Originally Posted by Platy
Harder to say what could be done about increasing human population, water shortages and soil salinization, though.
Many parts of the developed world (Italy, Scandinavia) are already experiencing negative population growth. Most upper-middle class families in the US have only one or two children, resulting in negative growth. The key to acheiving negative population growth, IMO, is the education of girls and women. When women can make good money in satisfying careers, they will put off having children, and will have fewer children.
The long-term danger of fundamentalist religions (especially Muslim and Christian) is that they devalue women and relegate them to being baby factories. If you want to help the environment long-term, struggle for schools for girls all over the world.