Great Barrier Reef in grave danger as vast swaths die off, scientists say
Overheated seawater bleached huge sections of Australia’s coral system
The Great Barrier Reef in Australia has long been one of the world’s most magnificent natural wonders, so enormous it can be seen from space, so beautiful it can move visitors to tears.
But the reef, and the profusion of sea creatures living near it, are in profound trouble. Huge sections of the Great Barrier Reef stretching across hundreds of kilometres of its most pristine northern sector, were recently found to be dead, killed last year by overheated seawater. More southerly sections around the middle of the reef that barely escaped then are bleaching now, a potential precursor to another die-off.
“In the north, I saw hundreds of reefs — literally two-thirds of the reefs were dying and are now dead,” said Terry Hughes, director of a government-funded centre for coral reef studies at James Cook University in Australia and the lead author of a paper on the reef that is being published Thursday as the cover article of the journal Nature.
In the paper, dozens of scientists described the recent disaster as the third worldwide mass bleaching of coral reefs since 1998, but by far the most widespread and damaging.
If most of the world’s coral reefs die, as scientists fear is increasingly likely, some of the richest and most colourful life in the ocean could be lost. In poorer countries, lives are at stake: Hundreds of millions of people get their protein primarily from reef fish, and the loss of that food supply could become a humanitarian crisis.
Scientists warned decades ago that the coral reefs would be at risk if human society kept burning fossil fuels at a runaway pace, releasing greenhouse gases that warm the ocean.
Emissions continued to rise, and now the background ocean temperature is high enough that any temporary spike poses a critical risk to reefs.
Corals require warm water to thrive, but are exquisitely sensitive to extra heat. Just two or three degrees Fahrenheit of excess warming can sometimes kill the tiny creatures.
Globally, the ocean has warmed by about 1.5 degrees Fahrenheit since the late 19th century, by a conservative calculation, and a bit more in the tropics, home to many reefs.
Australia relies on the Great Barrier Reef for about 70,000 jobs and billions of dollars annually in tourism revenue. Even in hard-hit areas, large patches of the Great Barrier Reef survived, and guides will most likely take tourists there, avoiding the dead zones.
“I don’t think the Great Barrier Reef will ever again be as great as it used to be — not in our lifetimes,” said C. Mark Eakin, a reef expert with Maryland’s National Oceanic and Atmospheric Administration.