Land-use change in the United States represents an enormous uncontrolled experiment in the ways habitat changes influence plants and animals. When cities were built, land was plowed, or forests were cut, the effects on our native biota were not considered. Of course, humans have influenced the flora and fauna of North America over the ages. Native Americans established settlements, practiced agriculture, hunted, and used fire to induce vegetation changes (Denevan 1992). Land-use changes, however, have been particularly profound since Europeans settled North America three centuries ago. Landscapes have become mosaics of natural and human-influenced patches, and once-continuous natural habitats are becoming increasingly fragmented (for example, Burgess and Sharpe 1981; Harris 1984). Our nation’s lands experienced tremendous changes in response to human activities, but our understanding of how land-use history affected the plants and animals in our modern landscapes is incomplete.