New Delhi: The window for saving the world’s coral reefs that are under siege from global warming is rapidly closing, said a latest study published on Thursday in noted international journal Science.

For the study, an international team of researchers measured the “escalating rate of coral bleaching at locations throughout the tropics over the past four decades".

The study documents a “dramatic shortening of the gap between pairs of bleaching events, threatening the future existence of these iconic ecosystems and the livelihoods of many millions of people".

Due to rising global temperatures, oceans are getting warmer, which can result in coral bleaching. When water is too warm, corals expel algae living in them causing the corals to turn completely white, and this phenomenon is called coral bleaching.

“The time between bleaching events at each location has diminished five-fold in the past 3-4 decades, from once every 25-30 years in the early 1980s to an average of just once every six years since 2010," says study’s lead author Terry Hughes, director of ARC Centre of Excellence for Coral Reef Studies (Coral CoE) in Australia.

“Before the 1980s, mass bleaching of corals was unheard of, even during strong El Niño conditions, but now repeated bouts of regional-scale bleaching and mass mortality of corals has become the new normal around the world as temperatures continue to rise," Hughes added.

The study’s co-author Andrew Baird of Coral CoE said, “Coral bleaching is a stress response caused by exposure of coral reefs to elevated ocean temperatures."

“When bleaching is severe and prolonged, many of the corals die. It takes at least a decade to replace even the fastest-growing species," he added.

Dr C. Mark Eakin of US’s National Oceanic & Atmospheric Administration said, “Reefs have entered a distinctive human-dominated era—the Anthropocene."

“The climate has warmed rapidly in the past 50 years, first making El Niños dangerous for corals, and now we’re seeing the emergence of bleaching in every hot summer," Eakin added.

Explaining further, Hughes said, “For example, the Great Barrier Reef has now bleached four times since 1998, including for the first time during back-to-back events in 2016 and 2017, causing unprecedented damage. Yet the Australia government continues to support fossil fuels."

“We hope our stark results will help spur on the stronger action needed to reduce greenhouse gases in Australia, the United States and elsewhere," added Hughes.

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