#Status of Coral Reefs 2002 - International Coral Reef Action Network

Status of Coral Reefs of the World: 2002
significant mortality (see Box). At the time of writing this report, a mild to moderate El
Niño is developing in the Pacific, and there are concerns that the reefs will again suffer
more bleaching.
There has been no field evidence of corals having reduced calcification and growth rates
under the influence of increased concentrations of CO 2 in seawater, however, there has
been confirmation of the potential for these effects during research conducted in
Biosphere II in Arizona as well as in other mesocosm studies. This remains a strong
potential threat that increasing atmospheric CO 2 will reduce the abilities of corals to grow
and calcify their skeletons. Similarly the concentrations of CO 2 in the atmosphere
continue to increase, and the Intergovernmental Panel on Climate Change is now stating
definitively that global warming is occurring and that ecosystems will be altered as a
result. There have been strong predictions from climate models that coral reefs will
experience more regular and severe bouts of coral bleaching in the next decades.
It is clear that coral reefs will not become extinct, as some have predicted, but we will
probably witness considerable reductions in coral cover and species diversity if these
models are correct. Our current experience is that episodes of bleaching are becoming
more severe and frequent, thus we should assume that coral reefs will be subject to more
damage. A few reefs are demonstrating resistance and resilience (ability to recover) from
climate change impacts, including bleaching and disease; but most are susceptible. This
alone should be sufficient warning to governments to reduce greenhouse gas emissions
into the atmosphere.
Diseases and Plagues
There is a growing plague of the crown-of-thorns starfish (COTS; more correctly seastar)
on the Great Barrier Reef (GBR) of Australia, particularly concentrated in the Cairns
section and central parts of the GBR. These have caused severe reductions in coral cover
on affected reefs. There are also disturbing reports of larger than normal COTS
populations in the northern Red Sea, Japan, Palau and Fiji. It is apparent that the COTS
will remain a chronic problem for many reefs and a devastating problem for others in the
Indo-Pacific. There is limited evidence that the outbreaks are triggered by a humaninduced
change to coral reef environments, but the nagging suspicion is that this is true
and that the plagues are an inadvertent result of human activities.
Coral diseases have become a chronic and frequently catastrophic problem for coral reefs
in the Caribbean and wider Atlantic region. Diseases stripped many of the branching
corals from Caribbean reefs in the 1980s and 90s, with devastating effects on the major
shallow water coral, the elkhorn (Acropora palmata). The extent of the problems has been
recognised by the US Coral Reef Task Force, which convened a special task force to tackle
the problem. A wide range of coral diseases has so far been reported and the causative
agents for a few have been identified. Until recently it was considered that such major
disease outbreaks were confined to the wider Caribbean, with few reported incidences on
Indo-Pacific coral reefs. However, in early 2002 an outbreak of ‘white syndrome’ was
reported to be killing significant patches of corals on the Great Barrier Reef of Australia.
Thus wait to see whether coral diseases are another manifestation of human induced
stress to coral reefs.
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