Dire Warning About Ocean Acidification
November 20, 2013
Human activity is causing Earth’s oceans to grow more acidic at an “unprecedented rate,” threatening the survival of up to 30 percent of all marine species as well the livelihood of millions of people, according to an international report summarizing the current state of scientific knowledge about ocean acidification. In the report, 540 experts in 37 nations concluded that ocean acidification is occuring more rapidly than at any time in the past 300 million years. The report developed from the Third Symposium on the Ocean in a High-CO2 [carbon dioxide] World convened in 2012 by the Biosphere-Geosphere Programme. According to the experts, the primary cause of this radical change in the chemistry of seawater is “the release of atmospheric CO2 by human activities.”
The oceans naturally absorb carbon dioxide from the atmosphere as part of the carbon cycle—the natural movement of carbon between the air, the land, and the oceans. However, the amount of CO2 in the atmosphere has grown by about 40 percent since 1750, at the start of the Industrial Revolution. About one-quarter to one-third of all the CO2 that human beings have released into the atmosphere over the last 250 years has been absorbed by the oceans. When carbon dioxide dissolves into water, it produces carbonic acid. Thus, as the ocean absorbs increasing amounts of carbon dioxide, it becomes more acidic.
Rising acid levels are particulary harmful to ocean creatures that build shells from calcium carbonate, including clams, oysters, mussels, sea urchins, and corals. As the water becomes more acidic, these creatures have a more difficult time building their shells, making them more vulnerable to predators and disease. Ocean acidification also threatens many plankton, the tiny organisms that form the base of most marine food webs. Coral reefs, which provide habitat for many sea creatures, are especially vulnerable. The United Nations Environment Programme puts the economic value of coral reefs at about $170 billion per year. Nearly 500 million people across the globe depend on healthy coral reefs for at least some of their diet. An estimated 30 million of the world’s poorest people depend entirely on coral reef fish for food.
The Arctic and Antarctic oceans are becoming more acidic faster than any other region, symposium scientists said. They calculated that by 2020, species that build their shells from calcium carbonate will be unable to live in about 10 percent of the Antarctic Ocean. By 2100, the entire Antarctic may become inhospital to such animals.
Additional World Book articles:
- Fossil fuel
- Global warming
- Global warming (2012) (a Back in Time article)
- Ocean (2011) (a Back in Time article)
- The Ocean’s Changing Chemistry: Tipping the Balance? (a special report)