Planting prairies along midwestern roads is a promising way to bring back butterflies that are picky about their digs, according to a paper in the April issue of Conservation Biology. The study is the first to look at the effects of roadside restoration on native wildlife.
In central Iowa, more than 99% of the original tallgrass prairies have been converted to cornfields, paved, or put to other human use. The traditional approach for roadsides has been to use herbicides, plant nonnative grasses, and then maintain them by mowing. Recently, some Iowa counties' departments of transportation are actively returning roadsides to the classic prairie vegetation--more to reduce maintenance costs than to benefit wildlife, says Leslie Ries, a conservation biologist at Northern Arizona University in Flagstaff. An intermediate strategy, employed by other counties, is just to stop mowing and give the roadside over to naturally growing weeds. Ries wondered which is better for butterflies.
During the summer of 1998, Ries and her colleagues at Iowa State University studied butterflies at 12 prairie roadsides and at nearby weedy or grassy roadsides. All the sites bordered fields of crops. Of the 24 butterfly species researchers found at the sites, nine tolerate human disturbance and 15 are more discriminating. Prairie roadsides had twice as many of these less common, habitat-sensitive species; in addition, the numbers of these butterflies were five times higher at prairie roadsides than at grassy roadsides. In addition, butterflies at prairie roadsides were about half as likely to cross the road--a potentially perilous activity for butterflies.
Ries says roadsides are often considered marginal, even detrimental, habitats, "so the idea they may have some benefit is surprising." And adding habitat along roadsides wouldn't be expensive in many places, notes Cheryl Schultz, a conservation biologist at the University of California, Santa Barbara. "Usually these little areas get ignored because they are not big enough to make a difference to large wildlife," Schultz says. "But they could make a difference to insects."