SCIENCE
03/29/2016 06:42 am ET

This Is What Climate Change Has Done To The Great Barrier Reef

Researchers say the widespread coral bleaching across the vast ecosystem is the worst on record.

Credit: ARC Centre of Excellence for Coral Reef Studies
A patch of bleached coral stands out in a section of the Great Barrier Reef photographed during a recent survey of the structure's health.

A new aerial survey of the Great Barrier Reef shows the vast extent of a "severe" bleaching event that's caused widespread coral death over the past several weeks.

The National Coral Bleaching Taskforce study found 95 percent of individual reefs in the most pristine section of the ecosystem showed severe bleaching. The research covered 520 reefs across more than 600 miles of coastline and found just four that didn't show signs of damage.

Coral becomes "bleached" when the usually kaleidoscopic reefs are harmed by warmer oceans or other environmental factors. The colorful algae that feed coral polyps leave the structures during times of stress, leading to the ghostly white appearance

Credit: ARC Centre of Excellence for Coral Reef Studies
Coral takes on a ghostly white appearance once bleached. The bleaching can spread and entire structures can die if the oceans don't normalize.

If the stressors go away -- the ocean cools down or pollutants dissipate -- the algae is able to return and coral can recover.

If the oceans don't normalize, the bleaching can spread and entire structures can die. That's exactly what's happening across the Great Barrier Reef, the largest living structure on Earth.

Terry Hughes, a professor at Australia's James Cook University and the convener of the National Coral Bleaching Taskforce, said the data reflected the worst widespread bleaching across the reef ever seen. Up to 50 percent of the damaged coral could die, he said. The last major bleaching event in 2002 only saw 18 percent of reefs severely damaged.

Credit: ARC Centre of Excellence for Coral Reef Studies
A band of starkly white coral that has been bleached in the latest event.

Hughes said the prime driver behind the bleaching is warmer temperatures caused by man-made climate change. Corals are highly sensitive to even minuscule temperature shifts, and a prolonged increase of just 1 degree Celsius above normal for a few weeks can cause bleaching.

"In each case, the bleaching mapped perfectly onto where the hottest water was occurring," Hughes said. "There's a very clear link."

The dire photos have prompted Australia's environment minister to raise the reef's threat rating to its highest level. But some have criticized the government's conservation response so far, as the most recent proposal to protect the reef failed to name climate change as the main culprit behind the region's woes.

Take a look at more images and a video clip of the damage below.

Credit: ARC Centre of Excellence for Coral Reef Studies
Credit: ARC Centre of Excellence for Coral Reef Studies

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