Most corals in the Arabian Gulf could be lost this century to climate change, study suggests

Corals will not expand into cooler waters fast enough to cope with damage caused by warming waters, according to research

Coral reefs, which are crucial to the health of marine ecosystems, are under severe threat from climate change. Photo: Getty Images

Most corals in the Arabian Gulf could be wiped out this century because of the continued warming of the seas, a new global analysis has indicated.

According to the research, coral cover in the Gulf between 2090 and 2099 is expected to be between 75 and 100 per cent less than it was between 2010 and 2019.

While the forecasts vary according to future greenhouse gas emission levels, the study calculates that under a “middle-of-the-road” scenario, coral cover globally will decline by about 58 per cent by the end of the century.

The study also found that corals in the hottest parts of the world will not be able to expand fast enough into cooler areas to cope with the damage they will experience from the warming of the oceans.

Writing in Science Advances, the scientists said that “the most severe declines in coral cover will likely occur within 40 to 80 years”, but that large-scale expansion of coral reefs into cooler waters to compensate for this “requires centuries”.

Some regions, such as the southern coast of Australia, are forecast to see increases in coral cover, but most will see a decline, with the Arabian Gulf among the hardest hit.

The study’s first author, Dr Noam Vogt-Vincent, of the University of Hawaii at Manoa, told The National that it was “well-established that coral reefs are facing a precipitous decline over the coming decades” and this is being observed in multiple “bleaching” events, where high temperatures make coral expel algae that live inside them.

Corals face growing threat

Corals in the south Gulf and on the UAE's east coast have been affected. All photos: Rebekka Pentii / NYUAD

There is total bleaching in some parts although there is still a chance of recovery.

Bleaching happens when heat stress forces a coral lose their algae - which provides colour and most of their energy

Corals can stay alive after bleaching but if cooler temperatures do not return they will die

Coral reefs support the well-being and livelihoods of close to 1 billion people

Corals in the Arabian Gulf have proved to be able to survive at significantly higher temperatures but they are operating at the edge of their limits

“As the ocean warms, conditions suitable for reef formation will shift away from the tropics,” he added. “It was previously thought that parts of the subtropics and temperate seas might be able to act as ‘refugia’ for tropical coral species, possibly allowing them to avoid extinction as they experience catastrophic losses in the tropics.

“Our study suggests that, although coral range expansion will eventually occur, it will probably take centuries, which is far too slow for these new higher latitude environments to act as refugia, given that they’re already threatened.”

He said that the problem was not that coral larvae could not reach new environments, but that their growth in numbers was too small for them to develop into larger populations that could sustain themselves.

While the study forecasts that most coral in the Arabian Gulf will be lost this century, Dr Vogt-Vincent said caution should be exercised when interpreting the finding, partly because the model looks at global-scale changes and as the area has extremely high temperatures, the corals are not typical of the Indo-Pacific region.

The new study, Anthropogenic climate change will likely outpace coral range expansion, is also written by scientists from the University of New Hampshire in the US and Victoria University of Wellington in New Zealand.

The Arabian Gulf is “very likely to continue warming as a result of climate change”, said Dr Diana Francis, an assistant professor and head of the environmental and geophysical sciences lab at Khalifa University in Abu Dhabi.

“Recent studies have shown that the Gulf has warmed by approximately 1.0 to 1.5 °C over the past 40 to 50 years,” she said.

She said that the rate of warming in the Arabian Gulf was faster than the global average because it was shallow, semi-enclosed and received much sunlight.

As well as making seas warmer, climate change is also causing them to rise, through expansion of the water and the melting of ice sheets and glaciers.

Prof John Burt of New York University Abu Dhabi, who was not involved in the latest study, but who researches corals around the UAE, said that the more that range expansion of corals was studied, the more it became apparent that “these were this was “not sufficient to keep pace with the impacts of climate change in the tropics”.

He said that only a limited range of coral species, typically more “generalist” types adapted to a wider range of environments, could make the leap to new environments.

“We are not replacing the diversity or functioning of these amazing tropical ecosystems through range expansion,” he said.

“The present paper adds a further nail in the coffin for this line of thought by showing the rates of expansion are only a fraction of what is needed just to replace the total amount of live coral that will be lost on tropical reefs under climate change, not even considering species diversity.”

He said that while Arabian Gulf corals were the most heat-tolerant in the world, they “are not immune to climate change”.

“Recent marine heatwaves and global-scale bleaching events have caused the loss of over 80 per cent of corals from many regional reefs in the past decade alone,” he said.

Taking action

The shells will help to form biological building blocks to create artificial reefs. All photos: Dubai Oyster Project

Pupils from The Arbor School in Dubai have teamed up with a restaurant group for the Dubai Oyster Project.

They are using used oyster shells from The Maine restaurants in Dubai, which are usually just thrown out and end up in landfills, to create artificial reefs.

They placed more than 250,000 of the used shells near the Ghantoot border.

They used illegal fishing nets seized by authorities to help transport the shells to the water's edge.

The project will also help to reduce the amount of food waste.

Efforts are being made to protect corals, with Abu Dhabi having recently revealed plans to plant millions of coral colonies across more than 900 hectares.

The initiative is led by the Environment Agency Abu Dhabi, which said its efforts had seen it restore more than one million colonies.

Dr Burt and his colleagues are looking at selective breeding to produce heat-tolerant coral larvae, an approach that could lead to the production, he said, of millions of offspring better able to cope with higher temperatures.

“However, unless we get CO2 emissions under control, the long-term vulnerability of even these robust individuals in the wild remains an open question,” he said.

Researchers say that reducing other factors that stress corals, such as pollution and overfishing, can have a positive effect on reefs, but Dr Vogt-Vincent said that such measures alone were not enough to protect these ecosystems.