To get you on the right track, here are a few resources.
A huge Ning community for educators is The Educator's PLN: A Personal Learning Network for Educators.
A Google search of "Ning.com" and "Environment" gives you a good 6+ million hits.
Plus here's a few more on the eco-theme:
Green & Clean Mom
Pursuit of a Green Planet
And another one for education:
Transforming Education for the 21st Century
(Note: The only Ning community I'm a member of is the above mentionioned Educator's PLN, so I cannot speak on any of these other ones. But, find your passion, align it with Ning, and your networking life will take on a life of its own.)
Letter N picture from http://www.fromoldbooks.org/Tymms-Illuminating/pages/43-letterN/. The Ning photo is the logo for the home Ning site, where you can create your own.