When we hear about surface-water pollution, we tend to look for the nearest city water intake, or the homes in the area that are still using wells. As long as the water supply is sound or treatable, we relax.
But when a group of migrating waterfowl see a body of unoccupied surface water, they might just land there. If it's flowing water, fish and other aquatic animals might just follow it. If its banks have green vegetative cover, aquatic and semi-aquatic animals might just come to it, looking for habitat and/or drinking water.
Wild animals, at times in their lives, migrate. It's in their genes. They look for new territory. Even if it's polluted (and they don't notice right away) they might just find it and try to make a go of it: finding shelter, searching for food, and maybe finding a mate and trying to start a family.
But if it's polluted, then they're eating, drinking, and living in the pollution.
We can relax because we've got our safe homes, our clean underground water and filtering systems, the buffer zones we keep between our residential areas and our industrial areas, our doors, windows, and air filters.
The wildlife don't have these comforts, and they can't relax.
That's why environmental quality is an animal issue.
NASA.2008. “Berkeley Pit: Butte, Montana.” National Aeronautics andSpace Administration (NASA).