A light dusting of snow is falling as I leave the house at 8 a.m. Traffic is light, but the skies thicken as I head southwest from Chicago. Within a mile of Midewin, the light dusting turns into a near squall, with big, fat flakes coming down fast and furious in a swirling wind.
But that doesn’t keep 14 volunteers from heading out to cut brush. We caravan to a sight immediately west of where I did my grassland bird monitoring last year – part of a 350-acre parcel that includes a former bunker field. Throughout Midewin, there are several bunker fields. Built of reinforced concrete and covered with mounded earth, the Quonset hut-like structures – also know as “igloos” – were used to cure TNT or store munitions during the Joliet arsenal years. Today, the constant temperatures within the bunkers make them ideal for overwintering native prairie plant seedlings. But in the swirling snow, it would take little imagination to see them as Hobbit hollows if only a little wood smoke escaped from their vent stacks.
Until such time as the bunker field can be returned to prairie, it has been regularly mowed to keep invasive plant species at bay. Soon, the entire site will be herbicided to kill off all of the non-native weeds and grasses, providing a clean slate for prairie plugs and seeds. However, here and there are a few pockets where rare native prairie species have hung on in spite of all the changes to the landscape over the years. To protect these rare species, such pockets will not be blanket herbicided. Rather, it’s our job today to cut invasive brush by hand and then dab each cut stump with herbicide that kills only the intended target.
And so we get to work on multiflora rose, autumn olive and some kind of willow. Left untended, these non-native invasives will form thickets that crowd out native species. Fortunately, other work crews have done the heavy lifting before us. What’s left for us to do is nip sprouts that have sprung from seed or resprouts from insufficiently treated stumps. Pencil-thin, the sprouts and resprouts are easily snipped using hand pruning shears. For the occasional thicker stems, a pair of loppers makes short work. We snip and lop in teams, with one or two cutters trailed by a state-certified herbicide applicator, who “paints” each six-inch stem with garlon dyed a deep blue so it’s easy to see what’s been treated.
Without an application of herbicide, invasives will only resprout, often more vigorously than before, crowding out such rare prairie gems as Sullivant’s coneflower (Rudbeckiafulgida var. sullivantii.) Found in just a few counties in Illinois, this native forb – a flowering plant that dies down to the ground over winter – is one of several varieties of coneflower. In the dead of winter, it’s merely a branched stem of spent seed heads. But come next August, it will burst forth with deep yellow flowers to rival those of black-eyes Susans; a species with which it is often confused. In a conservation assessment for Sullivant’s coneflower published in 2004, Midewin’s horticulturist, Eric Ulaszek, identified several remnant populations on site, including its occasional colonization of bunker fields such as the one we’re working in this morning.
In brief, our goal in cutting brush is to help native prairie species such as Sullivant’s coneflower successfully compete. Prior to human settlement, naturally-occurring fires largely kept competition from woody species – trees and shrubs – from overrunning the prairie landscape. Once humans suppressed fire, trees and shrubs crept across the landscape almost as aggressively as the farmer’s plow. And if that one-two combination wasn’t enough, the introduction of fast-growing non-native species all but killed off the prairie. A survey conducted in the late 1970s revealed that seven-hundredths of one percent of quality native prairie remained anywhere in Illinois.
As I pointed out in The State of our Chicago Wilderness: a Report Card on the Health of the Region’s Ecosystems (http://www.chicagowilderness.org/pdf/cw_report_card_summary.pdf), to get a sense of how little that is imagine a 2,500 square-foot home. Seven-hundredths of one percent equals 1.75 square feet – about the footprint of a small bedside table. Now imagine that table broken up into hundreds of smaller pieces and scattered throughout the house. That’s about the state of our prairie in the Prairie State.
Once Midewin’s 20,000 acres are restored – and it’s going to take many years to undo the changes wrought over the past century and a half – they will constitute nearly enough prairie to equal that bedside table – all in one place – in a 2,500 square-foot home.