The Great Barrier Reef Has Been Forever Changed By Global Warming, Scientists Warn

A bleak new study describes the profound damage that climate change has wreaked on Australia’s Great Barrier Reef. Rising temperatures in 2016 “cooked” swathes of corals, the scientists found, causing the catastrophic die-off of almost 30 percent of the world’s largest coral reef system.

Global warming has already radically — and possibly permanently — transformed the reef’s ecology, according to the study, published Wednesday in the journal Nature. If action is not taken promptly and comprehensively to curb warming, it could be “game over ” for the reef, scientists warned.

“It’s catastrophic,” Sarah Perkins-Kirkpatrick, a New South Wales-based climate researcher who was not involved in the new study, told Australia’s ABC News after reviewing the research. “There might have been a glimmer of hope that it wasn’t as bad or might recover faster than we thought. But this paper made the reality very present. The bleaching will forever change the Barrier Reef.”

The extent of the coral die-offs in 2016  — and another severe bleaching event in 2017 — had already been known to scientists, but the new research chronicled specifically how rising temperatures had affected different reef species and the reef’s ecological health at large.

The study’s authors said they were alarmed by their findings.

Though some coral species proved more resilient to rising temperatures, some died much more rapidly than expected.

“The conventional thinking is that after bleaching, corals died slowly of ... starvation. That’s not what we found. We were surprised that about half of the mortality we measured occurred very quickly,” Terry Hughes, the author’s lead author, told The Guardian .

Hughes said some corals, such as branching staghorn corals and table corals, had essentially been “cooked” to death by rising temperatures and had suffered staggering rates of mortality.

“There’s a small number of species that are very robust to heat stress and they’ve survived quite well. On the other hand, the so-called losers [had] mortality rates of 90 percent or more in the worst-affected portion of the reef,” Hughes told ABC News.

With coral bleaching events expected to become ever more frequent  as global temperatures rise, populations of these “losers” could struggle to recover and continue to perish en masse. That could prove devastating to reef ecosystems, researchers said.

“Diverse coral communities are needed to have diverse fish and shrimp and crab and worms and all of the other species that live on reefs,” Mark Eakin, one of the study’s authors, told NPR . “So as these events continue into the future, we’re going to see much simpler coral reefs ... and if we don’t take care of the problem of human-caused climate change we’re going to lose a lot of the world’s coral reefs.”

As it stands, the makeup and mix of species of the Great Barrier Reef have already started to change. “That transition is already well underway,” said Hughes. 

The study comes as the International Union for Conservation of Nature develops its new Red List of Ecosystems . Hughes said the new research should allow the Great Barrier Reef to be assessed by the IUCN. He said the reef as a whole would likely be classified as “endangered” under the new IUCN framework. This classification could help guide future conservation and governance efforts.

Composed of thousands of individual reefs, the Great Barrier Reef is the world’s largest living structure . Estimated to be 20 million years old, the ancient reef is greater in size than the United Kingdom, Holland and Switzerland combined and can be seen from space .