In 30 years the world's coral reefs will be devastated by warming tropical oceans which will 'bleach' them white and eventually kill most of them, unless projected levels of climate change are stopped, according to a new scientific report released internationally today by Greenpeace.
The report "Climate Change, Coral Bleaching and the Future of the World's Coral Reefs" found that if global temperatures increase as projected by Australia's CSIRO and Germany's Max Plank Institute, "coral bleaching" would increase in frequency and intensity all over the world until it occurs annually by 2030 to 2070, depending on the reef system. The UN's Intergovernmental Panel on Climate Change that advises world leaders on climate change science uses these two climate projection models.
Coral bleaching occurs when the corals become stressed and expel the microscopic organisms, known as zooxanthellae, which colour their tissues and provide them with nutrients. This happens when the maximum water temperature rises only slightly, in most cases one or two degrees. The six major episodes of coral bleaching over the past 20 years have been caused by periods of increased water temperature. The worst occurred in 1998 when it affected virtually all of the tropical reefs systems around the world.
The report found that the vast majority of the world's largest coral reef, the 2100 km long Great Barrier Reef off Australia's north-east coast, will be dead in around 30 years unless these projected levels of climate change are stopped.
"Coral reefs could be eliminated from most areas of the world by 2100," said the report's author Professor Ove Hoegh-Guldberg, a marine biologist with the University of Sydney who has studied coral bleaching for 15 years.
"Our current understanding of coral bleaching suggests that corals are not keeping up with the current rate of warming and that they may be the single largest casualty of climate change. While they will not become extinct, their health and distribution may be severely compromised for at least 500 years unless climate change is stopped."
The key findings of this study include:
- Increased sea temperature is the main reason why mass coral bleaching has occurred with increasing intensity and frequency over the past two decades.
- Globally, coral bleaching events are projected to occur with increasing severity and regularity, depending on the reef system, until they occur every year. This is expected to begin some time between 2030 to 2070 and would be ongoing.
This heightened level of bleaching is expected to severely degrade all major reefs by around 2050.
The destruction of these fragile ecosystems would cost billions of dollars in lost revenue from tourism and fishing industries, and damage coastal regions that are currently protected by coral reefs.
"As global temperatures increase due to increases in greenhouse gases, more and more corals will die from coral bleaching," said Erwin Jackson, Greenpeace Australia's Project Co-ordinator. "We must begin to phase out the causes of global warming, the burning of oil, coal and gas, in order to ensure the long-term survival of the world's coral reefs."
