Even as coral reef scientists from the Australian
Institute of Marine Science (AIMS) are saying the GBR may escape a
major bleaching event this year, the upcoming launch of the UN's
Intergovernmental Panel on Climate Change (IPCC) report on climate
change is turning up the heat on the issue of global warming.
The report, entitled Climate Change 2007: The
Physical Science Basis, will summarise current scientific
knowledge on climate change and will provide irrefutable evidence that
human activities, by increasing greenhouse gas concentrations, are
having a measurable effect on global climate.
AIMS climate expert Dr Janice Lough says the report
won’t contain any surprises.
"The report is based on scientific literature that has
been published over a number of years so most of the information is
already out among the scientific community.
"For AIMS, this report further justifies the
significant effort we have been investing in climate research over the
years and reaffirms the relevance of our ongoing research into the
nature of global climate change and its potential impact on
Australia’s tropical marine ecosystems such as the Great Barrier
Reef."
Another IPCC report on the impacts of global climate
change (scheduled for release in April 2007) will contain a chapter on
the expected impacts of climate change in Australia and on the Great
Barrier Reef.
Dr Lough and her colleagues believe that climate
change will have significant consequences for coral reefs. AIMS coral
expert Dr Ray Berkelmans says the pace of global warming presents a
major concern for reef building organisms like corals.
"These animals can’t adapt quickly enough to respond
to our rapidly changing climate. As a result of recent global warming
we have seen increased mass bleaching events on the GBR and elsewhere
since the mid-1970s."
The GBR has warmed an average of only 0.4oC
since the 19th century but scientists say this is enough to
cause major damage. Corals live near the upper limit of their
temperature tolerance. During the large-scale bleaching events of
1998, 2002 and 2006, local water temperatures rose 1-2oC
above the seasonal average. The pace of warming is of major concern as
it gives organisms little time to respond or adapt to the changed
climate conditions and Dr Berkelmans says the GBR could be 1-3oC
warmer by the end of this century, making coral bleaching an annual
event and causing widespread destruction to coral reef communities.
As if the predictions for reefs experiencing global
warming are not dire enough, Dr Lough points out that rising
temperatures are not the only climate change threat to coral reefs.
There is general scientific consensus that increasing ocean acidity
due to rising carbon dioxide (produced by the burning of fossil fuels)
has serious implications for coral reefs and other marine calcifying
organisms and is likely to alter the makeup of marine ecosystems and
weaken coral reef structures.
"Approximately 30% of excess atmospheric carbon
dioxide has been absorbed by the world’s oceans, increasing their
acidity. More acidic waters make it difficult for corals and other
marine calcifying organisms (such as animals with shells) to form
their skeletons which are ultimately responsible for building the
physical structure of the reef," says Dr Lough.
Scientists believe that increased intensity of
tropical cyclones will also cause more frequent damage to coral reef
structures and that changes to the physical structure of coral reefs
will have significant impacts on the thousands of other organisms that
rely on these structures to provide habitats and food.
In addition to the stresses of temperature increases
and rising ocean acidity, coral reefs must contend with land-based
run-off containing high levels of sediment and nutrients. Poor water
quality on nearshore reefs inhibits their ability to recover from
coral bleaching events.
Dr Lough says that while local efforts to manage reef
systems are important, drastic global actions are necessary
immediately to stabilize and reduce greenhouse gas emissions and
reverse the effects of climate change on reefs.
"Well-protected and well-managed reefs are more
resilient to stresses but are still not immune to the large-scale
effects of rising water temperatures and changing ocean chemistry.
"In short, we have a sensitive ecosystem that we
predict will be spending an increasing amount of time in warmer, more
acidic waters. The outlook for the GBR is anything but bright unless
we can make some major changes very quickly.
"
The IPCC report is
a grim reminder that we need to act now to reduce our energy
consumption and reverse the high greenhouse gas concentrations that
are already having a measurable impact on our world."
Ongoing scientific research at AIMS directly addresses
key issues associated with the regional impacts of global warming.
Scientists from AIMS are approaching the issue of climate change using
technologies ranging from genetic analysis to monitoring of whole
ecosystems. AIMS scientists are:
-
monitoring detailed changes in weather, climate and
circulation on the GBR.
-
looking back into the past using centuries-old coral
cores to detect recent environmental trends and track the growth
responses of corals to changing environments.
-
studying the potential for reef corals to adapt to
climate change by focusing on the key relationship between corals
and the single-celled algae living within their tissues. Prior
research suggests that this relationship is critical in predicting a
coral’s ability to withstand varying environmental conditions.
Visit
www.aims.gov.au
for the AIMS position paper on climate change and coral reefs.
