The world’s oceans have crossed a critical threshold for acidity, threatening marine life and global climate stability, scientists warn.
According to the Potsdam Institute for Climate Impact Research, ocean surface pH has dropped by about 0.1 units since the industrial era, a 30-40% increase in acidity. This marks the first time oceans have failed their planetary health check, making them the seventh of nine planetary boundaries now transgressed.
Cold-water corals, tropical reefs and Arctic ecosystems are at particular risk, with cascading effects for oysters, clams, salmon and whales. Human food security and coastal economies are also vulnerable.
Ocean acidification stems from fossil fuel emissions. When carbon dioxide dissolves in seawater, it forms carbonic acid, reducing calcium carbonate availability that many organisms need to form shells or skeletons. Scientists fear this will also weaken oceans’ ability to absorb heat and draw down carbon, undermining their role as climate stabilisers.
The report highlights worsening trends in all previously breached boundaries, including climate change and biosphere integrity. Levke Caesar of the Planetary Boundaries Science Lab described the data as “really scary”, warning that urgent fossil fuel reductions, pollution cuts and better fisheries management are essential.
While the outlook is grim, researchers stress progress is possible. International cooperation has already succeeded in preventing ozone layer collapse and reducing aerosol emissions. Johan Rockström, director of the institute, said: “Failure is not inevitable; failure is a choice. A choice that must and can be avoided.”
