Publisher : Oxford University Press
Place of publication :
Publication year : 1994
Thematic : Biodiversity
Language : English
Note
Coral reefs are threatened by numerous anthropogenic impacts,
some of which have already had major effects worldwide. These unique
tropical environments harbor a high diversity of corals, reef invertebrates,
fish and other animals and plants. In most taxa, the species diversity of
reef-associated organisms is poorly understood because many ofthe spe?
cies have yet to be collected and described. High coral mortality has been
associated with natural events such as hurricanes, predator outbreaks and
periods of high temperature, but has also resulted from excess nutrients
in sewage and from specific pollutants. Reef corals and associated organ?
isms are also threatened by the possibility of global warming which will
result in rising sea levels and periods of increased temperature stress, and
which may also bring increased storm frequency and intensity. Although
the recent extensive episodes of coral bleaching in the Caribbean and
eastern Pacific cannot be causally related to global warming at this time,
the close link between bleaching and temperature suggests that global
warming will result in severe changes in coral assemblages. Major reef
destruction has followed outbreaks of the predatory seastar Acanthaster
planci in the Pacific. Although this is considered part of a natural distur?
bance cycle, there are indications that altered land use patterns and reduc?
tion of predators on this seastar by human activities may have increased
the severity of outbreaks. Recreational and commercial use of reefs has
also increased, and has caused extensive damage, especially near areas of
high population density. One ofthe most obvious and widespread losses
to reef biota is the reduction in fish populations from intense overfishing
in most reef areas ofthe world. Coasts without adequately managed reefs
have suffered intense overfishing for both local and export purposes, to
the point where the positive effects of fish on those reefs have been compromised.
The combination of these destructive factors has altered reefs
in all localities, and many that were once considered protected by distance
and low population density are now being exploited as well. On the pos?
itive side, improved understanding of ecoiogical processes on reefs com?
bined with concerted conservation efforts have managed to protect some
extensive areas of reef for the future.
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Keywords : variance
Encoded by : Pauline Carmel Joy Eje
