Foundation: real-world examples

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.

• 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.

• 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.

  Whanganui River, New Zealand Environmental worldviews

• 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.

  Environmental worldviews

1.2.4Flows are processes that may be either transfers or transformations.

• 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, 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, Oracle, Arizona, USA Systems and systems diagrams

• 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.

  Systems and systems diagrams

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.

• 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.

  Feedback loops

• 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.

• 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.

  Yellowstone National Park, USA Feedback loops

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.

• 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.

  Feedback loops

• 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

1.2.13A 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.

• 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.

  Systems and systems diagrams

1.2.14Simplification of a model involves approximation and, therefore, loss of accuracy.

• 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.

  Crawford Lake, Ontario, Canada Systems and systems diagrams

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 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 resilience

• 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.

• 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.

  Lake Erie, USA System resilience

• 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.

  Ireland System resilience

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.

• 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.

  Development and the SDGs

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.

• 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.

  Measuring sustainability

• 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.

  Amsterdam, Netherlands Models

• 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 sustainability

• 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

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 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.

  Measuring sustainability

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.

• 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.

  Development and the SDGs

1.3.17There are a range of frameworks and models that support our understanding of sustainability, each with uses and limitations.

• 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.

  Models

• 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.

  Potsdam, Germany Models

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.

• 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.

  Development 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, 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.

  Sustainability

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.

• 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

• 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.

  South Africa Sustainability