Global climate change is one of the greatest threats to the long term future of coral reefs. In combination with other natural and human-induced pressures, warming seas pose a serious risk to the world's coral reef ecosystems. Summer sea temperature increases of just 2-3°C for a week or two, or 1-2°C for a month or two, are enough to kill sensitive corals.
Australia's tropical marine ecosystems are already reflecting the consequences of global warming with a 0.4°C rise in the tropical ocean temperatures, including the Great Barrier Reef, over the past 100 years. Further increases in sea temperature will lead to increased coral bleaching and more frequent outbreaks of coral disease.
Other impacts of climate change on tropical marine systems include:
- gradual acidification of the ocean (which will reduce the ability of various marine calcifying organisms to form their skeletons and shells);
- increased intensity of tropical cyclones (causing local physical destruction);
- more extreme rainfall events (with increased amounts of freshwater and sediment extending further out from the coast);
- gradual sea-level rise (affecting coastal erosion, storm surges and the area available for shallow-water marine organisms); and
- and changes in ocean circulation and up-welling patterns (presently ill-defined but fundamental to many ecological processes).