One great environmental impact is the sheer number of humans. I believe I've mentioned taking trips through southern Utah, where the air is (or at least was, before St. George turned into a boom-town) extremely pure and clear. Anyone with any knowledge of science or even just of the material world we live in realizes that the earth's carrying capacity is finite. Thus, low population areas, like southern Utah are less impacted, even in the absence of environmental controls, than are areas of high population density.
Thus, the links that some of the Republican contenders - namely, Rick Perry, Michele Bachmann and Rick Santorum - have with the dominionist Quiverfull Movement count as attacks on science and reason. For those not familiar with this name, it comes from Psalms 127:3 - 5:
Lo, sons are a heritage from the LORD,
the fruit of the womb a reward.
Like arrows in the hand of a warrior
are the sons of one's youth.
Happy is the man who has
his quiver full of them!
He shall not be put to shame
when he speaks to his enemies in the gate.
The Quiverfull movement urges Christian families to keep popping out children as long as the woman's womb lasts. In one case, after a woman had to have her 18th. child by emergency caesarian section and the doctors strongly urged her not to get pregnant again, her friends in the movement told her it was her duty to have child #19. The idea of this movement seems to be to grow a dominionist army. Quiverfull families commonly have 12 o 20 children.
This is part of the general fundamentalist contempt for environmental concerns. It apparently includes contempt for mathematics as well. While, to my knowledge Gingrich, Romney, Paul and Huntsman are not tied to either dominionism or the Quiverfull movement, Paul would abolish the EPA, while the others would apparently put environmental concerns on the back burner.