The history of humankind’s subjugation of the planet is in many respects a history of migration. In the past 500 years, the colonization by Europeans of the Americas and Australasia, in particular, has transformed the ecology of three continents. And the forced movement of some 15 million African slaves to America and a similar number of Russian political prisoners to Siberian gulags fundamentally changed the social ecology of those regions.

People move for many reasons: political, ethnic, economic, military or environmental – often a combination of several such factors. Migration is a natural safety valve for local problems and
a source of labor and capital for fast-growing economies. But high rates of migration may denote a serious environmental crisis in the source region – and can trigger environmental degradation in the receiving area.

Up to 10 million people fled drought and famine in the Sahel region of Africa in the 1970s and 1980s, settling in wetter coastal regions, including neighboring countries. At least half of them never returned home². In Mauritania, environmental degradation has helped to force the proportion of the total population living in the coastal zone from 9 to 41 percent since 1968.

In the 1980s, land scarcity caused by a fast-rising population in Bangladesh led to conflicts that drove 12 to 17 million Bangladeshis into neighboring Indian states of West Bengal and Assam³. Millions fled Rwanda in the 1990s during ethnic conflicts triggered in part at least by the country’s poverty, water scarcity and declining soil fertility, all stemming from its very high population density of 400 people per square kilometer⁴.

Defining “environmental refugees” is hard. The numbers could be much higher than those with refugee status under the United Nations High Commissioner for Refugees (UNHCR) definition. A study for the Washington-based Climate Institute includes among environmental refugees people displaced by land shortages, deforestation, soil erosion, desertification, water deficits, extreme weather events and disease. It put the current annual total of such people at 25 million, which the author⁵ called “cautious and conservative”. The same study suggests that factors such as climate change and rising sea levels could put the figure at 200 million by the year 2050.

The distinction between environmental refugees and economic migrants is also sometimes far from clear. Though nominally economic migrants, many of the estimated 1 million people who flood illegally into the United States annually from Mexico are in part driven by declining ecological conditions in a country where 60 percent of the land is classified as severely degraded⁶. Likewise, an estimated 1.3 million Haitians have fled their deforested and degraded island in the past two decades.

Mass migration frequently causes environmental damage on a similar scale. The desperate hand-to-mouth existence of many migrants, coupled with the likelihood that their settlement will be temporary, encourages a short-term attitude to their new surroundings. Rwandan refugees destroyed large areas of forest in neighboring Zaire (now the Democratic Republic of Congo) in the mid-1990s. Even state-sponsored migrants often find that the land set aside for them is insufficient to make a living. Surrounding natural resources, such as forests, are plundered in the immediate interests of survival. Examples include migrants from large Brazilian cities to the Amazon and Indonesia’s transmigrants, who are a major cause of illegal deforestation in Kalimantan, Irian Jaya and other receiving regions.

Another major form of migration is business and leisure travel, by some measures the world’s largest industry, accounting for 11 percent of global GDP⁷ and a similar proportion of world employment. Tourism and business travel are temporary migrations with a growing global environmental impact. Civil aircraft alone are responsible for 5 percent of anthropogenic sources of greenhouse gases.

International tourism displaces the environmental impacts of rich nations to the often poorer destinations favored by holiday-makers. Those impacts can sometimes be beneficial. In many parts of the world, tourism sustains natural ecosystems and populations of wildlife by providing a strong financial incentive for their preservation. Examples include the elephant and gorilla parks of Africa and the coral reefs of the Caribbean.

But equally the pressures of mass tourism may destroy what the tourists come to see. In Nepal, trekkers burn about 6 kilos of wood each per day in a country desperately short of fuel. A big hotel in Cairo uses as much electricity as 3 600 middle-income households. In the Caribbean, tourist demand for seafood is a prime cause of the decline of lobster and conch populations, while cruise ships are calculated to produce 70 000 tons of waste a year⁸.

The natural ecosystems of the Mediterranean, already under stress from local populations, are further damaged by the region’s status as the destination of almost a third of all cross-border tourism. Typical is Malta, which receives a million tourists a year – three times its permanent population – turning the whole island into a peri-urban area and exhausting local water supplies.

Concern about such damage has fostered a growing interest in “ecotourism”. The fastest growing sector of the business in the 1990s, it is intended to maximize the local social benefits from tourism, provide incentives for conservation and minimize environmental damage9. Well designed programs can encourage tour operators and hoteliers to invest in renewable energy and waste reduction measures, as well as involve the tourists themselves in local conservation initiatives. But badly designed ecotourism can have the reverse effect – for example expelling inhabitants from their land to provide parkland for animals and using scarce “natural” construction materials to provide authentic tourist experiences.