“Vulnerability hotspots”: Integrating socio-economic and hydrological models to identify where cereal production may decline in the future due to climate change induced drought

Abstract

The purpose of this paper is to identify which of the world's cereal producing regions are likely to become vulnerable to climate change over the 21st century by identifying those regions that will be (1) exposed to climatic stress and (2) have a limited capacity to adapt. First, we use a global hydrological model to identify regions likely to be exposed to drought, defined here as a location where the available soil moisture is projected to decline by the 2050s and 2080s relative to the mean soil moisture observed between 1990 and 2005. Second, we use agricultural, meteorological and socio-economic data to develop models of adaptive capacity and run these models to show where adaptive capacity is likely to decline by the 2050s and 2080s relative to the baseline period of 1990–2005. Third, we contrast the hydrological and adaptive capacity model outputs to identify “vulnerability hotspots” for wheat and maize. Here, a vulnerability hotspot is defined as a region that the models project as likely to experience both a decline in adaptive capacity and in available soil moisture. Results from the hydrological model project significant drying in many parts of the world overt the 21st century. Results from the adaptive capacity models show that regions with the lowest overall adaptive capacity for wheat include much of western Russia, northern India, southeastern South America, and southeastern Africa. In terms of maize, regions with the lowest adaptive capacity include the northeastern USA, southeastern South America, southeastern Africa, and central/northern India. When taken together, this study identifies five wheat and three maize growing regions likely to be both exposed to worse droughts and a reduced capacity to adapt. For wheat, these are: southeastern USA, southeastern South America, the northeastern Mediterranean, and parts of central Asia. For maize, our analysis suggests that vulnerability hotspots are: southeastern South America, parts of southern Africa, and the northeastern Mediterranean.

Introduction

Crop models demonstrate that food production is vulnerable to climate change in many regions through a combination of temperature change, water stress and extreme weather (Challinor et al., 2009, Challinor et al., 2010, Lobell and Field, 2007). Although there is considerable uncertainty in these models, and some debate way that ozone pollution, carbon dioxide fertilization, and water shortages may interact with climate change to affect productivity, there is a general concern in the literature that these problems are likely to cause food production to fall over the next 100 years (Jaggard et al., 2010, Long et al., 2005, Royal Society, 2008, Sitch et al., 2007). These concerns sit alongside economic and demographic models that project a rising demand for food thanks to population growth (Foley et al., 2011, Lutz and KC, 2010), urbanization (Satterthwaite et al., 2010), and a shift towards more meat consumption (Kearney, 2010). This leads some to argue that global food security is threatened unless production increases by as much as 70% (Bruinsma, 2009, Godfray et al., 2010a, Godfray et al., 2010b). Therefore, new technologies (Brown and Funk, 2008), and in particular biotechnologies (Tester and Langridge, 2010), may be needed to create more productive crops and ensure food security during the 21st century.

In addition, the socio-economic, ecological, and institutional context of farming has a tremendous influence on whether a producer can adapt to environmental stressors and remain productive (Adger, 2006, Brooks et al., 2005, Patt et al., 2005, Smit and Skinner, 2002, Thomas et al., 2007, Watts and Bohle, 1993). For example, degraded soils, a lack of off-farm employment, social upheaval, and a dysfunctional government prevented the Ethiopian population from adapting to drought in the 1980s (Comenetz and Caviedes, 2002). As a result, it only took a very minor drought (measured in terms of rainfall) to trigger a famine (Fraser, 2007). By contrast, there are cases where even major climatic problems were adapted to without serious losses in agricultural productivity or human life (DeRose et al., 1998). The implication of this is that institutional reform, poverty reduction, and gender equality will help boost adaptive capacity and that this may be as important as developing new crops to meet the challenges of feeding future generations (Fraser et al., 2003, Paavola and Adger, 2006).

Overall, therefore, the vulnerability of crop production to climate change is seen by many scholars as a function of both an exposure to a climatic stress, such as a drought, as well as an ability to adapt to that stress (Fraser et al., 2011b, Intergovernmental Panel on Climate Change, 2001, Watts and Bohle, 1993). To date, however, most quantitative and global scale projections of how food crop production is vulnerable to climate change have focused on the ways in which new temperature and rainfall patterns will affect plant growth (Zhang and Cai, 2011). Those studies that do include socio-economic factors in future projections are most often based only on two socio-economic variables, GDP and population, and there is limited or no assessment as to whether, or under what context, these variables are significant (Diffenbaugh et al., 2007).

The aim of this paper is to better integrate socio-economic and meteorological data to conduct a global scale quantitative assessment that identifies which of the world's cereal producing regions may become vulnerable to climate change over the 21st century. We do this by identifying those regions that will be both exposed to climatic stresses and will not have the capacity to adapt to these problems. The climate impact we focus on is declining cereal harvests since these provide the world with approximately 90% of its calories and are likely to be affected by changing weather patterns (International Development Research Council, 1992). In terms of climate change exposure, we have chosen to focus our attention on droughts as many climate models project that droughts will be a major factor in limiting future crop growth (Intergovernmental Panel on Climate Change, 2007). To assess adaptive capacity, we use a range of socio-economic and ecological data and employ statistical methods to identify proxy indicators of adaptive capacity. We then use different socio-economic and climate projections to identify regions that, given current trends, are likely to be both exposed to worse droughts in the future as well as have a diminishing capacity to adapt. While this project does not provide conclusive results, this nonetheless represents an important step in the field of research devoted to better understanding when, where, and why food systems are likely to be vulnerable to climate change in the future.