Global assessment of the non‐equilibrium concept in rangelands

Abstract

Abstract. The non-equilibrium concept of rangeland dynamics predicts that the potential for grazing-induced degradation is low in rangelands with relatively variable precipitation. To date, evidence in support of the non-equilibrium concept has been inconsistent. Using a standardized protocol, including a newly developed global map of rainfall variability, we reviewed the incidence of degradation in relation to rainfall variability across 58 published studies. We distinguished between (1) zonal degradation (i.e., degradation independent of water and key resources), (2) degradation in the presence of key resources, and (3) degradation in the presence of water. For studies not affected by proximity to permanent water or key resources, we found strong support for the non-equilibrium concept for rangelands. Zonal degradation was absent at CV (coefficient of variation) values above 33%, which has been proposed as a critical threshold. Grazing degradation was almost entirely restricted to areas with relatively stable annual precipitation as expressed by a low CV, or to rangelands with key resources or water points nearby. To better understand rangeland dynamics, we recommend that future studies use globally comparable measures of degradation and rainfall variability. Our work underlines that rangelands with relatively stable rainfall patterns, and those with access to water or key resources, are potentially vulnerable to degradation. Grazing management in such areas should incorporate strategic rest periods. Such rest periods effectively mimic natural fluctuations in herbivore populations, which are a defining characteristic of non-degraded rangelands occurring under highly variable precipitation regimes.

What value for pastoral livelihoods? An economic valuation of development alternatives for ephemeral wetlands in eastern Mauritania

“…Pastoralism actively exploits asymmetric distribution of resources -it does not seek uniformity (Behnke et al 1993;von Wehrden et al 2012;Krätli and Schareika 2010). Mobile herders maximise feeding quality and as a result their herd health and productivity, through mobility, targeting different types of forage at different times of year.…”

“…One reason stems from a mind-set of experts who only know about equilibrium environments, in which climatic conditions are predictable and factors other than rainfall have measurable effects on production. Conversely, capital investment and agricultural impacts have no impact on production in non-equilibrium systems if there is inadequate rainfall (Ellis and Swift 1988;Behnke et al 1993;von Wehrden et al 2012). The failure to understand pastoralism as an intelligent system that maximises production in uncertain environments means that investment is not made to strengthen and support this system of natural resource management (Behnke et al 1993;Niamir-Fuller 1999;von Wehrden et al 2012;Krätli and Schareika 2010).…”

“…Conversely, capital investment and agricultural impacts have no impact on production in non-equilibrium systems if there is inadequate rainfall (Ellis and Swift 1988;Behnke et al 1993;von Wehrden et al 2012). The failure to understand pastoralism as an intelligent system that maximises production in uncertain environments means that investment is not made to strengthen and support this system of natural resource management (Behnke et al 1993;Niamir-Fuller 1999;von Wehrden et al 2012;Krätli and Schareika 2010). Likewise, the 'command and control' approach to policymaking that seeks to regulate all areas of a system can actually undermine the system's capacity to work (Krätli and Schareika 2010) -as is the case when ephemeral wetlands are managed under an equilibrium model.…”

Sustainability and Land tenure: Who owns the floodplain in the Pantanal, Brazil?

“…Ecological systems may shift between multiple alternative temporarily stable states, without ever progressing to a climax (Ellis and Swift, 2006;Wehrden et al, 2012) but also without undergoing irreversible degradation or collapse (Derry and Boone, 2010). This thinking has tremendous implications for human use of biodiversity (Berkes, 2006).…”

Rangelands: Where Anthromes Meet Their Limits

“…Different rangeland ecosystems respond differently to livestock grazing, for various reasons, and grazing itself is a complex, highly variable disturbance. In many rangelands, the effects of domestic livestock may be ecologically similar to those of wild animals, other organisms, or abiotic drivers such as fire or drought (Vavra et al 1994 [21] [39]). For all of these reasons, we conclude that the extent of anthropogenic transformation of Earth's ice-free surface, as reported by Ellis and Ramankutty (2008 [2]), is substantially overstated.…”