Fame
Not that he's merely known for his environmental advocacy, but Al Gore is pretty famous, no? And it can be argued that his concern for the environment is a more determining characteristic than his bid for the presidency. A sad truth, maybe.
With environmental issues being brought more to the forefront of our sociological and political landscapes these days, who knows? If you can make an incredible discovery or be responsible for a phenomenal advancement in the field, you just may be the world's most famous environmental scientist.