.
Pro Natura and WWF Switzerland wolf campaign
Swiss NGOs Pro Natura and WWF Switzerland, despite far smaller budgets than the state, used direct democracy by gathering 65,000 signatures to trigger the 2020 wolf referendum, ran media campaigns, and challenged individual culls in court to halt some shooting orders.
Illustrates how NGOs compensate for weak financial resources by leveraging political influence, media and legal challenge to shape conservation outcomes.
3.3.11Positive feedback loops that enhance biodiversity and promote ecosystem equilibrium can be triggered by rewilding and habitat restoration efforts.HL
Knepp beavers and dragonflies, River Adur
Along Knepp's restored River Adur, Eurasian beaver (Castor fiber) held in an enclosure dammed the flow and created wetland that supports more aquatic plants and prey, and dragonfly and damselfly abundance rose by around +871% between 2005 and 2025.
Quantifies a rewilding-triggered positive feedback loop in which beaver-created wetland reinforces the conditions supporting more wetland species.
Knepp thorn and oak self-reinforcing loop
At Knepp Estate, West Sussex, grazing and trampling by free-roaming herbivores let thorny scrub such as blackthorn and hawthorn establish, which shelters oak seedlings from browsing ('the thorn is the mother of the oak'); more trees and scrub support more insects, birds and seed dispersal, which builds still more scrub: a self-reinforcing loop.
Demonstrates how rewilding triggers a positive feedback loop through food-web interactions that amplifies biodiversity past a threshold into a new wood-pasture stable state.
Knepp Estate, West Sussex, England Rewilding Knepp: tipping points, trade-offs and tourism
3.3.12Rewilding projects have both benefits and limitations.HL
Gorongosa Restoration Project wildlife recovery
In Gorongosa National Park, Mozambique (4,067 km²), civil war left only ~7,000 large animals by 1994, but the Gorongosa Restoration Project begun in 2008 lifted this to over 100,000 by a 2022 aerial survey, with waterbuck rising from under 500 to over 55,000 and lions from ~15 to over 100, though rising elephant numbers now damage crops on surrounding farms.
Illustrates the benefits of restocking wildlife in a rewilding project alongside the limitation of rising human-wildlife conflict as populations recover.
Gorongosa National Park, Mozambique 2008–2022 Rewilding Knepp: tipping points, trade-offs and tourismKnepp Estate rewilding review
Knepp took 1,400 hectares of loss-making arable and dairy farmland out of food production from 2001; its twenty-year review reported breeding birds up around +900% and nightingale singing males rising from 9 to 62 (1999–2025), but the estate has no apex predators (no wolves or lynx) so cattle, ponies, pigs and deer must be controlled by culling, and it depends on stewardship grants and private income.
Shows both the biodiversity/ecosystem-service benefits and the limitations (culling need, funding dependence, lost food production) at the heart of the food-versus-rewilding land-use tension.
Knepp Estate, West Sussex, England 1999–2025 Rewilding Knepp: tipping points, trade-offs and tourism
3.3.13The success of conservation or regeneration measures needs to be assessed.HL
Swiss Hunting Act referendum
In Switzerland's 27 September 2020 referendum on a revised Hunting Act to make wolves easier to shoot, 51.9% voted no (keeping strict protection), but rural Alpine cantons voted heavily for easier culling (~69% in favour in Valais and Uri, 67% in Graubünden) while urban cantons opposed it (only ~37% in favour in Geneva and Basel-City), against a backdrop of ~1,480 farm animals killed by wolves in 2022.
Quantifies Level 2 (community reception): a measure popular nationally is rejected by the rural communities that bear its costs, so acceptance is uneven.
Wolf recolonisation of Switzerland
The gray wolf recolonised Switzerland naturally, with a single male (M1) crossing from the Italian Apennine population into Valais in 1995; the first pack formed at Calanda in 2012, and by the 2025/26 KORA monitoring year there were 43 confirmed packs with 148 cubs, against habitat capacity of 50–100 packs.
Demonstrates Level 1 (outcome) success, since a native apex predator absent for a century is now established and breeding, and distinguishes natural recolonisation from reintroduction.
3.3.14Ecotourism can increase interdependence of local communities and increase biodiversity by generating income and providing funds for protecting areas, but there can also be negative societal and ecological impacts.HL
Gorongosa community-based capitalism model
Gorongosa National Park's 'community-based capitalism' model uses donor funding plus profits from tourism, aviation and agriculture to pay for rangers and restocking, and in 2025 employed 1,894 people (99% Mozambican), including paying farmers to grow coffee on Mount Gorongosa to restore the rainforest feeding the park's rivers.
Shows in a named protected area how tourism income funds biodiversity protection and ties local livelihoods to conservation, while remaining vulnerable to donor withdrawal and long-haul-flight emissions.
Knepp nature-tourism business
Knepp's nature-tourism business (guided wildlife safaris, camping and glamping, and pasture-fed wild-range meat) turns over roughly £800,000 a year, funding the rewilding and reducing reliance on grants while bringing trade to nearby pubs, shops and B&Bs, though it risks disturbing wildlife, causing trampling and over-dependence on visitor income.
Demonstrates how ecotourism income funds area protection and builds local interdependence while also carrying ecological and societal downsides.
Knepp Estate, West Sussex, England Rewilding Knepp: tipping points, trade-offs and tourism
4 Water
4.1.1Movements of water in the hydrosphere are driven by solar radiation and gravity.
Mer de Glace retreat, France
On the Mer de Glace glacier in the French Alps, solar radiation drives summer meltwater into the Arve and Rhône and winter sublimation off the ice, while gravity drives the ice downhill at ~75 m/year; since 1850 it has retreated ~2.5 km and thinned ~200 m, forcing repeated relocation of access from the 1909 Montenvers station.
Shows both drivers of the hydrosphere at one site (solar-driven melting and sublimation versus gravity-driven ice and meltwater flow), with outputs now exceeding inputs.
4.1.5Human activities, such as agriculture, deforestation and urbanization, can alter these flows and stores.
Lake Urmia shrinkage, Iran
Intensive irrigated agriculture (sugar beet, apples, wheat, grapes) in the catchment of Lake Urmia, north-western Iran, involving over 50 dams and more than 88,000 wells, cut river streamflow and depleted groundwater so severely that by 2015 the lake had lost about 88% of its surface area and 95% of its volume, leaving a 5,000 km² salt desert whose dust storms harm about 6 million people.
Demonstrates how agricultural diversion of inflows and groundwater abstraction shrinks a surface freshwater store and reduces streamflow and groundwater flows.
Valencia DANA floods, Spain
During the Valencia DANA of 29 October 2024, over 490 mm of rain fell in 8 hours onto a heavily sealed and deforested floodplain, so infiltration dropped near zero and run-off surged; the barranco del Poyo rose to a peak discharge of ~2,300 m³/s in under two hours, producing flash floods that killed over 230 people, Spain's deadliest in modern history.
Shows how urbanisation reduces infiltration and evapotranspiration while increasing surface run-off, converting rainfall into a rapid, deadly flood peak.
4.1.6The steady state of any water body can be demonstrated through flow diagrams of inputs and outputs.
Lake Geneva water balance, Switzerland-France
Lake Geneva (Lac Léman) holds ~89 km³ of freshwater and stays roughly in steady state with annual inputs and outputs both around 7.1 km³/year (Rhône inflow 5.7, outflow 6.6, evaporation 0.4, abstraction 0.1), supplying drinking water to about 1 million people.
Quantifies steady state as balanced inputs and outputs in a real water budget, letting sustainable abstraction limits be calculated.
Lake Geneva Water SystemsSalar de Atacama aquifer, Chile
The freshwater aquifer beside the Salar de Atacama in northern Chile receives ~180 million m³/year of Andean recharge against outputs of ~165 million m³/year (120 seepage to flamingo wetlands and Atacameño farms, 30 evaporation, 15 town abstraction), so a lithium mining request for an extra 40 million m³/year would push outputs above inputs and deplete the store.
Shows how a flow diagram of inputs and outputs sets the maximum sustainable harvest and reveals when abstraction breaches steady state.
Salar de Atacama, Chile Water Systems
4.1.7Water has unique physical and chemical properties that support and sustain life.HL
Lake Geneva deoxygenation, Switzerland
Lake Geneva (309 m deep) has not mixed completely since winter 2011/12: in 2024/25 the surface only cooled to 7.8 °C (1.5 °C above the 1991–2020 average), so mixing reached just 110 m. As a result, dissolved oxygen at 300–309 m fell from 8.4 to 2.4 mg/L between 2012 and 2025 (CIPEL data).
Shows how temperature-dependent density sets up thermal stratification that wind cannot break, and traces the knock-on effect on gas supply to deep water as the climate warms.
Lavaux vineyards and lake climate, Switzerland
The Lavaux vineyards sit on terraced slopes above Lake Geneva. The lake's high specific heat capacity keeps local temperatures mild and stable, which helps the grapes ripen.
Demonstrates how water's high specific heat capacity moderates the climate of the land around a large water body.
Lavaux, Vaud, Switzerland Properties of Water and Carbon Sink
4.1.8The oceans act as a carbon sink by absorbing carbon dioxide from the atmosphere and sequestering it.HL
StudyOcean CO₂ absorption, Global Carbon Budget
According to the Global Carbon Budget 2025, the ocean absorbed about 29% of human CO₂ emissions over the past decade, even as atmospheric CO₂ reached about 425.6 ppm. Over 2015–2024, however, the ocean sink was about 7% smaller than it would have been without climate change.
