Coral
bleaching event now biggest in history – and about to get worse
US
weather agency says bleaching is now the most widespread on record
and is likely to continue for unprecedented third year
Michael Slezak
Monday 20 June 2016
22.01 BST
The coral bleaching
event sweeping the globe and destroying vast tracts of valuable coral
reef is now officially the most widespread in recorded history, and
is likely to continue for an unprecedented third year, according to
the US weather agency.
For the coming four
months, National Oceanographic and Atmospheric Administration says
its forecasts show warm ocean temperatures are expected to cause
bleaching in the northern hemisphere, including around Hawaii,
Micronesia, the Florida Keys and Puerto Rico.
“All northern
hemisphere US-coral reefs are on alert for coral bleaching this
year,” said Mark Eakin, coordinator of Coral Reef Watch at Noaa.
“If we see bleaching in Florida or Hawaii this year it will be
three years in a row.”
Coral in every major
reef region has already experienced severe bleaching. About 93% of
the reefs on Australia’s Great Barrier Reef have been affected, and
almost a quarter of the reef on the 2,300km stretch is now dead.
Hawaii and the
Florida Keys, which will probably be hit by bleaching in the coming
months, have been affected twice already, in mid-2014 and mid-2015.
Reefs in the Indian Ocean around the Maldives and Western Australia
have suffered severe bleaching, as have those in the rest of the
Pacific, the Red Sea and the Caribbean.
Although the
bleaching event was already the longest in recorded history and was
predicted to run past the middle of the year, Noaa’s latest climate
model-based forecasts now suggest it will run at least through to the
end of 2016.
Coral bleaches when
water temperatures are a couple of degrees above the normal summer
maximum for longer than about two weeks. Climate change has caused
global sea surface temperatures to rise by about 1C over the past
century, pushing corals closer to their bleaching threshold. A strong
El Niño, as well as other weather phenomena, raised the temperature
further this year.
“It’s time to
shift this conversation to what we can and are doing to conserve
these amazing organisms in the face of this unprecedented global
bleaching event,” said the director of Noaa’s coral reef
conservation program, Jennifer Koss.
Coral reefs can
often recover from bleaching when there is enough time between
bleaching events, provided there aren’t too many other stressors,
such as overfishing and water pollution.
Coral bleaching
spreads to Maldives, devastating spectacular reefs
Read more
Relieving the local
stressors was important, but not enough, Koss said. “Globally, we
need to better understand what actions we all can take to combat the
effects of climate change.”
Noaa tracks the
water temperature from satellite data and uses that to estimate the
probable bleaching it will cause. Eakin said the information was then
given to scientists and managers on the ground.
“The biggest
bleaching threat over the next six months is to the reefs in two US
freely associated states: Palau and the Federated States of
Micronesia,” he said. “Islanders there are very dependent on
their coral reefs and diving tourism is a major contributor to their
economies. This event may have major ecological and economic impacts
on those islands.”
He added: “It is
crucial that scientists and the public continue in-water monitoring
to track the actual extent and severity of the bleaching it causes.”
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