TL: CORAL REEFS UNDER THREAT (GP)
SO: Greenpeace Pacific Campaign- Greenpeace US and NZ
DT: Spring 1989
Keywords: oceans coral south pacific islands gp reports /


     Coral reefs are among the earth's most biologically
productive and diverse ecosystems. Reefs provide critical habitat
for an abundance of sedentary and migratory sea life and in turn,
yield fish, shellfish and crustaceans on which many Pacific
islanders depend. The presence of reefs and sandy beaches (which
corals help form), have made tourism the leading economic sector in
several Pacific islands. Of foremost importance for humans however,
is a reef's ability to protect a coastline, preventing erosion and
creating sheltered harbors.
     Although they are one of the planet's most long-lived
natural communities, only recently has progress been made in
understanding their importance on a local and a global scale. In
the tropical Pacific where coral reefs are a dominant feature,
these fragile ecosystems are facing unprecedented destruction.    
 Throughout their range in the South Pacific, vulnerable coral
reefs are showing signs of stress and damage. Many human
activities, both inland and in or near the coastal environment,
have impacts which harm coral reefs thus rendering them incapable
of fulfilling their vital role in the ecology of the Pacific.

What Are Coral Reefs?

     Coral reefs are tropical, shallow water ecosystems, largely
restricted to the area between the latitudes 30 degrees south and
30 degrees north. In the tropical Pacific, warmth, sunlight and
clear, well-circulated water help promote the growth of corals,
which generally have very specific requirements for temperature,
water clarity, light, salinity and oxygen.
     Reef-building corals or stony corals are animals (polyps) that
collectively deposit calcium carbonate to build colonies. The coral
polyps have symbiotic algae (zooxanthellae) within their tissues
which process the polyps waste products, thus retaining nutrients.
A reef is a population of stony corals which continues to build on
products of its own making, however not all reefs are constructed
solely of corals. In particular, certain types of red algae also
contribute to the formation of the reef framework.      
     Reefs fall into two main categories: shelf reefs, which form
on the continental shelf of large land masses, and oceanic reefs,
which develop in deeper waters, often in association with oceanic
islands. Some peoples of the Pacific live on coral atolls, which
are roughly circular reefs around a central lagoon and are
typically found in oceanic waters.
     Many reef-building corals have slow growth rates, which may be
slowed further by sources of natural stress such as storms,
predation, disease and sea level changes. Although reefs are well
adapted to recover from these disturbances, recovery rates can vary
from a few years to several decades. Despite a reef's
experience with constant change, there is increasing evidence that
a reef's recovery rate may significantly slow as a result of human
impact, combined with natural disturbance. Human-induced damage is
also more apt to be chronic rather than temporary.

Threats to Coral Reefs

Sedimentation

     Soil run-off substantially increases the sediment load of
coastal waters and is one of the most widespread problems in the
region that has damaging effects on corals. The reefs most
affected are fringing (nearshore reefs) around high islands where
the soil is eroded after deforestation, slash and burn
agriculture, mining and mangrove destruction. Once removed from the
land, soil can be carried to the sea by a nearby river and
deposited on coral reefs. Severe damage results when corals can not
tolerate the level of sediment or do not have the behavioral or
physiological responses to remove sediment. When the coral reef
community is damaged, the diversity and abundance of fish
decreases. Increased silt load could act indirectly, for example,
on a tuna fishery by killing planktonic larvae of coral reef fish
upon which tuna feed. Siltation is also caused by harbor dredging
(commercial and military), oil drilling, and construction work.

Domestic, Industrial and Agricultural Pollution

     The problem of soil run-off is often compounded by the input
of sewage, pesticides, and other pollutants. The uncontrolled
discharge of generally untreated sewage and industrial effluents
into coastal waters, is a common practice in many Pacific
islands. These pollutants accelerate the growth of algae which
smothers corals and depletes oxygen. If the pollution source is not
removed, a reef can rapidly deteriorate and the fish and
invertebrates dependent on the reef, either leave or perish. In
addition, serious health hazards are posed to humans who swim in
polluted waters or consume fish/shellfish contaminated with fecal
bacteria or toxins.

