Go vegan. It is considered the #1 way to help the Earth and the enviro. Eating meat is the #1 cause of global warming.
I do recommend that anyone who tries this do their research first - learn what foods you need to eat to compensate for no longer eating meat and dairy.
Then go slowly - perhaps start with being a vegetarian and having one vegetarian meal per week. Then gradually build up to 2, 3, etc.