Expert Assessment: Ocean Acidification May Increase 170 Percent This Century

"Nov. 13, 2013 — In a major new international report, experts conclude that the acidity of the world's ocean may increase by around 170% by the end of the century bringing significant economic losses. People who rely on the ocean's ecosystem services -- often in developing countries -- are especially vulnerable."

A group of experts have agreed on their ‘levels of confidence’ about ocean acidification during the Third Symposium on the Ocean in a High CO₂ World in September 2012. The summary will be revealed in November 18, 2013. Experts agree that ocean acidification will affect marine life and subsequently lead to human consequences as well, specifically in economic losses because of a decline in shellfish.

Ulf Riebsel, one the lead coauthors of the summary, says that if we continue to emit CO2 the way that we do now, we must prepare for economic and ecosystemic losses. But, if the rate of CO2 gas were reduced, then this would slow acidification. An outcome that was emphasized was that the erosion of coral reefs could outpace the building of coral reefs this century. Another outcome is that coral reefs in the deep sea may become unsustainable. Wendy Broadgate mentions that there are many other consequences that the use of CO2 brings along. For example warming and deoxygenation are caused by a rise in CO2 emissions. She stresses that it is important to use less CO2 gas, but this will not make the ocean better; there are other problems such as overfishing.

There are three levels of confidence about the effects of ocean acidification, very high confidence, high confidence, and medium confidence. This is a summary from the article:

Very high confidence

• Ocean acidification is caused by carbon dioxide emissions from human activity to the atmosphere that end up in the ocean.

• The capacity of the ocean to act as a carbon sink decreases as it acidifies

• Reducing carbon dioxide emissions will slow the progress of ocean acidification.

• Anthropogenic ocean acidification is currently in progress and is measurable

• The legacy of historical fossil fuel emissions on ocean acidification will be felt for centuries.

High confidence

• If carbon dioxide emissions continue on the current trajectory, coral reef erosion is likely to outpace reef building some time this century.

• Cold-water coral communities are at risk and may be unsustainable.

• Molluscs (such as mussels, oysters and pteropods) are one of the groups most sensitive to ocean acidification.

• The varied responses of species to ocean acidification and other stressors are likely to lead to changes in marine ecosystems, but the extent of the impact is difficult to predict.

• Multiple stressors compound the effects of ocean acidification.

Medium confidence

• Negative socio-economic impacts on coral reefs are expected, but the scale of the costs is uncertain.

• Declines in shellfisheries will lead to economic losses, but the extent of the losses is uncertain.

• Ocean acidification may have some direct effects on fish behaviour and physiology.

• The shells of marine snails known as pteropods, an important link in the marine food web, are already dissolving.