Conditions on Earth may be out of “safe operating space” for humanity, according to dozens of scientists

By | September 14, 2023

Human actions have pushed the world into the danger zone for several key indicators of planetary health, threatening to trigger dramatic changes in conditions on Earth, according to a new analysis by 29 scientists in eight countries.

Scientists analyzed nine interconnected “planetary boundaries,” which they define as thresholds within which the world must remain to ensure a stable and livable planet. These include climate change, biodiversity, freshwater and land use, and the impact of synthetic chemicals and aerosols.

Human activities have exceeded security levels for six of these boundaries and are pushing the world out of a “safe operating space” for humanity, according to a report published Wednesday in the journal Science Advances.

The nine boundaries, first established in a 2009 document, aim to establish a set of defined “limits” on the changes humans are making to the planet – from eliminating planet-warming pollution to cutting down waste forests for agriculture. Beyond these limits, the theory goes, the risk of destabilizing conditions on Earth increases dramatically.

The limits are designed to be conservative, to allow society to resolve problems before reaching a “very high risk zone,” said Katherine Richardson, a professor of biological oceanography at the University of Copenhagen and a co-author of the report.

He highlighted the unprecedented summer of extreme weather the world has just experienced with global warming of 1.2 degrees Celsius. “We didn’t think it would be like this at 1 degree [Celsius]” she said. “No human being has experienced the conditions we are experiencing now,” she added.

A man evacuates horses during a fire in Chasia, on the outskirts of Athens, on August 22, 2023. - Angelos Tzortzinis/AFP/Getty Images

A man evacuates horses during a fire in Chasia, on the outskirts of Athens, on August 22, 2023. – Angelos Tzortzinis/AFP/Getty Images

Of the three boundaries that scientists have found are still within safe space, two of them – ocean acidification and the amount of aerosols in the atmosphere – are moving in the wrong direction.

There is some good news, however. In the 1990s the ozone layer was on the wrong side of the border, Richardson said. But thanks to international cooperation to phase out ozone-depleting chemicals, it is on track to fully recover.

A “strong warning”

Crossing planetary boundaries does not mean the world has reached a disastrous turning point. Hitting one isn’t “falling off a cliff,” Richardson said. But it’s a clear warning sign.

He used the analogy of a bank account, where the currency is not money, but rather the Earth’s resources that humans, like all living organisms, use to survive. As humanity crosses planetary boundaries, our “bank balance” is declining, he said.

“We can celebrate, even if our money in the bank is dwindling – we just can’t celebrate forever. This is the situation we’ve gotten ourselves into,” she said.

The importance of the planetary boundaries model is that it does not analyze climate and biodiversity in isolation, the report’s authors say. Instead, it examines the interaction of both, as well as myriad other ways humans are impacting the planet. Exceeding one limit can have knock-on effects on others too.

Razing the world’s forests to the ground, for example, has enormous impacts on the climate. “We most likely cannot achieve the climate goals that the international community has adopted without, at the same time, meeting a limit on deforestation,” Richardson said.

A deforested area near the edge of the Cordillera Azul National Park in the Peruvian Amazon.  -Martin Mejia/AP

A deforested area near the edge of the Cordillera Azul National Park in the Peruvian Amazon. -Martin Mejia/AP

Simon Lewis, a professor of global change science at University College London in the United Kingdom, who was not involved in the research, said the report provides “a surprisingly grim update on an already alarming picture.”

“Humans are destroying biodiversity, changing the climate and polluting our home to such an extent that we have pushed our planet out of the stable conditions that allowed human civilizations to emerge,” he told CNN. “There couldn’t be a starker warning,” she added.

Andrew Fanning, a visiting researcher at the University of Leeds in the UK, who was also not involved in the report, said the planetary boundaries model provides “strong evidence-based support” for policymakers and others to help transform economies and societies to tackle the climate. crisis.

But there are criticisms of the model.

Raymond Pierrehumbert, a professor of physics at the University of Oxford, said planetary boundaries are useful where there is a clear basis for choosing a boundary, such as carbon pollution.

But for other factors, such as changing land use, “it can be a distraction to argue about where to place the border and whether or not it has been ‘crossed,'” he told CNN.

“It’s a heroic attempt to simplify the world, but it’s probably too simplified to be useful in the practical management of our many environmental problems,” Lewis said.

Stuart Pimm, professor of conservation ecology at Duke University and co-author of a critical paper on planetary boundaries in 2018, went further.

“The measures they use don’t make sense and they can’t estimate them,” he told CNN.

The challenge of data and monitoring is something Richardson recognizes. “We need more comprehensive data collection and comparison to be able to monitor the effects of humans on the ecosystem,” she said.

This report is the third update on the planetary boundaries framework. The previous one was published in 2015.

“What scares me is that transgression is increasing because of all the limits that were violated in 2015,” said Richardson, who added, “the situation is not getting better.”

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