Coral reefs, long considered one of Earth's richest and most delicate ecosystems, are even more precious than previously thought. The first comprehensive map of our planet's reefs indicates that they collectively cover just about 110,000 square miles, an area about as big as Nevada. That's about half the size that scientists had estimated.
The new atlas is the first attempt to assess the reef's health. "You see the same threats everywhere, even in the most remote places," says Mark Spalding, a senior marine ecologist at the United Nations Environment Program, which produced the new World Atlas of Coral Reefs.
Ove Hoegh-Guldberg, director of the Center for Marine Studies at the University of Queensland in Australia, studies the environmental conditions that reefs need to survive. Rising temperatures, he says, are one of the most insidious threats. If temperature increases seen in the past decade continue, Hoegh-Guldberg predicts that in 50 years coral reefs as we know them will be gone. Short of drastically decreasing our emissions of greenhouse gases, the best thing we can do for the reefs is reduce the amount of pollution they're exposed to, he says: "If you expose a person to a heat wave, you don't want to poison him too."