College of Forestry

Global Trophic Cascades Program

The Range Contraction Project

Image removed.Range Contractions of North American Carnivores and Ungulates

Many North American carnivores and ungulates have experienced dramatic changes in their geographic distribution since Euro-American settlement. The purpose of this study is to compare historic and current species ranges, identify large-scale patterns in species ranges and determine the degree of human influence on species range changes. Our results indicate that 17 of the 43 species analyzed experienced range contractions over more than 20% of their historic range. In areas of higher human influence, species were more likely to contract and less likely to persist. Species richness had declined considerably since historic times. The temperate grasslands and temperate broadleaf-mixed forest biomes lost the highest average number of species, while the boreal forest and tundra showed fewer numbers of species lost. These effects have been widespread and indicate a rapid collapse of species distributions over the course of only 1 to 2 centuries.

Scientific Articles
Laliberte, Andrea S. and Ripple, William J. Range Contractions of North American Carnivores and Ungulates. BioScience 54(2), 2004: 123-138.

For a related study of human influences along the Lewis & Clark trail, please visit the Lewis & Clark project page.

Range contraction maps
Please click on the images below to enlarge. All maps were created and intended for use at the continental scale.

Image removed.The maps for grizzly bear and gray wolf show areas of expansion, contraction and persistence, derived from comparing the species' historic and current geographic range. Similar maps were created for 43 North American carnivores and ungulates.






Image removed.The species richness map shows historic and current species richness for 17 species that experienced range contractions over more than 20% of their historic range. The change map was created by subtracting the current from the historic species richness map. The legend shows the number of species present and the number of species lost in the change map.



Image removed.The species lost by biome figure shows mean and number of species lost in each biome. Bars indicate means, and numbers following bars indicate maxima. The proportion of North American land that each biome constitutes is shown as a percentage after the biome's name.