One-Fifth of Coral Reefs Lost, Rest Threatened by Climate Change and Human Activities

Alice McKeown | May 07, 2009

About one-fifth of the world’s coral reefs have already been lost or severely damaged, while another 35 percent could be lost within 10–40 years, according to the latest review by the Global Coral Reef Monitoring Network.1 The review contained mixed news: the number of coral reefs considered at low risk stood at 46 percent, up from 30 percent only four years ago, but the number of effectively lost reefs remained constant during the same period—although this figure was double the 10 percent lost or severely damaged in the first global estimate in 1992.2 (See Figure 1.) Notably, the recent threatened reef estimates do not take into account risks from climate change; when these are included, all coral reefs are at danger and widespread mortality is predicted.3

Coral reefs in Asia and the Indian Ocean are most at risk, with 54 percent either lost or critically threatened and another 25 percent moderately threatened.4 (See Figure 2.) This marks a worsening trend since 1998.5 Southeast Asia, which contains the highest biodiversity of all coral reefs as well some of the world’s highest population densities, has already lost 40 percent of its reefs (36,680 square kilometers).6 (See Table 1.)

The wider Caribbean region also has a significant portion of at-risk coral reefs, including 38 percent either lost or critically threatened and 24 percent moderately threatened.7 A survey completed in 2008 found that reefs in the area were in poor or fair condition and that threats like tropical storms, tourism, and coastal development have grown consistently over the last 10–25 years.8

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