Many studies have emphasized agriculture”s negative impact on wildlife as farming became more intensive after World War II. But some changes in upland wildlife habitat on Illinois farms were greater before World War II than after it, according to a recent study that evaluated wildlife habitat from 1920 to 1987.
“This is the first time researchers have looked at changes in wildlife habitat at the county level over such a broad area and long time period,” says Christine Ribic, a wildlife ecologist with the University of Wisconsin-Madison College of Agricultural and Life Sciences. Ecologists Richard E. Warner and Philip Mankin of the University of Illinois were co-authors of the study.
“We found that the quantity and quality of upland wildlife habitat in Illinois has worsened from the pre-Depression period through the late- 1980s,” Ribic says. “Our results indicate that the most important changes in the amount of upland wildlife habitat occurred between 1920 and 1940. The most likely explanation is the use of the tractor, or in other words mechanization, which allowed farmers to become more efficient and able to cultivate more land. This left less habitat for wildlife.”
She says the quality of the wildlife habitat on farmland decreased most rapidly between 1940 and 1964 because of the increased use of manufactured chemicals.
Ribic believes the findings from Illinois are applicable to other parts of the Midwest that experienced similar historical changes.
“To the extent that changes in farming methods in Wisconsin and other states were similar to those of Illinois, I”d expect that the same patterns would be seen over the same time periods,” Ribic says.
To evaluate habitat changes, the researchers developed an index with separate components for the amount of wildlife habitat on farmland and for its quality. The index was based on agricultural census data such as the percentage of farmland in woods, pasture, and non-row crops, the percentage not prone to erosion, and the percentage where fertilizer and pesticides were not applied. The ecologists found that the habitat index correlated with rabbit and bobwhite populations in Illinois as reflected in hunting records.
The researchers used the index to evaluate wildlife habitat in all Illinois counties in 1920, 1940, 1964 and 1987. They selected those years as being representative of conditions before widespread mechanization, after mechanization was widely adopted, during intensive farming, and during the recent past.
The study shows that an index can be used to characterize wildlife habitat at the county level, according to Ribic. “This means that we have a technique policy makers may want to use in evaluating alternative programs,” she says. “Resource managers may also want to use an index like this to monitor agriculture”s large-scale impact on wildlife.”
Managers could use the method to monitor policy changes – for example, changes in the Conservation Reserve Program, which many think to be a major benefit for wildlife.
This study was one of a series sponsored by the U.S. Environmental Protection Agency to investigate the effect of agriculture on wildlife and wildlife habitat at different geographical scales in the Midwest.