We reported recently on the extreme bleaching of the Great Barrier Reef seen this year, highlighting a piece written as an “obituary.” Thankfully, though, the obituary is still in actuality a tentative one, as the reef continues to hold on for now.
As an update on that earlier coverage, it seems that a 700 kilometer portion in northern part of the Great Barrier Reef was the worst hit this year — with around 67% of its shallow-water corals dying over the last 8 to 9 months. Elsewhere, though, things were somewhat less (immediately) dire. There was a lower death toll in most southern and central portions (further from the equator).
“Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef. This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected,” stated Professor Terry Hughes, Director of the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies based at James Cook University.
This was determined through the undertaking of aerial surveys of the regions in question.
“The good news is the southern two-thirds of the Reef has escaped with minor damage. On average, 6% of bleached corals died in the central region in 2016, and only 1% in the south. The corals have now regained their vibrant colour, and these reefs are in good condition,” commented Professor Andrew Baird, also from the ARC Centre, who led teams of divers to re-survey the reefs in October and November.
For how long is the question. Mass bleaching events such as the one seen this year are becoming more and more common as the oceans warm, and also as they acidify (related to the warming). Will the Great Barrier Reef last in anything like its current condition for more than a few more decades? I’m skeptical.
Considering that the site is a major tourist spot, though, I’m not surprised to hear “good” news out there in the media right now, as a fall in tourism would hurt the pocketbooks of many people.
There is a piece of good news with this, though: the northern offshore corner of the Great Barrier Reef Marine Park was a spot that didn’t experience the mass mortality seen nearby — very likely as a result of a cold water upwelling there. This means that perhaps the area will be able to function as a refugia to some degree as the waters continue to warm. For awhile anyways. But who knows?
What I mean by “refugia” is that the spot could perhaps serve to keep local corals and associated fish and animals from going extinct as is likely at nearby reefs without the cold water upwelling. With the disappearance of these reefs, after all, there will likely be quite a lot of fish and other animals going extinct.
Professor Hughes noted: “We found a large corridor of reefs that escaped the most severe damage along the eastern edge of the continental shelf in the far north of the Great Barrier Reef. We suspect these reefs are partially protected from heat stress by upwelling of cooler water from the Coral Sea.”
The researcher involved in the survey claim that it will take at least 10 to 15 years for the lost corals to be replaced. If there’s another mass bleaching event before then, of course, then this won’t hold true. And for that matter, will it even hold true if there’s no mass bleaching but temperatures continue to rise and waters continue to acidify?
Photo Credit: Greg Torda, ARC Centre of Excellence for Coral Reef Studies