Follow the Butterflies

The moth known as Clancy's Rustic had never been seen in northwestern Europe. So what was it doing fluttering in a garden in Kent a few years ago? According to Britain's Centre for Ecology and Hydrology, moths and butterflies once found only in the Mediterranean and North Africa are venturing into Northern Europe in unprecedented numbers. The cause, says chief researcher Tim Sparks: global warming.

Just as Al Gore called the melting of the polar ice "the canary in the coal mine," so are migrating insects a bright yellow warning. With butterflies on the move, says Sparks, could people be far behind? Climate-induced migration is a survival mechanism as old as life. Human mobility helped cultures sidestep extinction and often worked as a catalyst for growth and evolution. It could do so again. "Environmental refugees could become one of the foremost human crises of our time," says Norman Myers, an environmental scientist at Oxford University who once painted an infamously scary scenario: 200 million environmental refugees by 2050—"a massive crisis," compounded by "famine and starvation."

That was in 1995. Today, his apocalyptic vision is accepted as a real possibility. Impoverished and climate-sensitive nations like Bangladesh and Kenya simply don't have the resources to provide relief for mass numbers of displaced people. Nor is there spare cash for construction projects—dikes and water reservoirs, for example—that could mitigate climatic calamities. In 1996, Myers estimated that sea-level rises induced by global warming would threaten the lives of 26 million people in Bangladesh, 73 million in China and 20 million in India. In the Mandera district of northeastern Kenya, a fourfold increase in drought has already forced half a million pastoral farmers to abandon their way of life.

Many developed countries, by contrast, could end up as winners. The Scottish government, for instance, is sponsoring "Highland 2007," promoting its northern moors as a desirable place to live in an effort to arrest declining population. Underpopulated areas like Sweden, a country the size of California but with a population of only 8 million, could reap the rewards of an influx of skilled workers, as might Norway and Finland. And as urban-heat islands like London, Paris and Tokyo turn airless and muggy, internal migration could usefully redistribute population from cities to the countryside.

Archeologist Arlene Rosen of University College London, author of a new book called "Civilizing Climate," notes how certain ancient societies adapted to climate change. "For every society that collapsed, there was one next door that got stronger." Droughts in China from 1900 to 1500 B.C. were accompanied by a period of growth and trade. And for 5,000 years the Sahara was green and fertile, until it began to dry up in 4000 B.C., causing the large-scale migration of people to the Nile region, a key step in the creation of Egyptian civilization. "Humans," says Rosen, "are a resilient species."