I can always go back into law, but I'm pretty content where I am now, and I don't regret law school at all. The most satisfying area of law will be the one that you enjoy the most - some people love working for non profits to advance social justice, whereas some people love paperwork and mergers. It really does depend on your interest. (By the way, environmental law can applies to many areas - so you have to find out which environmental sector you are interested in) Another good tip is that you don't have to major in traditional subjects like political science, it's actually to your advantage to have a major that is unique - ex: computer science major + law degree = can result in legal jobs at tech companies.
This was my 2 cents on this topic - and I hope it shed some light on your question. If possible, I would also seek the opinion and advice of other people that have practiced environmental law to get more focused answers and insight to that particular practice. Best of luck!