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October 2017    Download the Entire Issue (PDF) Available to the Public Vol. 43, No. 10   RSS Feed for Undercurrent Issues
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The Great Barrier Reef; Dive it Now

from the October, 2017 issue of Undercurrent   Subscribe Now

The Great Barrier Reef is under constant attack. Crowns-of-thorns starfish. Cyclones. Acidification. But the greatest threat is coral bleaching. Over the past two decades, three major bleaching events have hit the GBR -- one in 1998, one in 2002, and, most recently, the worldwide event that began last year and only ended this past June. These events are characterized by unusually high spikes in water temperature that disrupt the symbiosis between corals and their algal partners, causing corals to lose their color. Bleaching damages the corals, and prolonged bleaching can kill them. Some corals are more resistant than others, but recovery time for coral species that are good colonizers and fast growers can still take 10-15 years. When long-lived corals die from bleaching, however, their replacement can take many decades.

The first two events had been bad, but this most recent one was catastrophic. I spoke to Rebecca Albright, a marine scientist with the Academy of Sciences in San Francisco, whose research interest is acidification and how it impacts corals. She recounted a conversation with a colleague at the Great Barrier Reef Foundation: the two of them agreed that climate change was destroying the reef at such a fast rate that the reef would be long gone before acidification reached a critical stage.

Australian marine scientist Terry P. Hughes amplifies this thought: "We didn't expect to see this level of destruction for another 30 years." In an article in the March issue of Nature, Hughes and his colleagues reported the effects of the three major events, which together covered almost the entire GBR, except the southern, offshore reef, where Lady Elliot is located. They concluded that the chances of the northern GBR returning to its former structure are "slim." By one estimate, in 2016, 29% of all the coral on the GBR -- mostly that in the north -- had died.

An interesting side note is that the researchers speculate that the southern reefs actually benefited from cyclone Winston in 2016; in February that year the southern reefs were only 1C cooler than the northern reefs, but with the cloud cover Winston provided, this difference grew to 4 over the next two weeks. Folks on Lady Elliot said this phenomenon occurred again this year with Debbie -- the island was beginning to experience bleaching in February, but Debbie brought cooler waters, and by the time I arrived, all the coral had regained its color.

Netflix recently released Chasing Coral, a documentary film directed by Jeff Orlowski that documents the decline of coral worldwide, but especially on the Great Barrier Reef. The film claims that in the last 30 years, 50% of the ocean's coral has been lost and concludes that based on current trends, within the next 30 years, bleaching will kill most of the world's corals.

Rebecca Albright is slightly more optimistic. She cites two examples of reefs that have come back from heavy bleaching -- on Palau and in the Philippines. And she adds that Red Sea reefs seem to be adapting to warmer temperatures and says that marine scientists are looking into the possibility of transplanting corals that are adapted to warmer areas. Her conclusion? "I can say confidently that I don't think we're going to lose reefs entirely. I think we're going to lose a lot of them and it's going to be a long time before they come back. The reefs of tomorrow are not going to look like the reefs of today."

On June 19th the National Oceanic and Atmospheric Administration announced that coral bleaching was no longer occurring in all three ocean basins -- Atlantic, Pacific, and Indian. But who knows when the next bleaching event will occur? With politicians having no political backbone to deal with human-induced climate change, it's not a matter of whether this will happen, but when.


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