Prescription burns are carefully set fires that trained Forest Preserve District employees use in late fall and early spring to remove invasive plants and improve conditions for native species.
Why use fire?
- It turns dried plants into ash, which allows nutrients locked inside the plants to quickly reenter the soil and fertilize new growth in the spring.
- It prevents dead grasses and leaves from piling up. Too much accumulated plant “litter” can lower the temperature of the soil, which makes it harder for seeds and sprouts to develop.
- It kills or stunts nonnative shrubs such as buckthorn and honeysuckle. These plants have only been in the area for a century or two and can’t bounce back after fires as easily as native species, which have developed deeper roots or thicker bark.
Why are they called “prescription” burns?
The “prescription” is a set of directives. At the Forest Preserve District, each burn site has two.
The first outlines the site’s overall management plan. Ecologists use observations and data to determine what’s growing at a site and which tools — fire, mowing, brush cutting, herbicides, etc. — can improve the density and variety of native species. Ecologists may decide to use fire in different situations.
- If they’ve cut invasive buckthorn and honeysuckle but they’re seeing new sprouts, which fire can knock back
- If they’ve applied herbicides to invasive plants and burning the dead vegetation will expose the soil and allow the dormant invasive seeds to germinate for a second more exhaustive treatment prior to putting in native seed
- If there’s a mix of native and invasive grasses and burning will clear the entire site and allow them to better target and eliminate invasives as they sprout in the spring
The second prescription is a safety plan for the morning of that dictates whether or not the burn is a go.
- What’s the humidity? Is there rain in the forecast? Moisture on the plants will make it difficult to burn.
- What’s the wind speed and direction? If there’s a busy road east of the site, the Forest Preserve District can’t burn if winds are out of the west.
- Which equipment and how many employees are available? Forest Preserve District burn managers consider at-site conditions to determine minimum requirements.
- Where’s the site on the District’s priority list?
of a grant or formal agreement |
site with a lot of accumulated dry vegetation |
treated area with a lot of nonnative resprouts |
that needs clearing for future seeding or targeted herbicide application |
area that hasn’t been burned in three or more years |
or good-quality area that hasn’t been burned in three to five years |
that can benefit from a burn but isn’t as critical as others |
What about wildlife?
Naturally occurring fires were part of the landscape long before humans arrived. For centuries after that, Native Americans used fire to control flies and mosquitoes and to remove ground cover to make hunting and traveling easier. As a result, wildlife has learned how to avoid the slow-burning fires, which leave behind soils barely warm to the touch. Still, if an area has a rare species, such a Blanding’s turtles, the Forest Preserve District will avoid using fire during the spring breeding season as an added precaution.
What happens before the prescription burn season?
After selecting sites and outlining the prescriptions, the Forest Preserve District applies for burning permits from the Illinois Environmental Protection Agency and, if needed, local fire departments. It also mails postcards to people who live within 1,000 feet of each burn unit. (Depending on the size, a forest preserve can have more than one burn unit.) Residents with health conditions that smoke can aggravate can request calls the morning of the burn.
Who helps with prescription burns?
Only District employees who meet National Wildfire Coordinating Group standards can work on a prescription burn.
What happens on the morning of a burn?
What happens during a burn?
- The Forest Preserve District reviews site prescriptions and determines which, if any, it can burn that day. If a burn is a go, the District notifies local fire and police departments and the DuPage County sheriff’s office.
- The District also calls nearby residents who received postcards and requested calls.
- Employees post signs at entrances and along trails to ensure visitors remain at safe distances.
- Employees follow strict protocols on lighting, controlling and monitoring each fire.
- The Forest Preserve District remains in touch with fire and police departments.
- Crews remain on-site after the fire burns out to look for flare ups. At prairies and wetlands they may stay for an hour; in woodlands they may need to remain for several.
Click here to watch a prescription burn video.