Fergus Falls WMD |
Wetlands
Many species of wildlife depend on wetlands for their home, including waterfowl, wading birds, shorebirds, mammals, frogs, turtles, salamanders, and insects. Each species has various needs from wetland habitats. For example, dabbling ducks like mallards and teal seek shallow water to feed in, and marsh wrens and yellow-headed blackbirds like robust plants to perch on and nest in. Different types of wetlands provide these various habitat types. Wetlands consist of anything from consistently water logged soils to large open water lakes. The variety of habitat conditions provided by wetlands helps to support a diversity of wildlife use.
Wetlands provide more than just value for wildlife habitat. They absorb and hold run-off that could increase the effects of flooding. Wetland plants and soils filter chemicals and nutrients contained in run-off waters. Wetlands are an important component of the water cycle. They slow run-off into rivers, lakes and streams, and recharge or discharge ground water by seepage through the soil. Basically wetlands are sponges that clean and meter water in the water cycle.
Wetland Restoration and Management
When the Fergus Falls District acquires a new tract of land, typically it has been farmed. One of the first things done on a new unit is wetland restoration. A wetland expert analyzes the property and determines where wetlands have been drained or filled. Then heavy equipment is used to plug ditches, break tile lines, and scrape out soils to restore wetlands to their natural depth. Once the dirt work has been completed, the wetlands are allowed to fill with water naturally through rain water run-off and snow melt in the spring. If determined feasible and appropriate, water level control structures are sometimes installed so that water levels can be managed to maximize the habitat value.
The Fergus Falls District manages nearly 50 wetlands in a three county area with dam like structures that allow District staff to adjust water levels with boards. These structures are used to maximize the habitat value to benefit waterfowl and wetland dependant wildlife. The main objective of most water level management is to stimulate plant growth in wetlands. Many wetland plant seeds need exposed mud flat to sprout. Water levels are lowered to expose mud flat so wetland plant seeds can grow. Once the plants have matured, we flood the plants slowly until conditions in the marsh are approximately half open water and half standing plants. This is known as the hemi-marsh state.
The hemi-marsh state has been researched extensively and has been shown to be the most productive wetland state for waterfowl reproduction. The hemi-marsh state provides cover from predators and visually screens other territorial waterfowl. Food is abundant because of the abundance and variety of plants. Ducks feed on both the plants themselves and the insects that depend on plants for food. Other species benefit from water level management as well. When mud flats are exposed during low water levels, shorebirds actively feed on insects in the moist soils. Wading birds feed on frogs and sometimes fish in these marshes as well. Many species make their homes in these wetlands at varying stages of flooding because of the diversity of plants and water depths found in these managed marshes.
Invasive fish have become a problem in many wetlands in Minnesota. These fish disrupt natural processes in wetlands sometimes causing poor water quality and reducing the value of those wetlands for wildlife. Invasive fish can be eradicated from marshes if a wetland is drawn down before winter. The fish will freeze out or die from oxygen depletion over the winter. When we use draw downs to remove fish, a barrier is necessary to keep to fish from re-entering the system. We use sloped, smooth pipes called velocity tubes, pipe elbows, rotating screens, or swinging fingers to prevent fish from moving upstream into managed wetlands. Invasive fish can also be removed by stocking predator fish or chemical treatment with rotenone, which is a chemical derived from the roots of a South American plant. Rotenone kills fish by disrupting the way they absorb oxygen into their cells. All three methods of removing invasive fish can improve wetland quality and wildlife habitat.
