The Great Barrier Reef
106
bleached or die. Many other species form tight relationships with corals and hence are likely to be lost from coral
reefs as coral abundance declines. There may also be an
important density threshold in which some coral dwelling species require their coral colonies to be clustered
closely so that they can access mates for reproduction.
The changes that are set to occur on coral reefs will
also affect humans with direct and indirect dependence
on them. This topic is clearly important and deserves
considerably more space than a concluding paragraph
(Fig. 10.5). Australia’s coral reefs are currently an important economic engine for its communities and coastal
economies, generating over $6 billion per annum from
GBR tourism alone. Great Barrier Reef tourism is highly
dependent on its key competitive advantage of having
the reputation of being the most pristine coral reef on the
planet. This reputation allows the Australian tourism
sector to compete with other tourist destinations in
South-East Asia, the western Indian Ocean and the Caribbean that are closer to most international tourist domiciles in terms of travel time. Analysis of the potential
effect of loosing that competitive edge through the deterioration of coral reefs on the Great Barrier Reef through
climate change indicates that the costs could be significant. Estimated impacts vary depending on market characteristics and factors such as international trends and
politics, but if one uses the proportion of the income that
is due to people coming to Australia to see our Great Barrier Reef, it is clear that climate driven reef degradation
could potentially reduce international tourist income by
as much as $8 billion over the next two decades.
Reefs also have major importance to people in developing countries, with over 100 million people subsisting
on coral reefs as a source of food. While the details of the
socio-economic impacts from climate change will vary,
countries like Indonesia, Fiji and other Indo-Pacific
countries could all potentially face declining coastal resources. This decline would have flow-on consequences
resulting from the need to find alternative livelihoods
for the many millions of people that live in coastal zones
in Asia and the Indo-Pacific. Understanding the economic and social ramifications of climate change on
coral reefs will consequently be critical for preparing
people, industries and governments for the changes that
seem almost certain to occur over the next 50 years.
N RESPONDING TO THE CHALLENGE OF
CLIMATE CHANGE?
There is no clearer example of how biological systems
are affected by climate change than the impacts already
apparent on coral reefs. The combined effects of warming and acidification have already affected coral reefs,
and the effects will become devastating if atmospheric
CO 2 concentrations do not stabilise below 450 ppm. Stabilisation at or below these levels of CO 2 in the atmosphere will require drastic action within political,
economic and social spheres (at least a 90% reduction in
greenhouse emissions by 2050). The details of the required actions are beyond the scope of this chapter. The
fourth assessment report of the Intergovernmental
Panel on Climate Change (IPCC 2007), particularly the
analysis of working group 3, is a good place to start for
those people interested in this area.
Given the scale of the projected impacts of climate
change on coral reefs, there might be a temptation to
conclude that preventing and managing the other impacts on coral reefs (see Chapter 12) is now irrelevant.
This is a valid point of view if we do not deal with the
current unrestrained growth in greenhouse gas emissions. However, if society does pursue a policy of drastically reducing emissions such that atmospheric CO 2
concentrations stabilise at 450–500 ppm, it must go hand
in hand with good management of coral reefs themselves. Coral reefs will still experience increases in sea
temperature and very low carbonate concentrations that
will be outside any they experienced in millions of years,
and bleaching events will become more commonplace.
There is now substantial evidence that the ability of corals to recover from bleaching events is strongly affected
by how much they are being influenced by other
stresses. For example, elimination of grazing fish (from
overfishing) appears to increase the recovery of corals
after an ecological disturbance, like the mortality following coral bleaching, by 2–3 fold. Deteriorating water
quality might act synergistically with under-grazing to
further lower recovery after bleaching events. If, through
improved reef management, the recovery of reefs from
bleaching can be improved, then reefs will persist longer
under the stresses expected over the next 50–100 years.
Actively managing coral reefs in this current period of
106
bleached or die. Many other species form tight relationships with corals and hence are likely to be lost from coral
reefs as coral abundance declines. There may also be an
important density threshold in which some coral dwelling species require their coral colonies to be clustered
closely so that they can access mates for reproduction.
The changes that are set to occur on coral reefs will
also affect humans with direct and indirect dependence
on them. This topic is clearly important and deserves
considerably more space than a concluding paragraph
(Fig. 10.5). Australia’s coral reefs are currently an important economic engine for its communities and coastal
economies, generating over $6 billion per annum from
GBR tourism alone. Great Barrier Reef tourism is highly
dependent on its key competitive advantage of having
the reputation of being the most pristine coral reef on the
planet. This reputation allows the Australian tourism
sector to compete with other tourist destinations in
South-East Asia, the western Indian Ocean and the Caribbean that are closer to most international tourist domiciles in terms of travel time. Analysis of the potential
effect of loosing that competitive edge through the deterioration of coral reefs on the Great Barrier Reef through
climate change indicates that the costs could be significant. Estimated impacts vary depending on market characteristics and factors such as international trends and
politics, but if one uses the proportion of the income that
is due to people coming to Australia to see our Great Barrier Reef, it is clear that climate driven reef degradation
could potentially reduce international tourist income by
as much as $8 billion over the next two decades.
Reefs also have major importance to people in developing countries, with over 100 million people subsisting
on coral reefs as a source of food. While the details of the
socio-economic impacts from climate change will vary,
countries like Indonesia, Fiji and other Indo-Pacific
countries could all potentially face declining coastal resources. This decline would have flow-on consequences
resulting from the need to find alternative livelihoods
for the many millions of people that live in coastal zones
in Asia and the Indo-Pacific. Understanding the economic and social ramifications of climate change on
coral reefs will consequently be critical for preparing
people, industries and governments for the changes that
seem almost certain to occur over the next 50 years.
N RESPONDING TO THE CHALLENGE OF
CLIMATE CHANGE?
There is no clearer example of how biological systems
are affected by climate change than the impacts already
apparent on coral reefs. The combined effects of warming and acidification have already affected coral reefs,
and the effects will become devastating if atmospheric
CO 2 concentrations do not stabilise below 450 ppm. Stabilisation at or below these levels of CO 2 in the atmosphere will require drastic action within political,
economic and social spheres (at least a 90% reduction in
greenhouse emissions by 2050). The details of the required actions are beyond the scope of this chapter. The
fourth assessment report of the Intergovernmental
Panel on Climate Change (IPCC 2007), particularly the
analysis of working group 3, is a good place to start for
those people interested in this area.
Given the scale of the projected impacts of climate
change on coral reefs, there might be a temptation to
conclude that preventing and managing the other impacts on coral reefs (see Chapter 12) is now irrelevant.
This is a valid point of view if we do not deal with the
current unrestrained growth in greenhouse gas emissions. However, if society does pursue a policy of drastically reducing emissions such that atmospheric CO 2
concentrations stabilise at 450–500 ppm, it must go hand
in hand with good management of coral reefs themselves. Coral reefs will still experience increases in sea
temperature and very low carbonate concentrations that
will be outside any they experienced in millions of years,
and bleaching events will become more commonplace.
There is now substantial evidence that the ability of corals to recover from bleaching events is strongly affected
by how much they are being influenced by other
stresses. For example, elimination of grazing fish (from
overfishing) appears to increase the recovery of corals
after an ecological disturbance, like the mortality following coral bleaching, by 2–3 fold. Deteriorating water
quality might act synergistically with under-grazing to
further lower recovery after bleaching events. If, through
improved reef management, the recovery of reefs from
bleaching can be improved, then reefs will persist longer
under the stresses expected over the next 50–100 years.
Actively managing coral reefs in this current period of