Fire on the prairie: Minnesota's rich tradition of controlled burns

It's high noon in early May, and the gravel parking lot at the Louisville Swamp Unit of the Minnesota Valley National Wildlife Refuge between Chaska and Jordan is bustling with activity.

Instead of nature-seeking hikers, bird-watchers and photographers, 18 firefighters, most with the U.S. Fish and Wildlife Service (USFWS), are preparing their drip torches, chain saws, water hoses and other equipment for the work ahead. Several trucks and four-wheelers, some equipped with water tanks, are scattered in a semicircle. A mixture of gas and diesel fuel lingers in the air as a red-tailed hawk rides the thermals overhead. Most firefighters are either inhaling a quick lunch or enjoying some playful small talk. But their body language quickly turns serious when the "burn boss" begins the daily "burn briefing." It's time to work.

"OK, listen up," says Ryan Petersen, a range technician with the U.S. Fish and Wildlife Service, as he scribbles (in erasable black marker) the day's assignments on the so-called white board, which is actually one of the truck's white-colored passenger doors. "Act decisively, keep your wits and pay attention to what's going on out there."

In minutes, the fire crew, many of whom are friends, races off in their trucks and four-wheelers to conduct a prescribed (or controlled) burn on 250 acres of the scenic 2,600-acre unit, an outdoor oasis in one of the state's fastest-growing regions.

They're not alone. Each spring, federal and state wildlife officials intentionally set fires on public lands to improve grassland and forest habitat for numerous wildlife species — an old-as-dirt land management technique that has its roots in Native American culture. These prescribed fires are meticulously planned for months and conducted by seasoned professionals.

"Fire is often misunderstood by the public, because what they see on television — like a wildfire in California — isn't what we're doing here," says Lee Nelson, a retired fire management officer with the USFWS who occasionally assists his former co-workers on prescribed burns. "This is a controlled burn, and it's conducted only under predetermined weather conditions — when it's not too dry and not too windy, etc. We do have wildlife habitat management objectives, but safety is always our first and last consideration."

LONG RECORD OF BURNS

Native Americans intentionally set fires to stimulate plant growth on grasslands and to keep forest areas open to encourage blueberry production. Early European settlers used fires to keep pastures open and healthy.

"Truth is, fire is a big part of our natural history as a nation," says Nelson, who began "working with fire and learning its behavior" with the U.S. Forest Service after he graduated from college in 1978.

FIRE AS FERTILIZER

On this day, the controlled burn is being conducted on Louisville Swamp's "showcase" upland section, which sits just beyond the main parking lot in Shakopee. It's a rare ecosystem called oak savanna that features scattered oaks above a lush layer of prairie grasses and wildflowers. More than 200 species of birds depend on this habitat throughout the year.

"Minnesota has about 1 percent of its tall-grass prairie remaining, and intact oak savanna is even rarer," says Nelson, as he follows the burn crew on foot on one of the unit's fire breaks, which doubles as a public hiking trail. "Historically, this ecosystem evolved under fire; it needs it every few years to beat back undesirable woody vegetation that could turn into a forest of red cedar, buckthorn and box elder. Fire also helps remove thatch that accumulates over time. Fire is the most cost effective and ecologically effective land management tool we have for this type of habitat. That's why periodic prescribed burns are so important."

After a burn, Nelson says, nature works its magic. The blackened soil quickly absorbs sunlight. The warmed earth accelerates seed germination and the charred plant remains transform into a rich, natural fertilizer, setting the stage for new plant growth. "Once this prairie grows back, it will grow back thicker and healthier. Typically in the fall after a burn, we see a spike in seed production and insect populations, and both are beneficial to a host of critters out here."

The practice of prescribed burns does have its critics — even among hunters. The most common complaint, Nelson says, is that regulated grassland burns sometimes coincide with the spring-nesting season. While spring burns can displace ground-nesting birds, Nelson says most species (game and nongame) will re-nest. "You have to remember that most of these critters, in this ecosystem, evolved under a fire regime too," says Nelson. "They know how to escape. We may in fact lose a couple of nests, but the long-term benefits of improved habitat far outweigh the short-term costs."

ASSESSING THE AFTERMATH

The following day around lunch time, the smell of burned prairie grass still lingers in the air. Three red-tailed hawks survey the scene overhead, undoubtedly looking for an easy meal in the burn area. A few old tree stumps smolder and smoke, though they're quickly doused by a firefighter who is surveying the tract in a four-wheeler, which is outfitted with a water tank and hose. In the fire business, it's called mop-up duty.

A handful of cars sit in the parking lot. The Swamp has reopened for business. One hiker, a salesman from Forest Lake, is all smiles. "I love when they burn," he says, pointing to the charred earth. "In my experience, I've had good luck finding morel mushrooms after a burn. I'll be back to see if any pop."