Humanity is well into the Anthropocene⁶, the proposed new geological epoch where human pressures have put the Earth system on a trajectory moving rapidly away from the stable Holocene state of the past 12,000 years, which is the only state of the Earth system we have evidence of being able to support the world as we know it^7,8. These rapid changes to the Earth system undermine critical life-support systems^1,9,10, with significant societal impacts already felt^1,3, and they could lead to triggering tipping points that irreversibly destabilize the Earth system^7,11,12. These changes are mostly driven by social and economic systems run on unsustainable resource extraction and consumption. Contributions to Earth system change and the consequences of its impacts vary greatly among social groups and countries. Given these interdependencies between inclusive human development and a stable and resilient Earth system^1,2,3,13, an assessment of safe and just boundaries is required that accounts for Earth system resilience and human well-being in an integrated framework^4,5.

We propose a set of safe and just Earth system boundaries (ESBs) for climate, the biosphere, fresh water, nutrients and air pollution at global and subglobal scales. These domains were chosen for the following reasons. They span the major components of the Earth system (atmosphere, hydrosphere, geosphere, biosphere and cryosphere) and their interlinked processes (carbon, water and nutrient cycles), the ‘global commons’¹⁴ that underpin the planet’s life-support systems and, thereby, human well-being on Earth; they have impacts on policy-relevant timescales; they are threatened by human activities; and they could affect Earth system stability and future development globally. Our proposed ESBs are based on existing scholarship, expert judgement and widely shared norms, such as Agenda 2030. They are meant as a transparent proposal for further debate and refinement by scholars and wider society.

First, we identify ‘safe’ boundaries at subglobal and global scales for “maintain[ing] and enhanc[ing] the stability and resilience of the Earth system over time, thereby safeguarding its functions and ability to support humans and all other living organisms”⁴. To determine safe boundaries, we use assessments of tipping point risks among local and regional tipping elements, evidence on declines in Earth system functions, analyses of historical variability and expert judgement. We assess the uncertainty in and confidence of these ESBs. Tipping elements are those components or processes that regulate the functioning and state of the planet and that show evidence of having thresholds at which small additional perturbations can trigger self-reinforcing changes that undermine Earth system resilience^15,16. We do not exclusively rely on tipping points for setting safe ESBs, however, and the ESBs should not be interpreted as representing tipping points. As a reference state for human life support on Earth, we use an interglacial Holocene-like Earth system functioning dominated by balancing feedbacks that cope with, buffer and dampen disturbances.  Methods and Supplementary Information have details on how safe boundaries are determined.

Second, we use three criteria to assess whether adhering to the safe ESBs could protect people from significant harm (Box 1): ‘interspecies justice and Earth system stability’ (I1)¹⁷; ‘intergenerational justice’¹⁸ between past and present generations (I2a) and present and future generations (I2b); and ‘intragenerational justice’ (I3) between countries¹⁹, communities and individuals through an intersectional lens²⁰. These criteria sit within a wider Earth system justice framework that goes beyond planetary and issue-related justice to take a multi-level transformative justice approach focusing on ends (boundaries and access levels) and means^21,22.  Methods and Supplementary Information have more detailed discussions of the justice approach applied in this paper. We define harm as negative impacts on humans, communities and countries from Earth system change in addition to background rates. The most recent Intergovernmental Panel on Climate Change (IPCC) report identifies ‘severe’ risks and ‘high’ reasons for concern when tens to hundreds of millions of people are exposed to changes in climate, such as increases in temperature and extreme events²³. In this paper, we define significant harm as widespread severe existential or irreversible negative impacts on countries, communities and individuals from Earth system change, such as loss of lives, livelihoods or incomes; displacement; loss of food, water or nutritional security; and chronic disease, injury or malnutrition (a glossary is in the Supplementary Methods).

