Michael Donatti and Benoit Bégot
December 4, 2025
Ocean acidification has breached a key ‘planetary boundary’
This video is part of: Centre for Nature and Climate
Acidity in the sea has reached hazardous levels. Even more worryingly, scientists have discovered it crossed this critical threshold 5 years ago, much faster than they had assumed. The authors of a major study led by the UK’s Plymouth Marine Laboratory and the NOAA are sounding a red alert, calling the findings a ‘ticking timebomb’. But what causes ocean acidification? And what does it mean for ecosystems?
A new study has found that ocean acidification has already breached a key planetary boundary. Forty percent of the surface ocean and 60 percent of the subsurface ocean have become dangerously acidic. Scientists say the threshold was crossed five years ago, far earlier than expected.
Acidification happens when oceans absorb carbon dioxide from the atmosphere. This changes the water’s chemical balance, depleting calcium carbonate, which coral and plankton need to build their skeletons. In extreme cases, acidification can even dissolve shellfish shells.
Marine life and human health are both at risk
Plankton and coral reefs play a critical role in marine ecosystems. Plankton support the food chain, and coral reefs shelter 25 percent of marine species. As these foundations weaken, fish stocks may fall, increasing the risk of hunger for millions.
The ocean generates 50 percent of the oxygen all life on Earth relies on and absorbs 90 percent of the planet’s excess heat. It is not just vital for ecosystems but also central to global economies and human well-being.
Cut CO2 and conserve
Reducing carbon emissions is essential to slowing ocean acidification. In the meantime, targeted conservation can protect the most vulnerable marine areas. Scientists are calling this a red alert and a wake-up call to act now.
Watch the video to learn more about the impacts of acidification and what can still be done.
Topics:
Nature and BiodiversityMore on Nature and BiodiversitySee all
More on Nature and Biodiversity
See all
