Climate Change Is Killing the Great Barrier Reef

Upcoming papers will examine the impacts of the latter event - which mainly hammered the middle section of the Reef - and the scope for recovery. Experts believe that coral reefs across the tropics will probably continue to degrade until the climate change process stabilizes. They have mapped the patterns of the corals which is spread over more than 1,400 miles and monitoring about the dead corals so that the study will help them in future to understand the reefs.

The results of the model predict that the coral will become more sensitive to temperature swings, which will result in occasional die-offs.

The study's authors estimated how much coral had died in the immediate aftermath of the 2016 heat wave, and then returned nine months later to discern how many corals had regained their color - a sign of restored health - and how many had died.

"The scale of the damage from back-to-back bleaching is vastly bigger", Hughes said. "The bleaching will forever change the Barrier Reef". These were combined with underwater surveys of over 100 locations.

Finally, teams of divers took samples of corals and investigated their physiology in the laboratory. For past mass bleaching events, corals either recovered when the water cooled down, or died slowly of "starvation". On the Great Barrier Reef, less than 10% of reefs escaped with no bleaching, compared with more than 40% in previous bleaching events.

Reefs can recover from bleaching in about 15 to 25 years - but that can only happen if the temperature and acidity of the waters drop. Not before yet another bleaching event occurs.

A key guide is the number of so-called degree-heating weeks (DHW), such as waters a degree above average for a certain period.

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

"This episode should remind us that there is no reason to expect that climate change impacts should be slow and steady and predictable", she wrote. Extreme weather events due to anthropogenic global warming and El Nino are rapidly emerging as major threats to the ecosystems. Hughes said that the branching type corals which provide shelter to the fishes are being replaced by " bulky, less intricate dome-shaped corals".

The authors of the study say that it bridges the gap between theory and practice of assessing the risk of ecosystem collapse under the framework of the International Union for Conservation of Nature (IUCN) Red List of Ecosystems. These cover the requirements for such a listing.

"What we just experienced is one hell of a natural selection event", Hughes said in a statement. Replacement of lost corals through recruitment relies on healthy coral larvae arriving and finding suitable settlement substrate.

But, in the face of this widespread devastation, Hughes is hopeful that human action can protect the billion or so remaining coral at the Great Barrier Reef.

"Looking into the future of the Great Barrier Reef and reefs elsewhere, corals in the Arabian Gulf and other extreme temperature environments send both signs of hope and dire warning: reef communities can shift to states that tolerate more heat stress, however, this will likely come at the price of a loss of about 90 percent of coral species", he explained.

  • Santos West