Two other ways that capitalism will help save the environment.
Saving the environment will save you money! Well, in some cases. The strain on the environment comes from too many people using the same resources. When there is a high demand for a given resource the price goes up. Gasoline is an excellent example. Therefore, technologies that use less gas, electricity, water, or other resources become more attractive as the supply of the resources dwindle. Of course, even when your water bill is already low, most people would still like to have it lower, so new water saving technology in a capitalistic market will tend to do better than old water wasting technology.
Aside from the stark economic truth that using less costs less, capitalism has another stronger tool. Supply and demand will ensure that, all else being equal, the consumer gets what he wants. If the consumer wants polluting Hummers and stretch-SUVs, they will get them. if the consumer wants organic vegetables and cars that run on those same vegetables, they will get that. In a society of people who want to save the environment, the free market will provide good that will save the environment.
The big question now is if we really do want to save the environment.
There's a third way that capitalism 'helps' the environment. When economists talk about environmental problems they are often thinking of the environment in strictly human terms. The worst environmental problems are those that kill the most people, and these problems are by far the most severe in third world countries, where pollution in the atmosphere and diseases in the water are the big environmental problems. Bringing these communities up to a higher standard of living would result in lower levels of pollution and desease, lowering death rates, and thus 'help the environment'. It is entirely reasonable to assume that the free market will help improve these people's lives, given time.
This type of thinking is great for the humans, but doesn't do the spotted owls any good.