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Air pollution casts a cloud over coral reef growth

Tiny particles of air pollution can stunt the growth of coral reefs, according to a new study in Nature Geoscience. Using…

Air pollution has been found to have affected coral growth in the Caribbean over many decades. Lester Kwiatkowski, University of Exeter

Tiny particles of air pollution can stunt the growth of coral reefs, according to a new study in Nature Geoscience.

Using coral records from the western Caribbean between 1880 and 2000, researchers from the UK, Australia and Panama have shown for the first time how polluted air – from human activities such as burning coal or wood, as well as volcanic eruptions – can slow coral growth.

Since the 1950s, coral at two sites in Panama and Belize appears to have been affected by industrial air pollution.

Fine airborne particles, or aerosols, help scatter incoming sunlight and create cloudier, more reflective conditions.

This can reduce the sunlight reaching the sea, which means cooler sea temperatures and reduced photosynthesis that combine to slow coral growth.

The researchers discuss how coral reefs are vulnerable to a wide range of threats, including run-off from coastal development and mass bleaching events linked to climate change.

However, they say their new findings show for the first time how important air pollution could be to coral reefs.

The air pollution study coincides with a new journal article in Nature Climate Change, warning that the world’s oceans have been acting as a giant sink for extra heat from global warming, especially over the past decade.

They say if that heat is released back into the atmosphere, the effects of climate could quickly get worse.

Masking a bigger problem

Leading international coral expert Professor Ove Hoegh-Guldberg from the University of Queensland said the new air pollution study was “an important contribution” to understanding coral reefs.

Professor Hoegh-Guldberg, who is coordinating the oceans chapter of the next Intergovernmental Panel on Climate Change report, said the research highlights one of his biggest concerns: complacency about global warming, which is being partly masked by the cooling effect of aerosols.

The air pollution study describes how after World War II, booming industrial expansion in North America and to a lesser extent Central and South America led to rising air pollution, which appears to have caused a marked fall in sea surface temperature.

When clean-air policies were introduced in the 1970s, aerosol emissions dropped significantly. Sea surface temperatures then stabilized and subsequently began to rise again.

That was good news then. But Professor Hoegh-Guldberg is concerned about what today’s air pollution is masking.

“Aerosols may reduce the rate at which temperatures are increasing today, but given the health impacts and need to reduce aerosols, we may eventually have to pay the elevated temperature ‘debt’ as we clear up aerosols."

University of Southern Queensland Adjunct Professor Ian McPhail - a former chair of the Great Barrier Reef Marine Park Authority - said it was “a fascinating piece of work”.

“When it comes to looking after coral reefs, we tend to sweat over local issues like port development, dredging, nutrient flow from the land and so on,” Dr McPhail said.

“They’re all very important - but this is a reminder of some of the bigger regional and global atmospheric challenges we need to address too. We need to act on both those local and global fronts, and do it urgently.

“We must remember, we’re not just talking about the ecology of coral reefs, we’re also talking about the economy.

“Whether you’re talking about Belize - as this study does, which is home to the world’s second largest coral reef system - or you’re talking about Great Barrier Reef here in Queensland, these are places of extraordinary fauna and flora.

“That beauty and ecological diversity is what makes them major economic drivers for Belize and Australia alike. So the more we know about how these complex ecosystems work, the better we can protect them.”

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6 Comments sorted by

  1. Byron Smith
    Byron Smith is a Friend of The Conversation.

    PhD candidate in Christian Ethics at University of Edinburgh

    Thanks for this article. Does this research have implications for geoengineering suggestions based on solar radiation management? Would, for instance, high altitude sulphur injection be likely to have negative consequences for coral reefs?

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    1. David Arthur

      resistance gnome

      In reply to Byron Smith

      I'd expect that "solar radiation management" would have negative consequences for all sunlight-dependent species. What's more, stratospheric sulfate aerosols would also have negative consequences for stratospheric ozone.

      An idea that might have more promise is suppression of upper tropospheric cirrus clouds, on the basis that these clouds retard dissipation of thermal radiation to space (ie they are "greenhouse" clouds in the same sense that CO2 is a "greenhouse" gas).

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    2. Doug Hutcheson

      Poet

      In reply to Byron Smith

      Byron, the other major threat to coral reefs - in fact, to the oceans generally - is the lowering pH of the water, caused by dissolving CO2. Whether you refer to this as 'increasing acidification' or 'decreasing alkalinity', it is bad news for shell-forming organisms. High altitude sulphur injection may have some impact upon warming, but does not solve the pH issue. The only strategy that addresses both problems is reduction of atmospheric CO2.

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  2. George Harley
    George Harley is a Friend of The Conversation.

    Retired Dogsbody

    Hi and thanks for this. I disclose that I am a layman and dumb as a box of rocks. I can count though, so I am reasonably sure that global warming is happening and there is probably a significant anthropogenic contribution towards it.
    May I ask how much of the stunting of the reefs by airborne particles occurs because of known natural causes ( like volcanoes), possible natural causes (bush fires) and the obvious human ones? Does it matter, or am I a fish out of water?
    Regards

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    1. Greg North

      Retired Engineer

      In reply to George Harley

      I could say George that just because you're retired does not mean you should ask questions that are difficult to answer without more clouding and obscurity.
      However, I am sure someone will be able to tell you how all those events are factored into the modelling!

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    2. Greg North

      Retired Engineer

      In reply to George Harley

      Actually George, as much as the forever increasing human and animals populations, industry and use of fossil fuels is bound to have some impact on various workings of nature be it minor, accumulative or major, nature will still keep doing its own thing I suspect and we have many examples documented across just recent centuries let alone the hundreds before civilisation as even the Egyptians may have known it a few thousand years ago.

      Just recently I caught parts of programs by David Attenborough…

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