Drought, change and resilience in South Africa’s arid and semi-arid rangelands

Introduction Droughts are a frequent occurrence in South Africa’s arid and semi-arid rangelands and can have severe ecological and economic consequences. While these may be short-term and followed by recovery during subsequent years of higher rainfall, in some cases droughts can trigger substantial and irreversible ecological and socio-economic changes. Desertification, in the form of reduced perennial vegetation cover, increased bare ground, soil erosion and reduced rain use efficiency, is thought to occur in steps which can be triggered by extreme climatic events such as drought. Each step to a more transformed state comes with a higher cost to land users in the form of lost production, higher input costs and escalating costs of restoring lost function. Some droughts have had catastrophic effects on whole societies, leading to economic collapse and mass migration. Prolonged severe droughts can trigger socio-economic declines from which many people are unable to recover when normal climatic conditions return, and economic and ecological crises are often closely linked. For example, the Dust Bowl in the Great Plains of the U.S.A. during the 1930s led to the loss of several billion tons of topsoil and the displacement of some 3.5 million people, a third of the population in affected areas. Examination of past droughts shows that their ecological or economic impact is not always proportional to the severity of the climatic event, including its duration and rainfall deficit. In some cases relatively mild droughts have had surprisingly large ecological and socio-economic effects. This suggests that some social and ecological systems display greater resilience than others, and raises the question as to which attributes enable a social or ecological system to retain its essential structure and functioning through disturbances such as drought. The links between drought, land management and desertification have been highlighted in the research literature and government policies and legislation. Yet despite substantial (if sporadic) government investments in drought research, policy and action plans, our predictive understanding of the effects of drought on rangeland systems is limited and people living in these areas remain vulnerable to the ecological and economic effects of droughts. This is a cause for concern as the world is entering a period of unprecedented climate change, which is predicted to result in higher average temperatures, changes in precipitation patterns, increased risk of drought over many land areas and more frequent extreme weather events. Models predict that reductions in mean annual rainfall, increased inter-annual variation and more frequent droughts will lead to disproportionately large impacts on livestock production. Growing human populations, rising food and fuel prices, political changes and uncertainties around land reform add to the challenges of coping with droughts and climate change in South Africa’s arid and semi-arid rangelands. Resilience has become a prominent research topic in the context of achieving sustainability. Since the idea of alternative stable ecosystem states, thresholds and resilience emerged in the early 1970s, there has been an exponential growth in the number and diversity of publications on resilience, accompanied by an increasingly broad and ambiguous use of the concept. Initially defined as the time it takes an ecosystem to recover from disturbance, resilience has become more commonly viewed as the amount of perturbation a social or ecological system can absorb before it shifts to a qualitatively different state, including its essential structure, processes and functions. Two main lines of resilience research and literature have emerged, which use the concept of resilience in different ways. The first focuses on the functioning of ecosystems and is concerned with the identification of alternative stable states, the nature of the thresholds between them, the mechanisms by which switches are triggered and the attributes that make ecosystems susceptible or resilient to such regime shifts. The second applies resilience as a conceptual framework for sustainability that links production of knowledge, social learning and adaptive management to an underlying theory of complex adaptive social-ecological systems shaped by cross-scale interactions, nonlinear feedbacks and uncertainty. While both applications of the concept are relevant to understanding the effects of drought on rangelands, conceptual clarity and practical relevance are lost if these descriptive and normative aspects of the concept of resilience are not clearly distinguished.