One of the things I've noticed in my political musings is that liberals, democrats, and tree-huggers in general view the ecology in the same way that conservatives, libertarians/republicans and small government advocates in general view the economy: both view humans as screwing it up whenever they stick their filthy hands in! Ecologists lament that ecosystems are naturally sustainable and worked just fine until humans ignorantly overhunted certain species and overutilized certain resources, throwing the natural system out of whack. Free-marketeers, however, view the economy as a natural cycle of booms and busts based on the simple, unchangeable principles of supply and demand, and feel that whenever the government or some other centralized body tries to manipulate it to their advantage or dictate an economic outcome it likewise screws everything up. They favor the government keeping it's hands out of the economy to allow this natural cycle to work its magic, just as opponents of hunting or sharpshooting to reduce overpopulation endorse introducing natural predators as an alternative: Both wish to turn back the clock to the time when the system worked fine, before the silly humans got in the way.
The difference, from a government perspective, is that in order to fix this problem, environmentalists support MORE government intervention to counterbalance it. Rather than merely telling humans "stop invading the habitat of owls and cutting down their trees!" they advocate the government taking it upon itself to reintroduce the owls into the habitat. on economic issues, however, libertarians want the government to merely undo whatever perceived encroachment on the free market that exists, not enact new interventions to counteract the failures of the old. Another difference is that libertarians are focused purely on what's best for humanity, while many environmentalists feel humanity has a moral obligation to sacrifice for the well-being of other species. Libertarians have no problem with human greed, and construct a system that rewards it; environmentalists try to curb greed's effect on that which it injures.