‘Dead Corals Don’t Make Babies’

New Great Barrier Reef Coral Growth Declined 89% After Back-to-Back Bleaching Events

photo:Coral bleaching at Lizard Island on the Great Barrier Reef in March 2016. The Ocean Agency / XL Catlin Seaview Survey / Richard Vevers

The back-to-back coral bleaching events that damaged two-thirds of Australia's Great Barrier Reef in 2016 and 2017 have had a lasting impact on the health of the largest living structure on earth.

A study published in Nature Wednesday found that the death of corals in 2016 and 2017 has significantly decreased the ability of new corals to grow and thrive. In 2018, there has been an 89 percent decline in the number of new corals on the reef compared to the historic record.

"Dead corals don't make babies," lead author and James Cook University professor Terry Hughes said, as BBC News reported.

The researchers, from the ARC Center of Excellence for Coral Reef Studies in Australia, were surprised by the extent of the decline in new corals. It was the first time they had observed such a decline on the reef.

"We thought the Barrier Reef was too big to fail," ARC chief investigator Andrew Baird told The New York Times, "but it's not."

Baird added that the study was the first to document the collapse of the processes of an oceanecosystem.

Bleaching occurs when warm water forces corals to expel the algae that gives them color and nutrients. Reefs can recover from such events, but it takes about a decade. The Great Barrier Reef has suffered four since 1998 and, if greenhouse gas emissions continue at current levels, there could be two bleaching events every decade beginning in 2035.

The extent of the most recent bleaching events — covering 900 miles of reef — also made it harder for baby corals to replenish impacted coral populations, BBC News explained.

"Babies can travel over vast distances, and if one reef is knocked out, there are usually plenty of adults in another reef to provide juveniles," Baird told BBC News. "Now, the scale of mortality is such that there's nothing left to replenish the reef."

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