Great Barrier Reef coral bleaching
Ocean Acidification Has Quietly Crossed a Planetary Boundary — And It’s Worse Than We Thought
Fresh analysis from a global team of researchers—including the UK’s Plymouth Marine Laboratory (PML), NOAA, and Oregon State University—reveals a troubling truth: ocean acidification has already breached a planetary boundary, and alarmingly, this occurred around five years ago.
The planetary boundary framework defines Earth’s “safe operating space,” with nine environmental limits. Until now, ocean acidification had remained within this zone—barely. New findings, however, show that by about 2020, global seawater conditions had exceeded the boundary, defined as a >20 % decline in calcium‑carbonate saturation relative to pre‑industrial times.
Disturbingly, at depths of 200 m—where much ocean life thrives—60 % of waters have passed that threshold.
This creeping acidity threatens organisms that build calcium‑carbonate shells—corals, molluscs, crustaceans, pteropods, oysters—and the ecosystems and economies that depend on them.
As PML’s marine ecologist and Global Ocean Acidification Observing Network co‑chair Prof Steve Widdicombe starkly warns: “Ocean acidification isn’t just an environmental crisis —it’s a ticking time‑bomb for marine ecosystems and coastal economies.”
Deep Waters, Deeper Problems
Lead author Helen Findlay from PML highlights that acidification isn’t confined to surface waters. She notes: “Most ocean life doesn’t just live at the surface … the waters below are home to many more different types of plants and animals. Since these deeper waters are changing so much, the impacts … could be far worse than we thought.”
Indeed, coral reef habitats are already shrinking: a 43 % habitat loss in tropical/subtropical corals, up to 61 % for polar pteropods, and 13 % for coastal bivalves.
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Lower ocean pH hampers shell formation, metabolic functions, reproductive success, and resilience. The Guardian underscores that acidification is accelerating, exacerbating threats to biodiversity and coastal industries like oyster farming—already suffering in the Pacific Northwest .
Marine ecologist Widdicombe tells Oceanographic Magazine: “If we could see ocean acidification, we’d be way more scared. … Couple ocean acidification with warming temperatures … you’ve got a way bigger problem than plastics.”
What’s Being Done—and What Still Needs to Happen
The study, published in Global Change Biology, combines ice‑core chemistry, historical ocean samples, and advanced modeling to track trends over 150 years .
Researchers advocate for:
- Deep CO₂ emissions cuts to halt further acidification.
- Targeted conservation of reefs and vulnerable habitats.
- Upping acidification on policy agendas—it’s still largely sidelined.
Some are even exploring local fixes—like alkalinity enhancement—but scientists stress these remain unproven, and the real solution is still cutting fossil fuels out of our diet. Some companies like Make Sunsets in the US is going ahead and geo-engineering our planet, to the ire of ocean conservationists –- as we write here in this article.
Ocean acidification is dubbed the “evil twin” of climate change—and it has stealthily crossed a planetary limit, with cascading impacts on every layer of marine life, from shellmakers and corals to coastal economies. Professor Steve Widdicombe’s warning rings true: humanity is “gambling with both biodiversity and billions in economic value every day that action is delayed.”
We’re out of time. Reducing CO₂ emissions—and integrating acidification into global climate and biodiversity strategies—is no longer optional; it’s essential for the health of our oceans and ourselves. Greta Thunberg, can you come back to work?
