Winter 2002

Mapping with GIS

By Joe Newmann

Here’s a different way to experience a forest preserve. Instead of the wind among the trees, you hear the hum of a computer. I am in the Planning Department on the third floor of the headquarters of the Forest Preserve District of Cook County. On a computer screen is an aerial photo of Willow Springs Woods, a 320-acre site in the Palos area. I will spend the next hour or two helping GIS manager Irene Maue and intern Sandy Sussman map the natural habitat communities of this woods. Eyeing the computer screen glowing in the dark cubicle, Sandy declares: “It gives you a totally different perspective.” Yes, it does.

GIS stands for geographic information system. The GIS software allows the district to integrate aerial photo data with the on-the-ground knowledge of the district’s land management staff and volunteer stewards like me. Dozens of stewards are traveling to district headquarters to assist with the mapping of the sites they work on. The goal is to standardize and digitize habitat information for all the district’s natural areas, especially those undergoing ecological restoration. Where are the district’s prairies and how many acres do they encompass? Such information is only a keystroke away with GIS.

GIS map shows Palos Preserve area in southwest Cook County. Map produced by Futurity, Inc.

On the computer screen, the main features of Willow Springs Woods are evident. A light oval in the interior is Katydid Marsh. Using the GIS software, Sandy encircles it and labels it “Ma-01.” To the east, through a line of old oaks, lies Katydid Prairie and its dense stand of big bluestem grass. This prairie is shaped something like a staff. From its wide “handle” in the interior, a wedge of prairie runs a quarter mile to the west to 104th Avenue. I point out to Sandy a white spot at the base of the prairie’s “handle.” This is a small sedge meadow.

To the north of the prairie is an oak woodland. It has a more mottled texture reflecting its open character. In its best sections, Penn sedge – the woodland equivalent of a shaggy lawn – covers the slopes. High spring finds these slopes sprinkled with quality native wildflowers like yellow star-grass, false dandelion, and fire pinks. Red-headed woodpeckers wing their way overhead.

The area south and east of Katydid Marsh and Prairie is darker on the aerial photo. This dark zone covers a third of the site. A walk though it reveals it to be a tangled thicket. Aggressive nonnative species dominate here. In the district’s natural community classification system, this is what is termed “unassociated woody growth.” Such areas owe their existence to modern human land use practices. Sandy labels it “UW-01” on the GIS map.

In 1821 government surveyor John Walls skirted what is today “UW-01.” He set a post at a future property line. To aid in identifying the location, he and his crew measured the distance from their post to two trees. One was an oak 10 inches in diameter 77 feet away; another was an oak 15 inches in diameter and 68 feet away. Most assuredly, this was an open woodland where fire pinks and red-headed woodpeckers flourished.

An old aerial photo of this area from 1938 shows a different situation. What today we call “UW-01” was cleared from end to end. Most likely this area had been a cattle pasture in the years before the district acquired the property. Katydid Marsh was open water, having been dammed and drowned.

The question remains: what will the future of this area be? Can it be restored to a healthy native habitat? The answer is a qualified “yes,” if the resources can be found to eradicate the nonnatives and return the fires to the system that once controlled the thickets. If this work is done, future GIS maps are sure to show healthier habitat here.