Whether a species is being depleted by silt, agricultural or industrial run off, or other pollutants deposited in the water, it is reflecting the health of the riparian areas where it lives or where it has failed. One problem is a lack of riparian buffers. When trees are cut along small streams, for example, the waterways lose their natural shade, and direct sunlight can raise the water temperature, affecting the fish upon which mussels depend. Natural, vegetative buffers also protect banks against erosion. Development or the constant presence of livestock on river banks can cause the land to erode into the water and increase siltation in streams and rivers.
Dams are among the most destructive threats to freshwater mussels in New England.
They cause siltation, they create impoundments so that water ceases to flow, and they impede the migratory routes of mussel host fish. Plain old pollution is also a big problem for freshwater mussels, from pollutants discharged directly into waterways to toxic run off. When agricultural, industrial, and urban areas stretch right up to river banks, run off from the land pollutes the water and stresses the intricate food and reproductive systems upon which mussels rely. Lastly, many freshwater mussels are affected by introduced species that outcompete them for food or, like the zebra mussel in the Midwest and now in Vermont, New York and Connecticut,actually cover the individual mussel, preventing the native mussel from feeding or breathing. Dwarf wedge populations seem to be affected by Asian clams in some water systems, which probably displace the mussels from their habitat.