Quantifies how much the sink has moderated the rise in atmospheric CO₂, and gives measured evidence that warming is already weakening it as it moves towards saturation.
2015–2024 Properties of Water and Carbon Sink
4.1.9Carbon sequestered in oceans over the short term as dissolved carbon dioxide causes ocean acidification; over the longer term, carbon is taken up into living organisms as biomass that accumulates on the seabed.HL
StatisticOcean acidification since the industrial era
Since the industrial era began, surface ocean pH has fallen from about 8.2 to about 8.1, roughly a 30% rise in hydrogen ion concentration. This reduces the carbonate ions that corals, molluscs and plankton need to build calcium carbonate shells and skeletons.
Quantifies the short-term acidification pathway and links the logarithmic pH change to its biological consequence for organisms that calcify.
4.1.10The temperature of water varies with depth, with cold water below and warmer water above. Differences in density restrict mixing between the layers, leading to persistent stratification.HL
Lac de Joux ice safety decline
Lac de Joux in the Vallée de Joux, Vaud, is the largest lake in the Jura that freezes over, because fresh water below 4 °C floats and freezes at the surface. Safe ice is becoming rarer: skating was not possible for three years before January 2022, and in February 2026 only a few marked sections were open.
Shows that fresh water's 4 °C density maximum makes lakes freeze from the top down, and how warming is undermining this.
4.1.12Global warming and salinity changes have increased the intensity of ocean stratification.HL
StudyOcean stratification increase, top 2,000 m
Li et al. (2020) found that stratification in the top 2,000 m of the ocean increased by about 5.3% between 1960 and 2018. Around 71% of the rise was in the top 200 m, and over 90% of it came from warming.
Quantifies the intensification of stratification and shows that it is concentrated near the surface and driven mainly by temperature.
1960–2018 Stratification and Ocean CirculationSouthern Ocean surface freshening and stratification
The Southern Ocean surface freshened from the 1980s as ice melted, which strengthened stratification. Since 2015, surface salinity has risen and stratification has weakened, sea ice has hit record lows and the Maud Rise polynya in the Weddell Sea has reopened (Silvano et al., 2025).
Demonstrates how salinity changes control the strength of stratification in both directions, and the need for ongoing monitoring.
4.1.13Upwellings in oceans and freshwater bodies can bring cold, nutrient-rich waters to the surface.HL
Peru anchovy fishing season cancellation
Off Peru, trade winds drive upwelling of cold, nutrient-rich water that supports the anchoveta fishery. During the 2023 El Niño, weaker winds strengthened stratification and suppressed upwelling, so Peru cancelled its June 2023 anchovy fishing season.
Links upwelling directly to productivity and shows how ENSO switches it on and off, with economic consequences.
Upwelling event, Lake Geneva
On 28 June to 1 July 2017, a days-long south-westerly wind along Lake Geneva pushed the warm surface layer north-east, and cold deep water upwelled at the Bains des Pâquis, Geneva, dropping the water from 23 °C to 8 °C in 48 hours while Montreux and Évian stayed at about 22 °C.
Shows that wind-driven upwelling also happens in freshwater bodies, and that a thin early-summer mixed layer is easily displaced.
4.1.14Thermohaline circulation systems are driven by differences in temperature and salinity. The resulting differences in water density drives the ocean conveyor belt, which distributes heat around the world and thus affects climate.HL
StudyDeep AMOC flow decline, western North Atlantic
A study published in April 2026 used seafloor instruments at four sites along the western North Atlantic (about 16.5°N to 42.5°N). All four recorded the same decline in deep AMOC flow over nearly two decades, but records only began in the early 2000s.
Gives evidence that freshening may be weakening the conveyor belt, while showing why short records make the trend uncertain.
4.2.2Social, cultural, economic and political factors all have an impact on the availability of, and equitable access to, the freshwater required for human well-being.
Cape Town drought, South Africa
During Cape Town's 2015–2018 drought, dam levels fell to ~23% of capacity and authorities imposed a 50 L/person/day limit and rising block tariffs; wealthy suburbs drilled private boreholes while ~20% of residents in informal settlements shared communal taps, and agricultural water rights were cut by 60% amid rivalry between city and national government and the legacy of apartheid-era infrastructure.
Demonstrates how social, cultural, economic and political factors together produced deeply unequal water access within one city.
4.2.4Water supplies can be increased by constructing dams, reservoirs, rainwater catchment systems, desalination plants and enhancement of natural wetlands.
Dar Si Hmad fog harvesting, Morocco
In Morocco's semi-arid Aït Baamrane region, the NGO Dar Si Hmad runs the world's largest fog-harvesting project, with ~1,700 m² of mesh nets on Mount Boutmezguida collecting on average ~35,000 litres per day and piping water to over 1,000 people across ~16 villages, cutting women's daily water-collection time from around 3 hours.
Shows a low-energy rainwater/fog catchment system delivering village-scale supply where fog is reliable but not at city scale.
Aït Baamrane, Morocco Water Security and ScarcityGrand Ethiopian Renaissance Dam, Ethiopia
The Grand Ethiopian Renaissance Dam on the Blue Nile, inaugurated in 2025 with a ~74 km³ reservoir and ~5,150 MW capacity (costing ~US$5 billion), more than doubles Ethiopia's electricity but is fiercely opposed by Egypt, which draws ~97% of its freshwater from the Nile, and displaced 5,000–20,000 people.
Shows how dams and reservoirs increase supply while creating evaporation losses, displacement and international disputes.
4.2.5Water scarcity refers to the limited availability of water to human societies.
Haiti drinking water and sanitation gap
Haiti receives around 1,400 mm of rain a year yet roughly 70% of its population lacks safely managed drinking water and two-thirds lack basic sanitation, because political instability and disasters such as the 2010 earthquake left treatment plants, pipes and sewage systems under-built.
Shows economic water scarcity, where abundant rainfall exists but weak infrastructure and governance prevent safe delivery.
Jordan water scarcity
Jordan is one of the most water-scarce countries on Earth: in 2021 each Jordanian had only ~61 m³ of renewable freshwater per year (against the 500 m³ absolute-scarcity threshold), its Jordan and Yarmouk river flows are shared with Syria and Israel, and about half of households receive piped water only once a week despite near-universal connection.
Demonstrates physical water scarcity where extensive infrastructure cannot compensate for a genuine climatic and geographic lack of water.
4.2.6Water conservation techniques can be applied at a domestic level.
BASIX rainwater tanks, NSW
Under NSW's BASIX scheme all new Australian homes since 2004 must meet water-saving targets, usually via rainwater tanks, and ~26% of Australian households now have a tank (rising to ~50% in Adelaide).
Shows regulation-led domestic rainwater harvesting scaled through building codes.
Chennai Day Zero
Chennai's "Day Zero" arrived in June 2019 when all four city reservoirs ran dry and families queued for 25 L of water per day, prompting mandatory dual plumbing for grey-water reuse in many new buildings.
Illustrates rationing and grey-water recycling as domestic conservation responses forced by acute urban scarcity.
4.2.7Water conservation strategies can be applied at an industrial level in food production systems.
India International Year of Millets
India championed the 2023 UN International Year of Millets, expanding drought-resistant crops such as pearl millet, ragi and sorghum (viable on ~350 mm rainfall/year versus ~1,200 mm for rice) to 13.7 million ha by 2024, and highlighting that 1 kg of beef needs ~15,000 L of water against ~1,800 L for wheat.
Shows drought-resistant crops and diet as low-infrastructure industrial strategies that cut agricultural water demand.
Sundrop Farms solar greenhouse, Port Augusta
Sundrop Farms at Port Augusta, South Australia is a 20 ha greenhouse using solar-desalinated seawater to grow ~17,000 tonnes of tomatoes per year with no fresh water and no fossil fuels, built for ~A$200 million.
Demonstrates a capital-intensive greenhouse system that eliminates freshwater use in industrial food production.
Port Augusta, South Australia Water Conservation Strategies
4.2.8Mitigation strategies exist to address water scarcity.
Australia Millennium Drought response
Australia's national response to Millennium Drought scarcity combined near-universal metering with volumetric pricing, Melbourne's Stage 3a rationing (April 2007–April 2010) which nearly halved per-capita use from ~458 L/day in 1996 to 236 L/day in 2011, compulsory dual-flush toilets (all new toilets since 1993, saving ~32,000 L/household/year), and A$13 billion of Murray-Darling drip/sprinkler conversion saving ~700 GL/year by 2024.
Demonstrates how a high-income country combines domestic and industrial techniques into a coherent national mitigation strategy against drought-driven scarcity.
India water scarcity measures
India's response to physical and economic water scarcity blends traditional and regulatory measures: Tamil Nadu made rainwater harvesting compulsory for all buildings in 2003 (~5 million homes retrofitted in three years, raising Chennai's water table by up to 50%), Bengaluru's 2024 rationing banned drinking water for car washes and construction with ₹5,000 fines, and the PMKSY scheme put ~8 million ha under subsidised drip/sprinkler irrigation by 2024.
