I think there's another interpretation of these facts which you have neglected to consider. Many people might make substantial changes to their lifestyle if they believed that it would do any good. But do you know what happens when individuals make changes to lifestyle? Fuck-all. The majority of people can't or won't make substantial changes, so those people's efforts is just pissing in the wind.
The majority of environmental damage benefits not the poor, but the ultra-wealthy. Most of those people don't give one tenth of one fuck about you or me, and are utterly unwilling to make substantive changes in their lifestyles. The few that are willing to make changes have the economic power to have substantial environmental impact, but they are overwhelmed by the rest. The poor aren't shopping at Wal-Mart because they think it's fancy. They're not buying imported Chinese foodstuffs because they think they're of high quality. They're buying what they can afford.
TL;DR: You're not going to get poor people to make changes while rich people are flying past in their own private jets. And since most people in the world are poor, there's only one direction in which to look for where the changes need to occur.