Not all, but most pollution comes from nearby agriculture-
Studies Confirm Presence, Severity of Pollution in US National Parks. Science Daily
The worst of the problems is pesticides.
Studies Confirm Presence, Severity of Pollution in US National Parks
June 27, 2010 — Ralph Maughan4 Responses to “Studies Confirm Presence, Severity of Pollution in US National Parks”
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June 27, 2010 at 7:25 PM
I’m not surprised, given the proclivity of so many humans to traveling by mechanical means, not the two legs nature gave them. I’d be happiest to be able to put our cars behind us for just long enough to backpack a bunch of miles from the nearest road.
June 27, 2010 at 9:54 PM
It’s absolutely no surprises at all that pesticides are the biggest culprit.
What other creature on the planet *poisons* its own food on purpose?
We really are insane. That is the cold hard truth.
June 28, 2010 at 8:08 AM
Invasion of non-native species also tends to come locally from the outside if the Park. An exception to this can come to Parks that attract many vehicles from distant places.
June 28, 2010 at 11:02 AM
Slightly off-topic but a good source of invasives in the southwest:
http://www.desertmuseum.org/invaders/