Shows a middle-income country's subsidy-led national mitigation strategy drawing on both domestic and agricultural techniques to address recurrent scarcity.
4.2.9Freshwater use is a planetary boundary, with increasing demand for limited freshwater resources causing increased water stress and the risk of abrupt and irreversible changes to the hydrological system.HL
Sacramento Valley aquifer compaction, California
During the 2020–2022 drought, heavy groundwater pumping in California's Sacramento Valley pushed the aquifer from elastic (reversible) squeezing into permanent compaction: residual subsidence reached 20 cm a year or more and part of its storage capacity was lost for good (PNAS, 2026).
Shows the abrupt, irreversible hydrological change the freshwater boundary warns of: steady pressure, then a sudden shift that well levels alone could not predict.
4.2.10Local and global governance is needed to maintain freshwater use at sustainable levels.HL
Genevese aquifer over-abstraction and recharge
Uncoordinated Franco-Swiss pumping over-abstracted the Genevese aquifer, which hit record lows by the mid-1970s. A 1978 agreement funded artificial recharge from the Arve at Vessy (8–10 million m³ a year), and a 2025 convention caps pumping at 5 million m³ for France and 12.5 million m³ for Switzerland.
Shows why transboundary groundwater needs international governance, and why agreements have to be renegotiated as population and drought pressures rise.
Pays de Gex water restrictions, Ain
In summer 2026 the Ain prefect raised the Pays de Gex from alerte (29 June) to crise (20 August), banning daytime watering of vegetable gardens, filling of private pools and washing cars at home. Breaking the rules can bring fines of up to €1,500.
Gives a local regulation that escalates in stages as water resources fall, showing local governance enforcing sustainable use during drought.
4.2.11Water footprints can serve as a measure of sustainable use by societies and can inform decision-making about water security.HL
Swiss Water Footprint study
The 2012 WWF/SDC Swiss Water Footprint study found Switzerland's footprint is about 1,500 m³ per person per year (global average 1,385 m³), with 82% external, falling on hotspot basins such as the Aral Sea and the Indus. This led the SDC to set up SuizAgua in Colombia (2009), where Nestlé, Holcim and other firms committed to cutting their water footprints.
Demonstrates how virtual water makes a water-rich nation depend on other countries' basins, and how footprint data can drive real decisions on water security.
4.2.12Citizen science is playing an increasing role in monitoring and managing water resources.HL
CrowdWater app, University of Zurich
The University of Zurich's CrowdWater app lets volunteers record stream levels against virtual staff gauges on photos. In a crowd-checking game covering 841 observations, about 70% of players agreed with the original observer, which fills gaps in Switzerland's costly official gauge network.
Demonstrates that low-cost crowdsourced water-level data, with crowd quality control, can extend monitoring to unmeasured streams.
Zurich, Switzerland Planetary Boundary and GovernanceRiver Wye volunteer nutrient testing
When volunteer nutrient tests from the River Wye in 2021 were checked against a laboratory, 66% of nitrate strip results agreed, but only 17% of phosphate strip results did, rising to 62% with a handheld phosphate meter (von Benzon et al., 2025).
Shows that the accuracy of crowdsourced water-quality data depends heavily on the method and kit chosen, which is a key limitation to weigh.
4.2.13"Water stress" like "water scarcity" is another measure of the limitation of water supply; it not only takes into account the scarcity of availability but also the water quality, environmental flows and accessibility.HL
Bangladesh drinking water access and quality
Bangladesh has over 7,000 m³ of renewable water per person thanks to the Ganges, Brahmaputra and Meghna, yet the 2025 MICS survey found only 39.3% of people used safely managed drinking water, about 15% of sources exceeded the WHO arsenic standard and 84.9% of household water had microbial contamination.
Demonstrates that a country can be free of scarcity yet water-stressed, because poor water quality reduces the clean, accessible supply.
4.2.14Water stress is defined as a clean, accessible water supply of less than 1,700 cubic metres per year per capita.HL
Egypt water scarcity per person
Egypt receives over 98% of its renewable water from outside its borders via the Nile; its supply of about 56.8 billion m³ a year against a need of 123 billion m³ gives only about 472–490 m³ per person (2026), far below 1,700 m³, with a growing population of 111 million.
Applies the 1,700 m³ threshold to a named society and explains why it falls below it through aridity, external dependence and population growth.
4.2.15The causes of increasing water stress may depend on the socio-economic context.HL
Egypt New Delta project, Western Desert
Egypt's New Delta project aims to irrigate 2.2 million feddans of Western Desert for export crops, fed by a 114 km artificial river carrying 3.5 billion m³ a year; groundwater depletion beneath the Western Desert has doubled since 2014.
Shows how an emerging economy's drive for export-led growth and foreign currency increases water stress.
Western Desert, Egypt Water Stress and Industrial SolutionsKabul groundwater depletion and contamination
Kabul's population has more than doubled to about 6 million in two decades; unregulated wells over-abstract aquifers by 44 million m³ a year, water tables have fallen 25–30 m, half of boreholes have dried up and up to 80% of groundwater is contaminated (Mercy Corps, 2025).
Contrasts with Egypt by showing population-driven over-abstraction and weak governance in a low-income country.
4.2.16Water stress can arise from transboundary disputes when water sources cross regional boundaries.HL
Grand Ethiopian Renaissance Dam dispute
The Grand Ethiopian Renaissance Dam (begun 2011, inaugurated September 2025, 74 billion m³ storage) on the Blue Nile is disputed by Egypt, which relies on colonial-era 1929 and 1959 agreements that allocated nothing to Ethiopia; talks failed in 2023 and the 2024 Cooperative Framework Agreement is rejected by Egypt and Sudan.
Shows how upstream control of a transboundary river, rooted in colonial history, threatens downstream water security and quantity.
4.2.18Industrial freshwater production has negative environmental impacts that can be minimized but not usually eliminated.HL
UAE desalination and brine impacts, Wadi Ham
The UAE gets about 42% of its water from desalination; Gulf states release 55% of the world's 141.5 million m³ of daily brine, reverse osmosis uses 2.5–4 kWh per m³ powered largely by fossil fuels, and over-pumping at Wadi Ham, Fujairah, let saline water intrude 1.2–2.1 km inland.
Demonstrates multiple environmental costs of industrial water production that mitigation (diffusers, shifting to reverse osmosis at Taweelah) can reduce but not remove.
United Arab Emirates Water Stress and Industrial Solutions
4.3.2Humans consume organisms from freshwater and marine environments.
Atlantic salmon farming, Norway
The Atlantic salmon (Salmo salar) is an anadromous high-trophic-level predator whose wild populations have collapsed across most of its North Atlantic range, so that most salmon eaten globally is now farmed, with Norway the world's largest producer followed by Chile, Scotland, the Faroe Islands and Canada.
Shows a globally significant food species and links its high trophic level to the energetic inefficiency of producing it as food.
Norway From plankton to plateLake Geneva perch imports
Lake Geneva perch (Perca fluviatilis), served as filets de perche, is the region's signature dish, but while the lake yields only ~400 tonnes a year, lakeside restaurants sell ~7,300 tonnes annually, the rest imported frozen (mainly from Estonia); a 2017 Swiss investigation found 6 of 20 restaurants falsely claiming imported perch were locally caught.
Demonstrates a local freshwater species consumed by humans and quantifies how demand outstrips local stocks even before global trade.
4.3.4The increasing global demand for seafood has encouraged use of unsustainable harvesting practices and overexploitation.
Dogger Bank bottom trawling ban
The Dogger Bank in the North Sea is one of the most intensively bottom-trawled seabeds in the world with largely degraded seafloor habitats; the UK banned bottom trawling across four offshore Marine Protected Areas including it in 2022, though enforcement remains a challenge.
Illustrates bottom trawling as a destructive unsustainable method and the gap between banning and enforcing.
Ghost fishing gear recovery, Baltic Sea
In the Baltic Sea WWF and Healthy Seas estimate several hundred tonnes of fishing gear are lost each year, and recovery dives off the German and Polish coasts have pulled up Soviet-era nets some still actively catching cod, demonstrating how ghost gear kills marine life for decades.
Shows ghost fishing as an unsustainable method causing prolonged mortality because synthetic gear does not biodegrade.
Baltic Sea From plankton to plate
4.3.5Overexploitation has led to the collapse of fisheries.
Monterey sardine second collapse, California
The Monterey Pacific sardine recovered through the 1990s but collapsed a second time, falling ~97% after 2006, prompting regulators to close the fishery from 2015, again because fishing had been allowed to continue too far into a known decline.
Shows that repeated overexploitation during natural declines reproduces collapse even after an apparent recovery.
Pacific sardine collapse, Monterey Bay
The Pacific sardine (Sardinops sagax) fishery off Monterey Bay, California, once the largest in the western hemisphere at ~700,000 tonnes/year in the 1930s–40s, collapsed after its 1946 peak, falling ~90% in five years (from ~234,000 to ~24,000 tonnes) because the fleet kept fishing hard through a natural, temperature-linked decline; a ban ran 1967–1986 and the stock never fully recovered.
Demonstrates how overexploitation combined with a natural downturn drives a fishery to a collapse from which the commercial stock cannot recover.
4.3.6The maximum sustainable yield (MSY) is the highest possible annual catch that can be sustained over time, so it should be used to set caps on fishing quotas.
