The Great Barrier Reef Suffered Far Worse Bleaching Than Originally Thought

Lizard Island in the Great Barrier Reef suffered particularly badly during the bleaching event last year. The Ocean Agency/XL Catlin Seaview Survey/Christophe Bailhache

Last year, the Great Barrier Reef suffered its worst ever bleaching event, but now it seems that it was even more disastrous than previously thought. Earlier surveys suggested that around 22 percent of the shallow water coral was killed by warming temperatures, but a more detailed analysis reveals that this figure is actually closer to 29 percent.

The initial surveys were completed from the air and underwater, but they underestimated the full impact of the 2016 event, particularly in the deeper waters. It now seems more coral was killed off, with severe bleaching in regions north of the town of Port Douglas, where it is thought that roughly 70 percent of all shallow water corals have died.

Yet the bad news doesn’t stop there. The reef is currently going through an unprecedented second bleaching event in two years – although it is still too early to tell what the result will be, it’s not exactly expected to be good. “The amount of coral that died from bleaching in 2016 is up from our original estimates and, at this stage, although reports are still being finalised, it's expected we'll also see an overall further coral cover decline by the end of 2017,” Great Barrier Reef Marine Park Authority Chairman Russell Reichelt told AFP.

Researchers are currently looking for ways to try and ease the mounting pressure on the reef. Some institutions have been researching corals that have a higher heat tolerance, either seeking out species from other parts of the world known to thrive in warmer waters or attempting to selectively breed native species in order to accelerate evolution in the hopes that these can be used to repopulate the dying reef.

There are also teams focused on preventing land practices that impact the reef system, such as agricultural runoff. This happens when sediments, nutrients, and contaminants drain from farm land along the coast bordering the reef, reducing water quality and increasing sedimentation. Another research target is the explosion in the number of crown-of-thorns starfish, which have proliferated and are killing the coral by feeding on it.

While all this will help the reef to varying degrees, there is one solution that will save it: preventing climate change. “The Great Barrier Reef is a large and resilient system that's previously shown its capacity to bounce back, however the current changes are undermining the resilience of the reef,” says Reichelt. “Summit participants voiced their strong concern about the need for global action to reduce greenhouse gas emissions, the driver of climate change.”

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