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-170s."
The GBR has warmed an average of only 0.4oC since the 1thcentury 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 18, 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-oC 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 0% 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 Marine Backgrounder on climate change and coral reefs.
Dr Janice Lough , Principle Research Scientist
Telephone : 07 4753 4248
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Wendy Eller y, AIMS Media Liaison
Mobile : 0418 729 265
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