Debate Over Future of Coral Reefs
Billy.Causey at noaa.gov
Thu Jan 13 14:49:13 EST 2000
An article for your review:
PLANET ARK: Debate warms up over future of coral reefs
BRISBANE, Australia - It's the year 2100 and the once Great Barrier Reef
is a lifeless skeleton few people visit, a victim of global warming.
Or maybe not.
Some scientists see a very different picture and believe Australia's
Great Barrier Reef and other major world coral formations can adapt to
rising ocean temperatures.
Reefs are good barometers of climate change because they are sensitive
to ocean temperatures. Parts of them can die if the temperature rises
just a degree or two above normal and scientists are worried because
such events, called bleachings, are growing in frequency and intensity.
A report by the Australian Institute of Marine Science (AIMS) says the
Great Barrier Reef, off Australia's northeast coast, came through severe
bleaching in 1998 with a net increase in the amount of healthy hard
coral over the past two years.
Another report, sponsored by Greenpeace, had said global warming could
devastate the world's coral reefs by early in the new millennium and
could eliminate them from most areas of the planet by 2100.
"The future for the Great Barrier Reef may not be as gloomy as a recent
report claims," said Terry Done, senior principal scientist with the
Australian government's AIMS.
"The biodiversity of coral reefs may give them greater resilience than
the (Greenpeace) report gives them credit for," he said.
Bleaching occurs when coral becomes stressed and expels its life-giving
microscopic plants called zooxanthellae. The plants provide the coral
with food through photosynthesis.
AIMS examined 47 reefs which are part of the World Heritage-listed Great
Barrier Reef system and found that, while inshore reefs had lost up to
75 percent of corals in the 1998 bleaching, reefs in deeper water were
"The current state of coral is not as bad as you might be led to
believe," AIMS project leader Hugh Sweatman told Reuters.
"In general, the reef is in good shape. The reefs which made up most of
the world heritage area have shown net increases in hard coral in the
past two years."
ENTIRE REEF AT RISK
Sweatman's upbeat assessment contrasts with the Greenpeace-backed report
in July by Sydney University's Coral Reef Research Institute (CRRI).
That report predicted the Great Barrier Reef, which comprises 3,000
individual reefs, faced annual coral bleaching as oceans warm. It said
the entire reef was at risk of being killed off in 100 years.
The CRRI report's author, coral reef physiologist Ove Hoegh-Guldberg,
said there was no evidence coral reefs could simply adapt to changes in
the ocean's temperatures or repopulate with coral from other reefs.
"We don't have any experimental data to base that on," Hoegh-Guldberg
"Therefore to make the escape clause that coral bleaching isn't a
problem because corals will get better at adapting over time is
unfounded," he said.
Hoegh-Guldberg, who has studied coral bleaching for the past 15 years,
said coral reefs would not have time to recover if bleaching became a
LIVING ON THE EDGE
He said corals were now living close to their upper temperature
tolerance limit and bleaching events will be triggered by even slight
water temperature rises of one or two degrees Celsius.
"Corals tend to die in great numbers immediately following coral
bleaching events, which may stretch across thousands of square
kilometres (miles) of ocean. Bleaching events in 1998, the worst on
record, saw the complete loss of live coral from reefs in some parts of
He said bleachings are likely to occur annually in tropical oceans by
the end of the next 30 to 50 years, meaning reefs won't have time to
The result would be bleached skeletons unable to support a fraction of
the fish species that now depend on them.
Hoegh-Guldberg also said the loss of the reefs would have dire
consequences for tourism as well as fisheries.
His report said A$1.5 billion (US$960 million) was generated annually by
tourism at the Great Barrier Reef, A$2.5 billion by Floridean reefs and
about A$140 billion by Caribbean reefs.
AIMS scientist Done argued that most of the Great Barrier Reef had
escaped the 1998 bleaching lightly, even though some areas had been
"Even on the handful of reefs where most of the corals died, hard
individuals survived the trauma," Done said.
"This suggests there are genotypes out there that are ready to take over
as the seas warm. Currents will also tend to transport warm-adapted
types from the northern Great Barrier Reef to the warming waters in the
south," he said.
The AIMS survey measured corals in six separate belts of the Great
Barrier Reef and included fish counts and videotaping of coral to
calculate coral cover.
AIMS scientists said climate changes would likely alter the Great
Barrier Reef rather than kill it off.
"We need more research to find the answers," he said.
"To risk industries like tourism and fishing ... with unfounded
statements like this seems foolhardy."
Billy D. Causey, Superintendent
Florida Keys National Marine Sanctuary
PO Box 500368
Marathon, FL 33050
Phone (305) 743.2437, Fax (305) 743.2357
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