This time, the warning concerns the oceans. With their increasing acidification, the planet is about to “inevitably” cross a new alert threshold. This crossing contributes to affecting the Earth’s stability, its resilience and its habitability, according to a report by the Potsdam Institute for Climate Impact Research (PIK).
Fifteen years ago, scientists defined nine “planetary boundaries,” physical thresholds that humanity should not exceed if it wants to remain in a “safe operating zone.”
As a result of human activity, six of these “limits” have already been crossed in recent years and, according to a new report published on Monday, a seventh, the acidification of the oceans, is about to be crossed “in the near future”.
The six limits that have been largely exceeded concern climate change, deforestation, loss of biodiversity, the amount of synthetic chemicals (including plastics), the scarcity of fresh water and the balance of the nitrogen cycle (agricultural inputs). Their situation continues to deteriorate, underlines Monday this Planetary Health Check, a health report of the planet that will now be updated every year.
Concerning acidification, this is linked to the absorption of carbon dioxide (CO2) by the oceans: while emissions of this greenhouse gas continue to increase, seawater sees its pH decrease and becomes harmful to many organisms (corals, shellfish, plankton, etc.) and ultimately the entire marine food chain, a phenomenon which also reduces in return the capacity to absorb CO2.
“Even if emissions are reduced rapidly, some level of continued acidification may be unavoidable because of the CO2 already emitted and the response time of the ocean system,” said Boris Sakschewski, a lead author of the Planetary Health Check.
“Therefore, exceeding the limit of ocean acidification seems inevitable in the coming years,” adds this researcher at PIK.
Well below the alert threshold is only the state of the ozone layer, which has been recovering since the ban on harmful substances in 1987. This recovery is expected to take several more decades, the report notes.
Finally, a ninth element – the concentration of fine particles in the atmosphere – is close to the alert threshold, but shows signs of improvement thanks to measures taken in some countries to improve air quality. However, the researchers warn of a risk of deterioration in rapidly industrializing states.
But the more limits are crossed, the greater “the risk of permanently damaging Earth’s life-support functions” and of triggering irreversible tipping points, the researchers warn.
While these nine ecological processes are interconnected, “tackling one requires tackling all”, “a holistic approach” that can be “a chance for sustainable progress”, also underlines the report, which aims to address decision-makers as well as the general public.