Parts of the Australian Great Barrier Reef have literally been scorched in the latest underwater heat wave and will not recover, according to the results of a new study by Australian scientists published on Thursday in the journal Nature.
More precisely, over 1000 out of a total of 2300 km long Great Barrier Reef has been completely destroyed due to the effects of ocean warming during 2016 and 2017.
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– The reefs did not die gradually and slowly, but suddenly, due to the effects of heat stress. They were scorched by excessively high sea temperatures, says Professor Terry Hughes, director of the Centre for the Study of the Great Barrier Reef at James Cook University in Townsville.
Hughes and his colleagues conducted aerial monitoring along the entire reef and detailed underwater research at 63 locations. The study also included data collected from satellite monitoring.
Main culprits: climate change and El Niño
They reminded that the sea temperature along the reef has increased by one degree Celsius compared to the average temperature, caused by a combination of climate change and El Niño.
– When the ‘bleaching’ process begins due to a heat wave, which means the cessation of the symbiosis between algae and corals, leaving only the white skeletons of corals, there are two possibilities – they can survive and very gradually regain their natural color, depending on the rate of decrease in sea temperature, or they can die, says Hughes, a scientist who has previously warned authorities that they must urgently find a response to climate change to prevent further devastating bleaching of the reef.
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– Since 1998, we have witnessed such events, specifically in 1998, 2002, 2016, and 2017. Initially, the gap was quite large, but the last one, unfortunately, was so short that it simply scorched them. In a nine-month period, between March and November 2016, 30 percent of corals were destroyed, says the scientist, who believes that action against global greenhouse gas emissions and fossil fuels, in favor of renewable sources, must be taken as soon as possible.
– Corals fade, then die and crumble, which is why some seabeds resemble deserts covered with remnants of skeletons. Coral contains millions of single-celled algae, whose pigment gives them beautiful colors. These algae cannot withstand rising water temperatures. When microalgae die, the coral gradually loses its color and turns into a calcified skeleton, hence the term ‘white death’. The death of corals has immediate consequences for marine life as fish need coral structures for hiding, feeding, and reproduction. In the long term, the decline of coral reefs also threatens humans, Hughes explained.
Prof. Hughes: Focus on the full part of the glass
Coral bleaching, which has been intensively ongoing for two years, first destroyed the central part of the reef and then spread to the north. However, Hughes is, as he says, an irreparable optimist and reminds that “billions of corals remain alive in the southern part of the reef. They are, on average, more resilient than those that have died. Therefore, we urgently need to focus on protecting the part of the glass that is still full and help the ‘survivors’ recover.”
– The Great Barrier Reef is undoubtedly threatened by climate change, but it is not entirely doomed if something is done very quickly about greenhouse gases. Our study has shown that even the remaining coral reefs are undergoing radical changes due to unprecedented heat waves, said Prof. Hughes.
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– The Great Barrier Reef, as we know it today, will be a completely different system in 10 or 20 years than the one we remember from the last 30 or 40 years. The results of our study have shown that there are coral species we can call ‘winners’ and those we can call ‘losers’. There are very few species resistant to heat stress. These are the ‘winners’. However, there are as many as 90 percent ‘losers’, Hughes warned.
Scientists are considering genetically modified corals, the use of geoengineering in the atmosphere, and even a kind of ‘sunshade’ over the sea surface that would protect coral reefs from sunlight.
Australian scientists say that corals will continue to decline and die until the climate stabilizes. According to some estimates, by 2050, as much as 90 percent of corals in the world will disappear.
