The National Park Service’s wetland protection policies prevent most new activities in parks from harming wetlands. However, there is substantial existing wetland degradation in parks from past or ongoing land use activities, and there are many other threats that the NPS and others are working to minimize. Here are some of the activities that threaten or have already damaged wetlands in national parks and elsewhere:
- Roads, dikes and levees can have damaging impacts on wetlands if they alter natural fresh water or tidal flow patterns or hinder movement of aquatic life. For example, Everglades National Park is working to restore water flow that has been diverted by canals and levees for many decades, and Cape Cod National Seashore plans to replace a tide-restricting dike near the coast with a new bridge that would reconnect the Herring River Estuary to the ocean.
- Drainage ditches or canals built for agriculture, mosquito control or other purposes can alter wetland hydrology dramatically, even converting them to uplands. Assateague Island National Seashore, Jean Lafitte National Historical Park and Preserve, Indiana Dunes National Lakeshore and Rocky Mountain National Park are among the many parks that have backfilled or plugged ditches or canals to restore wetlands.
- Depositing fill for development or other purposes destroys wetlands and can have offsite impacts by blocking flow or hindering movement of aquatic life. Channel Islands National Park in southern California and Cuyahoga Valley National Park in northern Ohio are two of the many parks that have removed fill to restore wetlands or “daylight” buried streams.
- Pollution such as oil spills near Gulf Islands National Seashore and airborne mercury or sulfur compounds at Acadia National Park and Gates of the Arctic National Park and Preserve can degrade wetlands and other aquatic habitats.