Given that the Federation is generally described as a paradise, it's safe to say it's pollution free. We also got a general view of Ferengi views of environmentalism in the Deep Space Nine finale. How do the other powers of Star Trek universe view environmentalism?
Please avoid any jokes about green women ;-)
This question could be pretty open-ended so I'll restrict it to a few of the main races depicted; Ferengi, Klingon, Cardassian
Although Ferenginar is depicted as being somewhat unpleasant (at least to human eyes), it's evidently not polluted:
a fetid dismal swamp, subject to a near-endless downpour. The capital city of the homeworld rises out of the swamp, a series of dome-like structures piled almost haphazardly one atop another.
In Little Green Men Quark makes it abundantly clear that causing environmental damage to your own homeworld is anathema to the Ferengi, despite their world-view that profit is king.
In the original continuity the Klingon homeworld is heavily polluted as a result of the destruction of Praxis. Their callous disregard for their planet's wellbeing probably extended to the home planet as well:
The moon's decimation means an almost eighty percent loss of available energy and a deadly pollution of their ozone...They do not have sufficient resources to manufacture air shelters in large enough quantities to sustain anything like their current population.
In the Abrams continuity things are far worse: According to Scott Chamblis;
Ultimately, that took us to a place of trying all different kinds of environmental pieces of this overall picture of toxified Qo'noS
and from Ben Grossman:
“As we start to descend down through the atmosphere," stated Ben Grossmann, "we had the idea to almost give it an underwater feel. We figured that with that much humidity and moisture to create a toxic cloud, you’d imagine there’s a lot of toxic sludge around.
The Cardassians seem to have a "devil may care" attitude to pollution on their homeworld. Various companion books describe the collapse of the farming industry due to industrial pollution, leading to famines which necessitated the need to invade their neighbours (setting the scene for DS9):
Weyoun: Did you know that when we arrived, children were starving on Cardassia Prime? It was heartbreaking.
