Great Barrier Reef could face another mass bleaching by end of January, forecast | Great Barrier Reef


Corals in large parts of the Great Barrier Reef could be affected by massive bleaching for the fourth time in just seven years by the end of January, according to forecasts from a US government agency.

Reef scientists are hoping favorable weather conditions, including cloud cover and rain or a cyclone, could further cool the corals and ward off the threat.

The US National Oceanic and Atmospheric Administration (Noaa) forecast shows that the heat accumulated in the northern and central parts of the reef will be high enough for the corals to start bleaching by the end of January.

Forecasts from the Meteorological Bureau also show an increase in heat on the World Heritage listed reef in January.

Dr David Wachenfeld, chief scientist at the Great Barrier Reef Marine Park Authority, said water temperatures were currently above average “almost everywhere”, with some areas warmer by 2 ° C.

He said: “The current situation is not what we want, but in a world with a changed climate, it is not surprising.”

He said neither Noaa nor BoM’s forecasts were able to predict cyclones that can quickly lower temperatures. “I wish clouds and rain,” he said.

The cyclone season in Australia is considered to be from November to April, and the eastern part of the country, including the reef, receives an average of four cyclones per year.

The Bureau of Meteorology says there is only a slim chance of exceeding the average number of cyclones this current season.

A spokesperson said the office’s ocean outlook “indicated increased heat stress over the Great Barrier Reef for the remainder of the year and January 2022, decreasing in February.”

According to Noaa’s forecast, provided by its Coral Reef Watch service, by the third week of January, sections of the reef just south of Airlie Beach to the tip of Cape York – a distance of about 1,300 kilometers – will probably be whitewashing.

By mid-February, forecasts show that large areas from Cairns would be at ‘alert level 2’ – the highest heat stress level where coral mortality is considered likely.

Australia’s climate is currently influenced by a La Niña weather model and Wachenfeld said this would generally provide more cloud and rain in the reef waters.

“But we just haven’t seen that this summer yet. We hope that these typical La Niña conditions will kick in. Weather events over the next few weeks are critical.

Coral bleaching is a stress reaction to excess heat. The process separates the corals from a special algae that gives them their color and much of their nutrients.

Corals can recover from less severe bleaching, but studies suggest that those that survive are weakened.

Although 2020 was the most widespread bleaching on record, Wachenfeld said heat levels were not as intense as previous events and so with low levels of coral mortality, the reef had had several years to recover. .

The latest State of the Reefs report from the Australian Institute of Marine Science showed 2021 to be a “low disturbance year” with an increase in the amount of corals. But this increase in coral cover was dominated by weaker fast-growing species prone to bleaching.

University of Queensland Professor Peter Mumby said the reef was in a critical period for recovery, but was concerned about Noaa’s forecast “especially because they tend to be quite conservative.”

“Everyone is feeling a little depressed at the prospect of another bleaching event,” he said.

Dr Selina Ward, Academic Director of the University of Queensland’s Heron Island Research Station, said: “I am always worried when I see temperatures rise and stay high.

“This prediction from Noaa suggests that we will likely have a bleaching event and that it would occur sooner this summer than expected.”

Professor Terry Hughes, from the ARC Center of Excellence for Coral Reef Studies at James Cook University, is a coral bleaching expert who examines the reef during bleaching events.

The Great Barrier Reef has experienced five episodes of mass bleaching – 1998, 2002, 2016, 2017 and 2020 – all caused by rising ocean temperatures due to global warming. A study by Hughes in November found that only 2% of individual reefs along the 2,300-kilometer system had escaped bleaching since 1998.

Hughes said Noaa’s forecast was unusual in predicting an early onset of concentrated bleaching in the north. But he said the forecast also suggested a rapid reduction in heat in early March, which would help the corals survive.

But he said historically an El Ni̱o weather pattern Рthe hottest, drier alternative to La Ni̱a Рwould trigger the bleaching.

“It’s scary that we no longer need an El Niño to trigger a mass bleaching event – we just need another heat wave, brought on by global warming.

“In the tropics, average sea temperatures today during La Niña periods are warmer than they were during El Niños 30 years ago.”

He said the Weather Bureau’s forecast was “milder” than Noaa’s, but temperatures across the reef had been about a degree above average over the past month.

“With the conditions in La Niña strengthening, we hope the reef will dodge the bullet for another year,” he said.

He said if the northern parts of the reef were to bleach again this summer, the young corals that have started growing in recent years would be in danger.

Professor Tom Bridge, an ecologist and reef scientist at the Museum of Tropical Queensland, said Noaa’s forecast did not make him more or less worried about the prospect of bleaching like any other year.

“It is now warmer every year,” he said. “Every summer now, we run this challenge where the bleaching depends on the vagaries of the weather like rains, cyclones and heat waves. “

Research last month suggested that parts of the reef would be affected by temperatures high enough to kill corals five years a decade by the middle of this century if global warming was kept below 2 ° C.

Unesco science advisers said earlier this year that the reef should be placed on a list of “endangered” World Heritage sites, but fierce lobbying from the Morrison government has delayed the decision until at least June to next year.

Coral reefs are considered to be one of the ecosystems most sensitive to the climate crisis.

The Morrison government has been asked to send a progress report to Unesco by February of next year.

Unesco has not yet scheduled a reef monitoring mission, expected in the first half of next year.

Lawyers representing three young Queenslanders wrote to the 21-country world heritage committee on Friday, urging it to place the reef on the “endangered” list at its next meeting in June in Russia.

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