Restoring Heterogeneity on Rangelands: Ecosystem •, Management Based on Evolutionary Grazing Patterns

Rangelands are the most common form of terrain WE PROPOSE A PARADIGM THAT in both the United States (where it accounts for 61% of all land surface) and the world (70% of all land surface). ENHANCES HETEROGENEITY Rangelands consist primarily of native plant communities managed, typically, for livestock production (Holechek et al. INSTEAD OF HOMOGENEITY TO PROMOTE 1998). Because they can embrace extensive native plant com­ munities, rangelands can serve as biodiversity repositories. BIOLOGICAL DIVERSITY AND WILDLIFE However, in the Great Plains of the United States, where de­ HABITAT ON RANGELANDS GRAZED BY cisions about land use are made largely at the discretion of the private landowner, many plant and animal species dependent LIVESTOCK on rangelands are imperiled. For example, according to data from the North American Breeding Bird Survey, 70% of the 29 bird species character­ istic of North American prairies experienced a decline in rangelands and grazing. This rangeland management ap­ population between 1966 and 1993. Indeed, these grassland proach is incapable ofproviding an ecological framework for species are declining at a faster rate than any other guild ofter­ alternative management objectives that have become more im­ restrial birds in North America (Knopf 1994). Excessive her­ portant over the past quarter-century. For example, the main­ bivory by domestic livestock may have contributed to the tenance ofbiodiversity, as well as the preservation ofhabitat decline in some of these species, but many species endemic for many individual species, depends on the interspersion of to North American prairies evolved with large grazing animals. diverse habitat types throughout a heterogeneous landscape. The Mountain Plover (Charadrius montanus), Baird's Spar­ We contend that traditional rangeland management tech­ row (Ammodramus bairdii), and Chestnut -collared Longspur niques reduce rangeland heterogeneity by favoring the most (Calcarius ornatus) are examples ofbirds that occur in high­ productive, most palatable forage species for domestic cattle. est densities in grazed landscapes (Kantrud 1981, Renken In this article, we propose a paradigm that promotes the po­ and Dinsmore 1987, Knopf 1996). tential heterogeneity of landscapes through an alternative There are many potential causes for this decline in grass­ approach to managing those rangelands with a long evolu­ land bird populations, but the fact that it occurred when the tionary history of large-ungulate grazing (Milchunas et al. condition of rangelands had improved, according to traditional 1988). Hence, for these rangelands we attempt to link the goals means of evaluation (Holechek et a1.l998), suggests that techniques currently used to manage rangelands may be in­ Samuel D. Fuhlendorf (e·mail: [email protected]) is as· sufficient to maintain biological diversity. sistant professor, and David M. Engle is professor, of rangeland ecol­ Most techniques of rangeland management were developed ogy and management in the Department of Plant and Soil Sciences, under the paradigm of increasing and sustaining livestock pro­ Oklahoma State University, Stillwater OK 74078-6028. © 2001 duction by decreasing the inherent variability associated with American Institute of Biological Sciences.