Since the first contact with European man, which occurred when the Lewis and Clark expedition traversed the region in 1805 and 1806, the North American shrub-steppe has undergone substantial and irretrievable change. Unfortunately, of the few written records left by the early explorers, traders and trappers regarding the original, pristine condition, those that have survived are sparse indeed.
The text contained within the following links is taken from Chapter 1 of the book "Shrub-steppe: Balance and Change in a Semi-arid Terrestrial Ecosystem", W. H. Rickard, L. E. Rogers, B. E. Vaughan and S. F. Liebetrau (editors), Elsevier Science Publishing Company Inc., 52, Vanderbilt Avenue, New York, NR 10017. 1988. ISBN: 0-444-42990-5 (Vol.20)