Uh. No, neo, environmentalism doesn't hurt the poor more than other demographics. They're actually the ones that feel its
lack the hardest. It ain't the rich or middle class that's doing much living besides toxic swamps and dealing with flaming tap water. Also tends to be the poorer parts of an area that gets screwed the hardest when the infrastructure keeping the ocean off the land breaks, and so on, and so forth.
Logically we already have plans in place due to the Cold War making the prospect of "The USSR, but not separated from the US by miles and miles of ice, tundra, and snow" a very spooky one. It's now a lot less spooky (a lot fewer nuclear weapons are involved, although that's of little consolation to those of us still living in potential future "post-apocalyptic parking lot" locations), but a lot more real.
For what it's worth, so far as I can recall a post-melt arctic (north in general) would by and large be
harder to wage a land war across than the current ice, tundra, and snow, if that's the sort of thing you're talking about. And that's not even getting into what it means for actually getting to places, heh.
Part of the thing folks seem to forget about the thought of the colder parts of the earth heating up is that it's not going to turn up something fresh and happily nourishing daisies, it's going to turn up a massive bog of terrifyingly bad land that occasionally spews out clouds of noxious death and/or falls out from under you. That ain't exactly prime farmland hiding under all that permafrost, heh.