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ocean acidification
'Red Alert' as 7th of 9 Planetary Boundaries On Verge of Being Breached: Report
The authors found that safe planetary boundaries had already been crossed for the climate, freshwater, land use, biogeochemical flows, novel entities, and biosphere integrity—in keeping with a study in Science Advances last year. They found a "clear trend towards further transgression"—moving deeper into the danger zone, where irreversible tipping points are more likely to be triggered—in each of the six categories.
"Our updated diagnosis shows that vital organs of the Earth system are weakening, leading to a loss of resilience and rising risks of crossing tipping points," Levke Caesar, a PIK climate physicist lead author of the report, said in a statement that announced a "red alert."
The health check also showed that ocean acidification, a seventh category, has reached a dangerous precipice, putting the foundations of the marine food web at risk. Ocean acidification, which can threaten coral reefs and phytoplankton populations, is caused by the buildup of carbon dioxide from burning fossil fuels and other human activities.
Caesar said a "safe operating space" threshold for acidification could be crossed in the next few years.
"Looking at the current evolution, I'd say it’s really, really difficult to prevent that [boundary] crossing," she told Mongabay.
A graphic shows the status of nine environmental categories, four of which have been broken down into two control variables. Image from Planetary Health Check 2024. Design by Globaïa.
PIK director Johan Rockström, a co-author of the new report, helped develop planetary boundary research in the late 2000s. In a seminal 2009 paper in Nature, he and his co-authors found that three of the nine boundaries had already been crossed. That number has gradually gone up based on a series of studies over the last decade.
The planet boundary framework, which is often connected to the degrowth movement, emphasizes that the categories are interconnected.
"The interconnectedness of [planetary boundary] processes means that addressing one issue, such as limiting global warming to 1.5°C, requires tackling all of them collectively," the new report says.
Boris Sakschewski, a climate scientist who, along with Caesar, is a lead author of the report said that, "We know that all planetary boundary processes act together and each one needs protection to protect the whole system."
The consequences of continued ocean acidification, which is primarily measured by aragonite saturation, would be severe, the report warns.
Ocean acidification is approaching a critical threshold, with significant declines in surface aragonite saturation, particularly in high-latitude regions like the Arctic and Southern Ocean. These areas are vital for the marine carbon pump and global nutrient cycles, which support marine productivity, biodiversity, and global fisheries. The growing acidification poses an increasing threat to marine ecosystems, especially those reliant on calcium carbonate for shell formation.
Some researchers believe that the ocean acidification threshold has already been crossed, especially given regional variability, with cooler polar waters absorbing more carbon dioxide, causing a faster drop in pH levels.
The report was written with a general audience in mind and is not peer-reviewed, though it's based on peer-reviewed studies, the authors said.
The final pages of the report present solutions, especially agricultural. A radical overhaul of the global food system, heavily dependent on fertilizer and other harmful inputs, will be necessary to reverse the disturbing trends documented in the report, the authors wrote.
"Sometimes overlooked compared to the impacts of energy production and consumption—particularly the use of fossil fuels—the food systems we depend on are among the largest drivers of environmental degradation. The global food system is the single largest driver behind the transgression of multiple planetary boundaries," the report says.
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