The displacement of thousands of U.S. Gulf Coast residents in the aftermath of Hurricane Katrina is emblematic of a human migration challenge that will likely become more severe in the years and decades ahead. The Intergovernmental Panel on Climate Change (IPCC) predicts that climate change will manifest in dramatic ways-extreme weather events, droughts, heat waves, increased cyclone (hurricane, typhoon) activity, sea level rise, etc.-and some of these effects may induce large scale human migration, both within and among countries. The increasing trend of environmental migrants is clashing with widespread anti-immigrant sentiment in both developed and developing countries around the world. Some countries are describing migration-and particularly unauthorized international migration-as a security threat and are turning to military forces to deter or manage the human flows, a trend that is likely to grow.