Sahelian Rangeland Development; A Catastrophe?

Rietkerk, Max; Ketner, P.; Stroosnijder, L.; Prins, Herbert H. T.

doi:10.2307/4002292

Cited by 64 publications

(54 citation statements)

References 30 publications

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“…Lockwood and Lockwood, 1993; Rietkerk et al, 1996) (Figure 1). Grass-shrub 16 transitions exhibit (1) bimodality, which is when an ecosystem has two distinct 17 vegetation states (represented by the two surfaces of the cusp), i.e.…”

Section: Non-linear Dynamics 11mentioning

confidence: 99%

“…Catastrophe theory, originally outlined by Thom (1975) has been drawn upon 27 to provide a qualitative description of the nature of system change, in both ecology 28 (Loehle, 1985;Ouimet and Legendre, 1988;Rietkerk et al, 1996) and 29 geomorphology (Graf, 1983;Thornes, 1980) in systems that possess a tendency 30 to exhibit catastrophic behaviour (i.e semi-arid environments). 31…”

Section: Non-linear Dynamics 11mentioning

confidence: 99%

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A conceptual framework for understanding semi‐arid land degradation: ecohydrological interactions across multiple‐space and time scales

2008

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15Land degradation is a problem prolific across semi-arid areas world-wide. Despite 16 being a complex process including both biotic and abiotic elements, previous attempts 17 to understand ecosystem dynamics have largely been carried out within the disparate 18 disciplines of ecology and hydrology which has led to significant limitations. Here, an 19 ecohydrological framework is outlined, to provide a new direction for the study of 20 land degradation in semi-arid ecosystems. Unlike other frameworks that draw upon 21 hierarchy theory to provide a broad, non-explicit conceptual framework, this new 22 framework is based upon the explicit linkage of processes operating over the 23 continuum of temporal and spatial scales by perceiving the ecosystem as a series of 24 structural and functional connections, within which interactions between biotic and 25 abiotic components of the landscape occur. It is hypothesised that semi-arid land 26 degradation conforms to a cusp-catastrophe model, in which the two controlling 27 variables are abiotic structural connectivity and abiotic functional connectivity, which 28 implicitly account for ecosystem resilience, and biotic structural and function 29 connectivity. It is suggested therefore that future research must (1) evaluate how 30 abiotic and biotic function (i.e. water, sediment and nutrient loss/redistribution) vary 31 over grass-shrub transitions and (2) quantify the biotic/abiotic structure over grass-32 2 shrub transitions, to (3) determine the interactions between ecosystem structure and 1 function, and interactions/feedbacks between biotic and abiotic components of the 2 ecosystem. 3 KEY WORDS 5Ecohydrology, vegetation transition, structure, function, biotic, abiotic, connectivity, 6 cusp catastrophe 7 8 Introduction 9

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Section: Non-linear Dynamics 11mentioning

confidence: 99%

Section: Non-linear Dynamics 11mentioning

confidence: 99%

A conceptual framework for understanding semi‐arid land degradation: ecohydrological interactions across multiple‐space and time scales

2008

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“…The bare soil fixed point is stable, since the desert is robust against small perturbation (a small amount of vegetation) for which the positive feedback is too weak while the active state is selfsustained. Accordingly, the system may cross over from vegetation to bare soil in two routes: First, a disturbance that pushes the system to the basin of attraction of the bare soil fixed point, and second, when the vegetation fixed point losses stability, i.e., when a change of an external parameter takes the system over its tipping point [16].However, the bare soil is an absorbing state: it corresponds to a complete destruction of the vegetation (or at least of a given species), hence it is not affected by noise. In a finite system the process must reach eventually the absorbing state.…”

