Potsdam Institute - We Have Now Transgressed 7 Of 9 Planetary Boundaries As Ocean Acidity Hits Critical Level

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The world’s oceans have failed a key planetary health check for the first time, primarily due to the burning of fossil fuels, a report has shown. In its latest annual assessment, the Potsdam Institute for Climate Impact Research said ocean acidity had crossed a critical threshold for marine life. This makes it the seventh of nine planetary boundaries to be transgressed, prompting scientists to call for a renewed global effort to curb fossil fuels, deforestation and other human-driven pressures that are tilting the Earth out of a habitable equilibrium.

The report, which follows earlier warnings about ocean acidity, comes at a time of record‑breaking ocean heat and mass coral bleaching. Oceans cover 71% of the Earth’s surface and play an essential role as a climate stabiliser. The new report calls them an “unsung guardian of planetary health”, but says their vital functions are threatened. The 2025 Planetary Health Check noted that since the start of the industrial era, oceans’ surface pH has fallen by about 0.1 units, a 30-40% increase in acidity, pushing marine ecosystems beyond safe limits.

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Near the bottom of the food chain, this directly affects species like oysters, molluscs and clams. Indirectly, it harms salmon, whales and other sea life that eat smaller organisms. Ultimately, this is a risk for human food security and coastal economies. Scientists are concerned that it could also weaken the ocean’s role as the planet’s most important heat absorber and its capacity to draw down 25-30% of the carbon dioxide in the atmosphere. Marine life plays an important role in this process, acting as a “biotic bump” to sequester carbon in the depths.

In the report, all of the other six breached boundaries – climate change, biosphere integrity, land system change, freshwater use, biogeochemical flows, and novel entities – showed a worsening trend. But the authors said the addition of the only solely ocean-centred category was a alarming development because of its scale and importance.

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https://www.theguardian.com/environment/2025/sep/24/worlds-oceans-fail-key-health-check-as-acidity-crosses-critical-threshold-for-marine-life

Potsdam Institute report:

https://www.planetaryhealthcheck.org/