Conceptual Pitfalls and Rangeland Resilience

The history of rangeland ecology has been largely a struggle to overturn the early-20th-century notions of climax, balance of nature, stability, and equilibrium.1 These ideals prevailed for decades under the infl uence of Clements’ super-organismic model of vegetation,2 Dyksterhuis’ practical method for evaluating rangeland trends on the basis of similarity to climax vegetation,3 and the Stoddart, Smith, and Box textbook on range management, which relied on succession to climax for grazing management and the balance-of-nature interpretation of ecology.4 These ideas were challenged by plant ecologists such as Henry Gleason, whose mapping of vegetation convinced him as early as 1917 that plant species assorted individualistically,5 and by Robert Whittaker, whose work showed that plant species respond individualistically to environmental gradients.6 By 1975 it was generally agreed among ecologists that “the Gleasonian paradigm had overthrown the Clementsian one.”7 The rangeland profession somewhat belatedly questioned the climax and balance-of-nature paradigms as evidence mounted that reducing or eliminating grazing did not necessarily cause succession toward climax8 and that rangelands often did not exhibit equilibrial properties.9,10 In one of the most infl uential papers in rangeland ecology, the state-and-transition model of nonequilibrium vegetation dynamics was introduced by Westoby, Walker, and Noy-Meir in 1989.11 It seemed by the 1990s that rangeland ecology had embraced a nonequilibrium, individualistic view of the world in which vegetation dynamics and responses to management were contingent on the myriad details of local environments: the physical characteristics of ecological sites, including topography, soils, and microclimates; the traits of individual plant species, including grazing and drought tolerance; and the long history of events at particular sites, including weather, grazing, fl ood, fi re, and accidents of seed dispersal. The achievement of this historically contingent, individualistic, nonequilibrium viewpoint was a triumph for rangeland ecology. Today I see a danger to this achievement lurking in the recent developments of rangeland ecology that embrace complex adaptive systems as models of rangelands. This viewpoint takes the form of management for ecosystem health and resilience, which has effectively become the new dominant paradigm in rangeland ecology.12,13 Most of the theorists and scientists who have developed this paradigm understand that such terms as self-regulation, self-repair, integrity, and health14 are metaphors and analogies, not actual properties of rangelands. However, the formalization of rangeland health as a goal of US public land management,15 the Bureau of Land Management’s process of standards and guidelines that stress ecosystem “integrity,”16 and the National Park Service’s “vital signs”17 pose conceptual pitfalls for range practitioners and the public, whose view of rangelands may slide comfortably into the recently vacated niche of the balance-of-nature, super-organism interpretation. In this paper I urge caution about a wholesale acceptance of the complex systems approach to rangelands, and I hope to clarify the conceptual basis of the new range management paradigm by a critical evaluation of three central concepts: ecosystem, function, and resilience.