Elsevier

Earth-Science Reviews

Volume 126, November 2013, Pages 48-57
Earth-Science Reviews

Climate hazards in drylands: A review

https://doi.org/10.1016/j.earscirev.2013.07.008Get rights and content

Abstract

Virtually all types of natural hazard occur in drylands, but climate hazards assume a greater relative importance in these highly dynamic environments. Here, we present a review of climate hazards research with a specifically drylands focus, distinguishing between hazards that are a direct manifestation of atmospheric processes and those that are indirectly driven by atmospheric conditions. About a billion poor rural inhabitants of drylands whose livelihoods are directly dependent on the physical environment face particularly high levels of risk from climate hazards, some of which are widely predicted to become more frequent, more widespread and/or more intense with climate change in many parts of the world during the twenty-first century. Recognising the particular characteristics of these hazards is an essential precursor to the development of dryland-centred policy options that can help mitigation and preparedness strategies and hence improve the well-being of dryland populations.

Introduction

Deserts and semi-deserts, commonly referred to as drylands, are critical global environments for a number of reasons, not least because they cover about 40% of the world's land surface and are home to more than 2 billion people (Safriel et al., 2005). These areas encompass a wide variety of physical terrains including sandy deserts, temperate grasslands and savanna woodland but all have their aridity in common: they are characterised by limited water resources because precipitation is characteristically scarce and unreliable and evaporation is typically high. Most of the natural hazards that occur in drylands take place in a wide range of environments and are not therefore unique to drylands. However, some hazards assume a greater relative importance in drylands, notably those driven by the climate which determines the nature of dryland environments. The dryland system is shown in Table 1, categorised by degrees of aridity as defined by the aridity index, which is the ratio of precipitation to potential evapotranspiration (Middleton and Thomas, 1997). This scheme excludes high-latitude (polar) and mountainous drylands, although in this paper we follow Middleton et al. (2011) by including the dryland high-altitude plateaus of Tibet and the Altiplano-Puna.

Research on natural hazards and resulting disasters has focused on a number of physical environments, including coasts (e.g. Kron, 2012), mountains (e.g. Hewitt and Mehta, 2012) and small islands (e.g. Pelling and Uitto, 2001) but, as far as we are aware, synthesis of hazards research with a specifically drylands focus is not common (see Bryant, 2005, Smith, 2013), except for studies of particular types of hazard (e.g. Wiggs, 2011 on geomorphological hazards in drylands), particular dryland areas (e.g. Huho et al., 2011 on northern Kenya) or particular combinations of dryland hazards (e.g. Sternberg et al., 2009 on drought and extreme winter in Mongolia). The justification for this paper lies in the association between drylands and rural poverty and the particularly high levels of risk faced by the poor. Drylands are found on every continent but most drylands are located in developing countries and the majority of dryland inhabitants – some 90% – live in these countries (Safriel et al., 2005). Globally, about half of all dryland inhabitants are poor, about a billion people in total, dubbed the ‘forgotten billion’ because they have habitually been neglected in development processes (Middleton et al., 2011). Poverty is multi-dimensional, and reflects overlapping deprivations that members of a household experience. These can be assessed in measures of income, standard of living, health and education, indicators that are closely linked to human well-being (Alkire and Santos, 2010). Poverty is important when it comes to vulnerability or strength to cope with a disaster. This can be illustrated at the national scale by the conclusions of Gaiha and Thapa (2006) who found that people in low-income countries are four times more likely to die due to natural disasters and that the cost per disaster as a share of GDP is considerably higher in developing than in OECD countries.

Many people living in drylands depend directly upon a highly variable natural resource base for their livelihoods and this variability is driven primarily by climatic factors (Stringer et al., 2009). Principal among these is the variability of precipitation. Rainfall totals often vary greatly from year to year and over short geographical distances. Indeed, there is a well established relationship between declining rainfall levels and increasing variability in rainfall totals (Nicholls and Wong, 1990) and this relationship is particularly evident across the four dryland subtypes defined by the aridity index (Table 1). The livelihoods of most dryland inhabitants are based on herding in the drier areas and rain-fed cultivation in those less arid dryland regions, with many people also engaged in wild harvesting from common resources. Long experience of coping with the vagaries of their environment has engendered numerous strategies for managing risk and variability, but many dryland inhabitants remain vulnerable to natural perturbations, particularly those driven by the highly variable climate regimes that characterise drylands.

The importance of climate hazards for poor dryland inhabitants seems set to increase because several types of extreme climate event are likely to become more frequent, more widespread and/or more intense in most parts of the world during the twenty-first century (IPCC, 2012). Mitigation of the effects of climate hazards is therefore an essential component of any attempt to reduce poverty and improve environmental sustainability in the world's drylands.

Section snippets

Natural hazards in drylands

A wide range of natural hazards cause death, damage, and/or other types of losses (in combination referred to here as natural disasters) and these natural hazards can be classified in many different ways. A distinction can be made depending on the spatial scale of impact between small-scale hazard events (e.g. tornado, landslide, lightning strike) that may cause localised damage, injuring or killing a few individuals, and large-scale events (e.g. tropical cyclone, major drought, large volcanic

Drought

Globally, droughts are frequently described as the most damaging natural hazards in economic terms, collectively affecting more people than any other form of natural disaster (Keyantash and Dracup, 2002), and drought is the principal natural hazard faced by communities living in most drylands. Although droughts occur in virtually all climatic zones, it is probably fair to say that their effects are proportionally greater in drylands because of the naturally scarce availability of water in

Climate change and climate hazards in drylands

People have always been at risk from natural hazards, but the perception that the world is becoming a more hazardous place is widespread. Documenting the frequency of hazard events over time is not straightforward because of the paucity of reliable comprehensive, long-term worldwide databases of hazards or disasters. Nonetheless, an increase in disaster frequencies has been reported, with the time trends for climate-related disasters showing the greatest increase, well above all geological

The disaster risk-poverty nexus in drylands

Drylands and poverty are linked at various geographical scales, from the global and regional to the national and subnational (Middleton et al., 2011). The Millennium Ecosystem Assessment (MA) shows that people living in drylands lag behind the rest of the world in terms of human well-being and other indicators of development. For instance, the average infant mortality rate for all dryland developing countries is at least 23% greater than non-dryland countries (Safriel et al., 2005). The MA

Conclusions

Drylands are characterised by large numbers of people whose livelihoods are directly dependent on the physical environment. This environment is primarily driven by its variable climate and notable for numerous climate-related natural hazards that together result in a highly variable and generally low natural rate of provision of ecosystem services. Drylands also lag behind the rest of the world in terms of human well-being and other indicators of development. These traits are related via the

Acknowledgements

The authors thank the Leverhulme Trust, the British Academy and the Royal Geographical Society (with IBG) for research support and five anonymous referees for their comments. The idea for this paper originated at the 2010 Oxford Deserts Conference.

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