Tropical Drylands Research Articles

Insistent Dryland Narratives: Portraits of Knowledge about Human-Environmental Interactions in Sahelian Environment Policy Documents

The drylands in the West African Sahel region have, since the catastrophic drought event in the 1970s, been a focal point of interest in the cross field between environmental research, knowledge systems and policy intervention strategies. Major international institutions, agencies and conventions have played an important role in shaping national planning efforts aimed at reducing environmental degradation in tropical drylands and at limiting their vulnerability to external stressors such as economic globalization, climate variation, and demographic pressure. The paper summarizes how significant, internationally initiated policy documents, such as National Environmental Action Plans (from the 1980s), National Adaptation Plan of Action (from the 2000s), or the Great Green Wall Initiative (signed in 2010), refer to and explain the state, complexity, and change processes in the human-environmental systems that they aim at guiding towards sustainability. It specifically looks at characterizations of land use changes and their relation to multiple driving forces. The paper asks if apparent discrepancies between contemporary scientific advancements and dominant narratives in policy documents can, in part, be interpreted as persistence of environmental myths caused by the repetition of the keywords, which turns theories into blueprints for action.

Building resilience to drought in desertification‐prone savannas in Sub‐Saharan Africa: The water perspective

Abstract Securing sustainable livelihood conditions and reducing the risk of outmigration in savanna ecosystems hosted in the tropical semiarid regions is of fundamental importance for the future of humanity in general. Although precipitation in tropical drylands, or savannas, is generally more significant than one might expect, these regions are subject to considerable rainfall variability which causes frequent periods of water deficiency. This paper addresses the twin problems of “drought and desertification” from a water perspective, focusing on the soil moisture (green water) and plant water uptake deficiencies. It makes a clear distinction between long‐term climate change, meteorological drought, and agricultural droughts and dry spells caused by rainfall variability and land degradation. It then formulates recommendations to better cope with and to build resilience to droughts and dry spells. Coping with desertification requires a new conceptual framework based on green‐blue water resources to identify hydrological opportunities in a sea of constraints. This paper proposes an integrated land/water approach to desertification where ecosystem management supports agricultural development to build social‐ecological resilience to droughts and dry spells. This approach is based on the premise that to combat desertification, focus should shift from reducing trends of land degradation in agricultural systems to water resource management in savannas and to landscape‐wide ecosystem management.

Assessment of dryland condition using spatial anomalies of vegetation index values

A landscape's long‐term capacity to retain, utilize and recycle local resources is an objective basis for assessing its ecological functionality or condition. In subtropical and tropical drylands, where plant growth is moisture‐limited for much of the time, land condition is reflected in the local water balance. The ratio of long‐term actual evapotranspiration and precipitation (E a/P) is proposed as an objective indicator of dryland condition. A spatial modelling framework is developed for the quantification of E a/P over large areas using remotely sensed vegetation density patterns. Model parameters are defined by two particular situations: (i) non‐vegetated sites, where E a/P depends on the long‐term runoff coefficient of bare soil surfaces (RCbs), and (ii) non‐degraded sites with a vegetation density close to the potential value for which E a/P≅1.0. Specht's evaporative coefficient is used as an independent variable for the prediction of the potential vegetation density, whereas RCbs is estimated with the curve number method. The performance of the method was evaluated in a 900 km2 area in south‐east Spain, where predicted land condition was found to be in good agreement with qualitative field observations on the nature and intensity of land degradation processes.

Pastoral Mobility: A Review

Introduction Mobility is often regarded as an important characteristic of pastoral societies and their ways of production in Africa. However, the interpretation of the rationale and importance of pastoral mobility changes along with the various discourses and depending on the professional background of the researcher. While the positive perception of mobility is relatively new among researchers of drylands, this is not a new line of thought among social scientists studying pastoralists (e.g. Dyson-Hudson and Dyson-Hudson 1980, Stenning 1957). Both anthropologists (e.g. Dyson-Hudson 1966, Evans-Pritchard 1940, Nicolaisen 1963, Stenning 1959) and others studying pastoral societies (e.g. Gallais 1967, Johnson 1969) have pointed to the flexible strategies employed by pastoralists. In the late 1980s, a new understanding of drylands dynamic gained importance and led to the so-called 'new rangeland paradigm' which has been called the 'state-and-transition' paradigm (Westoby et al. 1989) or 'instability-but-persistence' paradigm (Warren 1995). The first papers concerned dryland functioning, but soon implications for pastoral management, and hence pastoral mobility, were included (e.g. Ellis and Swift 1988). This meant that concepts such as degradation and desertification were reinterpreted and it has now been demonstrated that 'sustainable resource management' is far from equivocal. This review will show how pastoral mobility is understood in the context of range ecology, the focus being on how pastoralists' perceptions can add to this understanding. Pastoral Mobility Within the New Rangeland Paradigm The 'new rangeland paradigm' has been thoroughly analysed in three seminal books: Range Ecology at Disequilibrium (Behnke, Scoones and Kerven 1993), Living with Uncertainty (Scoones 1995a), and Managing Mobility in African Rangelands (Niamir-Fuller 1999a). While the first book is concerned mainly with the ecological aspects of dryland ecosystems, the second elaborates on management implications for pastoral production systems, and the third emphasises a particular aspect of pastoral systems, namely mobility. According to the new rangeland paradigm, drylands are considered disequilibrial (changing from one state to another) due to strong external controls, e.g. droughts, fires, or insect attacks. These external controls strongly affect primary production and thus livestock density. As a result, dryland productivity is controlled mainly by the highly variable precipitation; because livestock seldom reaches densities high enough to influence vegetation productivity, precipitation is the principal factor controlling inter-annual vegetation dynamics (Coppock 1993). The perception of pastoral mobility within the new rangeland paradigm can be summarised as follows: pastoral mobility is highly appropriate in variable and unpredictable environments. An important characteristic of tropical drylands is the heterogeneity of natural resources. Pastoral mobility implies that pastoralists can move to areas with pasture for their livestock. Moreover, pastoral mobility means that the effect of unforeseen events, e.g. outbreak of disease, bush fire, locust attack, can be mitigated. Finally, migration between different agro-ecological zones means that more animals can be kept than in each of the zones (Niamir-Fuller 1998, Scoones 1995b). In the book on pastoral mobility (Niamir-Fuller and Turner 1999), the so-called 'mobility paradigm' is developed. When analysed in the light of disequilibrium ecology, management practices, institutions, etc. that were once characterised as destructive, are now seen as ecologically rational. Hence, the 'mobility paradigm' provides a framework for understanding pastoral mobility based on the findings of the new rangeland paradigm and examines the various aspects of mobility. The main arguments of the 'mobility paradigm' will be discussed here. …