What’s in your wetland?

Prior to the 1800s, Wisconsin contained nearly 10 million acres of wetlands. In fact, Milwaukee, which lies at the mouth of three converging rivers, was itself originally a marsh. The marsh covered portions of present-day downtown, the Menomonee Valley, the Third Ward, Jones Island, Walker’s Point, and Bay View, according to historian John Gurda in The Making of Milwaukee.

But over the last two centuries, nearly half of Wisconsin’s wetlands-Milwaukee’s marsh included-have been drained and filled to create space for cities and agriculture.

Such wetland losses have slowed in the last several decades due to regulations and an increased appreciation of the role wetlands play in preventing flooding and improving water quality. “Wetlands used to be the place where you dumped your old refrigerator, but now they’re gems,” said Joy Zedler, a UW-Madison botanist who studies wetland plants. Still, Wisconsin’s remaining wetlands face other threats today. Near the top of the list are invasive plants.

Beetle Battle

In their natural state, wetlands support a rich diversity of plants that provide food and habitat for more animal species than any other type of Wisconsin landscape. But when an invasive plant moves in, there’s little to keep its growth and spread in check and so it can quickly crowd out native plants. The resulting invasive-dominated wetlands are less stable than diverse wetlands, and provide little food for native animals, said Wisconsin Department of Natural Resources (DNR) ecologist Brock Woods.

Woods coordinates control projects for invasive purple loosestrife, a Eurasian plant that was brought to the East Coast in the 1800s for ornamental use. Now found throughout Wisconsin as well as around the country, the prolific plant spreads via cut roots and stems and through the millions of sand-grain-sized seeds it produces each year.

Woods and other managers around the country have succeeded in stifling the plant’s growth and spread in many places by introducing special purple loosestrife-eating beetles. Though themselves non-native, the beetles live exclusively on purple loosestrife and are not a threat to other plants, according to the DNR.

But Woods cautioned that the purple loosestrife battle doesn’t end with the beetle. As a plant infestation is brought under control-a process that can take years-the newly opened wetland space must be “filled with what we want so it doesn’t get filled with what we don’t want,” said Woods. “You won’t get native insects and animals back until you get the wanted vegetation back.”

Difficult to Control

Other major invasive plants in Wisconsin include reed canary grass and hybrid cattails. Reed canary grass is a Eurasian native and one of Wisconsin’s oldest and most common wetland invaders. In the past, people intentionally planted this grass to control stream bank erosion because it grows quickly and densely, said U.S. Army Corps of Engineers ecologist Brook Herman. Those very qualities now make reed canary grass difficult to control.

Hybrid cattails, a cross between a native wide-leaved cattail and a non-native narrow-leaved cattail, also pose a challenge. They tolerate a broad range of water levels and are very aggressive, crowding out native species above ground with their dense stands and below ground with a network of wiry stems and roots, Zedler said.

“Biocontrols” such as beetles are not available for reed canary grass or cattails. Instead, attempts to manage them usually rely on the use of herbicides or mechanical means such as mowing or burning.

For the most part, though, these and other invasive plants that are already established in Wisconsin “are here to stay,” Woods said. “The only ones we have a good chance of getting rid of are the ones that are just starting to show up.”

Towering Grass

One such plant is the common reed, often referred to by its scientific name, Phragmites (pronounced frag-MY-tees). A grass that can tower up to 12 feet tall, non-native Phragmites is well established along Lake Michigan in northeastern Wisconsin, Woods said, but has just begun invading further inland. It tends to spread along highway ditches because, unlike many other plants, it tolerates road salt well.

“People need to learn to identify and control it while distinguishing it from native Phragmites,” Woods said. “It’s early enough that there’s still hope of keeping it out of most of the state.”

Woods and Zedler said the public can and should play a role in fighting invasive plants. “These are marvelous opportunities for neighborhoods,” said Zedler. “They can find out if their local wetlands have invasives, they can get to know what’s out there.” Woods said individuals and school and community groups can help the DNR raise purple loosestrife-eating beetles. “They’re fun to rear. Anyone who wants a project that’s part of the solution can do it,” he said.

“Each of us has to become knowledgeable…and demand tools [for dealing with invasives] that will be successful,” Woods said. “The quality of where we live is up to us.”

Jennifer Yauck is a science writer at the Great Lakes WATER Institute. GLWI (glwi.uwm.edu) is the largest academic freshwater research facility on the Great Lakes.

More About Wetlands and Invasives

• Wetland Gems – Learn about 100 notable wetlands in your area and around the state by visiting the Wisconsin Wetland Association website at wisconsinwetlands.org/gemslist.htm.
• Beetle rearing - Get involved in rearing purple loosestrife eating-beetles by contacting the DNR’s Brock Woods at brock.woods@wisconsin.gov or (608) 221-6349.
• Invasive roll call - Find more information about Wisconsin’s invasive plants at dnr.wi.gov/invasives/plants.asp and ipaw.org/information.aspx.

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