Disappearing Destinations: 37 Places in Peril and What Can Be Done to Help Save Them

Great Barrier Reef
THE GREAT WHITE SCAR: The Great Barrier Reef is showing signs that it needs our help (WestStock)

While astronauts who saw the Great Barrier Reef from space called it a "great white scar upon the earth," most people know it as a natural wonder of the world without equal. It is, of course, made up of vast coral communities, but also mangroves, sea grass, sandy islands, and sponge gardens whose colors even Crayola couldn't replicate. The Reef is also believed to be the epicenter of earth's marine biodiversity.

The endangered dugong, or "sea cow," and humpback whale breed in its warm tropical waters and share the surf with dwarf and minke whales, hammerhead and whale sharks, and over 1,500 other kinds of fish.

To understand what endangers the Great Barrier Reef it helps to know that coral is a sensitive creature, a skeletal animal with algae growing in its tissue. A single coral colony is composed of thousands of individual coral polyps which, like pixels in a photo, combine to form the entire image of the reef. Algae living symbiotically within coral photosynthesizes sunlight, feeding the coral and giving it its color. Healthy reefs are rich green, brown, and yellow.

Coral is what Ray Berkelmans of the Australian Institute of Marine Sciences calls "thermally sensitive." The past several years have included the hottest years ever recorded on the continent and, when hotter-than-average air causes ocean temperatures to rise, the coral suffers. When coral is stressed, which happens often because it thrives only within a narrow temperature range, it begins to shut down. In an effort to survive, its resident algae release toxins, forcing the coral to expel them. Without their algae lifeline, sickly reefs drain of color and "bleach" white. Bleaching isn't necessarily a death sentence for coral, which can bounce back if the ocean cools. But the likelihood of that seems slimmer every year. "Now we're finding that 'unusually warm summers' are happening more often," says Berkelmans.

Published: 17 Jul 2008 | Last Updated: 15 Sep 2010
Details mentioned in this article were accurate at the time of publication


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