The biggest threat to wetlands is losing them to draining and filling. The overall goal at both state and federal levels is to maintain and even increase wetland acreage. Wetlands’ water quality also suffers from pollutants and water volume overloading from stormwater.
Alterations in water movement
When there are major changes or fluctuations in a) water levels, b) the movement of water, or c) barriers made in a wetland — for instance, when a road is built across it or stormwater is directed towards it — the wetland’s natural plant community can suffer and invasive plant species can take over. About 80% of Minnesota wetlands that have experienced even moderate water alterations now have abundant invasive plants growing in them — permanently replacing the native plant communities. This can change wildlife habitat and the wetland's ability to transform nutrients.
A hardwood swamp in which invasive cattails have taken hold.
There is a long history of draining and filling Minnesota wetlands to accommodate settlement and development. Nearly 40% of the state was some form of wetland 150 years ago; now that percentage has been cut in half. The loss of wetlands has meant a loss of water quality benefits and has contributed to the degradation of streams, lakes, and groundwater.
Phosphorus — bad for ducks?
Statewide, we’ve found elevated levels of phosphorus in 31% of our “prairie pothole” wetlands, negatively affecting the insects, snails, and leeches that live there. These macroinvertebrates are a vitally important food source for ducks and other birds that depend on wetlands during breeding or migration.
Land use impacts on wetlands
With the potential to impact thousands of wetland acres, activities such as mining, agriculture, and road building in Minnesota highlight issues surrounding no-net-loss policies. For example, to comply with regulations, mining companies are required to compensate for wetland impacts, preferably by restoring previously drained wetlands in the watershed. But this option is often limited on the Iron Range where few wetlands have been drained. Alternatives such as restoring wetlands outside of the watershed, preservation, and stream restoration are being closely considered.