Abstract

Abstract. The High Plains of North America extends ffom Canada to northern Mexico. This grassland region is subject to prolonged drought, herbivory, and wildfire. Organisms that are indigenous to the High Plains are adapted to these environmental factors. Periodic droughts occur at inexact, but few year, intervals. The grazing by free ranging bison, the indigenous large herbivore, has been replaced by grazing of fenced domestic stock. Fire regimes throughout human occupation of the region have been greatly influenced by human activities. Cultivation of wheat and corn also is carried out in the region. Predicted climate changes in this region are increased temperature and reduced effective precipitation. Paleontological records document past climate changes from which certain predictions may be made about the effects of current models of Global Change. Ecological snrdies at the ecosystem, community, species, and population levels are defensible. Land use modifica-