What we tend to forget is that large changes in society tend to start with us. Try eating less meat, eat healthy food, reduce car and plane usage when possible, buy less stuff (especially online), these are things anyone can do (rich or poor). When you start, family members and friends might follow.
From there, more people will try to change their consumption, and when enough people do that, politicians that are willing to tackle these issues will be elected. And when politicians are elected at some point your government will take the right step. From there we go to countries and eventually a large part of the world will do what must be done to survive.
You want a better world? Start by improving your own life and health.