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Value
of Coral Reefs
Coral reefs are among nature’s
most spectacular creations. They are endowed with a multitude of
colourful marine plants and animals and are among the most biologically
diverse and productive ecosystems on earth. Coral reefs have many
functions:
Diversity
Coral reefs offer shelter, feeding and nursery grounds for many
marine animals and their young, sometimes they are called the “rainforests
of the ocean”. Reefs are considered to have the highest biological
diversity (biodiversity) of all shallow water marine ecosystems.
Living coral reefs are alive and busy with all kinds of creatures
such as fish, anemones, sponges, molluscs, crustaceans, echinoderms
and algae.
Protection
Coral reefs protect our coasts by acting as barriers against wave
action. As waves reach the shallow waters of a reef, they break
and lose most of their energy. Without the protection of coral reefs,
our coast would erode at a higher rate. It also creates ideal conditions
for other coastal ecosystems e.g. lagoons, sea grass beds and mangroves.
Tourism
& recreational value
Reefs are places of great beauty. Healthy reefs are popular destinations
for scuba diving, snorkelling and tourism, and boost the economies
of many countries.
Fisheries
and nutritional value
For many coastal communities, reefs are important sources of food
and daily income. Coral reefs contain rich feeding grounds for molluscs,
crabs, lobsters, fish and other edible species. Economies of many
countries are boosted 1prough the export of reef species. Reefs
also provide live fish and invertebrates for the aquarium trade.
Medicinal
Value
Coastal communities have for centuries exploited reef species for
medicinal and health purposes. In Palau, a particular Surgeonfish
is ground up and eaten for the treatment of a common illness of
chancre sores and fever. Amongst coastal communities of the Gulf
of Mannar in India, certain reef fish rich in iron are used to treat
anemia.
Some reef organisms
contain important pharmaceutical properties. For instance, chemicals
isolated from reef sponges have been used to develop drugs against
herpes and certain types of cancer.
Some coral skeletons
can be used as bone graft substitutes, as their structure is similar
to human bone tissue. As the human body is less likely to reject
a coral “bone”, these grafts are proving successful.
Sunlight contains
ultraviolet (UV) light that can be damaging to coral reefs. However,
corals contain pigments that protect them from these harmful uv
rays. These pigments are used in the development of sunscreens for
humans.
Threats
to Coral Reefs
Coral reefs in Sri Lanka and elsewhere in the tropical world, are
under severe stress due to a variety of different factors. Many
reefs have been lost as a result of man-made ( anthropogenic) threats
as well as natural causes. Rigorous efforts are needed to prevent
any further damage to these fragile ecosystems.
Man-made
pressures placed upon reefs.
Over-fishing and Destructive fishing practices
Over-fishing happens due to the increase in coastal populations
who depend on fishery resources, as large numbers of people compete
for limited resources. Certain technologically advanced fishing
methods also contribute to over-fishing as fishermen have easier
and faster access to fishing grounds and hence marine resources
are depleted faster than they can be replenished.
There are a
number of methods specifically designed for reef fisheries which
are now illegal as they are harmful to the reef and result in over-fishing,
which could lead to the ultimate collapse of the fisheries industry.
Such methods are known as unsustainable (short-term methods that
destroy important habitats and resources). What are the commonly
used destructive fishing methods ?
The
use of small mesh sized nets
By the use of this method, in addition to large fish, younger fish
(juveniles) are also caught. This hampers the reproduction cycle
of many species. The fish population takes longer to recover from
the impacts of fishing, as the young fish are removed before they
have a chance to grow into adults and breed.
The
use of bottom set nets
This method is used to capture marine species dwelling within the
reefs (e.g. lobsters, crabs). Corals are invariably damaged when
the bottom set nets are hauled in with its catch. In addition, ornamental
fish collectors use moxy nets to catch live fish, which also damages
the reefs. A moxy net is similar to a cast net. A diver places the
net over a patch of coral and chases the fish out of the coral by
disturbing the coral under the net with a crow bar
Blast/Dynamite
fishing
This activity is generally carried out over reefs in shallow water,
by throwing dynamite sticks into the water. The impact of the dynamite
kills most fish in the vicinity and can also cause severe damage
to the reef- destroying the “home” of reef species.
Dynamite fishing is extremely risky and can result in serious injuries
to the fishermen. In Sri Lanka, dynamite fishing is carried out
over relatively deep reefs (Rock habitats where fish congregate).
Scuba diving equipment is used to collect the dead fish. Dynamite
fishing is illegal in Sri Lanka.
Cyanide
fishing
Cyanide acts as an anaesthetic, and was originally introduced to
catch live fish for the aquarium trade. This practice is common
in countries such as the Philippines and Indonesia. Cyanide is toxic
and its use on the reef kills and damages large tracts of coral
and many non-target species of fish and invertebrates. The divers
crush cyanide tablets into plastic squirt bottles of seawater and
puff the solution at fish on coral heads. The fish often flee into
crevices, obliging the divers to pry and hammer the reefs apart
to collect their stunned prey. Cyanide fishing also poses health
risks to fishermen, through accidental exposure to the poison due
to the careless use of often poorly maintained, compressed air diving
gear by untrained divers.
Coastal
Development and Pollution
Many people are moving to coastal cities, attracted to job opportunities
found there. It is estimated that 60% of the world’s population
live within the coastal zone. It is also estimated that half a billion
people -8% of the total global population live within 100 kilometres
of a coral reef. To meet the demands of an eve~-increasing population,
expansion of cities and towns, shoreline construction and modification
of the coastline is often required.
Many of the
serious impacts of coastal development are related to pollution
and sedimentation. Rivers act as a transporting medium for pollutants
and sewage, directly into the marine environment. Sewage and other
organic pollutants cause problems as they act as fertilisers and
encourage algal growth, sometimes to such an extent that corals
become overgrown with algae. Algae also reduces the amount of light
reaching the corals, which reduces the level of photosynthesis (amount
of energy/food created).
Sedimentation of reefs occurs when shoreline currents and river
mouth currents change. This is often due to land clearance and removal
of vegetation upstream (e.g. deforestation) as well as the construction
of structures close to or at the waterfront e.g. harbours and hotels.
Marine transport
and shipping routes passing coral reef areas can also pose risks
e.g. Oil spills and ship groundings
Tourism
In general, tourists, both local and foreign, wish to see .a healthy
reef with many marine species. Therefore tourism often helps protect
coral reefs. However, certain tourist activities can be harmful
to reefs due to the lack of understanding of the fragility of reefs,
as well as the lack of planning and co-ordination. Construction
and shoreline development related to tourism -Refer to above description
on coastal development and pollution.
Boat and anchor
damage -In certain areas in Sri Lanka e.g. Hikkaduwa, boat trips
for tourists are known to have devastating effects due to excessive
numbers in a rather small area, and careless boat operators who
break parts of the reef by dropping boat anchors or by scraping
the reef tops with the bottom of their boats.
Trampling by
snorkelers, divers and bathers -tourists often walk on corals or
break pieces of coral to take back as souvenirs (eg. In Unawatuna,
Weligama and Polhena reefs in Sri Lanka). In many instances, tourists
are unaware of the damage they cause and the.time it would take
for the coral reef to recover. Scuba divers who accidentally kick
or touch corals can also cause damage to the reef ecosystem.
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