The world’s oceans have officially failed a key planetary health check for the first time, according to the Potsdam Institute for Climate Impact Research. Ocean acidity has crossed a critical threshold for marine life, making it the seventh of nine planetary boundaries now transgressed.
Since the industrial era, surface pH has fallen by about 0.1 units, a 30–40% increase in acidity. This threatens coral reefs, Arctic marine ecosystems, and cold-water corals, while also weakening the ocean’s role as a carbon sink and heat absorber. Species such as oysters, clams, and molluscs are directly impacted, while salmon, whales, and other predators are indirectly at risk, creating broader dangers for food security and coastal economies.
The changes are primarily driven by fossil fuel burning, which increases carbon dioxide in the atmosphere. When absorbed by the ocean, it forms carbonic acid, reducing the calcium carbonate that many species rely on for shells and skeletons. Scientists warn that this could diminish the oceans’ capacity to draw down 25–30% of atmospheric CO₂.
Researchers stress urgent action is still possible, especially through reducing fossil fuels, tackling pollution, and better fisheries management. Levke Caesar of the Planetary Boundaries Science Lab said the findings are deeply concerning: “When I allow myself to connect to it emotionally, then I am afraid. This really scares me.”
The report highlights that global cooperation has already succeeded in protecting the ozone layer and reducing aerosol pollution. Johan Rockström, director of the institute, said: “Even if the diagnosis is dire, the window of cure is still open. Failure is not inevitable; failure is a choice.”
