Where the Waters Are Rising

A close-up look at the low-lying Maldives, where global warming hits the seawall

By J. Madeleine Nash Monday, Apr. 18, 2005
    • DILIP MEHTA / CONTACT FOR TIME

    CITY ON A LILY PAD: On the capital island of Male, where 80,000 people live less than 4 ft. above sea level, the margin of safety is increasingly slim

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    On a pier off the airport island, justa cross the lagoon from Malé, is a tide gauge that has been beaming data to the University of Hawaii Sea Level Center in Honolulu since 1989. The good news, says the center's director, oceanographer Mark Merrifield, is that sea levels around Malé do not appear to be rising quite as fast as in many other places in the world. That may sound odd, but the simple expansion of water as it warms is complicated by local wind and current patterns. Beyond that, changes in the height of land masses as soils compact or tectonic plates slip and slide can offset--or magnify--sea-level changes.

    The bad news: across a big swath of the globe, the sea is still rising, eroding what for low-lying places was already a slim margin of safety. Making the problem even worse is the loss of what Florida International University coastal expert Stephen Leatherman calls "living landforms," which would otherwise buffer that rise. Consider the wetlands that are an integral part of all river deltas, he says. Plants trap sediment from floodwaters flowing downriver, and the more they trap, the higher these wetlands grow. The problem is, people don't much like floods, so they build levees, which keep sediments from washing out of the rivers. They also don't much like wetlands, so they drain them. As a result, the world's river deltas are sinking rather than rising. To a large extent, the increased impact of flooding in places like New Orleans and Venice is self inflicted.

    Whether the islands of the Maldives are subsiding is uncertain. Clearly Malé is not yet in the same pickle as Venice, where a combination of sinking land and rising seas has opened the city to regular inundation by storm-generated waves and unusually high tides. Still, it won't take much of a rise in sea level--between 6 in. and 1 ft., says Ahmed Ali Manik, senior environmental analyst in the Ministry of Environment and Construction--before the southwestern corner of the Maldivian capital will be threatened by the same problem. And a 3-ft. rise would allow the biggest tides to wash over the whole city.

    How long does Malé have before that happens? It depends. At present the global rate of increase is between 2 mm and 3 mm a year, around a tenth of an inch, meaning it will take about a century to produce a 1-ft. rise. This is cause for concern, of course, but a 1-ft. rise in sea level over the course of a century or more is unlikely to prove fatal. A century, after all, is a long time--long enough to raise sea walls and breakwaters and to adapt in myriad other ways.

    But that rate could accelerate. Starting in the 1990s, say scientists, ocean temperatures have been increasing at a faster clip--enough to more than double their contribution to sea-level rise. At the same time, the global warming has dramatically increased the meltwater and ice discharged by glaciers, ice caps and ice sheets. It's still unclear whether other factors--such as changes in the amount of snow that falls on Antarctica or the amount of water trapped in reservoirs--will speed the rise in ocean levels or slow it, or even send it into reverse.

    ROBUST OR FRAGILE?

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