Most
coral dead in central section of Great Barrier Reef, surveys reveal
As
mass bleaching sweeps the world heritage site, scientists also find
an average of 35% of coral dead or dying in the northern and central
sections of the reef
Michael Slezak
Sunday 29 May 2016
21.00 BST
The majority of
coral is now dead on many reefs in the central section of the Great
Barrier Reef, according to an underwater survey of 84 reefs, in the
worst mass bleaching event to hit the world heritage site.
An average of 35% of
coral was now dead or dying in the northern and central sections,
according to the surveys led by the Australian Research Council’s
Centre of Excellence for Coral Reef Studies.
But in good news for
tourists and the tourism industry, only 5% of coral has died on reefs
south of Cairns.
The in-water
mortality studies followed earlier aerial surveys, which found that
93% of the Great Barrier Reef had been affected by bleaching.
Coral bleaches when
it gets too hot for too long. The water temperature stresses the
coral and it expels the colourful algae it relies on to give it
energy. If warm conditions persist, the coral dies and can get taken
over by seaweed.
But if the water
returns quickly to temperatures that are no longer stressful, the
coral can recover, regaining its symbiotic algae. That is what
researchers expect to happen to most of the bleached coral south of
Cairns.
“Fortunately, on
reefs south of Cairns, our underwater surveys are also revealing that
more than 95% of the corals have survived, and we expect these more
mildly bleached corals to regain their normal colour over the next
few months,” said Mia Hoogenboom from James Cook University.
The conditions that
led to the bleaching event were estimated to have been virtually
impossible if it were not for the greenhouse gases humans have
released into the atmosphere. Models showed they would be average
conditions within 20 years.
Terry Hughes from
James Cook University, who led the survey work, said: “This year is
the third time in 18 years that the Great Barrier Reef has
experienced mass bleaching due to global warming, and the current
event is much more extreme than we’ve measured before.
“These three
events have all occurred while global temperatures have risen by just
1C above the pre-industrial period. We’re rapidly running out of
time to reduce greenhouse gas emissions.”
John Pandolfi from
the University of Queensland said the reef was already struggling to
cope with the regularity of the bleaching events.
He said the reef was
no longer as resilient as it once was. “It is critically important
now to bolster the resilience of the reef, and to maximise its
natural capacity to recover,” said Pandolfi.
The reef’s ability
to recover from the increasingly regular bleaching events is being
hampered by water pollution.
A recent study
suggested $10bn investment was needed to adequately reduce pollution
levels and improve the reef’s resilience.
The bleaching
hitting the Great Barrier Reef is part of a global bleaching event,
partly driven by a massive El Niño and climate change. By February
this year, the event was already the longest-running global bleaching
event in history, and it is expected to continue into the coming
months.
Sem comentários:
Enviar um comentário