Researchers have found that ocean acidification entered a “danger zone” in 2020, suggesting increased carbon dioxide levels have caused Earth to breach another planetary boundary.
The new study suggests our planet’s oceans are becoming too acidic to remain healthy. (Image credit: Philip Thurston via Getty Images).
Earth’s oceans are in worse condition than scientists thought, with acidity levels so high that our seas may have entered a “danger zone” five years ago, according to a new study.
Humans are inadvertently making the oceans more acidic by releasing carbon dioxide (CO2) through industrial activities such as the burning of fossil fuels. This ocean acidification damages marine ecosystems and threatens human coastal communities that depend on healthy waters for their livelihoods.
Previous research suggested that Earth’s oceans were approaching a planetary boundary, or “danger zone,” for ocean acidification. Now, in a new study published Monday (June 9) in the journal Global Change Biology, researchers have found that the acidification is even more advanced than previously thought and that our oceans may have entered the danger zone in 2020.
The researchers concluded that by 2020, the average condition of our global oceans was in an uncertainty range of the ocean acidification boundary, so the safety limit may have already been breached. Conditions also appear to be worsening faster in deeper waters than at the surface, according to the study.
“Ocean acidification isn’t just an environmental crisis — it’s a ticking time bomb for marine ecosystems and coastal economies,” Steve Widdicombe, director of science and deputy chief executive at Plymouth Marine Laboratory, a marine research organization involved in the new study, said in a statement. “As our seas increase in acidity, we’re witnessing the loss of critical habitats that countless marine species depend on and this, in turn, has major societal and economic implications.”
In 2009, researchers proposed nine planetary boundaries that we must avoid breaching to keep Earth healthy. These boundaries set limits for large-scale processes that affect the stability and resilience of our planet. For example, there are boundaries for dangerous levels of climate change, chemical pollution and ocean acidification, among others.
A 2023 study found that we had crossed six of the nine boundaries. The authors of that study didn’t think the ocean acidification boundary had been breached at the time, but they noted it was at the margin of its boundary and worsening.
Katherine Richardson, a professor at the Globe Institute at the University of Copenhagen in Denmark who led the 2023 study and was not involved in the new study, told Live Science that she was “not at all surprised” by the new findings.
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What causes ocean acidification?
Ocean acidification is mostly caused by the ocean absorbing CO2. The ocean takes up around 30% of CO2 in the atmosphere, so as human activities pump out CO2, they are forcing more of it into the oceans. CO2 dissolves in the ocean, creating carbonic acid and releasing hydrogen ions. Acidity levels are based on the number of hydrogen ions dissolved in water, so as the ocean absorbs more CO2, it becomes more acidic.
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LiveScience, 12 june 2025. Press release.
