U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

April 2001


Published in Wildlife-Habitat Relationships in Oregon and Washington. David H. Johnson and Thomas A. O’Neil, Managing Directors. Corvallis, Oregon State University Press, 2001. Pages 423-443. Permission to use.


Each species of wildlife occurs as part of an ecosystem, interacting in many ways with other plant and animal species in that system as well as with the abiotic components such as soil, air, water, and other substrates. The array of wildlife species around the globe has been shaped by geological and climatological events as well as by eons of evolution and natural selection. Species have come and gone and those remaining have, in most cases, co-evolved or co-adapted with many other species so that relatively stable, and often complex, relationships exist. Usually, a great many niches have been carved out and occupied, creating a distinct flora and fauna in each region of the globe that is maintained under conditions of relative stability over time. Natural disturbances (wind, fire) and large-scale events (volcanic eruptions, drought) may occasionally alter that stability and the relationships between species, but an overall homeostatis "a return to the climatic community steady state" usually prevails. These and other concepts of biogeography have been discussed in detail.