Threats to Wetlands

 

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.

 

Non-native tamarisk and Russian olive trees have invaded the riparian zone at Canyon de Chelly National Monument.

• Exotic plants like tamarisk at Canyon de Chelly National Monument or common reed (Phragmites australis) at Gateway National Recreation Area can squeeze out native plants, alter or eliminate habitat for some wildlife species, and even damage cultural landscapes.

 

Nutria is an invasive species in Southern Louisiana.

• Exotic animals like the nutria, a large semi-aquatic rodent native to South America, can damage wetlands. Nutrias were imported to the U.S. for fur production, but they escaped captivity and quickly established large, wild populations in the marshes of Jean Lafitte National Historical Park and Preserve in Louisiana and in other Gulf Coast wetlands. They burrow into banks and eat vast amounts of wetland vegetation down to the roots, which causes soil and bank erosion and alters plant communities. They also out-compete native mammals such as beavers, muskrats and mink.

 

• Livestock grazing, unless managed carefully, can remove plants that stabilize streambanks and protect soils from erosion. This can damage some wetland types by causing channel formation and drainage, or can clog streams with sediment.

• Groundwater withdrawals for water supply can lower water levels in some wetland systems, changing habitats for plants, fish or other aquatic life.