Authors of a cover story in journal Nature this week called for
immediate global action to reduce the magnitude of climate warming
in order to secure a future for coral reefs.
Bleached coral in 2016 on the
northern Great Barrier Reef. Image via Terry Hughes et
al./Nature.
Great Barrier Reef – the world’s largest
reef system – is being increasingly affected by climate change,
according to the authors of a
cover story in the March 15, 2017 issue of the
peer-reviewed journal Nature. Large sections of the
reef are now dead, these scientists report. Marine biologist
Terry Hughes of the ARC Center of Excellence for Coral Reef
Studies led a group that examined changes in the geographic
footprint – that is, the area affected – of mass bleaching events on
the Great Barrier Reef over the last two decades. They used aerial
and underwater survey data combined with satellite-derived
measurements of sea surface temperature. Editors at Nature
reported:
They show that the cumulative footprint of multiple bleaching
events has expanded to encompass virtually all of the Great
Barrier Reef, reducing the number and size of potential refuges
[for fish and other creatures that live in the reef]. The 2016
bleaching event proved the most severe, affecting 91% of
individual reefs.
The NY Times published this map on March 15, 2017, based on
information from the ARC Centre of Excellence for Coral Reef
Studies. It shows that individual reefs in each region of the
Great Barrier Reef lost different amounts of coral in 2016.
Numbers show the range of loss for the middle 50% of
observations in each region. Study authors told the NY Times
this level of destruction wasn’t expected for another 30 years.
Hughes and colleagues said
in their study:
During 2015–2016, record temperatures triggered a
pan-tropical episode of coral bleaching, the third global-scale
event since mass bleaching was first documented in the 1980s …
The distinctive geographic footprints of recurrent bleaching
on the Great Barrier Reef in 1998, 2002 and 2016 were determined
by the spatial pattern of sea temperatures in each year. Water
quality and fishing pressure had minimal effect on the
unprecedented bleaching in 2016, suggesting that local
protection of reefs affords little or no resistance to extreme
heat. Similarly, past exposure to bleaching in 1998 and 2002 did
not lessen the severity of bleaching in 2016.
Consequently, immediate global action to curb future warming
is essential to secure a future for coral reefs.
According to the website
CoralWatch.org:
Many stressful environmental conditions can lead to
bleaching, however, elevated water temperatures due to global
warming have been found to be the major cause of the massive
bleaching events observed in recent years. As the sea
temperatures cool during winter, corals that have not starved
may overcome a bleaching event and recover their [symbiotic
dinoflagellates (algae)].
However, even if they survive, their reproductive capacity is
reduced, leading to long-term damage to reef systems.
Read more from Terry Hughes et al: Global warming and recurrent mass
bleaching of corals
Read more from CoralWatch about coral bleaching
Read more from NY Times: Large Sections of Australia’s Great Reef
Are Now Dead, Scientists Find
In March 2016, researchers could see bleached coral in the
northern Great Barrier Reef from the air. Image via James
Kerry/ARC Center of Excellence for Coral Reef Studies.
Bottom line: Authors of a cover story
published on March 15, 2017 in the journal Nature called for action
to curb warming, to help save coral reefs.
Deborah Byrd created the EarthSky radio series in 1991 and
EarthSky.org in 1994. Today, she serves as Editor-in-Chief ...
http://earthsky.org/earth/great-barrier-reef-bleaching-dying-nature-2017