This undated handout photo released on April 20 shows a diver checking the bleached coral at Heron Island on Australia’s Great Barrier Reef. (XL Catlin Seaview Survey/Agence France-Presse via Getty Images)

THE WORLD’S coral is in trouble. Coral reefs support animal and human communities, underpinning ocean food chains and breaking rough surf as it approaches land. But humanity is doing a poor job of keeping these crucial organisms healthy, and the past year has been particularly bad. Australian surveys of the Great Barrier Reef have found signs of bleaching on more than 93 percent of its corals — an antiseptic white replacing the brilliant hues associated with healthy coral formations. A third of the world’s reefs are at risk, the New York Times reports.

This year seems to be particularly bad because of a strong El Niño and other ocean warming blips. These temperature anomalies appear to be stressing corals, and many reefs might not recover once the seas cool. Worse, these blips foreshadow what conditions might be like permanently as global warming worsens.

Many factors contribute to poor reef health. One is agricultural and urban runoff. Another is abusive fishing practices, such as dynamiting the seafloor to immobilize otherwise elusive sea life. These damage coral directly or cloud the water and thus inhibit the photosynthesis that sustains reefs. Better rules and better enforcement, particularly among major Pacific and Caribbean nations, would help.

Global warming poses a dual threat. First is ocean warming, which appears to throw off the delicate balance between the polyps that build coral reefs and the algae that provide the necessary oxygen and energy.

The second threat is the steady acidification of the ocean. This is not a matter of climate change per se, but rather a direct result of more carbon dioxide in the atmosphere. Even if the world does not warm as much as scientists fear, the oceans will become steadily more acidic as they absorb the carbon dioxide that humans have been spewing. Relatively acidic ocean conditions make it difficult for coral organisms to build the calcium shells that make up their dramatic undersea formations, and they weaken the structures the organisms do create.

There is no easy fix for these problems. Scientists are experimenting with speeding up coral evolution, figuring out how to adapt corals so that they can survive in stressful conditions. Researchers, for example, have examined algaes that can resist extremely high water temperatures in the Persian Gulf and corals that stand up better to the acidifying ocean in Palau. It may not be as easy as transplanting one brand of coral or algae from one place to another. The strategy also raises questions about the type and degree of humanity’s intervention into the natural world. But letting coral die off is a worse option. Scientists are also looking at engineering more favorable conditions for existing species, perhaps by shading coral reefs.

As researchers race to keep coral reefs alive, the rest of us should be working to minimize the potential problem. That means moving away from the fossil fuels that are responsible for changing the atmosphere’s chemistry.