Global warming and acidic ocean waters is set to kill all coral reefs by the year 2100, a new study says.
Climate change caused by human greenhouse gas emissions is on course to eliminate 70 to 90 per cent of coral reefs over the next 20 years.
Coral reefs are most at risk from emission-driven changes in their environment, a study by Hawaiian scientists revealed.
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Increasingly frequent marine heatwaves have been creating dead patches in the barrier reef, as pictured, by ‘bleaching’, in which corals are forced to expel their symbiotic algae
Restoration projects to protect coral reefs, including Australia’s 1,400-mile-long Great Barrier Reef, will also face serious challenges in years to come.
Future increases in human pollution will only have a minor impact on the elimination of reef habitat, because humans have already caused them such extensive damage.
‘By 2100, it’s looking quite 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 up the beaches is great and trying to combat pollution is fantastic – we need to continue those efforts,’ Setter said.
‘But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors.’
As ocean temperatures rise, warmer waters stress corals, causing them to release algae that lives inside them, which gives them up to 90 per cent of their energy.
This event causes the vibrantly-coloured communities of coral to turn white – an effect called coral bleaching.
Bleached corals are not dead, but are at a higher risk of dying, and these bleaching events become more common under climate change.
Conservationists have warned for years about the danger of coral bleaching, which killed about 30 per cent of the Great Barrier Reef’s coral in 2016.
Pictured, a clownfish peeps out from behind an anemone on the Great Barrier Reef. Fish are crucial for coral reefs to function as healthy ecosystems
Coral can survive bleaching if it receives nutrients soon enough, but if not, it can cause death within days, previous studies have shown.
Rising ocean temperatures are caused by an increase of greenhouse gases in the atmosphere, such as CO2.
Excessive C02 emissions caused by humans are also absorbed into the sea, making it more acidic and having harmful consequences for marine life.
The underwater speakers played recordings of the sounds of a healthy reef — including the noises made my shoals of fish, shrimps, and other reef dwellers. Pictured, young cardinal fish swimming around healthy coral on the Great Barrier Reef
One promising development has been scientific attempts to transplant live corals grown in the lab to dying reefs in the ocean.
It’s thought that these new lab-grown corals will boost the reef’s recovery as a whole and bring it back to a healthy state.
However, these transplanted corals often face low survival rates due to poor planning and site selection based on convenience, the University of Hawaii Manoa team said.
Other coral relief efforts have included playing the ambient sounds of a healthy reef via loudspeakers 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 Monday, April 10, 2017 of bleaching damages on the Great barrier Reef. Recent aerial surveys by the Australian Research Council’s Centre of Excellence for Coral Reef Studies has revealed only the southern third of the Great Barrier Reef has escaped unscathed from coral bleaching
In her coral bleaching study, Setter and her colleagues mapped which areas of the ocean would be suitable for further such coral restoration efforts.
They simulated ocean environment conditions like sea surface temperature, wave energy, acidity of the water, pollution and overfishing in areas where corals exist.
They found that most parts of the ocean where coral reefs exist today won’t be suitable habitats for coral at all by 2045.
By the turn of the next century, the simulation worsened, with few to no suitable sites by the year 2100.
‘Honestly, most sites are out,’ Setter said
The few sites that would still be viable ocean habitats for coral reefs in 2100 include small portions of Baja California and the Red Sea east of Africa – but these particular locations are too close to rivers for coral.
The team said their findings ‘can inform necessary modifications to restoration practices’ as well as increasing efforts to decrease CO2 emissions to prevent the loss of coral reefs.
‘Identifying more suitable sites in a higher atmospheric CO2 future will assist in the effectiveness of current programs and the likelihood for successful restoration efforts,’ they say.
More than 5,000 scientists are expected to present the latest research findings about the world’s oceans at the Ocean Sciences Meeting 2020, which runs until Friday in San Diego.
Also this week, Australian scientists have warned that the Great Barrier reef is set to undergo its third mass bleaching event in the space of five years.
Professor Terry Hughes, Director of the Australian Research Council Centre of Excellence for Coral Reef Studies, cited NASA data showing heat stress in the Australian summer.
‘Will we see mass coral bleaching again this year on the Great Barrier Reef? The next 2-3 weeks are critical,’ Professor Hughes tweeted.
The ARC Centre of Excellence has previously estimated that only the southern third of the Great Barrier Reef has escaped unscathed from coral bleaching.
WHAT IS CORAL BLEACHING?
Corals have a symbiotic relationship with a tiny marine algae called ‘zooxanthellae’ that live inside and nourish them.
When sea surface temperatures rise, corals expel the colourful algae. The loss of the algae causes them to bleach and turn white.
This bleached states can last for up to six weeks, and while corals can recover if the temperature drops and the algae return, severely bleached corals die, and become covered by algae.
In either case, this makes it hard to distinguish between healthy corals and dead corals from satellite images.
This bleaching recently killed up to 80 per cent of corals in some areas of the Great Barrier Reef.
Bleaching events of this nature are happening worldwide four times more frequently than they used to.
An aerial view of Australia’s Great Barrier Reef. The corals of the Great Barrier Reef have undergone two successive bleaching events, in 2016 and earlier this year, raising experts’ concerns about the capacity for reefs to survive under global-warming