[Happy Monkey]

Eventually, "nature" cares about as little about the wildlife killed by DDT in a stream as it does about how long a hoodoo stands. Our desire to maintain ecosystems is to some extent aesthetic as well. There's the additional butterfly effect issue of whether a particular disruption to an ecosystem will eventually impact our survival, but I would think that the National Park system was primarily set up to preserve aesthetics, and the ecological aspect (which is more important, but less politically viable) piggybacked on that.