6F – Corral reefs & global warming

Supporting article F: “This year more coral died of heat stroke than from all human causes to date ever.”


CORAL GRIEF: Fred Pearce talks to leading scientists monitoring the beautiful ecosystems and leading tourist attractions that are becoming the first major casualty of global warming.

‘The world has been caught with its pants down.’ So says John McManus, the nearest thing to a coral-reef czar for the planet. He is the man who knows (or rather does not know) what is happening to the world’s coral reefs – hotspots of biological diversity amid the vast expanses of the oceans that biologists have dubbed the ‘rainforests of the oceans’.

McManus is the point man on coral reefs for the International Centre for Living Aquatic Resources Management (ICLARM), a research centre based in Manila and backed by UNEP, the World Bank and others. There, surrounded by digital maps and databases, looking like the man who should know, he admits: ‘We have no direct knowledge on what is happening to the world’s coral reefs.’

He shrugs in despair. ‘We don’t know where most of the coral reefs of the world are, or what they look like. We know there are something like 600,000 square kilometres of them out there [roughly twice the area of Italy]. But I could only show you on a map where about a third of those are. And we have detailed mapping for only about a sixth.’

If ever there was a race against time, this is it. Up to 80 per cent of the reefs around the myriad islands that make up the Philippines are dying. Early this year, a United States Government study concluded that perhaps two-thirds of all the world’s coral reefs, many hundreds of years old, are also perishing. This is a biological tragedy on a dramatic scale.

Last November, scientists led by Thomas Goreau, President of the Global Coral Reef Alliance, grabbed the world’s attention by declaring that ‘this year more coral died of heat stroke than from all human causes to date ever’.

This year more coral died of heat stroke than from all human causes to date ever

The summer of 1998 had been a catastrophe because the ocean current known as El Niño, combined with global warming, brought unprecedentedly high sea temperatures washing through the world’s oceans. Goreau estimated that, as a result, more than three-quarters of the shallow coral reefs in the Indian Ocean and parts of the Pacific had died. In the Maldives in the Indian Ocean, divers reported, the mortality rate was over 90 per cent. Inshore reefs of Australia’s Great Barrier Reef were also widely damaged.

At first some scientists thought that only reefs already under stress from human development were affected. But then it emerged that one of the world’s largest, most remote and biologically richest coral atolls, the Chagos Islands in the middle of the Indian Ocean, had also been decimated. A rare visit by scientists in early 1999 revealed that ‘most of the coral was dead. At least half of the fish are gone’.

Coral is not rock – as many fishermen mindlessly blowing them up with dynamite to catch their prey often believe – but living matter. The coral itself is an invertebrate creature: when it dies its skeleton forms the structure on which new corals grow. It depends on algae, which live inside it and, in a close symbiotic relationship, provide most of its food and energy.

Coral reefs are among the oldest and largest living entities on Earth, whose individual components live or die together, rather like a forest. Vast numbers of other creatures live in them – including an estimated quarter of all the world’s sea fish, which feed, grow, spawn and hide from predators in their embrace. But this exquisitely complex ecosystem is very vulnerable to rising temperatures, which kill the algae. This is known as ‘bleaching’ because when the algae die the coral that it inhabits loses its colour.

Occasional bleaching is a natural phenomenon. It typically occurs, says Goreau, when sea temperatures rise to more than a degree Celsius above their normal maximum. But if this continues for more than two months, the coral will starve and die. As it dies, the whole reef structure begins to collapse. The coral skeletons become brittle, break up and form a ‘desert of coral rubble’ on the sea floor. That is what happened in 1998, when much of the Indian Ocean stayed above the temperature threshold for bleaching for more than five months.

The events of 1998 are likely to be repeated. ‘Before about 1980, we saw coral bleaching but it was always localized,’ says Goreau. ‘But since then we have seen it over thousands of miles of the oceans.’ Against a background of rising sea temperatures, every extra blip on the temperature graph produces coral carnage. Coral reefs, he says, are becoming ‘the first ecosystems to suffer large-scale damage from climate change’. Global warming, if unchecked, was ‘condemning all coral reefs to death’.

Until recently only the few could even dream of seeing the wonders of coral reefs. But with international travel making them more and more accessible, many of us will have the opportunity of swimming or sailing through them. Like most things of beauty, the reefs and the life they support are very fragile. To ensure that your visit is as environmentally benign as possible, try to follow these three basic rules:
• Respect reef life. While the curiosity and friendliness of marine creatures and the beauty of the corals may encourage you, touching or feeding sea animals can cause stress or disturb the natural feeding balance, and touching corals can kill them. And try to avoid your boat or diving gear touching the corals, too.
• Stay calm. Even seemingly insignificant currents can damage corals, while sand stirred up from the sea floor can smother them. So try to ensure that all your or your boat’s movements are as deliberate, even and gentle as possible.
• Go unnoticed. As all forms of pollution are potentially harmful, ensure you take your litter home. But only take what you brought – don’t break off souvenirs, or pick up items from the sea floor.
Sue Wells is Manager of WWF International’s Marine Programme.

Multiple threats
The reefs face many other perils. Pollution from dredging, deforestation and sewage discharge smothers and kills the coral or forms huge beds of toxic algae, which, for example, now cover almost all Jamaica’s reefs. New research now suggests that the extra carbon dioxide in the atmosphere, besides causing global warming, is also having a direct impact on coral growth. The gas dissolves in seawater to make it more acidic, slowing down the formation of calcium carbonate, which forms the skeleton of the living coral and ultimately the reef itself. An international study based at the United States Government’s National Center for Atmospheric Research concluded in April that, as a result, even healthy coral is already growing between 6 and 11 per cent more slowly than a century ago.

And then there is the threat from fashionable restaurants in East Asia, where big, brightly coloured reef fish swim in tanks ready to be chosen by the customer, then killed, cooked and brought to the table. To capture them live, fishermen dive to the reefs equipped with plastic bottles containing sodium cyanide solution, which they squeeze onto their chosen fish rather as you would squeeze washing-up liquid into a kitchen sink.

Result 1: A groggy fish that can be picked up and air-freighted to the best restaurants. ($40 million worth shipped out of Manila alone in one year.)
Result 2: Millions of dead invertebrates and small fish that cannot survive the poison. Entire reef systems have been ‘clear-felled’ in this way.

McManus now heads the International Coral Reef Action Network, a five-year project led by UNEP and ICLARM ‘designed to reduce coral reef degradation’. His first task is to bring together the world’s scientists, environmentalists and divers to close the knowledge gap. Divers can subscribe to McManus’s pet project, Aquanaut, in which he hopes to arrange the training of thousands of them to report back regularly on the state of the world’s reefs.

McManus says the dozens of governments with large reef systems need to realize that they are presiding over the collapse of one of the world’s most biologically valuable, and economically lucrative, ecosystems. One estimate puts the value of coral reefs, in fisheries, tourism and coastal protection, at more than $300 billion a year – substantially more than the gross domestic product of many countries. That makes the $20-million cost of his project look decidedly modest.