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confidence: 99%

Stochastic desertification

Weissmann¹,

Shnerb²

2014

EPL

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The process of desertification is usually modeled as a first order transition, where a change of an external parameter (e.g. precipitation) leads to a catastrophic bifurcation followed by an ecological regime shift. However, vegetation elements like shrubs and trees undergo a stochastic birth-death process with an absorbing state; such a process supports a second order continuous transition with no hysteresis. We present a numerical study of a minimal model that supports bistability and catastrophic shift on spatial domain with demographic noise and an absorbing state. When the external parameter varies adiabatically the transition is continuous and the front velocity renormalizes to zero at the extinction transition. Below the transition one may identify three modes of desertification: accumulation of local catastrophes, desert invasion and global collapse. A catastrophic regime shift occurs as a dynamical hysteresis, when the pace of environmental variations is too fast. We present some empirical evidence, suggesting that the mid-holocene desertification of the Sahara was, indeed, continuous.PACS numbers: 87.10. Mn,87.23.Cc,64.60.Ht,05.40.Ca The catastrophic bifurcation and its statistical mechanics analog, the first order transition, play a central role in the physical sciences. In these processes a tiny change in the value of an external parameter leads to a sudden jump of the system from one phase to another. This change is irreversible and is accompanied by hysteresis: once the system relaxed to its new phase, it will not recover even when the external parameters are restored.The relevance of these processes to the ecology of population and communities has been established while ago [1]. Recently, there is a growing concern about the possible occurrence of regime shifts in ecological systems [2][3][4][5]. The anthropogenic changes of local and global environmental parameters from habitat fragmentation to the increasing levels of CO2 in the atmosphere -raise anxiety about the possibility of an abrupt and irreversible catastrophe that may be destructive to the functions and the stability of an ecosystem [6]. This concern triggered an intensive search for empirical evidence that may allow one to identify an impending tipping point, where the most popular suggestion is to use the phenomenon of critical slowing down [5,[7][8][9][10][11]. Other suggested early warning indicators, especially for sessile species, deal with spatial patterns and the level of aggregation [4,12,13] Of particular importance is the process of desertification, which is considered as an irreversible shift from the "active" vegetation state to the "inactive" bare soil state, resulting from an increased pressure (e.g., overgrazing, declines in precipitation). As drylands cover about 41% of Earth land surface, desertification affects about 250 million people around the world [14]. Various models show that, when the vegetation state has a positive feedback, like an increased runoff interception or reduced evaporation close to vegetation pa...

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“…Case study D involves a semiarid rangeland ( Figure 2D), an ecosystem well studied for its potential threshold behavior (Rietkerk et al 1996, Scheffer et al 2001, Bestelmeyer 2006. The provisioning service in this case is forage consumed by livestock, which is proportional to stocking density.…”

Section: Challenging Situation 3: Dynamic Systems With Uncertainty Tmentioning

confidence: 99%

Trade-offs in ecosystem services and varying stakeholder preferences: evaluating conflicts, obstacles, and opportunities

King¹,

Cavender‐Bares²,

Balvanera³

et al. 2015

E&S

142

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ABSTRACT. In efforts to increase human well-being while maintaining the natural systems and processes upon which we depend, navigating the trade-offs that can arise between different ecosystem services is a profound challenge. We evaluated a recently developed simple analytic framework for assessing ecosystem service trade-offs, which characterizes such trade-offs in terms of their underlying biophysical constraints as well as divergences in stakeholders' values for the services in question. Through a workshop and subsequent discussions, we identified four different types of challenging situations under which the framework allows important insights to clarify the nature of stakeholder conflicts, obstacles to promoting more sustainable outcomes, and potential enabling factors to promote efficiency and sustainability of ecosystem service yields. We illustrated the framework's analytical steps by applying them to case studies representing three of the challenging situations. We explored the fourth challenging situation conceptually, using published literature for examples. We examined the potential utility and feasibility of using the framework as a participatory tool in resource management and conflict resolution. We concluded that the framework can be instrumental for promoting pluralism and insightful analysis of tradeoffs. The insights offered here may be viewed as hypotheses to be tested and refined as additional unforeseen challenges and benefits are revealed as the framework is put into practice.

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Sahelian Rangeland Development; A Catastrophe?

Cited by 64 publications

References 30 publications

A conceptual framework for understanding semi‐arid land degradation: ecohydrological interactions across multiple‐space and time scales

A conceptual framework for understanding semi‐arid land degradation: ecohydrological interactions across multiple‐space and time scales

Stochastic desertification

Trade-offs in ecosystem services and varying stakeholder preferences: evaluating conflicts, obstacles, and opportunities

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