Australia’s coral-bleaching crisis

spokesman Richard Leck. When coral is stressed by changes in temperature and acidity, it expels the symbiotic algae living in its tissue that provide it with essential nutrients. This causes brilliantly colored reefs to turn bone white. A resilient reef can recover or adapt if conditions return to normal or stabilize, but if temperatures rise too quickly or algae loss is prolonged, coral eventually dies. Ocean temperatures in northern Australia have averaged 1.8 degrees Fahrenheit above normal since January, but it’s more than a localized crisis—climate change and a strong El Niño have been heating seas all around the world, posing a threat to coral reefs almost everywhere. Marine ecologist Nick Graham of Lancaster University in England says the current bleaching event compares to the most severe on record, which wiped out 16 percent of the world’s reefs from 1997 to ’98. “This is the big one that we’ve been waiting for,” he tells The Guardian (U.K.). But Graham believes the situation isn’t hopeless. “The real question mark is how frequent these events are going to be. If it’s another 18 to 20 years until we get the next one, then a lot of reefs will have time to bounce back.”