Published: Thu, April 19, 2018
Sci-tech | By Carrie Guzman

Climate Change Is Killing the Great Barrier Reef

Climate Change Is Killing the Great Barrier Reef

"The longer-term transition that we have been predicting now for many years as a effect of global warming is well under way", added Hughes, the director of the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University in Townsville, Australia. This was followed by another mass bleaching the following year.

Great Barrier Reef bleaching 2016-17.

It found that the cover of coral declined by 30 percent between March and November 2016.

"We were very surprised to see a quarter of the corals die in just two to three weeks during the middle of the heatwave", he was quoted as saying by ABC.

While numerous most sensitive corals died immediately from heat exposure, many others died in the months that followed after they had been bleached and then been unable to recover. Extensive aerial surveys revealed widespread coral bleaching between March and April 2016. These were combined with underwater surveys at over 100 locations.

Finally, teams of divers took samples of corals and investigated their physiology in the laboratory.

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Another previous paper documented the reduction in time between bleaching events since the 1980s, down to the current interval of one every six years.

"Professor Hughes said scientists had called that the resulting from global warming, but &ldquos properly penalized". Bleaching events occur when the temperature rises above the average summer maximum for a sufficient period.

The US National Oceanic and Atmospheric Administration has suggested that bleaching generally starts at 4 DHW, and death at around 8 DHW.

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2016 was part of the third, and longest, mass coral bleaching event so far recorded.

Results showed 29 per cent of the 3,863 reefs which make up the world's largest reef system lost "two-thirds or more of their corals", which dramatically impacts the ability of the reefs to maintain full ecological abilities.

It can take staghorn corals at least a decade to fully recover; other coral species need more time, according to the study. The existing scientific understanding was that bleached corals - which depend on symbiotic zooxanthellae algae for nutrition and their bright colors - die slowly.

Whether or not targets such as those set out in the Paris climate agreement are met, Professor Hughes said a major transition in the reef's appearance was already well underway. This loss of hiding places is one of the reasons for the reduction of fish populations following severe bleaching events.

The study is unique because it tests the emerging framework for the International Union for Conservation of Nature (IUCN) Red List of Ecosystems, which seeks to classify vulnerable ecosystems as Safe, Threatened or Endangered. These cover the requirements for such a listing.

Scientists say the focus should be on protecting the surviving corals, which number about a billion after the two bleaching events in 2016 and 2017.

Eakin said that close to a billion people around the world rely on reefs for their main source of protein. We can save this reef, but the time to act is now.

"The Great Barrier Reef is certainly threatened by climate change, but it is not doomed if we deal very quickly with greenhouse gas emissions". That could prove devastating to reef ecosystems, researchers said. "We are learning that some corals are more sensitive to heat-stress than others, but reef fishes also vary in their response to these disturbances", said Richardson.

We also need to invest in looking after reefs at a local level to increase their chances of surviving the challenges of climate change.

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