Not So Much Trouble in Paradise Are Coral Islands Really Doomed?

Corbis

Part 2: 'Storms Are the Real Architects of the Islands'


The only local resident in the expedition is Ibrahim Naeem, director of the Maldives' environmental protection agency. The 38-year-old scientist is playing tour guide for the scientists as they explore the coral islands. Their first stop is an island that's about the size of a football field, with a name -- Bodukaashihuraa -- that no one on the boat can pronounce. The uninhabited speck of land is home to three palm trees.

The scientists are welcomed by swarms of mosquitoes but, caught up in the excitement of their work, they hardly even notice. They are more interested in determining whether it makes sense to drill into the reef to take a sediment sample. Together with Scott Smithers, an Australian geologist, Kench gets to work.

The two scientists have already drilled quite a few holes into the atoll. By studying the samples, they were able to determine that the Maldives attained their current form about 4,000 to 5,000 years ago.

The corals to which the islands owe their existence colonize underwater mountaintops, the remnants of sunken volcanoes. Their limestone skeletons are the building material of atolls. In the Maldives, they form a reef around the sunken volcanoes, which continues to grow until it rises above sea level in some spots. Waves and currents grind up the dead corals and deposit the sediment, which eventually accumulates to form beaches and islands.

Extremely Hardy

Kench, who, with his athletic physique, looks more like a surfer than a professor, grabs a shovel and plunges it into the loose sand directly above the beach. The roots of a young banyan tree permeate the soil. All it takes is a few cuts with the spade to reveal the structure of the island, which consists of alternating layers of gray and yellow material, resembling a sandwich. After digging about a meter into the soil, Kench has already exposed half a dozen of these layers.

He explains that the gray layers are the remains of weathered plants, while the yellow layers are coral sand that periodically washes across the island after heavy storms. "Storms are the real architects of the islands," says Kench. Even natural disasters like the 2004 tsunami, which killed at least 82 people in the Maldives, do not destroy the islands. On the contrary, the Indian Ocean tsunami even added new sediments. "We've measured up to 30 centimeters of growth in some places," he says.

In earlier epochs, the islands also proved to be extremely hardy. For example, when the glaciers melted after the last ice age, the Maldives held their ground against the resulting rise in sea level -- thanks to the constantly growing corals. Based on their sediment samples, the scientists conclude that, around 2,000 years ago, the water level must have been even higher than it is today. "Constant change is the real constant in the life of coral reefs," says Smithers.

But will the islands also survive the future rise in sea level, which is likely to occur more rapidly than in the past? As global warming continues, the sea level could rise by more than half a centimeter a year. According to the IPCC, the world's oceans could rise to levels more than half a meter higher than at the beginning of industrialization.

The reseachers theorize that rising tides will flush the sediment to higher and higher elevations behind the beach. Their biggest concern is the interior of the islands, which the coral sands are not as likely to reach. If the center of an island grows more slowly than the perimeter, its elevation will be lower and lower relative to the rising sea level. And if people live in this area, their houses will likely be flooded by spring tides with growing frequency. Dumping more sand into the central parts of the islands could avert this problem, however.

Adapting to Warmer Temperatures

Biologist Bernhard Riegl, 49, of the National Coral Reef Institute in Florida has just returned from a dive, where he inspected the coral reef. "Everything depends on how well the corals continue to grow in the future," says Riegl, who is originally from Austria. As the concentration of CO2 in the earth's atmosphere rises, so does the acid content of the oceans -- and acid dissolves the limestone skeletons of the corals.

Extreme heat is also stressful to many corals. "They are extremely well-adapted to their environment here, and they'll bleach out if the water temperature rises by only one or two degrees," Riegl warns. The year 1998, for example, was particularly warm, with temperatures in the Indian Ocean higher than normal. "In the end, the corals in many reefs were completely destroyed," says the biologist. If water temperatures continue to rise as a result of climate change, things could become dicey for the corals.

On the other hand, corals are also relatively adaptable. "I saw a coral species down there that's also found in the Persian Gulf," says Riegl. There, he explains, the species has adapted to the warmer temperatures. "It tolerates water that's 10 degrees warmer than the water here."

The Importance of Excrement

Riegl made another interesting observation during his dive. He saw large numbers of parrotfish swimming in the coral garden. Scientists now know how important a role the fish play in the development of the tropical islands.

"They gnaw at the algae on the coral, and in doing so they always remove a small amount of limestone from the surface," Riegl explains. The fish digest the material and excrete the limestone, which is then flushed onto the beaches by waves. "Their excrements help the islands grow," says Riegl.

But parrotfish often end up in fishing nets. "The people here control much of their future," says Riegl.

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