Monterey sardine fleet and the yield–effort curve, California
The Monterey sardine fleet illustrates fishing well to the right of the MSY peak: because fleet capacity far exceeded the effort needed to fish at MSY, boats kept working while the stock was already falling, pushing catch onto the downhill side of the yield–effort curve rather than staying at the sustainable maximum.
Demonstrates the syllabus point that real fisheries often fish at far higher effort than the MSY, running the stock down.
Monterey Bay, California, USA Collapse, limits and warming waters
4.3.7Climate change and ocean acidification are having impacts on ecosystems and may cause collapse of some populations in freshwater or marine ecosystems.
Lake Geneva mixing failure and deep-water oxygen loss
Lake Geneva (Léman) has failed to mix fully since the cold winter of 2012 because milder winters leave surface water too warm to sink, and monitoring by CIPEL and EPFL shows deep-water oxygen has fallen ~90% in ten years, below the level most aquatic life needs.
Demonstrates climate warming stressing a freshwater ecosystem via reduced deep mixing and deoxygenation, disrupting the food web.
Mass coral bleaching, Great Barrier Reef, Australia
Australia's Great Barrier Reef, the world's largest reef system, has suffered repeated mass coral bleaching as ocean temperatures rise, with corals expelling their symbiotic algae and dying, threatening the thousands of species dependent on living coral.
Shows warming waters causing marine ecosystem stress and potential collapse that fishing quotas cannot address.
Great Barrier Reef, Australia Collapse, limits and warming waters
4.3.8Unsustainable exploitation of freshwater and marine ecosystems can be mitigated through policy legislation addressing the fishing industry and changes in consumer behaviour.
Sustainable seafood certification schemes
Sustainable seafood certification schemes shift consumer demand: the Marine Stewardship Council (MSC) blue label certifies wild-caught fish, the Aquaculture Stewardship Council (ASC) certifies farmed fish, and the Marine Conservation Society Good Fish Guide advises shoppers, so producers gain a reason to fish and farm more sustainably even though labelling bans nothing.
Illustrates individual-level mitigation through consumer behaviour and food labelling working via demand rather than legal prohibition.
4.3.9Marine protected areas (MPAs) can be used to support aquatic food chains and maintain sustainable yields.
Lamlash Bay no-take zone, Scotland
Scotland's first no-take zone was created in Lamlash Bay, Isle of Arran, in 2008 (about 2.67 km²) after over ten years of campaigning by COAST; University of York surveys found king scallop density rose from about 6 to about 23 per 100 m² between 2010 and 2019, and legal-sized lobsters became around four times more abundant and larger than in nearby fished areas.
Quantifies how protecting one patch of sea allows adults to grow larger and denser, demonstrating the recovery mechanism behind MPAs.
South Arran Marine Protected Area, Scotland
In 2014 the ~280 km² South Arran Marine Protected Area was designated around Lamlash Bay, with scallop dredging banned from 2016; surveys show adult scallop density falls with distance from the boundary, a spillover sign the benefit reaches surrounding fished waters, while recovering seagrass, kelp and maerl now shelter juvenile fish including young cod.
Shows how a protected area seeds and supplies the wider sea via spillover and nursery habitat, maintaining sustainable yield beyond the reserve boundary.
4.3.10Aquaculture is the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. The industry is expanding to increase food supplies and support economic development, but there are associated environmental impacts.
Cleaner fish for sea lice, Scotland
To control sea lice without relying only on chemicals, Scottish salmon farms have placed cleaner fish (wrasse and lumpfish) in cages since the 1990s to eat lice off the salmon, but large numbers of cleaner fish die in the cages, demand has pressured wild wrasse stocks, and in 2025 one of the biggest producers stopped using lumpfish.
Shows a named management technique (biological control) that reduces one impact while creating new problems, allowing evaluation.
Farmed salmon impacts, west coast lochs, Scotland
Scotland is the world's third largest producer of farmed Atlantic salmon (after Norway and Chile), producing around 163,000 tonnes in 2016 with a target of 300,000–400,000 tonnes by 2030; open net sea cages cause seabed dead zones from waste feed and faeces, copper anti-fouling toxicity, antibiotic and sea-lice pesticide pollution, sea lice spread to wild salmon, and escapees that cause genetic introgression in wild stocks.
Demonstrates aquaculture's role in expanding food supply and economic development alongside a full range of named environmental impacts.
4.3.11Productivity, thermal stratification, nutrient mixing and nutrient loading are interconnected in water systems.HL
Lake Geneva mixing failure and whitefish decline
Lake Geneva has not mixed all the way to the bottom since 2012, so phosphorus released from the bed stays trapped below the thermocline. Together with the invasive quagga mussel (first recorded in 2015), this is being investigated as a cause of the sharp fall in the whitefish catch since 2014.
Demonstrates how warming-driven thermal stratification stops nutrients from mixing back to the surface, limiting productivity even when nutrients are present in the deep water.
Lake Geneva phosphorus and whitefish catch
In Lake Geneva, phosphorus loading from sewage and detergents rose from under 15 µg/L before the 1960s to 89.5 µg/L in 1979. Decomposing algae then used up the oxygen on the lake bed and smothered the whitefish spawning gravel, so the catch fell to 30–50 tonnes a year (1974–84). After sewage treatment and Switzerland's 1986 phosphate detergent ban, phosphorus fell to about 16 µg/L and the catch reached a record of about 971 tonnes in 2014.
Shows that nutrient loading increases productivity only up to a point, and that beyond it eutrophication reduces fish stocks, so nutrients and fish yield are not simply related.
4.3.12Accurate assessment of fish stocks and monitoring of harvest rates are required for their conservation and sustainable use.HL
OrganisationGlobal Fishing Watch apparent fishing effort mapping
Global Fishing Watch uses vessels' satellite AIS and VMS position signals to map apparent fishing effort in hours across the world's oceans, including the heavily fished shelf seas of the north-east Atlantic.
Demonstrates a method of monitoring where and when fishing happens. Its limit is that it records effort rather than tonnes caught, so it must be paired with logbooks and landing records.
ICES mackerel stock assessment methods, north-east Atlantic
ICES assesses north-east Atlantic mackerel by combining several methods. Each year 40,000–50,000 mackerel are fitted with electronic RFID tags, which factory scanners detect automatically (a Lincoln index approach). A triennial egg survey estimates spawning stock biomass, and a summer trawl survey covers the Nordic Seas. These are checked against catch records.
Shows how combining several stock assessment methods, each with known weaknesses, reduces error in the population estimates on which quotas depend.
4.3.13There are risks in harvesting fish at the maximum sustainable yield (MSY) rate and these risks need to be managed carefully.HL
North-east Atlantic mackerel overfishing and ICES advice
North-east Atlantic mackerel has no sharing agreement covering all fishing nations, and since 2010 their combined quotas have averaged 39% above ICES advice. By 2025 the spawning stock (about 2.74 million tonnes) had fallen below the 3.07 million tonne limit, and ICES advised a roughly 70% cut for 2026. In September 2026 the estimate jumped to about 3.2 million tonnes, so ICES more than doubled its advice for 2027.
Shows both risks of MSY-based management: unilateral overshooting of advice pushes a stock towards breeding failure, and large year-to-year swings in the estimates show how uncertain the MSY is, which is why precautionary harvest control rules are needed.
4.4.1Water pollution has multiple sources and has major impacts on marine and freshwater systems.
Lonza mercury contamination, Visp
The Lonza chemical plant at Visp, Valais discharged around 50 tonnes of mercury into a canal on the river Rhône between 1930 and 1976; the contamination was only discovered by chance in 2010 and clean-up continues today.
Shows how an identifiable point-source industrial effluent can persist in sediments and soil for decades, making pollution long-lasting and hard to remediate.
River Oder fish kill, Poland/Germany
The 2022 River Oder fish kill on the Poland–Germany border: salty waste water from upstream mines and industry, combined with low water levels and high summer temperatures, triggered a bloom of toxic golden alga (Prymnesium parvum) whose toxins attacked fish gills, killing around 250 tonnes of fish over hundreds of kilometres; the two nations ran a joint investigation, restricted salty discharges and set new salinity limits.
Demonstrates how a diffuse industrial pollution source interacts with climate conditions to cause a major freshwater impact and how transboundary management responds.
4.4.2Plastic debris is accumulating in marine environments. Management is needed to remove plastics from the supply chain and to clear up existing pollution.
Great Pacific Garbage Patch, North Pacific
The Great Pacific Garbage Patch in the North Pacific is the best-known accumulation of floating plastic trapped in the calm centre of one of the five great ocean gyres, where wind- and Earth-spin-driven currents concentrate debris that persists as plastic for decades.
Demonstrates how ocean gyre circulation concentrates persistent plastic debris, the mechanism behind marine plastic accumulation.
Great Pacific Garbage Patch, North Pacific Ocean Water Pollution and Water QualityMicroplastics in Lake Geneva
EPFL researchers towed a manta trawl across Lake Geneva and found microplastics in every beach sample, dominated by tiny polystyrene beads, at levels comparable to parts of the ocean, with the river Rhône carrying the plastic onward towards the Mediterranean.
Shows that plastic accumulation is not just marine: ~80% of ocean plastic originates on land, so lakes and rivers are the source of the problem.