Third, we combine these justice criteria with historical analyses, international health standards, Earth system modelling and expert judgement to quantify safe and just ESBs that minimize human exposure to significant harm (no significant harm (NSH)) from Earth system change. Minimizing significant harm is a cornerstone of national and international law and corrective justice^24,25. We focus on assessing the levels of Earth system change leading to widespread exposure to significant harm, which will lead to greater impacts when vulnerable populations are exposed³. Methods and Supplementary Information have details on how just boundaries are determined. The just (NSH) boundaries described here are necessary but not sufficient conditions for Earth system justice, which must also enable access to resources for all²⁶ and distributional and procedural fairness²². A foundation that enables minimum access to water, food, energy and infrastructure for all humans alongside a safe and just (NSH) ESB ceiling of maximum allowed human pressure on biophysical domains could constitute a safe and just ‘corridor’ over time^4,22 (Fig. 1).

Visualization of safe ESBs (dark red), just (NSH) ESBs (blue), cases where safe and just (NSH) boundaries align (green) and current global states (Earth icons). Radial axes are normalized to safe ESBs. Headline or central estimate global boundaries (Table 1) are plotted to support comparison with the current global state, but we emphasize that we have also defined subglobal boundaries and multiple likelihood levels for many domains (Table 1). For aerosols, however, we display the subglobal boundaries to compare safe and just boundaries. For nitrogen, we plot with a dashed blue line the boundary quantification for harm from nitrate in groundwater while noting that the just boundary must also incorporate safe considerations via eutrophication, leading to a more stringent safe and just boundary. Minimum access to water, food, energy and infrastructure for all humans (dotted green line) could constitute the foundation of a safe and just ‘corridor’ (green filled area), but we do not quantify this foundation here. Alternative visualizations are presented in Extended Data Fig. 1.

Our assessment builds upon and advances beyond previous research and science-based political consensus, such as the Planetary Boundaries (PBs) framework²⁷, doughnut economics²⁸ and the Sustainable Development Goals²⁹ in the following ways. (1) We define just ESBs for avoiding significant harm using the same units as the safe ESBs for the same domains and propose that actors use the stricter of the safe and just boundaries to inform target setting. The PBs identify only safe biophysical boundaries. The social goals related to access to or harm from natural resources adopted in Agenda 2030, doughnut economics and other approaches^28,30,31,32 are not quantified in comparable units or examine only the consequences of human activities on the Earth system, not harm to humans from Earth system change. Articulating sociopolitical notions, such as Earth system justice, and converting their implications into biophysical units can enable a better understanding of the space within which humans can function. (2) We define global and subglobal ESBs in most domains. The PBs’ emphasis on the global scale can be inappropriate for the assessment and management of domains such as the biosphere³³ and fresh water^34,35,36,37. (3) We set boundaries at multiple likelihood levels for Earth system states. (4) Tipping element assessments in climate, biosphere and other Earth system domains are key, although not exclusive, evidence for our ESBs. Recent PB assessments instead emphasize risks related to the departure from Holocene ranges of Earth system variability³⁸.

For each Earth system domain, we first quantify safe boundaries for maintaining Earth system resilience, with multiple levels of likelihood reflecting uncertainty or variability in the exact position of the boundary. Adhering to these safe boundaries implements our ‘interspecies justice and Earth system stability’ criterion (I1 in Box 1) and will safeguard future generations against significant harm from Earth system change (intergenerational justice; I2b in Box 1), but it may not avoid significant harm to current generations, particularly vulnerable populations (I2a and I3 in Box 1). Hence, (1) we propose that some boundaries be made more stringent to protect present generations and ecosystems; (2) we complement safe boundaries with local-level standards to protect present generations and ecosystems; and (3) if the boundary is likely to cause considerable difficulties for present generations, we propose that it is complemented with policies that account for distributive justice. We also assess the current state of the Earth system with respect to each safe and just ESB.

Climate

We identify safe ESBs for warming (Fig. 1 and Table 1) based on minimizing likelihoods of triggering climate tipping elements; maintaining biosphere and cryosphere functions; and accounting for Holocene (