Global warming and acidic ocean waters will kill all coral reefs by 2100, a new study says.
Climate change caused by greenhouse gas emissions from humans is on track to eliminate 70 to 90 percent of coral reefs in the next 20 years.
Coral reefs are most at risk for emission-driven changes in their environment, a study by Hawaiian scientists revealed.
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More and more heat waves at sea create dead spots in the barrier reef, as shown, by ‘bleaching’, whereby corals are forced to dispel their symbiotic algae
Restoration projects to protect coral reefs, including the 1,400-mile Great Barrier Reef in Australia, will also face major challenges in the coming years.
Future increases in human pollution will only have a small impact on the elimination of reef habitats, because people have already caused such great damage to them.
“By 2100 it will look rather grim,” said Renee Setter, a biogeographer at the University of Hawaii Manoa, who presented the new findings at Ocean Sciences Meeting in California this week.
“Trying to clean the beaches is great and trying to fight pollution is fantastic – we must continue those efforts,” said Setter.
“But ultimately, fighting climate change is really what we need to advocate to protect corals and prevent compound stressors.”
As the temperature of the ocean rises, warmer water emphasizes corals, releasing algae that live in them, giving them up to 90 percent of their energy.
This event causes the vividly colored coral communities to turn white – an effect called coral bleaching.
Bleached corals are not dead, but run a greater risk of dying, and these bleaching events are more common in climate change.
Conservationists have been warning for years about the danger of coral bleaching, which means that in 2016 around 30 percent of the Great Barrier Reef’s coral was killed.
On the photo an anemone fish peeps from behind an anemone on the Great Barrier Reef. Fish are crucial for the functioning of coral reefs as healthy ecosystems
Coral can survive bleaching if it receives nutrients quickly enough, but if not, it can cause death within days, previous studies have shown.
Rising temperatures in the ocean are caused by an increase in greenhouse gases in the atmosphere, such as CO2.
Excessive CO2 emissions caused by humans are also absorbed into the sea, which makes it more acidic and has harmful consequences for marine life.
The underwater speakers played recordings of the sounds of a healthy reef – including the sounds my schools made of fish, shrimp, and other reef dwellers. Pictured, young cardinal fish swimming around healthy coral on the Great Barrier Reef
A promising development are scientific attempts to transplant living corals grown in the laboratory to dying reefs in the ocean.
It is thought that these new laboratory-grown corals will stimulate the recovery of the reef as a whole and bring it back to a healthy state.
However, these transplanted corals are often faced with low survival rates due to poor planning and location selection based on convenience, the University of Hawaii Manoa team said.
Other efforts to illuminate the coral include playing the environmental sounds of a healthy reef through speakers to lure young fish back to damaged areas.
File photo taken in October 2016 shows coral bleaching at the Great Barrier Reef in Australia, a world heritage site
Image obtained on Monday, April 10, 2017 of whitening damage on the Great barrier Reef. Recent aerial investigations by the Australian Research Council’s Center of Excellence for Coral Reef Studies have shown that only the southern third of the Great Barrier Reef has escaped coral bleaching intact.
In her research on coral bleaching, Setter and her colleagues mapped out areas of the ocean that would be suitable for further coral recovery efforts.
They simulated ocean environments such as sea surface temperature, wave energy, water acidity, pollution and overfishing in areas where corals exist.
They discovered that by 2045, most parts of the ocean where coral reefs exist today will not be suitable habitats for coral at all.
The simulation deteriorated towards the beginning of the next century, with little to no suitable locations by the year 2100.
“Frankly, most sites are out,” said Setter
The few locations that are still viable ocean habitats for coral reefs in 2100 are small parts of Baja California and the Red Sea east of Africa – but these specific locations are too close to coral rivers.
The team said their findings “could lead to necessary adjustments to restoration practices,” as well as increasing efforts to reduce CO2 emissions to prevent the loss of coral reefs.
“Identifying more suitable locations in a higher CO2 future in the atmosphere will help with the effectiveness of current programs and the chances of successful restoration efforts,” they say.
More than 5,000 scientists are expected to present the latest research results on the world’s oceans at the Ocean Sciences Meeting 2020, which runs in San Diego until Friday.
Also this week Australian scientists have warned that the Great Barrier Reef will undergo its third massive bleaching event in five years.
Professor Terry Hughes, director of the Australian Research Council Center of Excellence for Coral Reef Studies, quoted NASA data heat stress in the Australian summer.
‘Will we see massive coral bleaching again this year on the Great Barrier Reef? The next 2-3 weeks are critical, “Professor Hughes tweeted.
The ARC Center of Excellence has previously estimated that only the southern third of the Great Barrier Reef has escaped coral bleaching intact.
WHAT IS CORAL BLEACHING?
Corals have a symbiotic relationship with a small seaweed called ‘zooxanthellae’ that live inside and feed them.
When the temperature of the sea surface rises, corals dispel the colorful algae. The loss of the algae causes them to bleach and turn white.
These bleached states can last up to six weeks, and while corals can recover as the temperature drops and the algae return, severely bleached corals die and are covered by algae.
In both cases, this makes it difficult to distinguish between healthy corals and dead corals from satellite images.
This bleaching has recently killed up to 80 percent of corals in some parts of the Great Barrier Reef.
This type of bleaching event occurs four times more globally than in the past.
An aerial view of the Great Barrier Reef in Australia. The corals of the Great Barrier Reef have undergone two consecutive bleaching events, in 2016 and earlier this year, causing experts to be concerned about the ability of reefs to survive global warming