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Evolutionary and Historical Ecology

"...the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation that most justly excites our admiration."

— Charles Darwin, Origin of the Species (1859)

To understand the conditions under which the ponderosa pine forests of the American Southwest evolved, a functional, evolutionary theory of ecosystem health is essential. Without it, we are unlikely to be able to provide prescriptions for the return of our forests to health, much less prevent or control wildfires.

Ponderosa cross-section from Canon de los Frijoles, Bandolier National Monument, New Mexico. Repeated surface fires cause a sequence of overlapping wounds called fire scars. The heat-killed wood tissues extend into the annual rings, which can be dated to the calendar year. Photo courtesy Craig Allen.
Ponderosa cross-section from Canon de los Frijoles, Bandolier National Monument, New Mexico. Repeated surface fires cause a sequence of overlapping wounds called fire scars. The heat-killed wood tissues extend into the annual rings, which can be dated to the calendar year. Photo courtesy Craig Allen. Click for larger image.

Ecology is the study of the interactions between organisms and their environments. Evolution is defined as any change in the gene pool. Evolutionary ecologists study the adaptation of organisms to their environment, from molecular to ecosystemic levels.

Humans have adapted to—and have been the periodic instigators of—ecosystem change for a least a million years. While most ecologists study nonhuman relationships, historical ecologists recognize that human action modifies the habits and distributions of nonhuman species.

Ecologists pursue an integrative approach to the study of ecosystem health by working with other natural and physical scientists such as biologists, geologists, anthropologists, archeologists and environmental historians. Their combined resources are many, including Native American land-use history, Anglo and Hispanic settlement history, soil phytolith analysis, packrat middens, land surveys, repeat photography, fire scars, and dendrochronology.

In the western United States ecologists are called upon to build meaningful links between basic research and practical application. They communicate the relevance of their science to federal agencies and to other institutions that benefit from their insights. They inform the public about the nature, progress, and implications of their discoveries.



Allen, Craig D. et al. 2002. Ecological restoration of southwestern ponderosa pine ecosystems: A broad perspective. Ecological Applications. 12(5), pp. 1418-1433. An important recent paper promoting a broad and flexible perspective on ecological restoration in southwestern forests.

Cooper, C.F. 1960. Changes in vegetation, structure, and growth of southwestern pine forests since white settlement. Ecology 42:493-499. Classic study of southwestern forest ecosystem changes due to grazing, logging, and fire exclusion associated with European settlement.

Covington, W. Wallace. 2003. The evolutionary and historical context. Pages 26-47 in Friederici, Peter, ed. Ecological Restoration of Southwestern Ponderosa Pine Forests: A Sourcebook for Research and Application. Washington, D.C. Island Press. The Director of the Ecological Restoration Institute summarizes the state of knowledge of ponderosa pine reference conditions in the Southwest.

Crumley, Carole L. ed. 1993. Historical Ecology: Cultural Knowledge and Changing Landscapes. Santa Fe, NM: School of American Research Press; [Seattle]: Distributed by the University of Washington Press. A useful collection exploring the theory and application of historical ecology.

Egan, David and Evelyn A. Howell, eds. 2001. The Historical Ecology Handbook: A Restorationist's Guide to Reference Ecosystems. Boulder, CO: Island Press. Why historical ecology matters to ecosystem restorationists, and the importance of reference ecosystems.

Fulé, P.Z., M.M. Moore, and W.W. Covington. 1997. Determining reference conditions for ecosystem management in southwestern ponderosa pine forests. Ecological Applications 7(3):895-908. Reconstruction of pre-European forest structure and fire regime at Camp Navajo, AZ.

Lee, Kai N., 1995. Compass and Gyroscope: Integrating Science and Politics for the Environment. Washington D.C.: Island Press. A succinct analysis of the relations between the ecological sciences and the political process.

Leopold, A. 1924. Grass, brush, timber, and fire in southern Arizona. Journal of Forestry 22:1-10. Pioneering observations about grazing, fire, and trees by the founder of ecological restoration.

Leopold, A. 1937. Conservationist in Mexico. American Forests 37:118-120, 146. Contrast between “natural” forests in northern Mexico and degraded forests in the southwestern U.S.

Leopold, A. 1941. Wilderness as a land laboratory. Living Wilderness 6:3. The need for a point of reference or “base-datum” of natural ecosystems.

Moir, William H., B. Geils, M.A. Benoit, and D. Scurlock. 1997. Ecology of Southwestern Ponderosa Pine Forests. Pages 3-27 in Block, William M. and D.M. Finch, tech. ed. Songbird ecology in southwestern ponderosa pine forests: a literature review. Gen. Tech. Rep. RM-GTR-292. Fort Collins, CO: U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 152 p. A fine technical review of the literature. Available online at

Pianka, E. R. 1974. Evolutionary Ecology. Harper and Row, New York. 356 pp. The most accessible text on the subject.

Swetnam, T.W., C.D. Allen, and J. Betancourt. 1999. Applied historical ecology: Using the past to manage for the future. Ecological Applications 9(4):1189-1206. Examples from the Southwest to illustrate some of the values and limitations of applied historical ecology, and the need for multiple, comparative histories from many locations. Available online at

Last edited June 25, 2003

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NAU's Program in Community, Culture and Environment Northern Arizona University