Residents of Haiti, Bangladesh, sub-Saharan Africa, the Pacific Islands and rural China don't drive Hummers, enjoy heating and cooling courtesy of fossil fuels or partake in other Western habits that help drive global warming — yet they're the ones suffering the effects. With their homelands ravaged by deforestation, desertification, coastal flooding, shoreline erosion and other environmental problems, many of the people in these countries feel they have no choice but to flee.

Environmental refugees are among the hidden costs of global warming, and experts warn that the exodus will only grow in the years to come. The U.N. refugee agency UNHCR emphasizes that urgent action by the international community is needed to prevent millions of people from being displaced. The International Red Cross says 25 million people have already begun to shift from places blighted by environmental issues.

The low-lying, river-fed plains of densely populated Bangladesh have seen monsoon flooding attributed to climate change, and could be swallowed altogether by the ocean if sea levels rise as predicted by climate experts. Surging saltwater has invaded rice paddies and freshwater wells, causing health and economic crises. Inhabitants of Bhola Island were forced into nearby large cities as the land was eroded by the sea, and now live in even greater poverty than before.

If the Bangladesh coastline is flooded by rising sea levels as predicted, 20 million additional people could be displaced. Government officials estimate that 10 million of Bangladesh's 140 million citizens are already threatened by annual floods and storms.

Professor Atiq Rahman, a Bangladeshi climate specialist, says richer nations will be forced to open their borders to climate refugees as land becomes scarce.

"Bangladeshis are already being displaced because of climate change. It's not happening in the distant future. It's happening now," he says. "Being displaced is just one of the problems of rising sea levels. People will lose their livelihoods, food security will be under threat and so will water security."

The 10,000 residents of Tuvalu, a picturesque chain of South Pacific islands, are facing the very real possibility of their nation disappearing entirely. The rising seas have all but wiped out traditional root crops, a situation made worse by lingering droughts. Tuvalu faces extinction within a century and its inhabitants are already making plans for their migration. Nearby Australia has provided some help and New Zealand has offered to take in the whole of the population.

In China, explosive economic growth paired with climate change has brought on unprecedented environmental challenges. The rural population has been dwindling for decades, forced from their homes due to air and water pollution, droughts and desertification. Western China has been transformed into one big dust bowl, as freshwater lakes dry up and the growing middle class's appetite for meat drives overgrazing. The Chinese government has been relocating rural residents to settlements that basically act as environmental refugee camps.

Haiti's situation is even more complex. The poorest country in the Americas has been hit by storm after storm, the effects of which are worsened by deforestation and civil unrest. There are many reasons why Haitians suffer so much more than the people of neighboring Dominican Republic, with which it shares the island of Hispaniola, ranging from less farmable land and less fertile soil to rapid population growth and voracious consumption of wood.

Haitians depend on charcoal for energy, and their appetite for wood is greater than their resources. Eighty percent of the country is covered in mountains and there is very little tree cover on the remaining lands, making them vulnerable to flooding. This has forced rural Haitians to flee to the crowded and impoverished cities, from which the country's refugees flow out of the island like water through a sieve.

Climate change is also driving migration in sub-Saharan Africa, exacerbating weather extremes such as flooding, drought and desertification. Al-Hamndou Dorsouma of the Tunis-based Sahara and Sahel Observatory says the phenomenon starts with soil breaking down, which leads to smaller crop yields, thus deepening poverty. The resulting social tensions force people to move either to urban areas or to other countries.

Problems like air and water pollution, deforestation, loss of soil fertility and a dramatic decline in biodiversity are becoming more severe and most of these countries are so crippled by poverty that they simply don't have the resources to manage the environment.

Therein lies the monumental challenge of stopping the flow of environmental refugees across the globe. Refugees who can't get help from their own governments may be turned away by other countries, too. Victims of environmental disasters aren't currently recognized under international agreements as refugees, so they're being denied access to the same assistance that victims of violence or political persecution receive.

The United States and Europe will come under increasing pressure to accept people attempting to escape harsh environmental conditions in Africa and Asia, and such industrialized nations aren't even safe from the same problems occurring within their own borders. Tony Oliver-Smith, a natural hazards expert at the University of Florida, provides an ominous assessment of what could be ahead.

"Around the world vulnerability is on the increase, due to the rapid development of megacities in coastal areas. Combine this trend with rising sea levels and the growing number and intensity of storms and it is a recipe for a disaster, with enormous potential to create waves of environment-driven migration."

As President Obama takes his place as leader of one of the world's most influential countries, many hope that the first step will be taking real action against climate change even while struggling with the gargantuan economic crisis. While experts say it's not too late to avoid the darkest predictions of climate change effects, international cooperation will be necessary to keep the worst from happening.