Scientists check health of state's wetlands

Mike Bourdaghs
Minnesota Pollution Control Agency scientist Mike Bourdaghs makes his way through a wetland in rural Otter Tail County while assessing the condition of the wetland. This wetland is considered "degraded" because invasive species have pushed out many native plants. Scientists are assessing the condition of wetlands across the state to help determine if conservation programs are working.
MPR photo/Dan Gunderson

Scientists are slogging through wetlands across the state and poring over thousands of aerial photos. It's all part of a big project to check the health of Minnesota wetlands. The results will determine if conservation programs are working, and could influence policy decisions far into the future.

About 10 million acres of wetlands are scattered across the Minnesota landscape. Some are big areas of open water ringed by cattails. Others are little more than grassy spots a couple hundred feet wide.

That's the kind of wetland Minnesota Pollution Control Agency scientist Mike Bourdaghs examined recently.

Tucked between cornfields just off a highway in Otter Tail County, the wetland is a mix of grass and cattails, brush and small trees. Like many Minnesota wetlands, this one is not in the best of health.

"I'd be fairly confident in saying that this area was probably plowed at some point and now abandoned and now what we have here is dominated almost entirely by invasive species," Bourdaghs said.

Where there should be hundreds of native plant species, Bourdaghs mostly found a thick matte of invasive reed canary grass that chokes out most native plants.

Bourdaghs and a student intern spent a couple of hours walking across a designated area, logging all the plant species they found.

Mike Bourdaghs
Minnesota Pollution Control Agency scientist Mike Bourdaghs clarifies spelling of the scientific name of a plant while intern Andrew Grean adds the name to a list of plants found in a wetland in rural Otter Tail county. Scientists score the health of wetlands based on the diversity of native plants found during an assessment. Scientists just completed an examination of wetland conditions across the state.
MPR photo/Dan Gunderson

"We've got marsh marigold here, caltha palustris," he said.

The research project is the first large-scale objective measurement of wetland quality in Minnesota. Scientists assign a value to each plant species based on the kind of habitat it needs to survive and its ability to adapt.

"We've gone out to sites that we know are in really good shape. We've gone out to sites that we know are in really bad shape," Bourdaghs said. "From those data we're able to calibrate some benchmarks that we can use with what we're collecting here today."

Minnesota enacted a no net loss of wetlands policy in 1991. Until now, it's just been a goal, with no comprehensive way to measure success or failure. But most experts agree the state has lost wetlands in the past 20 years.

According to a recent report from the Environmental Working Group, Minnesota farmers have converted 1.3 million acres of conservation land to farmland since 2008. A U.S. Fish and Wildlife study in 2009 estimated Minnesota had a net loss of 96,000 acres of wetlands since 1980.

Conservation programs restore wetland habitat. But the state continues to lose wetlands when those programs expire, said Doug Norris, wetlands program coordinator for the state Department of Natural Resources.

Since the Wetland Conservation Act was passed 20 years ago, Norris said, many exemptions have been added to allow for destruction of wetlands.

Mike Bourdaghs
Minnesota Pollution Control Agency scientist Mike Bourdaghs identifies a plant while checking the condition of a wetland in rural Otter Tail county. Healthy wetlands have hundreds of species of native plants. This wetland has been taken over by invasive species not native to Minnesota.
MPR photo/Dan Gunderson

"We've never felt like we had a real good handle on what's happening with the loss, both in terms of the exemptions and what might be being done illegally," he said.

While Minnesota Pollutions Control Agency scientists explore some 250 wetlands to monitor quality, DNR researchers are measuring wetland quantity.

Aerial photographs are taken every three years of 5,000 locations around the state. Analysts then examine those photos and compare the size of wetlands. Using a statistical model, they can then determine if the state is gaining or losing wetlands.

Norris hopes this scientific work will stop arguments over whether Minnesota is losing wetlands and focus the debate on wetland regulation.

"If it turns out that we find we're not meeting those goals, it might drive changes in those regulations," he said. "Hopefully more than just being a number gathering exercise it would drive policy and action on the ground."

In Otter Tail County, Bourdaghs' assessment of the wetland he walked through shows that it is clearly in a degraded condition, taken over by invasive species. He said the least healthy wetlands are generally in agricultural areas and most healthy wetlands are in the northeast part of the state where there's been little land disturbance.

But assessing the health of wetlands is just the first step. About 250 wetlands across the state will be monitored every three years by researchers using the science-based ranking system.

Bourdaghs said researchers have key questions in mind: "Is it getting worse over time? Or is it getting better? Are conservation programs paying off in terms of meeting the statewide goal of not only maintaining wetland quality but enhancing it over time?"

The first answers to those questions will come sometime next year when MPCA and DNR officials complete the analysis of all the data they've collected the past six years.

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