The wetland management districts and national wildlife refuges of the northern Great Plains are bastions of Americas prairie heritagerelics of a landscape some consider the nations most endangered. Many were acquired from 1930 to 1960, when managers thought the best way to conserve land was to leave it alone. But in the modern era, idle land quickly can become degraded.
An active approach is taking shape on 20 WMDs and refuges in Montana, North Dakota, South Dakota and Minnesota, where biologists and managers are collaborating to apply realtime research to a landscapescale management strategy.
The goal of the fiveyearold Native Prairie Adaptive Management program (NPAM) is to find the best techniques to stem an advancing tide of Kentucky bluegrass and smooth brome grass. The invasive grasses are crowding out native grasses, eliminating habitat for native butterflies and birds, and perhaps rippling up the food chain.
I dont think we have a prairie left that you could call pristine, says Sara Vacek, wildlife biologist at 52,000acre Morris WMD in Minnesota. NPAM coordinator Cami Dixon says it is unlikely pristine prairie exists anywhere in the four states.
Dixon, an inventory and monitoring regional zone biologist based in North Dakota, has the data to back that up115,000 field observations, taken at the same locations yearly on the 20 participating WMDs and refuges.
The resulting database tracks changes in the plant community and guides management of each unit. Its a homegrown experiment in adaptive management, inspired by U. S. Fish and Wildlife Service staffers who suspected invasive grasses were spreading, did field research that confirmed it, and developed the modeling and management strategy with help from the U.S. Geological Survey and others.
In the early 2000s, managers and biologists recognized all of us had the same problem with invasive grasses, says Todd Frerichs, manager at Audubon National Wildlife Refuge Complex in North Dakota. All of us were too shortstaffed to really aggressively manage it and monitor it, so we decided to pool our efforts.
A wild lily on the prairie of North Dakota.
Credit: Cami Dixon/USFWS
Heres how it works: Each site manager selects a group of three or more study plots. Biologists lay out transects, one per five acres, on each plot. Every summer they walk the transects, stopping at 50 preset points to note the plants. Its very quick, says Vacek. We can get 20 or 30 transects done in a day.
The observations go into a computer model that produces a recommendation for each plot: burn, graze or rest. Managers follow through; the results are monitored the next summer and go back into the model to refine it.
So far, no strategy is obviously best, but one thing is clear, Dixon says: Prairie doesnt like to be idle. It likes to be burned or grazed, because thats how it evolved.
Native grasses evolved with grazing bison and elk, which defoliated the plants, spread seeds, pushed them into the soil with their hoofs, and fertilized them with droppings. Frequent fires halted the spread of shrubs and trees.
By mimicking natural processes, managers hope to give native grasses an edge. Timing is critical, and tricky, because growth patterns between natives and invaders seem similar. Some units are trying variationsburning twice per season, combining burning with cattle grazing, or varying grazing intensity. They use NPAMs monitoring to track the outcome.
Its making us be more aggressive with our management, which is good because thats the way we need to be going, Frerichs says.
Participants hope NPAM will identify strategies that work on a landscape level. And because NPAM is run by staffers, not graduate students whose research is usually shorter term, it can evolve as conditions change.
We have no end date in mind, Vacek says. Were not going to stop managing grasslands, so it could go on forever.
Heather Dewar is a Marylandbased science writer who formerly worked in the Refuge System Branch of Communications.