The world’s coral reefs are dying. It doesn’t take a trained eye to see the draining of color that results when the corals, stressed by heat due to global warming, expel the algae they rely upon for food that also provides their signature hues. It’s a death knell as well for reef fish.

Reefs have always grappled with destructive fishing practices, sediment and nutrient runoff, coral mining, tourism and coastal development. Scientists say the bleaching process is now accelerating. The World Resources Institute reports that nearly three-quarters of all ocean reefs are at risk of extreme degradation, on top of the 20 percent already lost or damaged beyond repair. Oceanographers think that all reefs will be at risk by 2050 because of increasingly acidified seas, the result of increasing levels of carbon dioxide in the atmosphere.

Coral reefs, covering less than 1 percent of the ocean floor, harbor 25 percent of the ocean’s biodiversity and are home to more than 4,000 species of fish. In developing countries, reefs account for nearly 25 percent of all fishing areas, feeding millions of people.

Scientists stress that it is more important than ever to control manmade factors such as overfishing and pollution to aid in corals’ survival.

Sources: The New York Times and U.S. National Oceanic and Atmospheric Administration