degradation, pollution, and food-web changes have had
significant impacts, resulting in formerly abundant species
now being rare and marked changes in resource utilization.
The 2008 Status Report of the World’s Coral Reefs
(Wilkinson, 2008) estimates that 19% of the world’s original reefs are effectively lost forever; 15% are seriously
threatened with loss likely in next 10–20 years; and 20%
are under threat of loss in 20–40 years. The latter two estimates are made without considering the looming threats of
global climate change or that effective future marine management may conserve more coral reefs. If current pressures continue, some consider that 60% of the world’s
coral reefs may be severely damaged by 2050.
Key threats to marine conservation and especially
coral reefs
1. Climate change – Climate change impacts on coral
reefs and marine ecosystems are already having
marked environmental effects, and the consequent
impacts are likely to flow onto the industries that
depend on these areas as well as coastal communities.
The impacts of climate change on marine biodiversity
are being observed throughout the world – carbon
dioxide concentrations have increased dramatically in
recent decades; the oceans are warming and becoming
more acidic, frequently bleaching large areas of coral;
and sea-level rise is now flooding some coastal
communities.
2. Land-based water quality – Coral reefs can be
impacted by a variety of land-based pressures including agricultural runoff, inadequate sewage and
stormwater treatment, siltation from coastal development, deforestation or beach re-nourishment projects,
contamination from petroleum products, etc.
Agricultural runoff can contain herbicides, pesticides,
and nutrient fertilizers. Elevated levels of nitrogen and
phosphorus may result in algal blooms that can potentially grow much faster and out – compete corals.
Human sewage, often untreated, can add nutrients,
microorganisms, and other pollutants to coral reefs
and can cause eutrophication.
3. Unsustainable harvesting (fishing or collecting) –
Unsustainable harvesting can cause a variety of negative impacts on coral reefs, including altering trophic
interactions causing indirect environmental effects.
For example, where predators have largely been
removed, increases in the population of their prey have
resulted in unexpected flow-on effects. Unsustainable
fishing or the depletion of fish spawning sites can also
reduce genetic variation in a population, making it
harder for species to adapt to environmental change.
Over-fishing can have major impacts on target species and has led to the extinction of species in some
areas (e.g., Queen Conch), but can also have major
impacts on non-target species (by-catch) as well as
cause habitat destruction.
Discarded fishing gear (e.g., ghost nets) can damage
reefs and also have major impacts on marine biodiversity. Marine debris, especially plastics and monofilament fishing line, can abrade corals and prove lethal
for birds, fish, and turtles that become entangled in it
or mistake it for food and ingest it.
4. Direct physical damage (e.g., blast fishing, dredging,
mining, infilling, etc.) – Many fishing practices harm
coral reefs by physically damaging habitat or by killing
non-targeted species. Blast fishing occurs in some parts
of the world, whereby underwater explosions are used
to injure fish so that they float to the surface where they
are easily captured. The blast, however, also destroys
coral and flattens the reef structure. In some places,
fishermen use cyanide or other poisons to stun fish so
that they can be captured alive, but small fish and coral
polyps may also be killed.
Limestone mining or infilling for coastal developments have obvious major impacts, completely
destroying coral reefs or severely altering hydrological
flow patterns.
The depletion caused by the harvest of coral and
“live rock” for the aquarium/curio trade has damaged
many reefs around the world.
5. Indirect impacts from marine or coastal developments –
Human activities on land such as the building of ports,
industrial infrastructure, deforestation, tourism facilities,
or other coastal developments can lead to increased rates
of sedimentation affecting adjacent reefs. High sediment
loads can smother corals or decrease light penetration,
thereby reducing the photosynthetic ability of the symbiotic algae in coral.
6. Unsustainable tourism/recreation – Anchors, accidental boat groundings, and propeller strike can all crush
and scar coral. The fins of divers and snorkelers and even
their diving equipment can inadvertently damage coral.
Well-meaning tourists may feed reef fish, but this can
change feeding behavior with other flow-on effects.
Similarly, shell collecting, fossicking, and uncontrolled
reef-walking can have detrimental impacts on corals.
7. Invasive species (pest plants, animals, diseases) or outbreaks of native species – Invasive marine species may
be introduced by a variety of vectors, including ballast
water discharge, biofouling on vessel hulls or within
internal seawater pipes in commercial and recreational
vessels, aquaculture operations (accidentally or intentionally) and aquarium imports, as well as marine
debris carried by ocean currents.
At high densities, outbreaks of species that eat juvenile or adult corals can cause major problems for reefs
and their associated species (e.g., the crown-of-thorn
starfish, a long-spined species of sea urchin, and
a small gastropod snail have all caused major problems
in many coral reefs around the world).
The types and extent of diseases attacking corals
have increased markedly in recent years and coral diseases such as Black Band and White Plague are
CONSERVATION AND MARINE PROTECTION AREAS
231
significant impacts, resulting in formerly abundant species
now being rare and marked changes in resource utilization.
