Coral Bleaching Event Has Begun, Scientists Say

Rising ocean temperatures have started a bleaching event that scientists say will affect more coral reefs worldwide than any of the previous three. The National Oceanic and Atmospheric Administration and its international partners made the announcement Monday, the New York Times reports. "The increasing frequency and extremity of marine heat waves driven by climate change is testing the tolerance levels of coral reefs," said the head of the Australian Institute of Marine Science. "Climate change is the biggest threat to coral reefs worldwide, and this global confirmation illustrates just how extensive its impact has been across the last 12 months."

Bleaching takes place when stressed corals turn white after losing the symbiotic algae required for survival and begin to starve. The corals can bounce back if conditions improve before long. Mass bleaching has occurred in at least 53 countries and regions in the Atlantic, Pacific, and Indian oceans, with the Atlantic having the worst of it, an expert said. More than 54% of coral areas globally have endured bleaching-level heat stress in the past year, said Derek Manzello of NOAA, who added that the total is increasing about 1% per week. "Now we're just reaching a point in this warming cycle where these events are becoming so extreme and they're just getting worse and worse and worse," Manzello said, per the Washington Post.

Carbon emissions are the drivers of warming oceans and therefore the bleaching, said experts who urged immediate action. Coral reefs are a crucial habitat for marine life, hosting roughly one-fourth of ocean species at some point, with the fish accounting for a vital food source for an estimated 1 billion people. In addition, they protect people from storms and rising sea levels; the value of the coral reefs is estimated at $2.7 trillion annually. The importance of the reefs makes the worsening bleaching "scary," Manzello said. "This should be a global wake-up call," he added. (NOAA has changed its reef alert system as the threat increases.)