You might be asking what women's reproductive rights have to do with environmentalism. Well, the answer to that is: pretty much everything. The root causes of our environmental ills are the wants, needs, and desires of unimaginably huge numbers of people. Family planning is also one of the keys in helping to relieve poverty, which in turn helps to further reduce fertility rates as people climb the economic ladder. Poverty reduction and family planning go hand in hand, one begetting the other in a closed loop.
From Gristmill
Naturally, populations start to decline as a society becomes more egalitarian, industrialized, urbanized, wealthier.
Why? Give women more choices and they won't have as many babies - they may work outside the home, delay marriage, and use contraception. Children are expensive and less of an asset in industrial, urban societies as opposed to agricultural societies. Wealthier populations tend to also be healthier, which means less infant mortality (which generally correlates with having fewer babies). More info here and here.
Environmentalists can't afford to ignore structural poverty, racism, social injustice, women's rights... because these things are really several sides of the same coin. The debate should never be framed as economics vs. environment. The most vulnerable in our world have the least to lose - they will be (in fact, they are already) affected by ecological changes that we see in abstract terms.
More on women's rights, class issues, environment, solidarity
