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UBC maps increasing rate of coral bleaching in tropics

Too much bleaching can kill coral, shutting down entire ecosystems and leaving communities vulnerable to rising oceans levels

UBC researchers use a measuring tape to take note of coral diversity and size.

UBC Public Affairs/Contributed

UBC researchers use a measuring tape to take note of coral diversity and size.

UBC researchers have mapped out coral bleaching events in the world’s tropics, an important contribution in the effort to save coral reefs.  

In order to create that map, geography professor Simon Donner took 25 years of data (1985-2010) and found the rate of bleaching was about seven times greater in the 2000s compared to the 1990s.

“We took the raw data and interpolated the data to say across the tropics each year, what is the probability that bleaching occurred,” he said.   

“What’s clear is every country in the world that has coral reefs, has experienced the bleaching in our dataset.”

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Bleaching occurs when ocean temperatures rise one to two degrees higher than the maximum summer temperature. Coral reefs can recover from heat waves but if bleaching happens too often, they die, said Donner.

This map of the Caribbean shows where coral bleaching most likely occurred.

Simon Donner/UBC

This map of the Caribbean shows where coral bleaching most likely occurred.

He and his team are working on mapping out data from the last several years but scientists already know it’s not a pretty picture.

“We know that there is even more [bleaching] in this decade,” he said.

Coral reefs are a key resource for countries in the tropics, attracting tourists every year and providing homes for a myriad of marine life.

Reefs also act as storm barriers, protecting entire islands and communities from rising ocean levels and extreme weather patterns.

Because coral bleaching is an event that coral can recover from, it’s difficult to pinpoint exactly how much of it has experienced bleaching in recent years, said Donner.

A commonly cited statistic is that 50 per cent of the world’s coral has died in the past 30 years. Donner says it’s an approximate number and that his research aims to improve the accuracy of that estimate.

He hopes his new database, which includes 79 per cent more reports than the old database, will encourage more scientists to offer their research. That information could help scientists predict where bleaching events will occur next and hopefully, do something to save the world’s coral reefs, he said.

“The planet would not be the same place without them.”

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