Lake Geneva, Switzerland Water Pollution and Water Quality
4.4.5Eutrophication occurs when lakes, estuaries and coastal waters receive inputs of mineral nutrients, especially nitrates and phosphates, often causing excessive growth of phytoplankton.
Lake Geneva eutrophication
Lake Geneva's decline from the 1950s was driven by phosphate from washing powders, sewage and farm run-off, with total phosphorus peaking near 90 µg/L in 1979 (far above the healthy 10–15 µg/L target) and triggering thick blooms, because phosphate is the limiting nutrient in most fresh water.
Shows that adding the limiting nutrient (phosphate) from detergents, sewage and fertilisers causes the excessive phytoplankton growth described in the point.
4.4.6Eutrophication leads to a sequence of impacts and changes to the aquatic system.
Ulva green tide hydrogen sulphide, Brittany
Brittany's green tides show the eutrophication sequence on a coast: living *Ulva* seaweed is harmless, but when piled a metre thick on beaches it decomposes under a dry crust in airless conditions, and this rotting step releases poisonous hydrogen sulphide.
Shows the decomposition step of the impact sequence is where harm arises, not the growth of algae itself.
Brittany, France The lake that turned green
4.4.7Eutrophication can substantially impact ecosystem services.
Marées vertes (green tides), Brittany
Brittany's *marées vertes* (green tides): rivers carry nitrate (over 90% from agriculture, according to the French Court of Auditors) into shallow sandy Atlantic bays where *Ulva* sea lettuce grows a metre thick, then rots to release toxic hydrogen sulphide that has killed animals including a horse and been linked to human deaths, closing beaches and harming fisheries.
Quantifies how coastal eutrophication simultaneously damages fisheries, recreation, aesthetics and health services.
Brittany, France The lake that turned green
4.4.8Eutrophication can be addressed at three different levels of management.
Lake Geneva phosphorus recovery
Lake Geneva (Lac Léman), source of drinking water for over 600,000 people, was badly eutrophic after 1950s phosphate inputs pushed total phosphorus to a peak of ~90 µg/L in 1979; a Franco-Swiss commission (CIPEL, 1963) drove recovery via Switzerland's 1986 laundry-detergent phosphate ban, upgraded phosphorus-stripping sewage works and reduced farm phosphate, bringing total phosphorus down to 15.6 µg/L by the 2025 report with far fewer blooms.
Demonstrates all three management levels (change activity, reduce release, clean up) working together to reverse eutrophication, quantified by the fall from 90 to 15.6 µg/L.
5 Land
5.1.2Soil is made up of inorganic and organic components, water and air.
Rhône glacier moraine around Geneva, Switzerland
Rhône glacier moraine around Geneva is an unsorted mix of clay, silt, sand, gravel and boulders that started out about 25% limestone. Weathering and leaching have since dissolved the limestone and left silica-rich rock behind, which explains why local fields are stony.
Demonstrates that the inorganic component of a soil depends on its parent material and how it was deposited, and that weathering changes that component over time.
Geneva, Switzerland Soil as a System
5.1.3Soils develop a stable, layered structure known as a profile made up of several horizons, produced by interactions within the system over long periods of time.
Geneva basin soil age
Soils in the Geneva basin, Switzerland, have formed on Rhône glacier moraine for about 16,000 uninterrupted years since the ice retreated, so they now carry well-developed profiles. At the Swiss average of about 1 cm per 100 years, that allows at most about 1.6 m of soil.
Shows that a horizon-layered profile builds up only through long, undisturbed interactions within the system, and that time limits how much soil can develop.
Geneva, Switzerland Soil as a SystemRhône valley flooding and soil development, Valais
Repeated floods kept burying soils on the Rhône plain in Valais (between Martigny and Sion) under fresh alluvium, so their profiles stayed young and mostly stacked river sediment. Only the river corrections (1863–1894 and 1930–1960) stopped the flooding and let horizons start developing in place.
Counter-example showing that profile development restarts whenever deposition resumes, so a soil is only as old as the last time deposition stopped.
5.1.4Soil system inputs include those from dead organic matter and inorganic minerals.
Irrigated market gardens, Rhône alluvium, Saxon
Irrigated market gardens on the Rhône alluvium near Saxon, Valais, rely on anthropogenic inputs such as irrigation water pumped from the Rhône, NPK fertiliser and compost. Their natural input of flood silt from another ecosystem stopped once the river was embanked.
Shows that a managed soil's input budget can be dominated by human inputs, and that a natural input from another ecosystem can be cut off by human intervention.
Saxon, Valais, Switzerland Soil as a System
5.1.6Transfers occur across soil horizons, into and out of soils.
Earthworm casts, Swiss soils
FiBL (Frick, Switzerland) reports that where earthworm populations are high, casts can reach 10 kg per m² per year, depositing up to 0.5 cm of soil a year in fields and 1.5 cm in meadows. Swiss soils form at only about 1 cm per century.
Puts a number on biological mixing and shows that bioturbation moves material far faster than soil forms.
Switzerland Flows, Functions and the Soil System DiagramNitrate leaching, Swiss groundwater
Nitrate leaching in Swiss groundwater: fertiliser nitrate percolates below the roots into aquifers, and the Swiss limit of 25 mg/L is exceeded at about one monitoring site in six nationally, rising to more than half in arable and vegetable-growing areas. The nappe du Genevois aquifer (about 80 million m³, shared by Geneva and Haute-Savoie) stays at only 2.5–4.5 mg/L because it is recharged mainly by the River Arve.
Links infiltration, percolation, leaching and groundwater flow into a single chain of outputs from the soil, and shows how land use and aquifer recharge source control how much leaches out.
Geneva, Switzerland Flows, Functions and the Soil System Diagram
5.1.10Soils contribute to biodiversity by providing a habitat and a niche for many species.
Urban gardens study, Zurich
A study of 85 urban gardens across Zurich (170 sampling sites) recorded 18 earthworm species and 39 springtail species alongside 600 plant species. Bacteria and fungi were not counted.
Shows how much hidden diversity soil supports even in urban gardens, and suggests that total soil biodiversity is underestimated because microbes and fungi were left out.
Zurich, Switzerland Flows, Functions and the Soil System Diagram
5.1.14Soils can act as carbon sinks, stores or sources, depending on the relative rates of input of dead organic matter and decomposition.
StudySoil organic carbon under forests and tundra
Duarte-Guardia et al. (2019) estimated soil organic carbon in the top metre at roughly 94–143 t/ha under tropical and subtropical forests, compared with about 310 t/ha under tundra.
Counter-intuitive evidence that high input does not create a large store: fast decomposition in warm, moist tropical conditions prevents carbon building up, while cold slows it in tundra.
UNEP Global Peatlands Assessment
UNEP's Global Peatlands Assessment (2022) found that peatlands cover only 3–4% of the world's land but hold up to a third of all soil carbon, twice as much as the world's forests. About 12% have been drained and degraded, and these areas now emit around 4% of annual human-caused greenhouse gas emissions.
Demonstrates a waterlogged soil acting as a long-term sink and then flipping to a carbon source once drainage lets air in and decomposition speeds up.
5.2.1Land is a finite resource, and the human population continues to increase and require feeding.
Swiss cropland protection, Switzerland
Since 1992 Switzerland has legally protected at least 438,460 ha of its best cropland (crop rotation areas), worked out from 2,340 kcal per person per day in a crisis. Geneva must keep 8,400 ha and held only 8,457 ha in 2023. Only 38% of Swiss farmland is arable and 58% is meadow and pasture.
Shows that the real limit is the small share of flat, fertile land that can be cropped, and that once it is built on it cannot be replaced.
5.2.2Marginalized groups are more vulnerable if their needs are not taken into account in land-use decisions.
Girjas case, Sweden
In the Girjas case (Swedish Supreme Court, T 853-18, 23 January 2020), the Girjas sameby in Gällivare won the right to grant hunting and fishing permits on its 5,449 km² of land through immemorial possession. It took 11 years of litigation, and the court did not rule on who owns the land.
Shows that an indigenous group holding only use rights is left out of land decisions and has to fight long, costly legal battles to have its needs recognised.
5.2.5Agricultural systems are varied, with different factors influencing the farmers' choices. These differences and factors have implications for economic, social and environmental sustainability.
Contrasting farming, Geneva plain and Girjas
A contrasting pair: on the Geneva plain, flat fertile soils, a long growing season and a nearby city market support intensive, mechanised commercial arable farming (56% of farmed area in field crops). In Girjas, Norrbotten, thin cold soils and a growing season of only weeks support extensive, nomadic, commercial reindeer herding.
Demonstrates how physical and human factors (including law) shape farmers' choices, and how economic, social and environmental sustainability differ between the two systems.
Geneva, Switzerland Land, Food and Farming Systems
5.2.6Nomadic pastoralism and slash-and-burn agriculture are traditional techniques that have sustained low-density populations in some regions of the world.
Jhum cultivation and soil recovery, Nagaland
Jhum (shifting cultivation) in Nagaland, north-east India: the traditional 15–20 year cycle has shrunk to 5 years or fewer as population grew. A Mokokchung district study (Temjen et al., 2022) found the topsoil quality index rose from 0.68 on cultivated land to 0.82 after a 12-year fallow, and soil organic carbon more than doubled.
