Saturday, December 23, 2006

Casualties of Warm?

Among the first peoples to suffer the impacts of the current global warming are the inhabitants of low lying islands. Warming raises sea level in two ways: by melting glaciers, and probably of more current importance, by thermal expansion of the oceans. The Independent is reporting the disappearance of a whole island with a former population of 10,000 people.

Rising seas, caused by global warming, have for the first time washed an inhabited island off the face of the Earth. The obliteration of Lohachara island, in India's part of the Sundarbans where the Ganges and the Brahmaputra rivers empty into the Bay of Bengal, marks the moment when one of the most apocalyptic predictions of environmentalists and climate scientists has started coming true.

As the seas continue to swell, they will swallow whole island nations, from the Maldives to the Marshall Islands, inundate vast areas of countries from Bangladesh to Egypt, and submerge parts of scores of coastal cities.

Eight years ago, as exclusively reported in The Independent on Sunday, the first uninhabited islands - in the Pacific atoll nation of Kiribati - vanished beneath the waves. The people of low-lying islands in Vanuatu, also in the Pacific, have been evacuated as a precaution, but the land still juts above the sea. The disappearance of Lohachara, once home to 10,000 people, is unprecedented.

Now it is true that global sea levels are rising. After 3000 years of near stasis, sea levels have risen about 20 cm in the last hundred years. Was that eight inches, or the half inch or so since 1992, really responsible for the submerging of a whole island?

It seems inherently implausible. Still, small changes can tip a vulnerable island to the point where wave action destroys it, but I would want to know the detailed geology before I accepted this explanation. Big chunks of the Louisiana coast have disappeared in the last few decades, not because of rising sea levels, but because of decline in the amount of sediment coming down the now dammed Missisipi. Islands in the ocean, at least those not protected by coral reefs, are inherently transitory. Not so many million years hence, the 14,000 foot mountains of Hawaii will have sunk into the sea.

I would be interested to hear a more expert opinion.

UPDATE: Another story gives a more up close and personal look at the deluge, which apparently happened about twenty-two years ago:
“I went to Lohachara island when I was 12 — in search of land,” Bhandari, now 55, said. “I and my wife had five bighas of land that we tilled.

“The sea had been eating away our island with every passing day. And then, one day, it engulfed everything that had remained untouched till then — our home, fields, the cattle… everything.”

Perhaps farming the island played a role in its destruction.