Queensland heatwave prompts new concerns for Great Barrier Reef

By Angela Heathcote 28 November 2018
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Coral bleaching can occur with or without an El Niño event, prompting concerns from scientists that Queensland’s record- breaking heatwave increases the likeliness of a third mass bleaching event in just four years.

QUEENSLAND IS currently experiencing a record-breaking heatwave, prompting concerns that the Great Barrier Reef may be in for yet another bout of coral bleaching.

Land temperatures reached 43.6°C across the state yesterday, smashing previous records by up to 6°C. Temperatures are predicted to remain high in the coming days.

The record-breaking heat follows forecasts by the National Oceanographic and Atmospheric Administration (NOAA), a US agency, that an underwater heatwave could cause widespread coral bleaching.

In the wake of Queensland’s heatwave and predictions by the NOAA, Australian coral biologists are warning of the consequences for the Great Barrier Reef.

“The record-breaking heatwave in Queensland, with land temperatures over 40°C, obviously marks a very hot start to the season,” said coral biologist Terry Hughes from James Cook University.

“We’re still three months away from peak sea temperature in early to mid-March. So, a lot could happen between now and then.”

Record sea temperatures and an El Niño event in 2016 resulted in the bleaching of two-thirds of the corals in the northern part of the Great Barrier Reef. Now, however, climate change means coral bleaching can happen outside of an El Niño event.

“In 2017, bleaching began a few weeks earlier, in February. It was also a very severe event, even though the summer occurred outside of an El Niño period,” Terry said.

“Because of global warming, we no longer need El Niño conditions to trigger bleaching. By comparison, 2018 was cooler, and we saw almost no bleaching that year.”

The southern Great Barrier Reef avoided bleaching thanks to ex-cyclone Winston, which cooled the water. Whether it will be spared again is something that worries scientists.

“It’s too early to predict which part of the reef might or might not bleach next,” Terry said.

“Certainly, the south is now the most vulnerable. It has the highest coral cover, and a lot of it is branching and table-shaped corals that are among the most vulnerable species to high temperatures.”

“Ex-cyclone Winston transited Fiji on 20 February, and then came to southern Queensland as a rain depression and reduced temperatures by 2-3°C in the nick of time. We could be lucky again, or not.”

If the Great Barrier Reef experiences another bout of coral bleaching in 2019, that will be the third bleaching event in four years, which is unprecedented.

Climate scientist Lesley Hughes from Macquarie University in Sydney explained that the closer together the bleaching events occur, the less time the coral has to recover.

“The bleaching event has killed a lot of coral so clearly there is simply less coral there now and less coral to reproduce to replenish.

“The coral that did survive is likely to have a reduced capacity to reproduce and may be subject to disease and other stresses. If we get another bleaching event this year the ability to recover will be reduced even further.”

If this level of bleaching continues, a breakdown of the Great Barrier Reef coral reef system may take place. “It could become dominated by algae,” said Lesley. This would significantly affect the availability of habitat for species that rely on the coral reefs – there would be something there, but people may not wish to snorkel in it.

Terry said we can no longer “ignore the elephant in the room”.

“The Australian government still supports expanding production of fossil fuels, even as the IPCC point to the urgent need to reduce global emissions to zero as soon as possible.

“We can’t ignore the elephant in the room and pretend we can climate-proof the reef with fans, floating sunscreen or by planting small patches of corals. The only way to reduce future temperature rises is to stop emitting greenhouse gasses.”

This week, a school climate strike is being staged by students across Australia in protest against what the students said is a lack of action against climate change. “We want them to not fund any new coal mines, and close down all the old ones,” leaders of the strike told Australian Geographic earlier this month.

“I think it’s great that school kids are responding to the climate crisis,” said Terry. “The next generation will have to deal with the consequences of anthropogenic global heating, and they have every right to have a strong voice and to be listened to.”