There we disagree. I actually agree with Arnold on that one, but not in the way most people would interpret it. A productive planet, with robust and dynamic complexity in its operating systems is more resistant to calamities such as asteroid hits, it produces the wealth we need to protect and care for it, it recovers from our extractive processes to its former capabilities more quickly, and it supports more life, both human and otherwise. A healthy planet is a good thing economically.
Most greens think that "the environment" is something separate from people. They believe that it is something that can be "preserved." It's a huge mistake. They believe in evolution while trying to enforce a genetic status quo. It can't work, either for man or nature.
Maybe SOMEtimes it's posed as a false choice, but to every choice there is a cost (or forgone benefit) and a potential benefit (or avoided cost). Maybe we don't always know what the dollar figures are, hence the need for an arbitrary "dollar value of a life" (or "of avoiding contracting cancer") in most cost / benefit analyses.
The systems I have designed actually motivate quantitative measurement of environmental risk as a means to determine actuarial risks. It is a way of inducing an objective pricing system.
It's a little icky to have to assign value like that, but it's simply liberal nonsense to refuse to assign ANY value and to insist that weighing costs against benefits is somehow an invalid "evil corporations" approach.
Well there are evil corporations, and bad landowners, government included. The key in a just system is to find ways of inducing responsible behavior simply because it is more profitable to do in a well designed market.