Australia's Great Barrier Reef, more than 25 million years in the making, is "an icon [of] primordial wilderness," says Dr. Vernon--it is the greatest structure created by life on earth. The idea that it might be mortally threatened within the span of a generation or two he would have once considered preposterous.
"I was wrong," he says.
Twin assailants, both creatures of climate change, threaten the reef and oceans more generally. The lesser of these is the warming of the water, which turns the single-celled algae on which corals rely or their sustenance toxic, compelling the coral to expel them and probably die--the event known as coral bleaching--or to keep them and certainly die.
The worst bleaching events of history will become commonplace by 2030, says Dr. Vernon, and by 2050, "The only corals left alive will be those in refuges on deep outer slopes of reefs. The rest will be unrecognisable--a bacterial slime, devoid of life."
The even greater threat is ocean acidification--the dissolving of carbon dioxide into the sea, forming weak carbonic acid. This is the climate change frontier to which science is swinging [with] increasing focus, as alarm grows at the threat it poses to marine ecosystems and to human food supplies and economies.