Coral Crisis

Two species of coral -- elkhorn and staghorn -- have been added to the list of threatened species under the federal Endangered Species Act. Worldwide, coral reefs are threatened by destructive fishing practices, disease, nutrient runoff and other forms of pollution. But the most comprehensive threat may be global warming. Not only do higher ocean temperatures pose dangers to corals already living near their thermal maximum, but excessive carbon dioxide in the atmosphere has also led the oceans to become slightly more acidic. That change in ocean chemistry threatens to undermine the ability of corals to generate their carbonate skeletons.