Global warming impacts on reefs unfolding as projected
Aerial surveys by Australian researchers shows that at least 40 percent of the Great Barrier Reef has been affected by bleaching. Photo courtesy ARC Centre of Excellence for Coral Reef Studies / Terry Hughes.
Staff Report
Global warming has been driving the worst and longest episode of coral reef bleaching on record, and the event is hitting the Great Barrier Reef especially hard. Australian scientists this week said their latest aerial surveys of more than 500 reefs show that the most pristine section of the Great Barrier Reef is currently experiencing the worst, mass bleaching event in its history, with the overwhelming majority of reefs being ranked in the most severe bleaching category.
Widespread coral reef bleaching started in 2014, even before El Niño kicked into high gear. As forecasts for this year’s El Niño became more certain, ocean scientists warned in advance that widespread bleaching, spurred by warm ocean temperatures, would occur. There’s plenty of research that enables scientists to project bleaching events, and last November, NOAA warned that reefs around the world would be affected this year. In February, NOAA announced that record and near-record ocean temperatures are prolonging the longest global coral die-off on record.
The latest data from the Australian researchers confirms all the projections and worst fears that global warming will likely decimate most coral reefs worldwide. That, in turn, could affect entire ocean ecosystems, since reefs are the nurseries of the seas.
“This has been the saddest research trip of my life,” said Prof. Terry Hughes, with Australia’s National Coral Bleaching Taskforce. “Almost without exception, every reef we flew across showed consistently high levels of bleaching, from the reef slope right up onto the top of the reef. We flew for 4,000 kilometers in the most pristine parts of the Great Barrier Reef and saw only four reefs that had no bleaching. The severity is much greater than in earlier bleaching events in 2002 or 1998,” Hughes said.
“Even more concerning, we haven’t yet found the southern limit of the bleaching,” he continued. “We’ll be conducting further aerial surveys this week in the central Great Barrier Reef to identify where it stops. Thankfully, the southern Reef has dodged a bullet due to cloudy weather that cooled the water temperatures down.”
Scientists have confirmed the aerial data from aboard research ships, finding that almost all species of coral are being hit hard.
“We could see extensive bleaching even among the most robust ‘massive’ corals,” said James Kerry, project manager of the National Coral Bleaching Taskforce, who also participated in the aerial surveys. “The fact that these hardy species have also turned white shows just how severe summer conditions have become on the northern Great Barrier Reef. “Residents we spoke to in Cape York were shocked by what they are seeing, telling us that they had never experienced anything like this before.”
“Scientists in the water are already reporting up to 50 percent mortality of bleached corals,” said Hughes, “but it’s still too early to tell just what the overall outcome will be. We will continue to conduct underwater surveys along the Great Barrier Reef in the coming months as the full impact of this mass bleaching event unfolds.”
