Every cave is sensitive, whether the cave is open to the public as a show cave or is an unexplored, wild cave. This fragile environment cannot repair itself like the environment on the surface. Because the cave is not visible to people living on the surface we often assume our actions will have no effect on the subsurface. This is as far from the truth as one can imagine. One of the most damaging environmental problems facing caves today is water pollution. Water is as vital to the life of a cave as it is to the life of humans. We have learned how caves are developed by groundwater seeping into the subsurface. Many caves also have rivers which start on the surface and enter the cave through a sinkhole or other entrance. Therefore, any materials that will dissolve in a liquid can enter the cave environment. Rain water and runoff carry pesticides from farming. Industrial wastes dumped into rivers may enter the cave if the river itself runs underground farther downstream.
In western Wisconsin and eastern and southern Minnesota, much of the water we drink comes from aquifers which are riddled with caves. Much of the water that replenishes these aquifers comes from rainwater seeping into the ground. Caves provide a more direct route for the water to reach the water table through soil and rock. As a result, contaminants reach the water table in a matter of a few hours or days rather than months or years. In rural areas, people will have wells and septic systems. This also may be true of small towns and villages. It is not unusual to find a homestead or even a village or town pumping well water from the same rock unit as they dispose of the sewage. We must keep in mind that anything we put into the ground will eventually reappear in our drinking water.