Rapid global climate change, due to human interference in the climate system, is one of the greatest threats to the long-term future of coral reefs. Human activities are taking coral reefs out of their comfort zone where they have thrived for hundreds of thousands of years.
In combination with other natural and human-induced pressures, warming sea surface temperatures and ocean acidification pose a serious risk to the world's coral reefs, increasing their vulnerability to coral bleaching, coral diseases and tropical cyclones.
Climate change impacts
Australia's tropical marine ecosystems are already reflecting the consequences of climate change with a 0.4-0.5°C rise in tropical sea surface temperatures, including the Great Barrier Reef (GBR), since the late 19th century.
Since the late 18th century about 30% of the extra carbon dioxide (the main greenhouse gas) that human activities have injected into the atmosphere has been absorbed by the oceans. If this had not occurred, the world would have warmed more than already observed.
More carbon dioxide in the oceans, however, changes their chemistry - known as ocean acidification. The pH (acidity) of the global oceans has already decreased from ~8.15 to ~8.05.
Modelling and experimental studies show that increased acidity impairs the ability of corals and other calcifying organisms to build their calcium carbonate skeletons. Sustained calcification, to withstand the natural forces of biological and physical erosion, is the backbone of tropical coral reef ecosystems.
The resulting complex reef structures provide food and habitat for many thousands of reef-associated organisms and the incredible biodiversity of tropical coral reefs.
Some of the predicted impacts of climate change on tropical marine systems:
- warmer sea surface temperatures increase the risk of thermal stress events resulting in mass coral bleaching;
- although the frequency of tropical cyclones may not change or even decrease, those that do occur are likely to be more intense, resulting in physical destruction and weakening of the reef structure ;
- more extreme rainfall events with increased amounts of low salinity freshwater and sediment extending further out from the coast;
- gradual sea-level rise affecting coastal erosion, the magnitude of storm surges and the area available for shallow-water marine organisms; and
- changes in ocean circulation and up-welling patterns. We have, for example, already observed a strengthening of the East Australian Current. Other changes in ocean circulation patterns are presently ill-defined but fundamental to many ecological processes such as connecting larval supplies between reefs.
Research at AIMS
- monitoring, reconstructing and modelling the changing ocean climate,
- assessing the cumulative impacts of climate change in combination with other stressors (such as poor water quality) on coral reefs and tropical marine organisms
- identifying the attributes of "healthy" coral organisms that make them more resilient to rapid environmental change
- identifying potential adaptation mechanisms, and locations that may provide refuges for marine species in a rapidly changing world.