Prescribed Burning of Prairies

The Nature Conservancy to Carry Out Prescribed Burns this Spring

MINNEAPOLIS, April 1 /PRNewswire/ -- The Nature Conservancy of Minnesota plans to conduct prescribed burns on native prairie across Minnesota this spring beginning April 13. Only about 150,000 acres (less than one percent) of the state's original native prairie remains. Of that total, the Conservancy owns and manages approximately 10 percent, or 15,043 acres*. Chapter burn crews are among the best trained, professional fire managers in the Midwest.

Why are prescribed burns conducted?

Fire prevents brush and trees from overtaking the prairie, prevents build-up of dead vegetation that encourages weeds and retards new growth, and improves habitat for prairie birds, mammals and butterflies, many of them endangered. Many "exotic" grasses (introduced from Europe or Asia) such as Kentucky bluegrass and smooth brome, threaten to overwhelm the native prairie community. These cool-season grasses which grow quickly and flower in spring can be set back by burns in May, allowing the summer-flowering native prairie grasses to flourish.

How are burns controlled?

Each individual on a six-person crew is responsible for the success of the burn. Burns will be undertaken only within "prescription" conditions--weather that permits safe burning. Mowed fire breaks or burned strips (black lines) outline the prairie unit to be burned. The "ring firing technique" is used: Using drip torches, crew members start by setting a back fire into the wind along a specified line. Generally several hours later a head fire is set. This eventually meets the back fire, extinguishing them both. Using water tanks and "flappers," crew members extinguish flames as necessary. The last step is "mop up". The crew makes certain that old fence posts, cow chips or tree limbs near the burn perimeter are completely free of smoke or flame before leaving the site. Permits are obtained from local offices of the Department of Natural Resources. Local fire departments, county sheriff's offices and preserve neighbors are notified the day of the burn.


Less than two hundred years ago, one-third of Minnesota was covered by vast expanses of treeless plains. The prairie was a rich world of abundant grasses and flowers that teemed with wildlife, from huge herds of bison, elk and antelope to an immense number of waterfowl. Since 1840, more than 99 per cent of Minnesota's natural prairies have been built upon or plowed under.

Scientists have been studying prairie since the 1930's. They have found that prairie grasses and flowers are well suited to fire--in fact, they thrive with it. These perennial plants grow back quickly from protected root systems which often extend 15 feet underground. Fires prevent brush and trees from invading the prairie; shade kills prairie plants. After a fire passes, the prairie grasses and other plants respond with a profusion of bloom. Fires also remove the build-up of dead vegetation, encourage new grass growth and control non-prairie plants like Kentucky bluegrass and smooth brome.

Studies show that wild mammals and birds recognize fire and nearly all escape the flames. Small mammals go underground while larger ones move away temporarily or jump unharmed across the fire line.

Occasionally slow-moving snakes and frogs may die and some bird nests may be lost if the fire occurs during nesting season. Birds are excellent re- nesters, however. No more than one-half of a preserve is burned at any one time and many sites are a matrix of burned and unburned patches. Thus, habitat remains for prairie animals immediately following the fire. While total numbers of some insect species are lower immediately after a fire, they regain their former abundance in nearly all cases. In the long run, fire is essential to the survival of all animals that must live in the open, tallgrass prairie.


The Conservancy believes that periodic controlled burns are an important tool in managing prairies. But these controlled burns take place according to carefully prepared plans and during safe weather conditions; if the correct conditions do not exist, the burn will be postponed.

With balanced use, determined by scientific data, controlled burning helps preserve the wild prairie in Minnesota. Area residents are invited to visit any of these burned areas to observe the renewal of life. Compare recently burned units with unburned areas and you will notice a clear difference. At any time or season, a native prairie has something of interest and beauty to be discovered by those who approach it with curiosity and a keen eye.

Last Updated on September 4, 1998 by Rolf Koford