Earth outside ‘safe operating zone’ for humans in key areas, scientists find

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New research shows that six of Earth’s nine critical regions exceed “safe operating” limits, compromising their ability to self-regulate and increasing the risk of sudden and irreversible changes caused by human activities.

Johan Rockström, director of the Potsdam Institute for Climate Impact Research and one of the 28 scientists behind the study, described the planet as “an unwell patient”, saying, nine realms will decide its fate.

“We don’t know how long we can continue to push these critical boundaries before combined stress causes irreversible changes and damage,” Rockström said.

Boundaries are defined as: climate change; biosphere integrity; land regime changes; freshwater use; significant phosphate and nitrogen flows; ocean acidification; and ozone depletion; and the addition of new aerosols and chemical compounds such as plastics and nuclear waste ) level measurement method.

Scientists say crossing planetary boundaries does not pose a threat of immediate collapse or irreversible change, but means reduced resilience and a higher risk of harm to human life.

However, climate change, which has driven global warming further beyond 1.5°C since pre-industrial times, may eventually lead to a tipping point.

The researchers found that only three of the nine areas – ocean acidification, aerosol levels and ozone depletion – were within the safe operating zone. But both ocean and air pollution are approaching danger points, with the latter already breaching limits in South Asia and China.

“Of those that were violated, we had no indication that they were moving in the right direction,” Rockstrom said.

However, scientists noted that all nine regions were still able to recover, noting that the ozone layer has partially recovered after the Montreal Protocol phased out chemicals responsible for ozone depletion.

A related study published in May assessed Earth system boundaries in the context of social justice issues and concluded that these boundaries have exceeded human safety limits based on rising temperatures, damage to water systems and destruction of natural habitats.

Researchers say it’s challenging to quantify interactions between boundaries, with excessive risk in one area increasing risk in others. For example, there is evidence that climate change limits and biosphere integrity are related.

“Biodiversity is fundamental to keeping the carbon cycle and the water cycle intact,” Rockstrom said. “Our biggest headache today is the climate crisis and the biodiversity crisis.”

Researchers say one of the most powerful solutions is to restore total forest cover to late 20th century levels and stop burning fossil fuels. But this goal is under threat due to the increasing use of biomass as an alternative to fossil fuels.

“We don’t have the biomass we need to extract carbon dioxide from the atmosphere,” said Catherine Richardson of the University of Copenhagen.

Richardson was also critical of advocacy for carbon capture and storage technology to capture greenhouse gas emissions from the burning of fossil fuels. “Carbon capture and storage is a continuation of ‘let’s use it and throw it away when we’re done.'”