Please clarify me if I am wrong, but isnt private/corporate environmental law, like minutia said, trying to help companys get around environmental laws? Sure I would love to come home to a sick paycheck but do I have to sacrifice that money to do something that I know is worth fighting for?
There are lots of legitimate natural resource/environmental disputes with no clear "good guy" or "bad guy." For example I know of a current dispute that will likely be headed to court, where and Indian nation purchased a very large water right and land for many millions of dollars, with the intention of permanently trusting (leaving in stream) the water right, but the state claims that the water right has not been used in 5 years and is no longer valid so it can not be trusted, but instead has been relinquished. I don't think I would feel too bad working on either side of that issue. Maybe there is also another side to that one in that the Indian nation may have a case against the person who sold them what turned out to be an invalid water right. Anyway, those are some of things many "environmental" lawyers actually deal with.
Also, if you are working for a firm as an environmental lawyer dealing with regulatory issues, much of what you will be doing is helping your clients figure out how to best comply with regulations, not how to get around them.
There are not a lot of jobs out there for the "save the wales" types of environmental lawyers, and those jobs don't pay very well, nor would that work be very interesting IMO. Most environmental law careers are with firms or the government, and in most of them you do have the potential to earn pretty good money.