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People once believed the planet could always accommodate us. That the resilience of the Earth system meant nature would always provide. But we now know this is not necessarily the case. As big as the world is, our impact is bigger.

In released today, an international team of scientists from the , of which we were part, identified eight “safe” and “just” boundaries spanning five vital planetary systems: climate change, the biosphere, freshwater, nutrient use in fertilisers and air pollution. This is the first time an assessment of boundaries has quantified the harms to people from changes to the Earth system.

“Safe” means boundaries maintaining stability and resilience of our planetary systems on which we rely. “Just”, in this work, means boundaries which minimise significant harm to people. Together, they’re a health barometer for the planet.

Assessing our planet’s health is a big task. It took the expertise of 51 world-leading researchers from natural and social sciences. Our methods included modelling, literature reviews and expert judgement. We assessed factors such as tipping point risks, declines in Earth system functions, historical variability and effects on people.

Alarmingly, we found humanity has exceeded the safe and just limits for four of five systems. Aerosol pollution is the sole exception. Urgent action, based on the best available science, is now needed.

So, what did we find?

Our work builds on the influential concepts of by finding ways to quantify what look like alongside safety.

Importantly, the safe and just boundaries are defined at local to global spatial scales appropriate for assessing and managing planetary systems – as small as one square kilometre in the case of biodiversity. This is crucial because many natural functions .

Here are the boundaries:

1. Climate boundary – keep warming to 1℃

We know the of 1.5℃ avoids a of triggering dangerous climate tipping points.

But even now, with warming at 1.2℃, many people around the world are being hit hard by climate-linked disasters, such as the recent extreme heat in China, fires in Canada, severe floods in Pakistan and droughts in the United States and the Horn of Africa.

At 1.5℃, could be exposed to average annual temperatures over 29℃, which is outside the human climate niche and can be fatal. That means a just boundary for climate is nearer to 1°C. This makes the need to halt further carbon emissions even more urgent.

2. Biosphere boundaries: Expand intact ecosystems to cover 50-60% of the earth

A healthy ensures a safe and just planet by storing carbon, maintaining global water cycles and soil quality, protecting pollinators and many other ecosystem services. To safeguard these services, we need 50 to 60% of the world’s land to have largely intact natural ecosystems.

puts the current figure at between 45% and 50%, which includes vast areas of land with relatively low populations, including parts of Australia and the Amazon rainforest. These areas are already from climate change and other human activity.

Locally, we need about 20-25% of each square kilometre of farms, towns, cities or other human-dominated landscapes largely intact natural ecosystems. At present, only a third of our human-dominated landscapes meet this threshold.

3. Freshwater boundaries: Keep groundwater levels up and don’t suck rivers dry

Too much freshwater is a problem, as unprecedented floods in Australia and Pakistan show. And too little is also a problem, with unprecedented droughts taking their toll on food production.

To bring fresh water systems back into balance, a rule of thumb is to avoid more than 20% of a river or stream’s water in any one month, in the absence of local knowledge of environmental flows.

At present, 66% of the world’s land area meets this boundary, when flows are averaged over the year. But human settlement has a major impact: less than half of the world’s population lives in these areas. Groundwater, too, is overused. At present, almost half the world’s land is subject to groundwater overextraction.

4. Fertiliser and nutrient boundaries: Halve the runoff from fertilisers

When farmers overuse fertilisers on their fields, rain washes runoff into rivers and oceans. These nutrients can trigger algal blooms, damage ecosystems and worsen drinking water quality.

Yet many farming regions in poorer countries fertiliser, which is unjust.

Worldwide, our nitrogen and phosphorus use are up to double their safe and just boundaries. While this needs to be reduced in many countries, in other parts of the world fertiliser use can safely increase.

5. Aerosol pollution boundary: Sharply reduce dangerous air pollution and reduce regional differences

shows differences in concentration of between Northern and Southern hemispheres could disrupt wind patterns and monsoons if pollutant levels keep increasing. That is, air pollution could actually upend weather systems.

At present, aerosol concentrations have not yet reached weather-changing levels. But much of the world is exposed to dangerous levels of fine particle pollution (known as PM 2.5) in the air, causing 4.2 million deaths a year.

We must significantly reduce these pollutants to safer levels – under 15 micrograms per cubic metre of air.

We must act

We must urgently navigate towards a future, and strive to return our planetary systems back within safe and just boundaries through just means.

To stop human civilisation from pushing the Earths’s systems out of balance, we will have to tackle the many ways we damage the planet.

To work towards a world compatible with the Earth’s limits means setting and achieving . To to actions will require urgent support from government to create regulatory and incentive-based systems to drive the changes needed.

Setting boundaries and targets is vital. The Paris Agreement galvanised faster action on climate. But we need similar boundaries to ensure the future holds fresh water, clean air, a planet still full of life and a good life for humans.

We would like to acknowledge support from the , which is hosted by , and is the science component of the

Steven J Lade receives funding from the Australian Government (Australian Research Council Future Fellowship FT200100381) and the Swedish Research Council Formas (Grant 2020-00371). He is affiliated with Future Earth and the Stockholm Resilience Centre at Stockholm University. This work is part of the Earth Commission, which is hosted by Future
Earth and is the science component of the Global Commons Alliance. The Global Commons Alliance is a sponsored project of Rockefeller Philanthropy Advisors, with support from the Oak Foundation, MAVA, Porticus, the Gordon and Betty Moore Foundation, the Tiina and Antti Herlin Foundation, William and Flora Hewlett Foundation and the Global Environment
Facility. The Earth Commission is also supported by the Global Challenges Foundation and the Frontiers Research Foundation.

Ben Stewart-Koster receives funding from Future Earth for his role in the Earth Commission under the Global Commons Alliance. The Global Commons Alliance is a sponsored project of Rockefeller Philanthropy Advisors, with support from the Oak Foundation, MAVA, Porticus, the Gordon and Betty Moore Foundation, the Tiina and Antti Herlin Foundation, William and Flora Hewlett Foundation and the Global Environment Facility. The Earth Commission is also supported by the Global Challenges Foundation and the Frontiers Research Foundation..

Stuart Bunn receives funding from Future Earth for his role in the Earth Commission under the Global Commons Alliance. This is a sponsored project of Rockefeller Philanthropy Advisors, with support from the Oak Foundation, MAVA, Porticus, the Gordon and Betty Moore Foundation, the Tiina and Antti Herlin Foundation, William and Flora Hewlett Foundation and the Global Environment Facility. The Earth Commission is also supported by the Global Challenges Foundation and the Frontiers Research Foundation.

Syezlin Hasan receives funding from Future Earth for her role in the Earth Commission under the Global Commons Alliance. The Global Commons Alliance is a sponsored project of Rockefeller Philanthropy Advisors, with support from the Oak Foundation, MAVA, Porticus, the Gordon and Betty Moore Foundation, the Tiina and Antti Herlin Foundation, William and Flora Hewlett Foundation and the Global Environment Facility. The Earth Commission is also supported by the Global Challenges Foundation and the Frontiers Research Foundation.

This paper was made possible through the voluntary commitment of
time and research by the Earth Commissioners and the support of the
researchers and secretariat from the Global Challenges Foundation;
the Global Commons Alliance, a sponsored project of Rockefeller
Philanthropy Advisors (with support from Oak Foundation, MAVA,
Porticus, Gordon and Betty Moore Foundation, Herlin Foundation and
the Global Environment Facility).