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The earth is beyond “safe operating” limits in six out of nine key areas, damaging its ability to self-regulate and increasing the risk of abrupt and irreversible change due to human activity, according to the latest research.
Describing the planet as “a patient that is unwell”, Johan Rockström, director of the Potsdam Institute for Climate Impact Research and one of 28 scientists behind the study, said the limits of the nine boundaries would determine its fate.
“We don’t know how long we can keep breaching these key boundaries before combined pressures lead to irreversible change and harm”, Rockström said.
The boundaries were defined as: climate change; biosphere integrity; land system change; freshwater use; vital phosphate and nitrogen flows; ocean acidification; and ozone depletion; as well as newly added measures of the levels of aerosols and chemical compounds, such as plastics and nuclear waste.
Crossing a planetary boundary does not carry the threat of immediate collapse or irreversible change, the scientists said, but meant a diminished resilience and a higher level of risk of harm to human life.
Climate change leading to further global warming of more than 1.5°C since pre-industrial times, however, could ultimately lead to tipping points.
Only three out of nine areas — ocean acidification, aerosol levels and ozone depletion — were in the safe operating zone, the researchers found. But both the oceans and air pollution were nearing danger points, with the latter already breaching limits in south Asia and China.
“Among those that are transgressed we don’t have any indication they’re trending in the right direction,” said Rockström.
However, the scientists noted that all nine areas were still able to be rehabilitated, pointing to the partial recovery in the ozone layer after the Montreal Protocol phased out the chemicals causing its depletion.
A related study published in May assessed earth system boundaries combined with social justice issues, and concluded these were past safe limits for humans based on temperature rise, water system disruption and the destruction of natural habitats.
Quantifying the interactions between the boundaries was challenging, the researchers said, with excessive risk in one area increasing the risk in others. For example, the evidence suggested that climate change limits and biosphere integrity were linked.
“Biodiversity is fundamental to keeping the carbon cycle and the water cycle intact,” Rockström said. “The biggest headache we have today is the climate crisis and biodiversity crisis.”
The researchers said that one of the most powerful solutions would be to return total forest cover back to the levels of the late 20th century, as well as ending the burning of fossil fuels. But this goal was endangered by the increasing use of biomass as a replacement for fossil fuels.
“There isn’t the biomass we’ll need to get carbon dioxide out of the atmosphere,” said the University of Copenhagen’s Katherine Richardson.
Richardson was also critical of the advocacy for carbon capture and storage technology to capture the greenhouse gas emissions from the burning of fossil fuels. “Carbon capture and storage is a continuation of ‘lets use it and throw it away when we’re finished with it’.”