IB Syllabus focus:
‘Planetary boundaries set science-based limits; doughnut economics links social foundation and ecological ceiling; circular economy designs out waste and regenerates nature. Each is useful yet simplified and challenging to implement.’
This section explores planetary boundaries, doughnut economics, and the circular economy, three conceptual frameworks that guide understanding of sustainability challenges and solutions in socio-ecological systems.
Planetary Boundaries
The planetary boundaries framework was developed by scientists to define thresholds within which humanity can safely operate. Crossing these boundaries risks destabilising Earth systems.
Circular diagram of the nine planetary boundaries surrounding a central safe operating space. Wedges indicate how far each boundary is from its threshold, illustrating the framework’s stabilising role. The colour shading also shows estimated transgressions—useful context but extra detail beyond the syllabus requirement. Source.
Planetary Boundaries: Science-based limits on key Earth system processes, beyond which irreversible environmental change may occur.
Nine key boundaries include:
Climate change (linked to greenhouse gases and energy balance).
Biosphere integrity (biodiversity loss and ecosystem function).
Biogeochemical flows (nitrogen and phosphorus cycles).
Land-system change (deforestation and land conversion).
Freshwater use.
Atmospheric aerosols.
Stratospheric ozone depletion.
Ocean acidification.
Novel entities (synthetic chemicals, plastics).
Safe operating space
Within limits, Earth systems remain stable and resilient.
Beyond limits, feedbacks may cause irreversible changes, such as climate tipping points or mass extinctions.
Boundaries are interconnected: exceeding one can destabilise others.
Simplifications and challenges
Thresholds are estimates, with uncertainties and regional variations.
Global-scale framing may overlook local environmental contexts.
Despite limitations, planetary boundaries highlight urgent environmental risks and the need for cooperative governance.
Doughnut Economics
Doughnut economics, proposed by economist Kate Raworth, connects environmental and social dimensions to frame sustainable development.
Doughnut Economics: A sustainability framework combining a social foundation (minimum standards for human well-being) and an ecological ceiling (planetary boundaries).
Structure of the doughnut
Social foundation: minimum thresholds for equity, food, water, health, housing, energy, education, and political voice. Falling below leads to human deprivation.
Ecological ceiling: planetary boundaries. Overshoot leads to environmental degradation.
Concentric-ring diagram of Doughnut economics with an inner social foundation and outer ecological ceiling. The safe and just space for humanity lies between these rings. This version is intentionally simple and does not display any data on transgressions. Source.
Safe and just space: the “doughnut” itself, where human well-being is achieved within ecological limits.
Implications
Encourages integrated policy that balances social and ecological priorities.
Recognises inequality as a driver of both resource overuse and social instability.
Highlights need for redistributive measures alongside ecological sustainability.
Challenges
Hard to measure simultaneously at global and local levels.
Application depends on reliable data and governance structures.
Simplified model that does not capture all socio-ecological complexities.
Circular Economy
The circular economy focuses on resource efficiency by rethinking production and consumption.
Side-by-side comparison of a linear economy (take–make–waste) and a circular economy with loops for reuse, repair, remanufacture and recycling. It emphasises reducing resource inputs and keeping materials in use—precisely the level of detail required here. Source.
Circular Economy: An economic model that designs out waste, keeps resources in use for as long as possible, and regenerates natural systems.
Principles
Design out waste: products and processes are created to minimise pollution and waste streams.
Keep materials in circulation: reuse, repair, remanufacture, recycle.
Regenerate natural systems: support ecosystems through sustainable practices, such as restoring soils and ecosystems.
Benefits
Reduces reliance on finite resources.
Lowers carbon footprint and environmental degradation.
Supports innovation and green jobs.
Challenges
Requires fundamental redesign of industrial systems and consumer habits.
High initial costs for businesses transitioning from linear models.
Global supply chains complicate implementation.
Comparing the Frameworks
Shared features
All three frameworks aim to ensure sustainability by identifying environmental and social limits.
Each is simplified to improve accessibility and communication.
They encourage systemic change rather than piecemeal solutions.
Key differences
Planetary boundaries: science-driven, focused on ecological thresholds.
Doughnut economics: combines social justice with ecological sustainability.
Circular economy: practical economic model focusing on design and resource management.
Implementation challenges
Frameworks may conflict with current economic systems that prioritise short-term growth.
Translating theory into policy and practice requires international cooperation.
Simplification risks overlooking regional and cultural differences in environmental values and priorities.
IB Examination Context
Students should be able to:
Explain the concepts of planetary boundaries, doughnut economics, and circular economy.
Identify strengths and limitations of each framework.
Recognise that frameworks are useful tools but imperfect models for sustainability.
Link these frameworks to case studies where governments, NGOs, or businesses attempt implementation.
FAQ
The planetary boundaries framework provides policymakers with science-based thresholds for Earth system processes, helping identify safe operating spaces for human activity.
It encourages governments and organisations to set environmental targets that avoid crossing critical tipping points. By doing so, it links scientific research directly with international agreements and national policies on climate, biodiversity, and resource management.
Doughnut economics emphasises that human well-being requires meeting social foundations such as education, healthcare, and equity, while staying within ecological ceilings.
It highlights that inequality often drives unsustainable consumption patterns. Redistribution of resources, fairer access to opportunities, and inclusive governance are therefore key strategies within the model to reduce both deprivation and environmental overshoot.
The circular economy provides businesses and industries with specific strategies for redesigning systems. Unlike planetary boundaries and doughnut economics, which are conceptual, it offers applied steps.
Examples include:
Designing products for durability and repair.
Creating closed-loop supply chains.
Expanding recycling and remanufacturing.
Its practicality lies in its focus on immediate implementation rather than broad theoretical targets.
Local governments may lack reliable data to measure planetary boundaries or ecological ceilings accurately.
Cultural differences can also shape how social foundations are prioritised in doughnut economics. Similarly, applying circular economy principles may face resistance due to existing infrastructure or costs.
Thus, while the frameworks provide global guidance, tailoring them to specific regions requires adaptation to local ecological, social, and economic contexts.
Planetary boundaries align with environmental SDGs such as climate action, life on land, and clean water.
Doughnut economics complements the SDGs by framing them as part of a balance between ecological limits and social needs.
The circular economy supports SDG 12 (Responsible Consumption and Production) by promoting waste reduction and sustainable resource use.
Together, they provide interpretive tools that reinforce and refine SDG targets through systems thinking.
Practice Questions
Question 1 (2 marks)
Define the term circular economy and explain how it differs from a linear economy.
Mark scheme:
1 mark: Correct definition of circular economy (an economic model that designs out waste, keeps resources in use for as long as possible, and regenerates natural systems).
1 mark: Clear distinction made with linear economy (take–make–dispose model where resources are discarded at the end of use).
Question 2 (5 marks)
Discuss the usefulness and limitations of the planetary boundaries and doughnut economics frameworks in guiding sustainability policies.
Mark scheme:
Up to 2 marks: Description of planetary boundaries framework (science-based ecological limits, safe operating space, risk of irreversible change when exceeded).
Up to 2 marks: Description of doughnut economics (social foundation and ecological ceiling, safe and just space for humanity, integrates social and ecological priorities).
1 mark: Identification of limitations (e.g., simplification, difficulty applying at local scales, data challenges, imperfect classification).
Award marks for balanced discussion that recognises both usefulness (clarity, integration of concepts, communication tool) and limitations.
Maximum 5 marks in total.
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