The stability and resilience of the Earth system and human well-being are inseparably linked1–3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)4. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.

Living within planetary limits requires attention to justice as biophysical boundaries are not inherently just. Through collaboration between natural and social scientists, the Earth Commission defines and operationalizes Earth system justice to ensure that boundaries reduce harm, increase well-being, and reflect substantive and procedural justice. Such stringent boundaries may also affect 'just access' to food, water, energy and infrastructure. We show how boundaries may need to be adjusted to reduce harm and increase access, and challenge inequality to ensure a safe and just future for people, other species and the planet. Earth system justice may enable living justly within boundaries.Rapid Earth system changes in the Anthropocene are harming nature and humans. The Anthropocene is also marked by increasing inequalities 1 and vulnerabilities 2 . Scientists have proposed planetary boundaries, such as climate targets, to reduce global environmental risks. Within the Earth Commission, we aim to propose 'safe and just Earth system boundaries' (ESBs) that go beyond planetary boundaries as they also include a justice perspective and suggest transformations to achieve them 3 . Safe and just ESBs aim to stabilize the Earth system, protect species and ecosystems and avoid tipping points, as well as minimize 'significant harm' to people while ensuring access to resources for a dignified life and escape from poverty. If justice is not considered, the biophysical limits may not be adequate to protect current generations from significant harm. However, strict biophysical limits, such as reducing emissions or setting aside land for nature, can, for example, reduce access to food and land for vulnerable people, and should be complemented by fair sharing and management of the remaining ecological space on Earth 4 . Behavioural experiments show that people contribute to common pool resource stewardship if they see the process and outcomes as just 5 . This perspective offers an approach to Earth system justice (ESJ) that can guide and operationalize the identification of 'just ends' in terms of Earth system boundaries (ESBs) and access indicators, and 'just means' in terms of sustainability transformations. It provides a discursive shift to reframe environmental science and policy to pay attention to distributive justice 6 .

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The Sustainable Development Goals aim to improve access to resources and services, reduce environmental degradation, eradicate poverty and reduce inequality. However, the magnitude of the environmental burden that would arise from meeting the needs of the poorest is under debate—especially when compared to much larger burdens from the rich. We show that the ‘Great Acceleration’ of human impacts was characterized by a ‘Great Inequality’ in using and damaging the environment. We then operationalize ‘just access’ to minimum energy, water, food and infrastructure. We show that achieving just access in 2018, with existing inequalities, technologies and behaviours, would have produced 2–26% additional impacts on the Earth’s natural systems of climate, water, land and nutrients—thus further crossing planetary boundaries. These hypothetical impacts, caused by about a third of humanity, equalled those caused by the wealthiest 1–4%. Technological and behavioural changes thus far, while important, did not deliver just access within a stable Earth system. Achieving these goals therefore calls for a radical redistribution of resources.

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