Robert McLeman, the University of Ottawa geographer, says four Canadian government departments have asked him for briefings on climate migration and security. Judging by the push to harden the Canadian border after 9/11, it's difficult to imagine we'd be friendlier neighbors in a hotter world. James Lovelock, never one to shy away from an extreme hypothesis, has suggested that a hot-and-bothered United States might try to take Canada by force.
If conditions do deteriorate to the point that humanity's survival is in doubt, nationalism will be put to the test. Man-made borders—between Mexico and the U.S., and between the U.S. and Canada—may well bring out the worst in us. When the cone of unlivability expands, we could all converge on the continent's pools of fresh water and start shooting at one another from gun boats. If we want to ensure the survival of American civilization, however, it would make more sense to form a Great Lakes collective.
Canadians have already put down stakes in a hostile environment once. Settling a country despite harsh conditions bred a national spirit of collectivism. You can see it in the proliferation of financial and agricultural co-operatives and in the country's universal health care coverage, which dates back to the 1940s. Homer-Dixon says that even if global warming hits Canada harder than the U.S., the Northerners might deal with it better than the individualistic, entrepreneurial Americans. The best hope for North America's survival: Hope that Canada's socialist tendencies rub off on all of us.