The 2008 Status Report of the World’s Coral Reefs
(Wilkinson, 2008) estimates that 19% of the world’s original reefs are effectively lost forever; 15% are seriously
threatened with loss likely in next 10–20 years; and 20%
are under threat of loss in 20–40 years. The latter two estimates are made without considering the looming threats of
global climate change or that effective future marine management may conserve more coral reefs. If current pressures continue, some consider that 60% of the world’s
coral reefs may be severely damaged by 2050.
Key threats to marine conservation and especially
coral reefs
1. Climate change – Climate change impacts on coral
reefs and marine ecosystems are already having
marked environmental effects, and the consequent
impacts are likely to flow onto the industries that
depend on these areas as well as coastal communities.
The impacts of climate change on marine biodiversity
are being observed throughout the world – carbon
dioxide concentrations have increased dramatically in
recent decades; the oceans are warming and becoming
more acidic, frequently bleaching large areas of coral;
and sea-level rise is now flooding some coastal
communities.
2. Land-based water quality – Coral reefs can be
impacted by a variety of land-based pressures including agricultural runoff, inadequate sewage and
stormwater treatment, siltation from coastal development, deforestation or beach re-nourishment projects,
contamination from petroleum products, etc.
Agricultural runoff can contain herbicides, pesticides,
and nutrient fertilizers. Elevated levels of nitrogen and
phosphorus may result in algal blooms that can potentially grow much faster and out – compete corals.
Human sewage, often untreated, can add nutrients,
microorganisms, and other pollutants to coral reefs
and can cause eutrophication.
3. Unsustainable harvesting (fishing or collecting) –
Unsustainable harvesting can cause a variety of negative impacts on coral reefs, including altering trophic
interactions causing indirect environmental effects.
For example, where predators have largely been
removed, increases in the population of their prey have
resulted in unexpected flow-on effects. Unsustainable
fishing or the depletion of fish spawning sites can also
reduce genetic variation in a population, making it
harder for species to adapt to environmental change.
Over-fishing can have major impacts on target species and has led to the extinction of species in some
areas (e.g., Queen Conch), but can also have major
impacts on non-target species (by-catch) as well as
cause habitat destruction.
Discarded fishing gear (e.g., ghost nets) can damage
reefs and also have major impacts on marine biodiversity. Marine debris, especially plastics and monofilament fishing line, can abrade corals and prove lethal
for birds, fish, and turtles that become entangled in it
or mistake it for food and ingest it.
4. Direct physical damage (e.g., blast fishing, dredging,
mining, infilling, etc.) – Many fishing practices harm
coral reefs by physically damaging habitat or by killing
non-targeted species. Blast fishing occurs in some parts
of the world, whereby underwater explosions are used
to injure fish so that they float to the surface where they
are easily captured. The blast, however, also destroys
coral and flattens the reef structure. In some places,
fishermen use cyanide or other poisons to stun fish so
that they can be captured alive, but small fish and coral
polyps may also be killed.
Limestone mining or infilling for coastal developments have obvious major impacts, completely
destroying coral reefs or severely altering hydrological
flow patterns.
The depletion caused by the harvest of coral and
“live rock” for the aquarium/curio trade has damaged
many reefs around the world.
5. Indirect impacts from marine or coastal developments –
Human activities on land such as the building of ports,
industrial infrastructure, deforestation, tourism facilities,
or other coastal developments can lead to increased rates
of sedimentation affecting adjacent reefs. High sediment
loads can smother corals or decrease light penetration,
thereby reducing the photosynthetic ability of the symbiotic algae in coral.
6. Unsustainable tourism/recreation – Anchors, accidental boat groundings, and propeller strike can all crush
and scar coral. The fins of divers and snorkelers and even
their diving equipment can inadvertently damage coral.
Well-meaning tourists may feed reef fish, but this can
change feeding behavior with other flow-on effects.
Similarly, shell collecting, fossicking, and uncontrolled
reef-walking can have detrimental impacts on corals.
7. Invasive species (pest plants, animals, diseases) or outbreaks of native species – Invasive marine species may
be introduced by a variety of vectors, including ballast
water discharge, biofouling on vessel hulls or within
internal seawater pipes in commercial and recreational
vessels, aquaculture operations (accidentally or intentionally) and aquarium imports, as well as marine
debris carried by ocean currents.
At high densities, outbreaks of species that eat juvenile or adult corals can cause major problems for reefs
and their associated species (e.g., the crown-of-thorn
starfish, a long-spined species of sea urchin, and
a small gastropod snail have all caused major problems
in many coral reefs around the world).
The types and extent of diseases attacking corals
have increased markedly in recent years and coral diseases such as Black Band and White Plague are
CONSERVATION AND MARINE PROTECTION AREAS
231