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Climate volatility and poverty vulnerability in Tanzania
2010
Syud Amer Ahmed, Noah S Diffenbaugh, Thomas W Hertel, David B Lobell, Navin Ramankutty, Ana R Rios, Pedram Rowhani

Acknowledgements: FANRPAN acknowledges The World Bank: Development Research Group as the source of this document


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Climate models generally indicate that climate volatility may rise in the future, severely affecting agricultural productivity through greater frequency of yielddiminishing climate extremes, such as droughts. For Tanzania, where agricultural production is sensitive to climate, changes in climate volatility could have significant implications for poverty. This study assesses the vulnerability of Tanzania’s population to poverty to changes in climate variability between the late 20th century and early this century. Future climate scenarios with the largest increases in climate volatility are projected to make Tanzanians increasingly vulnerable to poverty through its impacts on the production of staple grains, with as many as 90,000 additional people, representing 0.26 percent of the population, entering poverty in the median case. Extreme poverty-increasing outcomes are also found to be greater in the future under certain climate scenarios. In the 20th century, the greatest predicted increase in poverty was equal to 880,000 people, while in the 21st century, the highest possible poverty increase was equal to 1.17 million people (approximately 3.4 percent of the population). The results suggest that the potential impacts of changes in climate volatility and climate extremes can be significant for poverty in Sub-Saharan African countries like Tanzania.

Introduction

There is substantial evidence that the mean and extremes of climate variables have been changing in recent decades, and that rising atmospheric greenhouse gas concentrations could cause those trends to intensify in the coming decades (Diffenbaugh et al, 2005; Easterling et al, 2000; IPCC, 2007). These changes are particularly important for agriculture (Lobell et al, 2008; White et al, 2006; Mendelsohn et al, 2007) and therefore also have critical implications for developing countries, both because the majority of the poor reside in rural areas where farming is the dominant economic activity and also because the poor may spend as much as two-thirds of their income on food (Cranfield et al, 2003).

The importance of agriculture to the poor is particularly true for Tanzania, where agriculture accounts for about half of gross production, and employs about 80 percent of the labor force (Thurlow and Wobst, 2003). Agriculture in Tanzania is also primarily rain-fed, with only 2 percent of arable land having irrigation facilities – far below the potentially irrigable share (FAO, 2009). Tanzanian yields, especially of staple foods like maize, are particularly susceptible to adverse weather events. This threat has been recognized by policy makers, with Tanzania’s National Strategy for Growth and Reduction of Poverty identifying droughts and floods as among the primary threats to agricultural productivity and poverty vulnerability.

There is a substantial literature examining the effects of climate change on food security in developing countries (see review by Dinar et al, 2008). For example, Lobell et al (2008) used statistical models to assess the potential impacts of future changes in the mean climate state on crop production. In addition, Battisti and Naylor (2009) used historical examples to highlight the significant impact that changes in the frequency of heat stress may have on agricultural output. In both cases, analyses of food insecurity are driven by inferred declines in food supply. However, food insecurity and famines are influenced by forces that constrain people’s access to food, and not just its availability (Sen, 1981; Schmidhuber and Tubiello, 2007).

One such force is food prices, which have seen considerable volatility in recent years, and which is estimated to have increased poverty by 105 million people during the recent food price crisis of 2005-2008 (Ivanic and Martin, 2008). Recently, Ahmed et al (2009) provide evidence through a cross-country analysis that extreme climate events which reduce agricultural productivity can severely increase poverty in Sub-Saharan African countries. Climate induced changes in agricultural productivity thus may have severe implications for poverty through price and income effects. However, the link between climate variables and agricultural yields in this earlier work was based on simple extrapolation and lacked a tight connection between the two sets of variables.

Understanding the effects of climate volatility on crop production and food prices is thus critical to understanding the potential impacts of future climate change on poverty. However, few studies have focused on the economic effects of changes in the volatility of climate variables and the impacts on the poor. Thus, despite its expected significance for developing countries like Tanzania, the effects of changes in climate volatility on agriculture and development are not well-understood.

This paper thus fills an important gap in the literature by developing a quantitative framework that permits us to examine the vulnerability of Tanzania’s population to impoverishment due to interannual climate variability that affects agricultural productivity, both in recent history as well as in the near future1. The next section describes the poverty profile of Tanzania, while section 3 provides details of climate volatility and agricultural variability between 1971 and 2031. Section 4 subsequently analyzes Tanzania’s poverty vulnerability, while section 5 concludes.

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