Humanity is putting too much strain on the Earth system, scientists say

Man goes beyond seven of the eight limits of the “earth system” in order to continue to live in safety and justice on this planet. For example, tens of millions of people are already suffering from global warming, too much water is being extracted from rivers, lakes and the ground in many places, and nature has deteriorated too much.

This writes a group of 51 scientists in an article In Nature, published on Wednesday. Urgent systemic transformation is needed for a secure and just future “in the way we farm, design cities, produce energy, consume,” says Joyeeta Gupta, second author of the publication and professor of environment and development countries of the South at the University of Amsterdam.

The article is the sequel concept first invented in 2009 by planetary boundaries. It assumes that human civilization flourished in the Holocene (the geological era from 10,000 years ago to the present day), a period with a relatively stable climate, rich in nature and species, and with specific nutrient and water cycles. But the growing consumption of the wealthiest part of the world’s population in particular threatens to push this system beyond the boundaries of the Holocene, into a new, in many ways more threatening situation, with more extreme weather, water shortages and impoverished nature.

Nine borders

According to the 29 scientists who developed the concept of planetary boundaries suggested at the time, humans must stay within the boundaries of the Holocene Earth. They then set nine limits, including the amount of CO₂ in the atmosphere (as a measure of climate), ocean acidification, the amount of ozone in the stratosphere (as a measure of the ozone hole), and biodiversity loss.

The concept has been very influential since then, but it has also received a lot of criticism, says Frank Biermann, who was not involved in the publication and is a professor of global sustainability governance at Utrecht University. He wrote three years ago a journal article about the criticism. True, some of the nine boundaries were planetary, such as CO₂concentration, but others showed strong local variations and were not equally harmful everywhere (such as nitrogen and phosphorus cycles).

“Furthermore, the concept was conceived by Western, mostly male natural science professors,” says Biermann. Their recommendations met the global south a lot of resistance, partly because these countries feared a restriction of their economic development.

Critics continued

Also, the limits were considered very prescriptive. “A small group of scientists made judgments about concrete values ​​and goals which, however, should be judged by politicians and society as a whole.”

The concept was changed slightly in 2015, but the criticisms remained. Subsequently, a committee was set up in 2019 to review the concept of planetary boundaries judge. This Earth Commission, co-chaired by Joyeeta Gupta, is now reporting on its findings.

This time the authors also include scientists from India, Kenya and China. The term planetary boundaries is replaced by earth system boundaries, because global and local processes have been analyzed. It was also examined whether the limits are fair, in that they minimize “the exposure of people to significant harm”.

Tipping points

“Previously, only the limits in terms of the stability of the Earth system had been taken into account,” explains Peter Verburg, one of the authors of the article and professor of environmental geography at the VU University of Amsterdam. He cites global warming as an example. If it exceeds 1.5 degrees, there is a good chance that tipping points will be triggered in the Earth system, and the risk of damage to the biosphere will increase sharply. “But already tens of millions of people around the world are suffering from extreme weather conditions, especially vulnerable people in the poorest countries.” Hence the scientists in their Naturepublication already set the warming limit at 1 degree Celsius.

They further recommend that 50-60% of all land on earth should consist of “largely intact ecosystems”. Now it’s less than 50%. In human-suitable landscapes – cities and agricultural areas – every square kilometer should be made up of 20-25% “diverse semi-natural habitats”. They also set a limit for the excess nitrogen and phosphorus that can be applied to agricultural land worldwide and recommend a redistribution of nutrients from over-fertilized to under-fertilized soils. Air pollution also needs to be reduced in many places, especially in cities.

Technocratic

Biermann finds the Earth Commission “very technocratic”. He also awaits the necessary criticisms on this new version of land borders.

Erle Ellis, professor of geography and environmental systems at the University of Maryland, Baltimore County, says he has even more problems with this publication than with the original 2009 version. This is not how we discuss the issues of the Anthropocene.

Gupta and Verburg point out that the Earth Commission does not prescribe anything. She analyzed which boundaries derive from already existing political goals, such as the United Nations Sustainable Development Goals. Gupta: “Our publication is a contribution to a deeper debate on how we can achieve these goals. »