Demonstrates that slash-and-burn only stays sustainable at low density: the soil is degraded by the shortened fallow, not by the burn.
Sámi reindeer herding, Sweden
Sámi reindeer herding in Sweden: 51 samebyar with about 4,700 owners and around 230,000 reindeer use close to 40% of Sweden's land, and 33 communities migrate between mountain summer pasture and boreal winter forest. Forestry, mines and wind farms cut into the migration routes, and rain-on-snow icing forces herders to buy feed.
Shows nomadic pastoralism using land that cannot be cropped, and how fixed modern land uses and climate change weaken a system that depends on moving.
Norrbotten, Sweden Land, Food and Farming Systems
5.2.7The Green Revolution (also known as the Third Agricultural Revolution in the 1950s and 1960s) used breeding of high-yielding crop plants—combined with increased and improved irrigation systems, synthetic fertilizer and application of pesticides—to increase food security. It has been criticized for its sociocultural, economic and environmental consequences.
Green Revolution in Punjab
Green Revolution in Punjab, India: high-yielding wheat made Punjab (about 1.5% of India's land) grow roughly 20% of India's wheat. However, tube-well irrigation meant the 2022 Central Ground Water Board assessment classified 114 of Punjab's 150 blocks as over-exploited.
Shows yield gains from the package alongside its economic concentration and environmental cost (groundwater depletion), which supports a balanced evaluation.
5.2.8Synthetic fertilizers are needed in many intensive systems to maintain high commercial productivity at the expense of sustainability. In sustainable agriculture, there are other methods for improving soil fertility.
StudyHaber-Bosch process
The Haber-Bosch process fixes atmospheric nitrogen with hydrogen from natural gas at about 450°C and 200 atmospheres. Ammonia production uses about 5% of world natural gas and releases 1–2% of global CO₂ emissions.
Demonstrates why synthetic fertiliser keeps productivity high at the expense of sustainability, because it is built on fossil fuel.
5.2.9A variety of techniques can be used to conserve soil, with widespread environmental, economic and sociocultural benefits.
Lavaux vineyard terraces, Lake Geneva
The Lavaux vineyard terraces, Switzerland: dry-stone walls built from the 11th century by Benedictine and Cistercian monks cut steep slopes above Lake Geneva into about 830 ha of level terraces along roughly 30 km of shore. They hold soil and water in place, and the landscape was inscribed as a UNESCO World Heritage Site in 2007.
Shows terracing delivering environmental benefits (erosion control), economic benefits (nine centuries of wine production and tourism) and sociocultural benefits (community-backed protection) at once, while also showing the costs of hand maintenance.
Soil loss on Prosecco DOCG vineyards, Italy
A modelling study of the Prosecco DOCG hills in north-east Italy estimated potential soil losses of 43.7 t/ha/yr from conventionally managed vineyards on steep ground, which is 31 times Europe's tolerable rate.
Quantifies how severe erosion is on steep land without conservation, which justifies techniques such as terracing and cover crops.
Prosecco DOCG hills, Veneto, Italy Texture, Productivity, Carbon and Conserving Soil
5.2.10Humans are omnivorous, and diets include fungi, plants, meat and fish. Diets lower in trophic levels are more sustainable.
StudyLand use of beef and tofu protein
Poore and Nemecek (2018, Science) found beef needs 163.6 m² of land per 100 g of protein compared with 2.2 m² for tofu. Animal products use about 83% of global farmland but supply only 18% of calories.
Quantifies the land-use advantage of eating at lower trophic levels, giving hard evidence for the 10% energy transfer argument.
5.2.11Current global strategies to achieve sustainable food supply include reducing demand and food waste, reducing greenhouse gas emissions from food production and increasing productivity without increasing the area of land used for agriculture.
Swiss food waste action plan
Switzerland produces 2.8 million tonnes of food waste a year (about 330 kg per person). Its 2022 action plan aims to halve avoidable losses by 2030, but the 2025 interim review found only about a 5% fall against an interim target of 25%.
Shows a national waste-reduction strategy in practice and the gap between the policy target and actual results.
5.2.12Food security is the physical and economic availability of food, allowing all individuals to get the balanced diet they need for an active and healthy life.
Swiss food initiative vote, Switzerland
The Swiss food initiative vote of 27 September 2026 asks to raise self-sufficiency from 46% to 70% by shifting to plant-based food. Opponents argue that 58% of Swiss farmland is pasture unsuited to crops, and that Switzerland is already highly food-secure through imports.
Demonstrates that food security (physical and economic access) is different from self-sufficiency, and shows the limits of plant-based diets on land that can only grow grass.
8 Human populations and urban systems
8.1.1Births and immigration are inputs to a human population.
Switzerland natural increase versus population growth
Switzerland's natural increase is only 0.07 % a year (CBR 8.7, CDR 8.0 per 1,000), yet its population grows at about 0.96 % a year because net migration adds around 37,000 people a year.
Demonstrates that immigration can be the dominant input, so natural increase alone does not explain population growth.
Switzerland Human population
8.1.2Deaths and emigration are outputs from a human population.
Crude death rate versus life expectancy, Switzerland and Niger
Switzerland's crude death rate (8.0 per 1,000) is almost the same as Niger's (8.7), yet Swiss life expectancy is 84.4 years compared with 61.4 years in Niger, because Switzerland's older population produces more deaths per 1,000.
Shows the limits of crude death rate as an output measure, because it ignores age structure.
Switzerland Human population
8.1.3Population dynamics can be quantified and analysed by calculating total fertility rate, life expectancy, doubling time and natural increase.
Niger natural increase and fertility
Niger (2024) has a crude birth rate of 41.4 and a crude death rate of 8.7 per 1,000, giving a natural increase of 3.27 % and a doubling time of about 21 years, with a total fertility rate of 5.93 against a replacement level of 2.29.
Shows how natural increase, the rule of 70 and TFR together quantify very rapid growth in a high-fertility country.
8.1.4The global human population has followed a rapid growth curve. Models are used to predict the growth of the future global human population.
StudyUN World Population Prospects projection
The UN World Population Prospects put the world population at 8.2 billion in 2024, with a global TFR of 2.25 (down from 3.31 in 1990). Under the medium scenario the population peaks at about 10.3 billion in the mid-2080s, and the UN gives an 80% chance of a peak this century.
Quantifies the rapid growth curve and shows how the UN's high, medium and low projections differ according to assumptions about future fertility.
8.1.5Population and migration policies can be employed to directly manage growth rates of human populations.
Japan child-rearing policy and falling births
Japan's Children's Future Strategy (December 2023) raised child-rearing spending by 3.6 trillion yen, with child allowances up to 30,000 yen a month for third children and a 500,000 yen birth payment. Yet in 2025 births fell to a record low of 671,236 (TFR 1.14), and deaths exceeded births by 918,253.
Shows a direct pro-natalist policy built on economic levers that has so far failed to reverse falling fertility, which lets students evaluate policy effectiveness.
Thailand voluntary anti-natalist population policy
Thailand's 1970 national population policy was a voluntary anti-natalist programme. It delivered contraception through the Ministry of Public Health and village volunteers, using humour rather than compulsion. TFR fell from about 5.5 in 1970 to below 2.1 by 1990, and today it is around 1.2.
Demonstrates a successful direct anti-natalist policy delivered by persuasion, and the later problem of overshooting into below-replacement fertility.
8.1.6Human population growth can also be managed indirectly through economic, social, health, development and other policies that have an impact on births, deaths or migration.
Bangladesh Female Secondary School Stipend
Bangladesh's 1994 Female Secondary School Stipend paid girls 25–60 taka a month on condition that they kept up attendance and stayed unmarried until 18 or their SSC exams. Eligible rural girls gained about 0.4 years of schooling, married at least 0.4 years later and had their first birth at least 0.3 years later.
Shows an education policy with no population aim that indirectly lowered the birth input by delaying marriage and first birth, with quasi-experimental evidence.
Rwanda community health workers and Mutuelles de Santé
From 1995 Rwanda built a network of about 45,000 community health workers and Mutuelles de Santé health insurance (over 90% enrolment at its peak). Under-five mortality among the poorest fifth of households fell from 229 to 83 per 1,000 live births between 2000 and 2014.
Demonstrates an indirect health policy cutting the death output, while a family planning programme running at the same time makes it hard to tell which policy caused the change.
8.1.7The composition of human populations can be modelled and compared using age–sex pyramids.
Niger and Switzerland age–sex pyramids
Niger's age–sex pyramid has a very wide base and a median age of 16.5 years, while Switzerland's has a narrow base, a bulge in the working ages and a wide top, with a median age of 43.7 years (2024).
Compares contrasting pyramid shapes, using percentage of the total population, to show how birth rates and life expectancy shape population structure.
8.1.8The demographic transition model (DTM) describes the changing levels of births and deaths in a human population through different stages of development over time.
Niger population growth, stage 2 (demographic transition)
Niger is a stage 2 country: its crude birth rate of 41.4 per 1,000 and death rate of 8.7 per 1,000 give a natural increase of 32.7 per 1,000. That doubles the population in about 21 years, and its pyramid has a very wide base.
Shows how a fallen death rate combined with a still-high birth rate opens the wide gap that drives exponential growth in stage 2, and links that gap to a wide-based pyramid.
