A bulk of the coral reefs across the world is staring at an impending coral bleaching as a fallout of the rising heat in oceans and the environment.

This is despite the Paris Climate accord exceeding its aspiration target of keeping global warming below 2 degrees Celsius. The consequences of intense heat will accelerate coral bleaching by mid-century, says a new study.

The UN-sponsored report warns that if unbridled greenhouse gas emissions are allowed to continue, severe annual bleaching will erode 99 percent of the world's reefs within this century.

The report says coral bleaching would become an annual activity by 2054, if emissions continue at the current rate.

The findings of the research were published in the journal Nature Scientific Reports.

The study asserts that annual coral bleaching will start in 2043, with 5 percent of the reefs being hit within a decade, while another 11 percent facing annual bleaching a decade later. Bleaching spells death for many coral reefs as replenishment takes a minimum of five years.

Beyond the general forecasts, the study has also succeeded in telling where the annual coral bleaching will occur.

It used climate model projections of the world's coral reefs and high-resolution projections to pinpoint exactly where annual coral bleaching will act out.

Facing the brunt of annual bleaching will be the reefs lying closer to the equator, this would extend to more than 75 percent of reefs before 2070.

Ocean Warming

Coral bleaching is an offshoot of ocean warming from excessive heat.

"Bleaching that takes place every year will invariably cause major changes in the ecological function of coral reef ecosystems," said Ruben van Hooidonk, who is the leader of the study and working for the U.S. National Oceanic and Atmospheric Administration.

In his view, the adverse effect of annual bleaching will be the inability of coral reefs in delivering economic functions in terms of goods and services, fisheries and coastal protection, to communities.

"These predictions are a treasure trove for those who are fighting to protect one of the world's most magnificent and important ecosystems from the ravages of climate change," said Erik Solheim, head of UN Environment, reflecting on the utility of the study in preparing for conservation efforts.

Perennial Threat

According to studies, coral reefs are under ecological assault from tourism and overfishing. They have become easy preys of climate change as warming waters are killing them fast.

They are also called underwater cities thanks to the food, income, and coastal protection reefs are providing to millions of people.

They house at least a quarter of all marine life and the economic value generated is around $375 billion per annum from fisheries, coastal protection, and tourism.

Corals are born from the interaction between small animals called corals and zooxanthellae — tiny plants that give the corals great colors of the reefs.

When the water warms up, zooxanthellae retreat from the corals and the host loses its food and color. The coral then turns bone white as heat persists and dies.

At the positive side, if emissions reductions become a reality, that may help many reefs in Australia, the south Pacific, India, Coral Triangle, and the Florida Reef Tract to salvage at least 25 more years before bleaching hits them. This may hasten conservation efforts.

"We are going to need to be much more innovative and proactive if we want to see coral reefs thrive into the next century," noted study co-author Gabby Ahmadia who is a lead marine scientist with World Wildlife Fund.

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