How do wetlands protect land and water?

Originally, wetlands were thought of as wasted land that could be drained for agriculture, building housing developments and other structures. Even the word “swamp” implies that they are areas with little meaning. The truth is, wetlands are a crucial part of the earth’s ecosystem, one that we cannot do without!

water lily pads in a wetland

Water lilies, cattails and other plant life thrives in wetlands, and become an important part of the ecosystem. Lilies provide homes for insects, and calm waves; cattail roots are used as food for muskrats. Credit: SV Fisk

In the late 1980s, wetlands were recognized for the services they provide to our environment. Wetlands provide flood control, improve water quality, and are a vital habitat for wildlife. They are a huge part of the “Earth’s Kidney’s” – to read more on that, click here.

What exactly qualifies as a wetland? Wetlands are transitional areas between land and water ecosystems. The U.S. Fish and Wildlife Service definition is commonly used for regulatory purposes, and contains three criteria.

  1. A wetland must be an area where water accumulates on the landscape. Wetlands may be located in upland depressions or in low-lying areas next to streams, lakes, or oceans.
  2. The soil in a wetland must be saturated for an extended period of time each year.
  3. Wetlands must support plants which grow in wet or moist conditions.

Because of wetlands’ importance to our ecosystem, legislators included a provision in the 1986 Food Security Act referred to as the Swamp Buster Act. Swamp Buster stated that no wetlands can be destroyed unless a wetland of the same size is created elsewhere.

Aerial view of constructed wetlands

Airborne view of constructed wetlands that are used to remove excess phosphorus from water before discharging into the Everglades, called a stormwater treatment area. Credit South Florida Water Management

In theory, this seems to make sense. If a company wants to develop land that contains wetlands, for every wetland acre that they drain, they can reestablish an acre of wetland somewhere else. This would imply no net loss of wetlands, and preserve all the functions that wetlands serve on the landscape. Perfect!

In practice, creating wetlands isn’t quite so easy. To work correctly, wetlands must have proper hydrology, soil, and plant communities. Without all three components, wetlands will fail to serve their intended purpose. This is one of those “Goldilocks” situations: the wetland must hold water, but not for too long. The soil must be just right – not too sandy, or too clayey. Finally, the plants need to be the right type, or the typically soggy soils might kill them.

There can be other reasons to add wetlands to a landscape besides replacing wetlands lost to construction. Companies or municipalities are interested in building wetlands for their capacity to filter nutrients and clean water. Think of wetlands as huge versions of a raingarden.

wetland surrounding roads

Everglades STA supports the ecosystem around human-made roads and buildings. Credit: South Florida Water Management.

Wetland soil scientists are researching the effectiveness of a particular type of constructed wetland – Stormwater Treatment Area (STA) wetlands in the Florida Everglades. The STA wetlands were constructed in the 1980s in order to capture storm water that was damaging the Everglades ecosystem. In particular, the wetlands were placed on the landscape to slow down the flow of storm water running off of urban or agricultural development. They also provide a place for nutrients, like phosphorus, to be filtered out of the water before it flows into the greater Everglades area.

The STA wetlands rely on the flow of water from the Lake Okeechobee watershed to bring water into the wetlands. While the soils are highly variable throughout the constructed wetlands, they are able to become saturated and hold water for extended periods of time. This supports plants such as cattails and bulrush that only grow in wet conditions. The vegetation is particularly important in the STA wetlands because it provides a physical barrier to reduce the flow of water before it enters the Everglades. Cattails and bulrush also use up large amounts of nitrogen and phosphorus to fuel their growth. This reduces nutrient concentrations in the water through uptake into the plants! What a great trade-off! Because the STA wetlands were designed with all three criteria of a functional wetland in mind, they have proven to be an effective tool for flood control, nutrient management, and water quality in the Florida Everglades.

Wetlands provide several important functions on our landscape. Though most of our historic wetlands in North America were degraded or destroyed, constructed wetlands can rebuild these important services. They need to be properly built for hydrology, soil and plant communities. Newly constructed wetlands restore the lost wetland function on the landscape. Since the Swamp Buster Act, wetland conservationists have made great progress in preserving existing wetland acres and creating new wetlands. Ultimately, we need as many tools as possible to provide flood control, water quality, wildlife habitat, and biodiversity throughout the country.

Answered by Rachel K. Owen, University of Missouri

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