Ocean acidification is another catastrophic form of environmental damage that is resulting from the continued burning of fossil fuels — one that is only now being understood by scientists. Since the industrial revolution, people have added two hundred and fifty billion tons of carbon to the atmosphere by burning fossil fuels. This has changed the concentration of carbon dioxide in the air. The air now contains 380 parts per million CO2, which is 40 percent higher than prior to the industrial revolution. This change in the chemistry of the atmosphere causes the greenhouse effect.
Scientists have recently understood that the increased concentration of CO2 in the air is also changing the pH of the oceans. About half of the total carbon dumped into the air by humans in the last 150 years has been absorbed by the oceans. If not for oceans acting as a “carbon sink” the concentration of CO2 in the air would be as high as 500 parts per million, not the current 380 ppm. Because 70 percent of the earth is covered with water, up to 90 percent of the CO2 humans pour into the atmosphere will eventually be absorbed by the oceans.
When CO2 dissolves into water, it forms carbonic acid (H2CO3). This process has already changed the pH of the water near the surface of the oceans by .1. Seawater is naturally alkaline, with a pH ranging from 7.8 to 8.5. (A pH of 7 is neutral, neither acid nor basic.)
Changing the pH of the oceans risks causing a collapse of life in the oceans, since a wide variety of ocean life is sensitive to the pH of ocean water. Many ocean creatures — from clams to coral reefs — build their shells out of calcium carbonate — CaCO3. The oceans contain massive amounts of calcium carbonate dissolved in the water. When the pH of the ocean goes down, it reduces the supply of CaCO3 dissolved in the water (the saturation rate), and makes it harder for animals to build shells. If the CaCO3 supply in the water gets too low, existing shelled creatures and reefs actually begin to dissolve. Scientists forecast that if carbon continues to be released by humans at the current rates, CO2 in the air could reach 650 parts per million by 2075, which would reduce the supply of CaCO3 in the ocean so much that all shelled creatures would dissolve. Since the ocean food chain is largely dependent on creatures built out of CaCO3, the disappearance of these animals could lead to a collapse of life in the oceans.
There is historical precedence for what humans are currently doing to the climate. About 50 million years ago, for reasons that are not currently understood, huge amounts or carbon was released into the atmosphere. This event is called the Paleocene-Eocene Thermal Maximum (PETM). As a result of the extra carbon, temperatures rose dramatically and there were mass extinctions of animals. In the oceans, many shelled animals also went extinct because the pH of the oceans changed and dissolved shelled creatures. The ocean floor is normally covered with the shells of dead, shelled animals. At the time of PETM, however, no shells are found — core samples during this time are a band of clay between thick layers of CaCO3. Scientists believe the PETM took place over one thousand to ten thousand years — by contrast, carbon is now being released by humans as much as thirty times faster than during PETM.
The key to avoiding this future is a zero emissions future. Any carbon humans release into the air by burning fossil fuels goes somewhere. There is now wide understanding that CO2 in the air causes problems with the climate. But most of the carbon will eventually end up in the ocean — keep your mind on the coral reefs next time you turn on your space heater or put your clothes in the dryer. . .