Great Barrier Reef: Mass decline in 'coral babies', scientists say
89% since unprecedented bleaching events in 2016 and 2017, scientists say.
The events, which damaged two-thirds of the world's largest reef system, are now being blamed for triggering a collapse in coral re-growth last year.
"Dead corals don't make babies," said lead author Prof Terry Hughes, from Queensland's James Cook University.
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"Across the length of the Great Barrier Reef, there was an average 90% decline from historical [1990s] levels of recruitment," co-author Prof Andrew Baird told the BBC.
'Nothing left to replenish the reef'
Prof Baird said the "pretty extraordinary" decline was unexpected. It was most likely the reef's first re-growth problem on a mass scale, he added.
"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," Prof Baird said.
However, the bleaching in 2016 and 2017 affected a 1,500km (900 miles) stretch of the reef.
"Now, the scale of mortality is such that there's nothing left to replenish the reef," Prof Baird said.
The study also found that the mix of baby coral species had changed. It found a 93% drop in Acropora, a species which typically dominates a healthy reef and provides habitats for thousands of other species.
The researchers said coral replenishment could recover over the next five to 10 years if there were no future bleaching events.
However, given current estimates, this likelihood was "almost inconceivable", said Prof Baird.
"We've gotten to the point now where local solutions for the reef are almost pointless - the only thing that matters is action on climate change," Prof Baird said.
https://www.bbc.com/news/world-australia-47809500