Ocean Acidification

The Other CO2 Problem

Increased carbon dioxide is changing the chemistry of the earth’s oceans, threatening marine life

Earth’s atmosphere isn’t the only victim of burning fossil fuels. About a quarter of all carbon dioxide emissions are absorbed by the earth’s oceans, where they’re having an impact that’s just starting to be understood.

Over the last decade, scientists have discovered that this excess CO2 is actually changing the chemistry of the sea and proving harmful for many forms of marine life. This process is known as ocean acidification.

A more acidic ocean could wipe out species, disrupt the food web and impact fishing, tourism and any other human endeavor that relies on the sea.

The change is happening fast — and it will take fast action to slow or stop it. Over the last 250 years, oceans have absorbed 530 billion tons of CO2, triggering a 30 percent increase in ocean acidity.

Before people started burning coal and oil, ocean pH had been relatively stable for the previous 20 million years. But researchers predict that if carbon emissions continue at their current rate, ocean acidity will more than double by 2100.

The polar regions will be the first to experience changes. Projections show that the Southern Ocean around Antarctica will actually become corrosive by 2050.

Corrosive Impacts on Sealife

The new chemical composition of our oceans is expected to harm a wide range of ocean life — particularly creatures with shells. The resulting disruption to the ocean ecosystem could have a widespread ripple effect and further deplete already struggling fisheries worldwide.

Increased acidity reduces carbonate — the mineral used to form the shells and skeletons of many shellfish and corals. The effect is similar to osteoporosis, slowing growth and making shells weaker. If pH levels drop enough, the shells will literally dissolve.

This process will not only harm some of our favorite seafood, such as lobster and mussels, but will also injure some species of smaller marine organisms — things such as pteropods and coccolithophores.

You’ve probably never heard of them, but they form a vital part of the food web. If those smaller organisms are wiped out, the larger animals that feed on them could suffer, as well.

Disappearing Coral Reefs

Delicate corals may face an even greater risk than shellfish because they require very high levels of carbonate to build their skeletons.

Acidity slows reef-building, which could lower the resiliency of corals and lead to their erosion and eventual extinction. The “tipping point” for coral reefs could happen as soon as 2050.

Coral reefs serve as the home for many other forms of ocean life. Their disappearance would be akin to rainforests being wiped out worldwide. Such losses would reverberate throughout the marine environment and have profound social impacts, as well — especially on the fishing and tourism industries.

The loss of coral reefs would also reduce the protection that they offer coastal communities against storms surges and hurricanes — which might become more severe with warmer air and sea surface temperatures due to global warming.

What Can We Do About It?

Combating acidification requires reducing CO2 emissions and improving the health of the oceans. Creating marine protected areas (essentially national parks for the sea) and stopping destructive fishing practices would increase the resiliency of marine ecosystems and help them withstand acidification.

Evidence suggests that coral reefs in protected ocean reserves are less affected by global threats such as global warming and ocean acidification, demonstrating the power of ecosystem protection.

Ultimately, though, reducing the amount of carbon dioxide absorbed into the oceans may be the only way to halt acidification. The same strategies needed to fight global warming on land can also help in the seas.

The acidification of our oceans is the hidden side of the world’s carbon crisis, says Lisa Suatoni, an NRDC ocean scientist, and only reinforces that we need to make changes in how we fuel our world — and we need to do it quickly.

ACID TEST, a film produced by NRDC, was made to raise awareness about the largely unknown problem of ocean acidification, which poses a fundamental challenge to life in the seas and the health of the entire planet. Like global warming, ocean acidification stems from the increase of carbon dioxide in the earth’s atmosphere since the start of the Industrial Revolution.

Watch the complete NRDC video:


This groundbreaking NRDC documentary explores the startling phenomenon of ocean acidification, which may soon challenge marine life on a scale not seen for tens of millions of years. The film, featuring Sigourney Weaver, originally aired on Discovery Planet Green.



Ocean Acidification: The Other CO2 Problem