A United Nations University study predicts that rising sea levels, desertification and shrinking freshwater supplies will create up to 50 million environmental refugees by 2010, ; the number could rise to 150 million within a generation. Some can be displaced overnight by hurricanes like Katrina or Nargis. Others are driven out by slow but equally devastating climate change. Among the threatened regions are Bangladesh, the Philippines, Cambodia, Thailand, Egypt, China, coastal Latin America and sub-Saharan Africa. Indeed, many migrants from these countries are already fleeing economic and climate difficulties; many are murdered as they attempt to cross borders and seas into the industrial North. Millions more are exploited or persecuted, as “illegals”. There is no legal protection for these people, who already far outnumber those displaced by war, dictatorships, and ethnic persecution. North Americans still remember the 1930s “Dust Bowl” and the millions of “Okies”, internal migrants who fled to the green lands of California and BC, only to be treated as second- or third-class citizens -- a story told by John Steinbeck in his novel The Grapes of Wrath. The history of the coming migration will be even uglier; it has already stirred up ancient racial and religious prejudices in Europe and America.
See Ethan Goffman, Environmental Refugees: How Many, How Bad? , Wikipedia on environmental refugees and human security, an umbrella concept covering many forms of vulnerability. Researchers have begun to recognize that security is not a purely national issue but global; however, international law, ordinary voters and political leaders lag far behind.