Switzerland population growth and immigration
Switzerland has a birth rate of 8.7 and a death rate of 8.0 per 1,000, so its natural increase is only 0.07 per cent, which puts it at the boundary of stages 4 and 5. Yet its population is growing at nearly 1 per cent a year through immigration and is now 1.69 times its 1960 size.
Demonstrates both a low-and-close stage 4/5 profile and a key limitation of the DTM: the model leaves out migration, so it cannot explain growth in a country that has little natural increase.
Switzerland The demographic transition model
8.2.1Urban areas contain urban ecosystems.
Geneva tree cover and night-time heat
An RTS analysis of 129 City of Geneva neighbourhoods during the 2026 summer heatwaves found that every 10 percentage points of extra tree cover was linked with nights about 0.8 °C cooler. The Pâquis (5.6% tree cover) reached over +5.6 °C at 4 a.m. and gravel-covered Plainpalais reached +5.4 °C, while Bout-du-Monde was only +1.7 °C.
Shows biotic components (trees) and abiotic components (sealed mineral surfaces, air temperature) interacting within an urban ecosystem to shape its microclimate.
8.2.2An urban area is a built-up area with a high population density, buildings and infrastructure.
StudyUN urban population estimates, global
In 2018 the UN combined national definitions and reported 55% of the world's population as urban. In 2025 its single Degree of Urbanisation method, based on satellite and census data, put 45% of 8.2 billion people in cities (up from 20% in 1950), with the rest in towns or rural areas.
Demonstrates that how 'urban area' is defined, by population threshold, density or services, changes the urban statistics, so any figure must be quoted with its definition.
2018–2025 Urban areas
8.2.3An urban area works as a system.
Lagos resource inputs and Olusosun landfill
Lagos, a city of over 20 million people, depends on inputs of food, fuel and water from outside the city. Its solid waste output goes to landfills such as Olusosun, where in March 2026 trucks queued 5–14 days to unload and unmanaged waste released methane, while wastewater drains into the lagoon and the Atlantic.
Demonstrates a city as an open system with inputs, storages and outputs, and shows how a blocked output flow builds up storages and causes pollution, which reduces urban resilience.
8.2.5Due to rural–urban migration, a greater proportion of the human population now live in urban rather than rural systems, and this proportion is increasing.
Nigeria urbanisation and migration
Nigeria's urban population rose from about 14% in 1960 to 63% in 2024. By 2022 Lagos was about 40 times its 1960 size, with an estimated 5,000 internal migrants arriving each day. Voluntary pull factors (jobs, schools) combine with forced moves such as the roughly 2.4 million flood displacements of 2022 and violence in the North.
Quantifies rapid rural–urban migration, mostly internal, and separates push from pull factors and forced from voluntary moves.
8.2.6Suburbanization is due to the movement of people from dense central urban areas to lower-density peripheral areas.
Pays de Gex urban growth, France
Between 1970 and 1980 the City of Geneva lost 10% of its population (173,618 to 156,505), while the rest of the canton grew by 22%. Across the border, the Pays de Gex grew from 22,157 people in 1968 to 107,091 in 2023, mainly through in-migration. 309 ha of farmland, forest and natural land were built on there between 2011 and 2021, and 44% of its workers commute into Switzerland.
Shows suburbanisation as people move from a dense centre to lower-density edges while still commuting in, and the urban sprawl and land take that follow.
8.2.7The expansion of urban and suburban systems results in changes to the environment.
River Aire straightening and restoration, Geneva
The River Aire, Geneva, was straightened and concreted in the early 1900s. This sped up and concentrated floodwater towards the built-up area downstream, and water quality fell so far that fishing and swimming were banned from the 1980s. Since 2002, more than 4.5 km has been given a natural bed again, which won the Council of Europe Landscape Award in 2019.
Shows how channel modification changes river flows and water quality, and that planning can also reverse the damage.
Urban sprawl and sealed ground, Pays de Gex
In the Pays de Gex, 309 ha of farmland, forest and natural land were built on between 2011 and 2021 as suburbs spread out from Geneva. About two-thirds of the City of Geneva is now sealed ground, and the peak flows of its small urban streams are tending to rise.
Quantifies how suburban expansion causes loss of farmland and natural land, and how sealed ground raises peak river flows.
8.2.8Urban planning helps decide on the best way to use land and buildings.
Praille-Acacias-Vernets redevelopment, Geneva
Praille-Acacias-Vernets (PAV) in Geneva is a 230 ha industrial zone that the canton voted in 2011 to redevelop. The plan includes about 12,000 homes, 6,000 jobs, a 6–8 ha park, 3,000 trees, 20 km of cycle paths and the reopening of 450 m of the culverted River Drize, but existing firms must be moved elsewhere first.
Demonstrates planners balancing domestic, environmental, physical, industrial and financial stakeholder needs on a single site.
8.2.9Modern urban planning may involve considering the sustainability of the urban system.
Dubai wastewater recycling for irrigation
Dubai recycles about 90% of its wastewater (target 100% by 2030). About 265 million m³ a year irrigates around 10,400 ha of green space, saving about AED 2 billion a year compared with using energy-intensive desalinated water from Jebel Ali.
Shows water reuse as a sustainability measure in urban planning, and raises the question of whether desert greening is truly sustainable.
Dubai, United Arab Emirates Urban planning
8.2.10Ecological urban planning is a more holistic approach that treats the urban system as an ecosystem, understanding the complex relationships between its biotic and abiotic components.
Basel green roof building law
Since 2002, Basel's building law has required green roofs on new and renovated flat roofs, with at least 12 cm of native-planted substrate since 2015. This gives about 5.7 m² of green roof per inhabitant, the most of any city. The roofs cool the rooms below by up to 5 °C and cut runoff by 17–20%, and Brenneisen recorded 79 beetle and 40 spider species, some endangered, on the Rhypark roof.
Demonstrates ecological planning that links abiotic factors (soil depth, runoff, temperature) to biotic communities.
8.3.2Sources of primary pollutants are both natural and anthropogenic.
Saharan dust particulates, Geneva and West Africa
Saharan dust is a natural source of particulates at two ends of its range: about 15 dust days were detected over Geneva in 2025, with a strong episode on 12–15 November, and from December to February the harmattan wind carries dust over Lagos and other West African coastal cities.
Counter-example to the idea that all air pollution is caused by people, showing that natural primary pollutants raise PM levels even where traffic rules are strict.
8.3.3Most common air pollutants in the urban environment are either derived directly or indirectly from combustion of fossil fuels.
Air pollution deaths and costs, Lagos
Lagos, Nigeria: a 2020 World Bank study found air pollution caused about 11,200 early deaths in 2018 (60% children under five), costing US$2.1 billion (2.1% of Lagos State GDP), with mean PM2.5 of 68 µg/m³. Road transport (32%), biomass burning (19%), waste burning (9%) and bush burning (5%) are the main sources, and about half of household energy comes from petrol and diesel generators.
Shows how most urban pollution comes from combustion, with fossil-fuel traffic and generators as the largest share, and puts a number on the health and economic cost.
8.3.4A range of different management and intervention strategies can be used to reduce urban air pollution.
Léman Express and Lagos Blue Line ridership
The Léman Express cross-border rail network opened in December 2019 with 45 stations and carried over 80,000 passengers a day by 2024. By contrast, the 13 km Lagos Blue Line, opened in September 2023, carried only about 15,000 a day in 2025.
Compares improved public transport in two cities and shows that one new rail line cannot do much where biomass, waste and generator burning are major sources.
Stick'AIR emergency traffic plan, Geneva
Geneva's Stick'AIR emergency traffic plan, switched on in August 2025 for only the second time since 2020, kept out vehicles without the right sticker. These were about 11% of the canton's vehicles but produced 30% of vehicle NOx, and public transport can be made free on high-pollution days.
Demonstrates a limited-car-use strategy aimed at the highest emitters, so a small cut in vehicle numbers gives a much bigger cut in NOx.
8.3.5NOx and sulfur dioxide react with water and oxygen in the air to produce nitric and sulfuric acid, resulting in acid rain.
Acid rain from Italy, Ticino (Po Plain source)
Ticino, Switzerland: humid Mediterranean air picks up SO2 and NOx over the industrial Po Plain (Milan, Turin), then rises over the Alps and drops its rain, so much of the acid falling on Ticino comes from Italy, with 70–79% arriving as wet deposition.
Shows that acids form from emitted gases in the atmosphere and fall as wet deposition far from the source, crossing national borders as transboundary pollution.
Ticino, Switzerland Acid deposition
8.3.6Acid rain has impacts on ecology, humans and buildings.
Acidified mountain lakes, Ticino
Ticino's mountain lakes lie on base-poor rock with little buffering capacity. In 1995, 29% of 45 surveyed lakes had a pH below 6.0, compared with 10% of 52 acid-sensitive Swiss lakes in a 2018 study.
Shows that how much damage acid deposition does to freshwater depends on the underlying geology, and that ecosystems can recover once deposition falls.
St Paul's Cathedral balustrade erosion, London
St Paul's Cathedral, London: over 30 years, the limestone balustrade's erosion rate fell from 0.049 to 0.035 mm per year as London's daily SO2 fell from about 80 ppb (early 1980s) to under 3 ppb (late 2000s).
