<ir="ltr">Each spring, it happens like clockwork: the geese return, the rabbits procreate, the trees blossom and the arb burns. Although the signs of the controlled burn are familiar to many students on campus, the purposes of this practice often remain unclear.
“Most of the native habitats in this part of Minnesota evolved with fire,” said Nancy Braker, Director of the Cowling Arboretum. “Historically, fires got started through lightning strikes or from Native American burning.” Indigenous peoples of the region would burn grasses to facilitate travel, as well as to draw grazers—their food supply—to the area. With time, a freshly burned landscape every few years became the norm.
Braker noted that reducing invasion of woody plants—keeping grasses growing—was one of the main ecological purposes of fire. Burned landscapes were also preferred by many animal species. “Certain birds,” she offered, “prefer prairie that has almost no leaf litter built up.” Controlled burns of a portion of the arboretum are carried out in both the fall and the spring. “It’s usually about every four years for a given patch,” said Braker. “Sometimes it’s a little more frequently if we have a management problem we have to get under control.” Such management problems—such as invasive species—can necessitate additional burns in the summer.
“We try and burn as seldom as possible.” This approach to burning is largely motivated by management goals. “Any burn will have a particular timing depending on what our goal is for that area,” Braker said. Routine burns are timed to avoid damaging nesting birds; when it comes to control of invasive species, burning plants in flower is most effective.
Many of the arboretum staff’s management practices are based on convenience to the college and nearby residents. “We try to avoid putting a lot of smoke in sensitive times or sensitive places,” explained Braker, citing decreased visibility on Highway 19 as a possible concern. “I’d also not be very popular with the baseball coach if I dumped a bunch of smoke during a game over the baseball field,” she added. This year, hazy skies and the smell of smoke were noticeable both on Carleton’s campus and in downtown Northfield. However, Braker pointed to the recent wildfires across northern Minnesota and Alberta, Canada, as being the most likely sources of this smoke.
“When we burn in the arb we are careful to burn on days when smoke dispersal is good,” Braker observed. “Our burns are so small that the smoke is cleared out quickly.” Paying close attention to weather and wind speed help arboretum staff manage smoke and avoid issues like these, though variation from predicted weather can wreak havoc on management plans.
“A lot of times we’ll have everybody ready to go, and then we cancel the fire because the weather is … more extreme than predicted.”
The need for safety can also be limiting at times. “There’s always an issue with having enough people to burn safely, and having enough people who are trained,” explained Braker.”We typically need eight to ten people for any particular thing we’re burning.” Since the arboretum staff relies on volunteers—who must go through mandatory training—procuring enough volunteers can be difficult. “Once in a while we’ll have to cancel a burn because we don’t have quite enough people.”
Despite the inconveniences that come with caution, Braker is committed to prioritizing safety above all else. “Our biggest concern is that we want to be safe, but still implement our management strategies,” she summarized. “We’re not out there just to have a good time—even though it’s exciting and interesting, it’s really an important part of our management that we’re implementing.”