"Human-induced climate and hydrologic change is likely to make many parts of the world uninhabitable, or at least uneconomic," writes Jeffrey Sachs, director of the Earth Institute at Columbia University in New York, in the current online issue of Scientific American. As a result, he says, "Over the course of a few decades, if not sooner, hundreds of millions of people may be compelled to relocate because of environmental pressures." (Source)
Some Pacific Ocean island nations, such as Tuvalu, are concerned about the possibility of an eventual evacuation, as flood defense may become economically inviable for them. Tuvalu already has an ad hoc agreement with New Zealand to allow phased relocation.
In the 1990s a variety of estimates placed the number of environmental refugees at around 25 million. (Environmental refugees are not included in the official definition of refugees, which only includes migrants fleeing persecution.) The Intergovernmental Panel on Climate Change (IPCC), which advises the world’s governments under the auspices of the UN, estimated that 150 million environmental refugees will exist in the year 2050, due mainly to the effects of coastal flooding, shoreline erosion and agricultural disruption (150 million means 1.5% of 2050’s predicted 10 billion world population).
