Strategies for global rangeland stewardship: assessment through the lens of the equilibrium-non-equilibrium debate.
Abstract
This Review assesses the adequacy of current stewardship strategies to address the accelerating challenges confronting global rangeland systems. The assessment was conducted through the lens of the rangeland ecology debate that was initiated in the late 1980s to determine whether equilibrial or non-equilibrial models more accurately represented the ecological dynamics of rangeland systems. The following lessons have emerged from this prolonged debate: (a) equilibrial and non-equilibrial dynamics among plants and herbivores always coexist in individual systems; (b) herbivore persistence is strongly influenced by functional resource heterogeneity; (c) biotic feedbacks are highly dependent upon spatial and temporal scale; (d) multiple stable states separated by nonlinear trajectories may coexist on individual ecological sites and (e) management and policy decisions can have important consequences for rangeland systems despite high environmental stochasticity. These lessons demonstrate that scale and functional heterogeneity were critical 'blind spots' within the traditional rangeland profession. In contrast, pastoral strategies recognized these system variables as essential for exploitation of heterogeneous resource distribution, rather than assuming stable, uniform resource distribution. These divergent perceptions of scale and heterogeneity in grazed ecosystems largely explain the disparate interpretations of ecological carrying capacity that was central to the debate. Programmes supporting supplemental feeding and infrastructure development have created an anthropogenic category of non-equilibrial dynamics by sustaining large numbers of livestock during droughts. These programmes decouple livestock and rangeland resources to create an additional stewardship dilemma regarding complex trade-offs between livestock production and the capacity of systems to provision a broad array of global ecosystem services. Synthesis and applications. The fundamental challenge facing the global rangeland community may not be identification of a unified model of rangeland ecology-as assumed during the rangeland debate. Rather, the challenge may be how to best transform rangeland social-ecological systems to provide optimal combinations of ecosystem services to meet the needs of global citizens, while improving the well-being of millions of rangeland residents who are highly dependent upon provisioning services. A comprehensive accounting of rangeland ecosystem services, supported by institutional governance and delivered as state-community partnerships, may provide the foundation for an alternative stewardship strategy to pursue this critical goal.