The world’s oceans have breached a critical planetary boundary for the first time, with rising acidity driven by fossil fuel use.
The Potsdam Institute for Climate Impact Research’s annual Planetary Health Check confirmed ocean acidity has crossed a threshold that threatens marine ecosystems, making it the seventh of nine planetary boundaries now transgressed.
Since the industrial era, ocean surface pH has dropped by about 0.1 units, representing a 30-40% rise in acidity. This jeopardises species that depend on calcium carbonate, such as corals, molluscs and shellfish, with knock-on effects on salmon, whales and entire food chains.
Scientists warn this trend undermines the oceans’ role in absorbing heat and capturing up to 30% of atmospheric carbon dioxide, raising risks for climate stability, food security and coastal economies.
Levke Caesar of the Planetary Boundaries Science Lab said the findings were alarming: “When I allow myself to connect emotionally to the data, then I am afraid. This really scares me.”
The report highlighted that other breached boundaries, including climate change and biodiversity loss, are also worsening. However, successes such as the Montreal Protocol’s protection of the ozone layer show coordinated global action can work.
Institute director Johan Rockström urged urgent cuts to fossil fuel use: “Even if the diagnosis is dire, the window of cure is still open. Failure is not inevitable; failure is a choice.”
