Coral Reefs

Coral Reefs Under Global Threat

by Eric Matson

The world's coral reefs are under increasing pressure from local and global-scale environmental impacts. Will we lose forever one of the planet's greatest underwater attractions?

Every year around 2 million visitors travel to the world's largest living structure; Australia's Great Barrier Reef. Whilst marvelling at the 2,000 species of fish that inhabit its 2,000 kilometre long mass, they snorkel, dive and frolic in the crystal clear waters and kick around 6 billion dollars into Australia's economy.

Although protected by both UNESCO's World Heritage treaty and Australia's own Marine Park legislation, the Great Barrier Reef is crying out for help. Due mainly to rising greenhouse gases, global warming is having a subtle, yet widespread effect on the fragile and sensitive corals.

"Rising sea temperatures increase the frequency of mass coral bleaching events," explains Eric Matson a research scientist at the Australian Institute of Marine Science, "Corals live only 1-2oC below their upper thermal limit and sustained periods of water temperatures above this threshold stresses the coral and the symbiotic algae (the essential partner for reef-building corals) are expelled."

The frequency of mass coral bleaching events has increased since the mid-1970s, matching the rise in global temperatures. In 1998 (the hottest year on record) bleaching was observed in the majority of the world's coral reefs and approximately 16% are estimated to be permanently damaged. Continuing research by AIMS and other bodies is trying to determine more accurately the factors that impact on the growth and recovery of the world's corals. It is clear that reefs protected from other human impacts (such as overfishing, pollution etc) are more resilient.

"Increasing atmospheric carbon dioxide (CO2, the principal greenhouse gas) is also changing the chemistry of the oceans. About 30% of the CO2 released into the atmosphere by human activities since the Industrial Revolution has been absorbed by the oceans," continues Eric, "Changing the ocean chemistry essentially shifts the geochemical equation by which these organisms "calcify". The implication of continued change in ocean chemistry due to rising CO2 is that these organisms will not calcify as well as they did in pre-industrial times and thus produce weaker skeletons and grow more slowly."

It seems therefore, that in the foreseeable future at least, the coral reefs are currently the best we'll ever see. The risk we face is that, unless global climates stabilise, we could see the gradual destruction of the reefs as they succumb to a combination of both man-made and natural pressures.