Rising sea levels caused by global warming could be GOOD news for coral reefs

It all depends on your modelling

Global warming could do at least as much to protect the world’s coral reefs as it will to damage them, new research from Australia suggests.

Climate change has long been believed to be disastrous for the fragile marine environments, but fresh modelling has predicted that oceanic changes caused by the phenomenon will also work to the reefs’ advantage.

Rising sea levels, caused by melting polar ice caps, could help moderate the extreme and often damaging conditions found in many reef habitats, according to scientists at the University of Western Australia.

By studying reef systems off the coast of north-western Australia, they showed how rapid sea level rise could substantially reduce the volatile daily extremes of water temperatures in the shallow reef habitats over the next century.

The resulting changes, they say, may potentially ameliorate the other effects of global ocean warming.

Mounting levels of atmospheric carbon dioxide are predicted to cause substantial changes to ocean temperature over the next 100 years, increasing the frequency and severity of mass bleaching, where corals expel the symbiotic algae living in their tissues, turning them completely white.

In April scientists announced that 93 per cent of the famous 1,500 mile Great Barrier Reef, on Australia’s East Coast, had now been bleached as a result of an underwater heatwave caused by global warming.

The situation caused some scientists to urge the Australian government to decide which parts of the reef it wanted to save.

Reefs in the Caribbean and in other regions such as the Maldives have also been badly affected by bleaching.

Warming seas are part of a "triple punch" said to be hitting coral reefs as a result of global warming, along with ocean acidification, which makes it more difficult for corals to build and maintain their skeletons, and more frequent and powerful reef-wrecking storms.

The new research by Professor Ryan Lowe and his team is the first to attempt to predict in detail the positive effects rising surface levels on reef environments.

Temperatures within shallow reefs often differ substantially from the surrounding ocean, so predicting future patterns of bleaching and other stresses is difficult.

However, recent science has focused on trying to improve predictions of regional ocean warming patterns driven by long-term climate change, as well as by the intensification of short-term climate patterns such as El Nino.

Using a collection of detailed field measurements, Prof Lowe and his team developed a modelling framework for predicting how local temperature extremes in shallow reefs will change in the future as a result of rising sea levels.

They found that even a modest sea level rise could substantially reduce local reef water temperatures in the future, meaning the change may partially contribute to limiting reef heat extremes in an overall warming ocean.

Despite the international carbon emissions caps agreed at the Paris climate talks last year, atmospheric warming is still expected to rise to between 2.7 and 3C above pre-industrial levels, breaching the 2C threshold beyond which many scientists say heatwaves and significant sea level rises are inevitable.

In 2015 the United Nations World Heritage Committee agreed not to list the Great Barrier Reef as an "in danger" site, providing Australia reports back to the committee in December this year with an adequate account of what is being done to preserve the reef.

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