I don't think there actually are any "qualifications" in MMGB. the whole area is festooned with self-appointed "experts" (we all know the definition of expert !) who support the "cause" for either political or financial reasons.
Al Gore being the prime example - didn't he do well out of it ?
Hmn, there are. Many scientists have dedicated their whole lives to it and you can do environmental science A Levels and Degrees. Of course, green issues are not just about anthropogenic global climate change, loss of biodiversity, unsustainable use of resources, habitat loss, water depletion are also part of it.
I happen to agree with James Lovelock, I firmly believe humans are too stupid to deal with it. In evolutionary terms, we have be hard wired with all sort of traits that don't help our cause.