Here's a rather scathing PSA from Plane Stupid. (Note, if you get squeamish at the thought of seeing polar bear deaths depicted in a fairly gruesome-and slightly absurd-manner, or if you yourself are a polar bear, you might think twice about watching.)[vimeo][/vimeo]Wow. Granted, each flight doesn't literally kill a polar bear. This isn't some sick inversion of the ringing bells that beget angel wings from It's a Wonderful Life. But it does hammer home the increasingly annoying reality that most of the greatest technological advancements in human history-especially those related to convenience, mobility, and power-have brought about some of the worst environmental problems in the present. And the specific point is well taken: Air travel produces ungodly emissions, so if you're going to fly, make sure the trip is worth it.Via Treehugger. Thanks, Zach.