“Our results show the ability of the Great Barrier Reef to recover — its resilience — is compromised compared to the past, because there are fewer babies, and fewer large breeding adults,” Dietzel said.
Bob Richmond, a research professor and director of the Kewalo Marine Laboratory at the University of Hawaii at Manoa, called the study “a really excellent piece of work,” with the most comprehensive research on Great Barrier Reef coral populations that he’s seen.
“What they’re showing is these demographic changes are occurring on a regional scale … on reef slopes that make it difficult for coral reefs to persist over time,” Richmond said. In his long experience of visiting and researching reefs around the world, “if I don’t see one-year-old, two-year-old, three-year-old corals, I know that reef is dead. It just doesn’t know it yet.”
Although half of the Great Barrier Reef’s loss of abundance happened over three decades, Richmond said the world doesn’t have three more decades before the rest potentially disappears.
“The problem is it’s an accelerated loss,” he said. “It’s hard to have a crystal ball and say a date. Scientists are always trying to be careful, but if we don’t act meaningfully in the next five years, we will not have vital and vibrant coral reefs as a legacy for future generations.”
There is hope in Australia and other reef formations around the world, such as in Indonesia, said Gabby Ahmadia, director of ocean science at the World Wildlife Fund. Some coral is developing a resistance to rising temperatures and even acidification.
Ahmadia looks at coral reef conservation as if it were a management portfolio, with high and low risks. Reducing pollution and fish harvests on reefs is a reliable, low-risk solution for governments to consider. At the high end are attempts to harden reefs in labs and desperate heaves such as blocking sunlight and cooling water.
“We work in Indonesia and reefs haven’t been hit as hard there,” Ahmadia said optimistically. The peril faced by coral “really varies,” she said. “There are a lot of studies predicting the future. I don’t think we know.”
But her optimism only goes so far if aggressive action isn’t taken.
“A lot of people say 90 percent of the coral loss will happen by 2050,” she said.
Darryl Fears, October 2020