Coral reefs may yet survive global warming, study suggests

In the lottery of evolution, genetic diversity is like buying a lot of tickets, scientist says after study finds how one coral species managed to ride out extreme cold that descended on most of the Earth two million years ago

Orbicella, a reef-building coral, may be able to survive future climate change (Monica Medina, NMNH)

One of the most devastating consequences of climate change in the world’s oceans could be the almost complete loss of coral, which forms astonishing structures like the Great Barrier Reef off Australia that are home to a vast amount of marine wildlife.

If average global temperatures rise by much more than 0.5 degrees Celsius – on top of the 1C increase over the last 130 years – scientists fear coral bleaching and ocean acidification could cause widespread ecosystem collapse.

But new research about a time in the Earth’s history when the planet was extraordinarily cold suggests some species could actually be more robust than currently thought.

In the Caribbean, coral species increased steadily between 3.5 million and 2.5 million years ago.

But about two million years ago, the Earth cooled dramatically with glaciers covering much of the northern hemisphere.

The sea level fell, leaving little in the way of shallow waters near the coast that was ideal for corals.

But, amid mass extinctions, a few species of Orbicella coral survived, researchers from the Smithsonian Tropical Research Institute (STRI) reported in the journal Current Biology.

Researcher Dr Carlos Prada said the reason was its high genetic diversity – and that could help it cope in the future as temperatures rise due to global warming.

“We see hope in our results that Orbicella species survived a dramatic environmental variation event,” he said.

“It is likely that surviving such difficult times made these coral populations more robust and able to persist under future climatic change.”

When the environment dramatically changes, some animals and plants will not be able to cope and die out.

But a species made up of individuals with a large amount of genetic variation is more likely to have enough who are able to survive the changes and still form a viable population.

“Having a lot of genetic variants is like buying a lot of lottery tickets,” said Dr Prada.

“We discovered that even small numbers of individuals in three different species of the reef-building coral genus Orbicella have quite a bit of genetic variation, and therefore, are likely to adapt to big changes in their environment.”