Quantifies how acid deposition dissolves calcium carbonate building stone, and shows that damage slowed towards natural weathering rates once SO2 fell.
8.3.7Management and intervention strategies are used to reduce the impact of sulfur dioxide and NOx on ecosystems and to minimize their effects.
India coal plant scrubber rule relaxation
India's coal power stations emit over 6 million tonnes of SO2 a year. A 2015 rule required scrubbers, but only 57 of 600 units had them by August 2025. In July 2025 the rule was relaxed so that 77% of units were exempt. Rajpura (no scrubbers) emitted about 43,500 t of SO2 in 2025, roughly 11 times more than the similar Mahatma Gandhi plant, which has scrubbers.
Lets students evaluate control at the point of release (flue-gas desulfurisation) by weighing its proven effectiveness against cost, water use, limestone use and extra CO2.
Sulfur and nitrogen deposition decline, Ticino
Thanks to emission cuts across Europe, sulfur deposition in Ticino fell 81% (114 to 22 meq/m²/yr) between 1983–87 and 2018–22. Nitrogen deposition fell only 28% (158 to 114), and more than half of it now comes from farm ammonia.
Shows that international emission reductions worked for sulfur but less well for nitrogen, which comes from many diffuse sources, so further management strategies are needed.
HL.a Environmental law
HL.a.7International law provides an essential framework for addressing transboundary issues of pollution and resource management.HL
Great Lakes Water Quality Agreement
Under the 1972 Great Lakes Water Quality Agreement, Canada and the USA coordinate phosphorus reduction targets and monitoring to tackle algal blooms caused by agricultural runoff. The agreement covers eight US states and two Canadian provinces.
Shows why a binational legal framework is needed when pollution from one country's farmland degrades a shared water body.
HL.a.8UN conferences produce international conventions (agreements) that are legally binding, and protocols that may become legally binding, to all signatories.HL
PolicyKigali Amendment to the Montreal Protocol
The 2016 Kigali Amendment to the Montreal Protocol is legally binding on parties that ratify it. It phases down hydrofluorocarbons (HFCs) used in refrigeration, with separate schedules for developed and developing countries and trade restrictions on non-parties.
Shows how a protocol under a UN convention can be amended to become legally binding on its signatories, using differentiated responsibilities to win wider participation.
HL.a.9International agreements can generate institutions or organizations to aid their implementation.HL
OrganisationGreen Climate Fund, UNFCCC
The Green Climate Fund was established under the UNFCCC and has allocated over $13 billion (as of 2024) to climate adaptation and mitigation projects in developing countries. It reviews proposals, pays out funding and monitors how projects are carried out.
Demonstrates how an international agreement creates a dedicated institution to turn treaty commitments into funded action on the ground.
HL.a.10The application of international environmental law has been examined within international courts and tribunals.HL
South China Sea Arbitration, Philippines v China
In the Philippines v China arbitration (2016), the Permanent Court of Arbitration ruled that China's artificial island-building had caused severe harm to coral reef ecosystems, in breach of UNCLOS. China rejected the ruling, and it remains unenforced.
Demonstrates that international tribunals can test environmental obligations, but also shows the limits of enforcement when a powerful state refuses to comply.
HL.a.11There are an increasing number of laws granting legal personhood to natural entities in order to strengthen environmental protection.HL
Whanganui River legal personhood, New Zealand
In 2017 New Zealand's Te Awa Tupua Act recognised the Whanganui River as an indivisible living whole with legal personhood. Two guardians, one appointed by Māori iwi and one by the Crown, can bring legal action on the river's behalf.
Shows how legal personhood gives a natural entity standing in court, so harm to the river can be challenged directly rather than only through human property rights.
HL.a.12Both legal and economic strategies can play a role in maintaining sustainable use of the environment.HL
Payment for Ecosystem Services, Costa Rica
Costa Rica combines a legal ban on deforestation with Payments for Ecosystem Services to landowners who keep their tree cover, funded largely by a fossil fuel tax. This has helped reverse decades of forest loss.
Demonstrates that legal prohibitions work best alongside economic incentives, because conservation then becomes financially worthwhile for landowners.
Costa Rica Environmental laws #2
HL.b Environmental economics
HL.b.4When the market fails to prevent negative impacts, the polluter-pays principle may be applied.HL
PolicyCigarette butt clean-up law, Spain
Spain passed a law requiring tobacco companies to pay for cleaning up cigarette butts from streets and beaches, as part of an extended producer responsibility approach.
Shows the polluter-pays principle applied to producers, so that the cost of clean-up shifts from taxpayers to the companies whose products create the waste.
PolicyEU Emissions Trading System
The EU Emissions Trading System (since 2005) caps total emissions from power stations and heavy industry. Polluters must buy or trade permits for each tonne of CO₂ they emit, which puts a market price on carbon.
Demonstrates the polluter-pays principle working through a market mechanism, where the cost of the externality is internalised by the people who cause it.
since 2005 Environmental economics #2
HL.b.5"Greenwashing" or "green sheen" is where companies use marketing to give themselves a more environmentally friendly image.HL
StudyEU survey of green product claims
A 2020 European Commission survey found that 53% of the green claims made about products in the EU were vague, misleading or unfounded.
Quantifies how widespread greenwashing is across markets, which shows it is a systemic problem rather than the work of a few bad companies.
Volkswagen 'clean diesel' scandal
Volkswagen marketed its diesel cars as 'clean diesel', but in 2015 US regulators found it had fitted defeat-device software to about 11 million vehicles so they passed emissions tests while emitting far more NOx on the road.
Shows greenwashing at its most extreme: green marketing was used in place of real environmental performance, and the deception led to legal and financial penalties.
HL.b.6The tragedy of the commons highlights the problem where property rights are not clearly delineated and no market price is attached to a common good, resulting in overexploitation.HL
Ogallala Aquifer depletion, USA
Under the US Great Plains, farmers pump groundwater from the shared Ogallala Aquifer for irrigation much faster than it is naturally recharged, so water tables are falling.
Shows that open access to a shared resource with no price leads each user to overexploit it, until the resource runs down for everyone.
Ogallala Aquifer, USA Environmental economics #2Overfishing and the High Seas Treaty
International waters beyond national jurisdiction have no owner and no price on their fish, which has led to overfishing. The 2023 UN High Seas Treaty set up a framework for marine protected areas in these waters.
Demonstrates the tragedy of the commons caused by property rights that are not defined, and shows international governance as one response to it.
HL.c Environmental ethics
HL.c.2Environmental ethics is a branch of ethical philosophy that addresses environmental issues.HL
Palm oil expansion and orangutans, Borneo
Since the 1990s, Indonesian palm oil expansion in Borneo has brought economic development and jobs. It has also destroyed rainforest habitat and pushed the orangutan towards extinction.
Demonstrates the ethical tension between human livelihoods and the rights of other species, which is central to environmental ethics.
Wolf reintroduction, Yellowstone National Park
Wolves reintroduced to Yellowstone National Park in 1995 restored ecological balance but caused conflict with nearby ranchers losing livestock. Ecocentrics stress the wolves' intrinsic value, anthropocentrics favour hunting quotas and compensation, and technocentrics favour GPS tracking and electric fencing.
Shows how one environmental issue becomes an ethical dilemma when different value systems judge the same action as right or wrong.
HL.c.3A variety of ethical frameworks and conflicting ethical values emerge from differing fundamental beliefs concerning the relationship between humans and nature.HL
Japanese whaling
Japan continues to hunt whales, citing a cultural tradition of around 800 years and a whale-meat market of about $50 million, while anti-whaling groups argue that endangered, intelligent and social whales have a right to life and are worth more alive through whale-watching tourism (about $2.1 billion globally).
Shows how an anthropocentric belief (whales as a resource to be managed) and an ecocentric belief (whales with inherent rights) produce conflicting ethical values that rights-based ethics cannot settle, because it gives no ranking of cultural rights against animal rights.
Japan Ethical frameworks
HL.c.4Instrumental value is the usefulness an entity has for humans.HL
Elephant trophy hunting debate, Botswana
Botswana is home to about a third of Africa's elephants, and argues over whether to allow hunting so that the animals bring in money and the costs of living alongside them are reduced.
Shows wildlife being valued instrumentally (hunting revenue) and set against the view that elephants have intrinsic value and a right to life.
Botswana Ethical frameworks
HL.c.6The concepts of instrumental and intrinsic value are not exclusive.HL
Whales' instrumental and intrinsic value, Japan
Whales have instrumental value (meat, tourism, carbon storage) and intrinsic value (sentience, evolutionary uniqueness) at the same time. Japanese whalers also treat the hunt as cultural heritage that matters for its own sake.
Demonstrates that one entity can hold both kinds of value at once, and that each stakeholder chooses which value to stress.
Japan Ethical frameworks
HL.c.10Consequentialist ethics is the view that the consequences of an action determine the morality of the action.HL
Golden Rice, Southeast Asia
Golden Rice is genetically modified to produce vitamin A, so it could cut childhood blindness where rice is the staple food. Opponents warn it could contaminate thousands of traditional rice varieties and make small farmers dependent on multinational seed companies.
Shows consequentialist reasoning, where a large health benefit to many people is weighed against harm to biodiversity and to farmers' rights, and shows how technocentric and ecocentric views conflict.
Southeast Asia Ethical frameworks