I believe your confusion stems from defining what you term a "conservationist". At first you use it to describe someone who worries about peak oil / the finite nature of oil (presuming you understood the original context of the discussion), and later you use it to describe an environmental conservationist - one who is concerned that the costs of resources are underpriced because of the effect on the environment - to which you've helpfully provided examples of strictly environmental externalities.

Markets aren't perfect problem-solving devices - no one has said that they are, however, the regulatory "cure" is often worse than the disease. Regulations are certainly not the ideal way to deal with concerns a given resource are finite. Further, prices are signals in markets that themselves call for market innovation/adaptation - vocal calls for conservation are redundant.

(As a side note: it is also noteworthy however that the drop in sulphur dioxide emissions happened far before the creation of regulated markets suggesting that the fall in SO2 might have occurred irrespective of the regulation - further, from purely an economic efficiency standpoint, pigouvian taxes tend to be more efficient than the added structure of artificial pollution markets. Further, as an addendum to acid rain/"dead lakes" - this was a big concern for Canada until someone noticed that the primary reason the lakes were dead was because of reduced logging and the sediment that it disturbed)