Deleterious Fishing Methods/Overfishing

     Over-fishing and destructive fishing methods (DFMS) are
responsible for reducing the abundance of reef fishes, disrupting
spawning and feeding grounds, and reef degradation. In heavily-
populated islands, catch rates of shallow water reef fish have
fallen drastically due to heavy exploitation. The problem of over-
fishing is exacerbated by DFMs and by increased runoff and
siltation.
     Although prohibited in most Pacific nations, the practice of
blast fishing, commonly referred to as "dynamiting," and the use of
fish poisons or intoxicants are widespread. In addition to the
physical damage these inflict on a reef, they are indiscriminate
and wasteful 'fishing' methods. Blast fishing simply involves
dropping one or more charges from a boat into the water, then the
boat moves off to one side and later returns to retrieve the dead
fish. This practice results in a high kill rate of many species of
fish, only a portion of which are harvested. Fish are also killed
or stunned (for easy capture) - by fishermen and aquarium fish
collectors - with the use of bleach, cyanide and pesticides. These
toxic substances pollute the marine environment and pose a serious
threat to marine life, and because these substances are
incorporated into the reef food chain, humans who consume
contaminated harvested fish/shellfish are also at risk.
     Another human health problem associated with areas of
damaged coral is ciguatera poisoning. This distinctive type of food
poisoning is caused by the consumption of tropical fish, that have
been contaminated with a marine toxin. It has been demonstrated
that the ciguatoxin adheres to dead or damaged coral surfaces and
algae which fish species graze on. While doing no obvious harm to
the fish, the toxin becomes concentrated in humans by way of the
marine food chain. Ciguatera outbreaks often occur after the
disturbance of coral reefs by human activities or natural causes.
Ciguatera poisoning is a widespread concern, prevalent in French
Polynesia, Australia, New Caledonia, and some smaller island
nations.

Nuclear Weapons Testing

     The majority of nuclear weapons testing in the South Pacific
has taken place in, over or under low-lying coral atolls.
Consequences of nuclear testing are twofold - direct blast
effects and long-term radiation effects. Nuclear detonations
extensively damage fragile coral reefs by leaving behind deep
craters and creating fissures in the limestone substrate. In some
instances, nuclear weapons tests have caused the total
vaporization of atolls! Nuclear detonations and storms are
responsible for depositing tons of radioactive mud, scrap and waste
into the marine environment. The consequences of radiation exposure
to coral reefs and marine life are more subtle
(biochemical and genetic changes) and need to be further
investigated.

Exploitation of Reef Species

     The extraction of coral from reefs for profit and possession
is an increasing and ill-monitored problem. Souvenir-collecting
tourists and commercial coral operations can both be agents of a
reef's demise, as can a company which mines large quantities of
coral and sand for building materials. The over-exploitation of
many reef fishes, molluscs and invertebrates (particularly black
and stony corals, collected for the marine curio trade), may result
in an ecological imbalance of a reef and a decrease in its
diversity.

Climate Change

     For coral reefs and in particular low-lying atolls, a
growing concern is the potential impact of climate change on sea
level. The 'greenhouse effect,' a gradual increase in the
temperature of the Earth's atmosphere as a result of a buildup of
carbon dioxide and other gases, may cause physical expansion of the
ocean. Studies indicate that a one meter rise in sea level -enough
to drown many Pacific atolls entirely - could occur in the next 50
to 100 years. It is doubtful that reef growth could keep up with
sea level rise.      
     Reefs may also be affected by changes to weather patterns and
world-wide oceanographic conditions which are predicted to occur
also as a result of the greenhouse effect. The phenomenon of coral
"bleaching" (loss of symbiotic zooxanthellae) and
subsequent mortality is becoming far more extensive. Bleachings may
be caused by unusual meteorological and oceanographic events such
as the abnormally high sea-water temperatures which
accompanied the severe 1982-83 El Nino event.

Preserving Coral Reefs

     The preservation and management of coral reefs is an
international concern. Like their terrestrial analogs, tropical
rainforests, coral reefs are very productive and diverse
ecosystems that are being seriously threatened at a faster rate
than the rate of progress being made in our ecological and
scientific understanding of how they work. No one program can
reverse the current trend of widespread reef degradation, but
actions can be taken on local and international levels to help halt
further degradation and
facilitate the recovery of devastated areas.
     The knowledge and technology to avoid much human-induced
destruction to reefs is now available. For example, reforestation
of rainforests and mangroves can substantially reduce soil run-off
and waterless waste treatment practices can replace direct
discharge into coastal waters. To slow the surge of damage to reefs
caused by ill-planned development and ill-managed
activities, coastal zone management programs are now being
developed in many Pacific countries. Evidence supports the
concept of placing coastal management in the control of local
coastal communities. Public support for conservation of reefs is
essential where enforcement is often minimal. A more direct attempt
at reef management involves the establishment of marine protected
areas.      
     Many human activities associated with development do not have
to be in conflict with coral reef preservation and
management, but in some cases the two are not compatible.
Activities such as nuclear weapons testing and the disposal of
radioactive and hazardous wastes are incompatible with the
protection of low-lying coral atolls. A low-lying coral atoll
cannot be distinguished from its marine environment and must be
thought of as an inherent part of that marine environment. It is
unrealistic to imagine that toxic materials (from testing and
storage) can be kept on an atoll - a land area subject of
typhoons and tsunamis - and separated from the ocean environment.
Therefore, low-lying atolls should be designated as "specially
protected areas" deserving of protection and careful planning.

     It has been theorized that if a high island with a fringing
reef subsides slowly enough to allow the reef to keep growing, it
will eventually form an atoll, a chain of reefs enclosing a lagoon.

     The coral atoll of Moruroa in French Polynesia, has been one
of the sites of France's nuclear weapons testing program. There is
now evidence of underground subsidence, deep cracks and
fissures in Moruroa.


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