Coral reefs are already among the marine ecosystems at greatest risk of being destroyed by the effects of climate change. They're the hub of diversity in the oceans. Coral might look like a rock or a rocky plant, but what you're seeing is actually the outer skeleton of a living animal — yes, an animal — that has a stomach, a mouth, and even a sex life. Corals come in all shapes and sizes, twisting from left to right and in a rainbow of colors. They live all over the world, in both warm and cold waters, but they're mostly concentrated around Southeast Asia and the Caribbean. The reefs support a wide array of small living water plants and fish. Without the reef, the plants and fish have no home. And without the plants and fish, the bigger fish in the sea have no food, and so on.
cACRir/ty The IPCC reports that most, if not all, coral reefs will be bleached (meaning ^-¿^ss^y dead) if global average temperatures rise 3.1 degrees Fahrenheit (1.7 degrees Celsius) above 1850 levels — or 1.6 degrees Fahrenheit (0.9 degrees Celsius) above current levels. A sea surface temperature rise of 3.6 to 5.4 degrees Fahrenheit (2 to 3 degrees Celsius) above 1850 temperatures — or 0.4 to 4 degrees Fahrenheit (0.2 to 2.2 degrees Celsius) above current levels — is the danger zone for coral, unless it can adapt. With a temperature rise of 5.4 degrees Fahrenheit (3 degrees Celsius) above 1850 levels — or 4 degrees Fahrenheit (2.2 degrees Celsius) above today's levels — all coral reef systems would die.
Despite the increasing evidence linking climate change to coral reef destruction, you can't easily separate the effects of the climate from other major human pressures, such as pollution and fishing. The Caribbean, for example, has already lost 80 percent of its coral reefs because of other human pressures.
The IPCC predicts that areas covered by cold-water corals, such as those found off the east coast of Canada and the west coast of Norway, will go through a huge drop in productivity by the end of the century. Cold-water corals depend on nutrients that sink from the surface or arrive via ocean currents, so changes in ocean currents could be a threat to their survival.
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