A new atlas offers the most comprehensive estimate ever of the size of the world's total coral reefs: 284,300 square kilometers, or about the area of Nevada.
Around the world, coral reefs are in trouble. They've been stressed by warm oceans (ScienceNOW, 25 October 2000), overfishing, and pollution (ScienceNOW, 2 July). To compile what's known about coral reefs, scientists with the United Nations Environmental Program (UNEP) combined wildly disparate data, from recent maps based on satellite imaging to 18th century charts from the voyage of Captain Cook. The atlas covers only reefs in less than 30 meters of water, so the estimate of global reef area is smaller than previous studies have suggested. UNEP focused on such shallow reefs because they're considered to be the most important for marine life and coastline erosion control.
Most of the 428-page World Atlas of Coral Reefs (University of California Press) is a country-by-country accounting of reef area and status. It contains an unusual mix of maps, including those that show the distribution of protected areas, coral species, coral diseases, and commercial dive centers. The atlas is the first global reef survey to compile information about biodiversity, threats to reef health, and conservation efforts to cope with these threats.
"This volume contains a vast summary of material you would expect to find in an atlas, but its value lies more, I think, in its global synthesis," says Charles Sheppard, a marine ecologist at the University of Warwick, United Kingdom. The compilation is an important achievement, he says, because many countries do not know the extent of the coral reefs in their waters.