Reuters 9 Jun 09;
LONDON (Reuters) - Climate change has contributed to a flattening of the complex, multi-layered architecture of Caribbean coral reefs, compromising their role as a nursery for fish stocks and a buffer against tropical storms, a study shows.
The analysis of 500 surveys of 200 reefs, conducted between 1969 and 2008, showed the most complex types of reef had been virtually wiped out across the entire Caribbean.
Such reefs -- typified by Table Corals of over 1 meter across and huge antler-shaped Staghorn Corals -- act as a sanctuary for local fish stocks and a hunting ground for larger, commercially fished species.
Many have been replaced with the flattest types of rubble-strewn reef, which now cover about three quarters of the Caribbean's reef area, up from about a fifth in the 1970s, said the study, published in the Royal Society journal Biology Letters.
The biggest impact has occurred in the last decade, said the report by researchers from Britain's University of East Anglia and Canada's Simon Fraser University.
"Lack of ... refuges for species with commercial importance, such as lobsters and large fishes may compromise the long-term sustainability of fisheries and fishing communities," the report said.
Flatter reefs are also less effective in protecting coastal homes and villages from storm swells and tidal surges.
"The importance of this is going to increase," said Lorenzo Alvarez of the University of East Anglia, who led the study. "Many scientists think there will be more hurricanes in the future."
The degradation of Caribbean reefs is not entirely linked to climate change, with disease killing about 90 percent of Elkhorn and Staghorn Corals in the 1970s, but a second period of coral destruction is now under way.
New damage is typified by "coral bleaching," which occurs when the tiny organisms that build coral reefs become stressed and abandon their colonies.
"We suggest that the last period of decline is partly due to climate change, but also due to several other human impacts such as over-fishing and coastal development," Alvarez said. "In future, we'll need to change our behavior and reduce the stress on the reefs."
(Writing by Pete Harrison; Editing by Jon Hemming)
Caribbean reefs 'flattened' in just 40 years
Andy Coghlan, New Scientist 10 Jun 09;
In just 40 years, the Caribbean's spectacular branched corals have been flattened. Research reveals that the corals have been replaced by shorter rival species – and points to climate change as at least partly to blame.
Most of the reefs have lost all the intricate, tree-like corals that until the 1970s provided sanctuary for unique reef fish and other creatures, as well as protecting coastlines by sapping the energy of waves.
Coral diversity is important for both the many species that swell on reefs and for coastal protection, says Jennifer Gill of the University of East Anglia and a member of the research team.
She and her colleagues analysed data over the past 40 years from 500 surveys of 200 Caribbean reefs. They say that the flattening process took place in two main phases. Firstly, in the late 1970s, a condition called white-band disease swept through the reefs, killing 90 per cent of the most spectacular tree-like elkhorn and staghorn corals.
The second phase, in 1998, saw many of the remaining tree-like corals being wiped out during a massive bleaching event, probably driven by global warming.
Different corals – fast-growing but short-lived "weedy" species – then took over the reefs, outcompeting most of the remaining tree-like corals. The researchers found that flat reefs now cover 75 per cent of the Caribbean, compared to just 20 per cent in the 1970s.
"It's difficult to see how to reverse any of this," says Gill. The biggest problem, she says, is the sheer density of human habitation. Across the Indian Pacific, by contrast, where human habitation is sparse, reefs remain in almost pristine condition.
Decline warning
"The study confirms the dire ecological impacts of the widespread degradation of coral reefs globally, but particularly in the Caribbean," says Alex Rogers, a marine biologist at the Institute of Zoology in London.
"The loss of structural complexity that reefs provide is a huge disaster for the species associated with reefs," says Rogers. "Coral reefs are probably the most species-rich marine ecosystems and host an estimated 1 to 2 million species, including a quarter of all fish."
He says the only answer may be immediate cuts in emissions of carbon dioxide from burning of fossil fuels, which would curb the amount of bleaching and limit acidification of oceans that results when they absorb carbon dioxide. "A lethal combination of increased occurrence and severity of bleaching, along with ocean acidification, will mean that already severely damaged reefs will undergo a catastrophic decline in the next 40 years," warns Rogers.
A recent assessment of reef biodiversity by the International Union for the Conservation of Nature found that a third of shallow-water corals that build reefs faced extinction – with those in the Caribbean at greatest risk.
Journal reference: Proceedings of the Royal Society, B (DOI: 10.1098/rspb.2009.0339)
Caribbean Coral Reefs Flattened
ScienceDaily 9 Jun 09;
Coral reefs throughout the Caribbean have been comprehensively 'flattened' over the last 40 years, according to a disturbing new study by the University of East Anglia (UEA).
The collapse of reef structure has serious implications for biodiversity and coastal defences – a double whammy for fragile coastal communities in the region.
It was already known that coral cover in the Caribbean was in decline, but this is the first large scale study showing exactly what this means for the architecture of the region's reefs.
Published online on June 10 by the Proceedings of the Royal Society B, the researchers found that the vast majority of reefs have lost their complex structure and become significantly flatter and more uniform. The most complex reefs have been virtually wiped out.
The researchers, working with colleagues at Simon Fraser University in Canada, analysed changes in the structure of reefs using 500 surveys across 200 reefs conducted between 1969 and 2008. They found that 75 per cent of the reefs are now largely flat, compared with 20 per cent in the 1970s.
There have been two major periods of reef flattening. The first occurred when a widespread disease killed about 90 per cent of the Elkhorn and Staghorn corals in the late 1970s. The second period has been underway more recently and is thought to have been caused by an increase in the intensity and frequency of coral bleaching events, as a consequence of human-induced climate change increasing sea surface temperatures.
Lead researcher Lorenzo Alvarez-Filip, of UEA's School of Biological Sciences, said: "For many organisms, the complex structure of reefs provides refuge from predators. This drastic loss of architectural complexity is clearly driving substantial declines in biodiversity, which will in turn affect coastal fishing communities.
"The loss of structure also vastly reduces the Caribbean's natural coastal defences, significantly increasing the risk of coastal erosion and flooding."
Reversing declines in reef architecture now poses a major challenge for scientists and policy-makers concerned with maintaining reef ecosystems and the security and well-being of Caribbean coastal communities.
Journal reference:
1. L Alvarez-Filip, N Dulvy, J Gill, I M Côté and A Watkinson. Flattening of Caribbean coral reefs: region-wide declines in architectural complexity. Proceedings of the Royal Society B, June 10, 2009
Adapted from materials provided by University of East Anglia, via EurekAlert!, a service of AAAS.
Read more!
Posts
visitors since Nov 07