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Coral reefs head for 'knock-out punch' | Coral reefs head for 'knock-out punch' |
(about 3 hours later) | |
Repeat bouts of warmer seawater are posing a significant challenge to the world's tropical corals. | Repeat bouts of warmer seawater are posing a significant challenge to the world's tropical corals. |
A study of 100 reefs, published in Science Magazine, shows the interval between bleaching events in recent decades has shortened dramatically. | A study of 100 reefs, published in Science Magazine, shows the interval between bleaching events in recent decades has shortened dramatically. |
It has gone from once every 25-30 years in the early 1980s to an average of just once every six years today. | It has gone from once every 25-30 years in the early 1980s to an average of just once every six years today. |
Bleaching is caused by anomalously warm water, which prompts coral polyps to eject their symbiotic algae. | Bleaching is caused by anomalously warm water, which prompts coral polyps to eject their symbiotic algae. |
This drains the corals of their colour and is fatal unless conditions are reversed in a reasonably short time. | This drains the corals of their colour and is fatal unless conditions are reversed in a reasonably short time. |
But even if temperatures fall back quickly, it can still take many years for damaged reefs to fully recover. | But even if temperatures fall back quickly, it can still take many years for damaged reefs to fully recover. |
"If you go into the ring with a heavyweight boxer, you could probably stand up for one round, but once that second round comes - you're going down," said Dr Mark Eakin from the US National Oceanic and Atmospheric Administration (Noaa). | "If you go into the ring with a heavyweight boxer, you could probably stand up for one round, but once that second round comes - you're going down," said Dr Mark Eakin from the US National Oceanic and Atmospheric Administration (Noaa). |
"The acceleration in the return rate of bleaching events matches up very well with what the climate models have been telling us. They predict that by mid-century most of the world's coral reefs will be suffering yearly, or near-yearly, heat stress," he told BBC News. | |
One telling observation in the assessment is that as global warming has progressed - the "cold" phases in the famous La Niña-El Niño ocean oscillation have today become warmer than the "hot" phases were three decades ago. | One telling observation in the assessment is that as global warming has progressed - the "cold" phases in the famous La Niña-El Niño ocean oscillation have today become warmer than the "hot" phases were three decades ago. |
"There basically are no cool years anymore; there are just years that aren't too hot," said Dr Eakin. | "There basically are no cool years anymore; there are just years that aren't too hot," said Dr Eakin. |
Aside from their beauty, tropical corals provide important ecosystem services upon which the livelihoods of many millions of people depend. | Aside from their beauty, tropical corals provide important ecosystem services upon which the livelihoods of many millions of people depend. |
Reefs, for example, afford coastal protection from big waves, storms, and floods; they also act as key spawning and nursery grounds for economically important fish and other aquatic species. | Reefs, for example, afford coastal protection from big waves, storms, and floods; they also act as key spawning and nursery grounds for economically important fish and other aquatic species. |
This study concentrates on the climate challenge to corals, but many reefs are also experiencing other stresses, including pollution, overfishing and habitat destruction. | This study concentrates on the climate challenge to corals, but many reefs are also experiencing other stresses, including pollution, overfishing and habitat destruction. |
Unsurprisingly, the authors, led by Prof Terry Hughes from the ARC Centre of Excellence for Coral Reef Studies, Australia, call for renewed efforts to constrain and reduce emissions of greenhouse gases. | Unsurprisingly, the authors, led by Prof Terry Hughes from the ARC Centre of Excellence for Coral Reef Studies, Australia, call for renewed efforts to constrain and reduce emissions of greenhouse gases. |
But it is interesting to note how more radical conservation solutions are now increasingly being discussed. | But it is interesting to note how more radical conservation solutions are now increasingly being discussed. |
These touch on topics such as engineered super-corals that are better able to cope in very warm water, and how you might go about artificially cooling a reef at times of high stress. | These touch on topics such as engineered super-corals that are better able to cope in very warm water, and how you might go about artificially cooling a reef at times of high stress. |
But co-author Prof Nick Graham from Lancaster University, UK, cautions that such technical fixes cannot really address the size of the problem. | But co-author Prof Nick Graham from Lancaster University, UK, cautions that such technical fixes cannot really address the size of the problem. |
"These types of restoration techniques can be achieved at very small scales, but they're extremely costly, and you're talking about hundreds of square metres - whereas the size of coral reefs are hundreds to thousands of square kilometres," he told BBC News. | "These types of restoration techniques can be achieved at very small scales, but they're extremely costly, and you're talking about hundreds of square metres - whereas the size of coral reefs are hundreds to thousands of square kilometres," he told BBC News. |
"Coral reefs cover less than 0.1% of the world's oceans and yet they house a third of all marine biodiversity. And the oceans cover 70% of our planet so they're housing a huge amount of the biodiversity of our planet. So, anyone who cares about extinction, about biodiversity, needs to worry about the future of coral reefs." | "Coral reefs cover less than 0.1% of the world's oceans and yet they house a third of all marine biodiversity. And the oceans cover 70% of our planet so they're housing a huge amount of the biodiversity of our planet. So, anyone who cares about extinction, about biodiversity, needs to worry about the future of coral reefs." |
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos | Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos |