Not as bad as they thought: Coral can recover from climate change damage

From a University of Exeter press release, another inconvenient truth about our planet sure to be denounced by some who claim that global warming is irreparably damaging reef systems.

A study by the University of Exeter provides the first evidence that coral reefs can recover from the devastating effects of climate change. Published Monday 11 January in the journal PLOS One, the research shows for the first time that coral reefs located in marine reserves can recover from the impacts of global warming.

Scientists and environmentalists have warned that coral reefs may not be able to recover from the damage caused by climate change and that these unique environments could soon be lost forever. Now, this research adds weight to the argument that reducing levels of fishing is a viable way of protecting the world’s most delicate aquatic ecosystems.

Increases in ocean surface water temperatures subject coral reefs to stresses that lead quickly to mass bleaching. The problem is intensified by ocean acidification, which is also caused by increased CO₂. This decreases the ability of corals to produce calcium carbonate (chalk), which is the material that reefs are made of.

Approximately 2% of the world’s coral reefs are located within marine reserves, areas of the sea that are protected against potentially-damaging human activity, like dredging and fishing.

The researchers conducted surveys of ten sites inside and outside marine reserves of the Bahamas over 2.5 years. These reefs have been severely damaged by bleaching and then by hurricane Frances in the summer of 2004. At the beginning of the study, the reefs had an average of 7% coral cover. By the end of the project, coral cover in marine protected areas had increased by an average of 19%, while reefs in non-reserve sites showed no recovery.

Professor Peter Mumby of the University of Exeter said: “Coral reefs are the largest living structures on Earth and are home to the highest biodiversity on the planet. As a result of climate change, the environment that has enabled coral reefs to thrive for hundreds of thousands of years is changing too quickly for reefs to adapt.

“In order to protect reefs in the long-term we need radical action to reduce CO₂ emissions. However, our research shows that local action to reduce the effects of fishing can contribute meaningfully to the fate of reefs. The reserve allowed the number of parrotfishes to increase and because parrotfish eat seaweeds, the corals could grow freely without being swamped by weeds. As a result, reefs inside the park were showing recovery whereas those with more seaweed were not. This sort of evidence may help persuade governments to reduce the fishing of key herbivores like parrotfishes and help reefs cope with the inevitable threats posed by climate change”.

Professor Mumby’s research was funded by National Environment Research Council (NERC) and the Khaled bin Sultan Living Oceans Foundation.

Reef facts

• A coral reef is made up of thin layers of calcium carbonate (limestone) secreted over thousands of years by billions of tiny soft bodied animals called coral polyps.
• Coral reefs are the world’s most diverse marine ecosystems and are home to twenty-five percent of known marine species, including 4,000 species of fish, 700 species of coral and thousands of other plants and animals.
• Coral reefs have been on the planet for over 400 million years.
• The largest coral reef is the Great Barrier Reef, which stretches along the northeast coast of Australia, from the northern tip of Queensland, to just north of Bundaberg. At 2,300km long, it is the largest natural feature on Earth.
• Coral reefs occupy less than one quarter of one percent of the Earth’s marine environment, yet they are home to more than a quarter of all known fish species.
• As well as supporting huge tourist industries, coral reefs protect shorelines from erosion and storm damage.

To download high quality reef videos by Professor Peter Mumby: www.reefvid.org

The main funding for the research came from Khaled bin Sultan Living Oceans Foundation and the Natural Environment Research Council.

The Khaled bin Sultan Living Oceans Foundation (www.livingoceansfoundation.org) is dedicated to conservation and restoration of living oceans and pledges to champion their preservation through research, education and a commitment to Science Without Borders®.