Tuesday, September 23, 2008

It's not about the heat...

In the scientific community most people I know believe that global warming is a real phenomenon caused by humans starting with the industrial revolution. However, not everyone I know is in the scientific community, and many don't fully believe any notion of human-caused global warming. Well, we can have that argument another day, because it's not the warming that matters - it's the carbon dioxide.

Any marine scientist can tell you that carbon dioxide has a direct effect on salt water. When salt water absorbs the carbon dioxide gas, it reacts with ions in the water to break down into carbonic acid. The more carbon dioxide we release into the atmosphere, the more acid there is in the ocean, changing the pH of ocean water. The pH of the water controls a lot of processes, including the one by which corals and plankton create their calcium carbonate skeletons. Lower the pH too much and calcium carbonate dissolves, and we'll have an end to the ocean food chain as we know it.

Since the ocean seems so big, you might figure that there's enough water that our carbon dioxide production makes little impact. However, that's just not the case. As chemical oceanographers Long Cao and Ken Caldeira of the Carnegie Institution's Department of Global Ecology in the journal Geophysical Research Letters, ocean acidification could devastate coral reefs and other marine ecosystems even if atmospheric carbon dioxide stabilizes at 450 ppm (well below that of many climate change forecasts).

"Before the industrial revolution, over 98% of warm water coral reefs were surrounded by open ocean waters at least 3.5 times supersaturated with aragonite [the biotic form of calcium carbonate]" says Cao. "But even if atmospheric CO2 stabilizes at the current level of 380 ppm, fewer than half of existing coral reef will remain in such an environment. If the levels stabilize at 450 ppm, fewer than 10% of reefs would be in waters with the kind of chemistry that has sustained coral reefs in the past."

The story for the poles is no different. "At atmospheric CO2 levels as low as 450 ppm, large parts of the Southern Ocean, the Arctic Ocean, and the North Pacific would experience a rise in acidity that would violate US Environmental Protection Agency water quality standards." The shells of most organisms would dissolve, destroying the base of the food chain for one of the most productive ecosystems on earth.

"If current trends in CO2 emissions continue unabated," says Caldeira, "in the next few decades, we will produce chemical conditions in the oceans that have not been seen for tens of millions of years. We are doing something very profound to our oceans. Ecosystems like coral reefs that have been around for many millions of years just won't be able to cope with the change."

So you still think our carbon dioxide emissions aren't important? Think about how much we rely on the animals and plants in the ocean. Commercial fish species would plummet even more than they already have, and would likely go extinct without the basis of their food web for sustenance. That is not even accounting for the economic tourism losses that coral reef destruction would have. So even if you don't believe in global warming, believe this: we are raising the concentration of carbon dioxide in the atmosphere, and if we continue to do so, marine life as we know it will simply cease to exist.