I've just started the Big List of Environmental issues - on Envirowiki. You should add to it. Hopefully, after a few decent edits, this page will list all the big issues, and after a few more related issues.
The reason that all the links are red is that those pages haven't been created yet. Click on the links to start editing! Also, check out some of the blue links - some of those pages could do with some improvement.
You don't even need to log in to edit pages on envirowiki, but if you're not logged in, you'll need to enter the answer to a maths captcha after you press save (to make sure you're not a spambot).