Human influences on historical and current wildlife distributions from Lewis & Clark to today

Graduation date: 2004Although it is well known that humans are strong modifiers of their\ud environment, there is a need for greater understanding of human-wildlife interactions,\ud both historically as well as currently. Historical journals can help shed light on early\ud human-wildlife interactions, and the Lewis & Clark journals contain some of the\ud earliest and detailed written descriptions of a large part of the United States before\ud Euro-American settlement. I used the journal entries to assess the influence of humans\ud on wildlife distribution and abundance. Areas with denser human population, the\ud Columbia Basin and the Pacific Coast, had lower species diversity and abundance of\ud large mammals. The opposite was observed on the Plains. Overhunting before Euro-\ud American contact accentuated by the introduction of the horse may have been major\ud contributors responsible for the historic absence of some species that are present in the\ud archaeological record. The information gained from the Lewis & Clark journals shows\ud the considerable human influence on wildlife under relatively low human population\ud densities. This has major implications for conservation biology and ecological\ud restoration, since human influence is often underestimated when considering the pre-settlement\ud condition.\ud Species ranges are dynamic and change greatly over time. In order to identify\ud large-scale patterns in range contractions and/or expansions, I compared historic and\ud current geographical ranges of 43 North American carnivores and ungulates. Seventeen\ud of the species had undergone range contractions over >20% of their historic range. In\ud areas of higher human influence, species were more likely to contract and less likely to\ud persist. Species richness declined considerably since historic times, and the temperate\ud grasslands and temperate broadleaf/mixed forest biomes lost the highest average\ud number of species, while the boreal forest and tundra showed fewer numbers of species\ud lost. The study of species range changes contributed new quantitative information about\ud human influences on range contractions in North America. The results can be used to\ud improve our knowledge of historical reference conditions, for the creation of wildlife\ud reserves, and for wildlife re-introductions