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A bleached reef in the Maldives has been reduced to a lifeless coral wasteland.
Photo: Genevieve Johnson

March 26, 2003
Coral Bleaching - Paradise in Peril
  Real Audio Report

Log Transcript

During our time researching sperm whales in the Maldives, the crew dove on some of the most spectacular and in tact coral reefs found anywhere in the world. Yet even on these heavily protected reefs there are signs of trouble.

Many coral reef communities across the globe are suffering as a result of human interference, in many equatorial regions, they are disappearing all together.

Humanity is destroying reefs in numerous ways and at a staggering rate. Erosion from the clearing of mangrove forests is smothering corals, overfishing and the collection of corals and shells for the tourism trade has become widespread. In South East Asia, reefs are being poisoned with cyanide and blasted into oblivion with dynamite, in an effort to collect highly prized reef fish for the lucrative aquarium and live food trades. Yet, by far the greatest threat to coral reefs comes from sea temperature rise as a result of climate change and ozone depletion, which together create a deadly phenomenon called coral bleaching.

A common misconception about coral reefs is that they are made up of rock, when in fact they are living colonies of small invertebrate animals. Reef building coral animals thrive in warm shallow tropical waters between 30 degrees north and 30 degrees south latitude. They are sensitive to even the most minute of changes to their delicately balanced ecosystem and will only tolerate a narrow range of environmental conditions.

A blizzard of life thrives on a healthy coral reef.
Photo: Genevieve Johnson

If the water temperature changes too much, the coral animals will expel the colourful symbiotic algae that provide them with food. As a result, the coral becomes bleached and lifeless. Some of the reefs the crew have seen over the past three years, particularly those nearer the surface that are subjected to warmer temperatures, resemble a wasteland. Stark and barren, a bleached reef lacks the colourful splendour and complexity of a healthy, vibrant coral reef community. Sadly, thousands of square miles of coral reef have been bleached and reduced to rubble throughout the tropical regions of the worlds oceans.

So what causes the temperature of the ocean to change? There is now little doubt according to a United Nations (UN) scientific panel formed to investigate global warming, that the temperature of the earths atmosphere is rising. This Intergovernmental Panel on Climate Change (IPCC) is made up of more than 3,000 scientists who have concluded that the underlying cause is our release of too many greenhouse gases.

Warmth from the sun heats the earths surface; much of this heat energy is in turn radiated outwards. Some of this heat escapes into space, while increasingly more is trapped and absorbed in the atmosphere by greenhouse gases. These gases are causing the lower atmosphere to heat up at an unnatural rate. Although a natural greenhouse effect is essential in maintaining life on earth, the amount of greenhouse gases such as CO2 being pumped into the atmosphere is greater than ever before. The release of these gases is due primarily to pollution from car exhausts, burning forests, and fumes from power stations and industrial plants.

The past decade was the warmest on record. 1998 was the warmest year, in the warmest decade, in the warmest century of the past millennium - 1997 and 1995 were the second and third warmest years respectively.

Sea temperature rise as a result of global warming is severely stressing many coral species already living near the upper temperature limit for warm water. This explains why the bleaching witnessed by the crew was far more widespread among the species living closest to the surface. The coral animals in deeper, therefore cooler waters have not been so badly affected.

Increased sea temperatures cause the coral animals to expel the symbiotic algae that give them their vibrant color.
Photo: Genevieve Johnson

Such bleaching episodes were first observed during the 1982-83 El Nino event when corals were bleached along the west coast of North, Central and South America. El Nino is a natural occurrence that causes a reversal of the winds and ocean currents, spreading warm waters from west to east in the Pacific Ocean. A second major El Nino event in 1997-98 contributed to the most brutal coral bleaching events ever recorded. Widespread bleaching was reported in all the worlds reef regions, except the Central Pacific. In many regions, over 75% of corals were affected. During this warming event, not only were the surface corals affected, but also species living as deep as 150 feet.

Coral reef communities are known for the greatest species diversity of any marine ecosystem and are often compared to rainforests on land - Although increasing evidence is suggesting that the deep sea floor may well rival or even surpass coral reefs in species richness. To stand by and watch as the equatorial oceans lose these ancient, complex communities would be a tragedy to horrific to contemplate. Fortunately nothing is inevitable and the choice is ours if we want to act to make a difference. We need only modify our lifestyles in order to reduce our own contribution to greenhouse gas emissions.

Many call the greenhouse problem the most serious threat not only to coral reefs, but also to the continued stability and habitability of our planet.

As stated by Kofi Annan
"The task before us is enormous. If we are to bring greenhouse gases down to a sustainable level, we need to make radical changes in the world economy and in the way we live."
- Kofi Annan. United Nations Secretary General, 2000.

This is Genevieve Johnson speaking to you from the Odyssey in the Maldives.


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