Page 96 - Climate Change and Food Systems

climate change and food systems: global assessments and implications for food security and trade
switching, then the Ricardian analysis is carried out to assess the net revenue impacts of that adaptive choice. Climate impact damage assessments are calculated by applying the estimated land-value relationships to country- level changes in climate derived from outputs
of GCM scenarios that vary among the studies. Synthesizing the findings of the African project, Dinar et al. (2008) observe that farmers’ perception of a changing climate is already high, and that there are many country-specific differences in the ways that they adapt. General recommendations are the promotion of irrigation and mixed-crop/livestock operations, increased farmer education, and investments in extension and transportation infrastructure.
Building on the full set of South American surveys, Seo and Mendelsohn (2008a) carry out a cross-country analysis that examines how South American farmers adapt to climate by changing crops. They find substantial adaptive activity, with farmers choosing to grow fruits and vegetables in warmer locations; wheat and potatoes in cooler locations; rice, fruits, potatoes, and squash in wetter locations; and maize and wheat and in dryer locations. They project the effects of climate change on crop choice by applying output from the SRES A1 scenario of three GCMS to their estimated parameters, finding that the scenario that projects a relatively dry and hot future will lead farmers to grow more squash, fruits and vegetables and less maize, potatoes, soybeans and wheat in 2020, with little effect on rice. The scenario that predicts a milder and wetter future will lead farmers to grow more potatoes, fruit and vegetables. These crop choices become magnified over time.
Building on this study, Seo and Mendelsohn (2008b) develop a continental-scale analysis
of the impacts of climate change on South American farmers, taking into account both the yield effects of climate change and adaptive crop-switching. Explanatory variables include seasonal and country fixed effects, soil types and electricity use. Equations are estimated
for small and large farms, irrigated and non- irrigated farms, and all farms. For all farms, they
estimate elasticities of farm value of -1.55 with respect to a 1C increase in temperature and -1.60 with respect to a 1 mm/month increase in precipitation. Climate sensitivities are significantly higher for commercial farms with respect to rainfall (-3.31) and irrigated farms with respect to temperature (-2.36). To project climate change, the elasticities are applied to climate change scenarios from three GCMs, chosen because they provide the broadest range of climate outcomes for the South American countries in the study. Across the entire sample, they find that South American farmers will lose on average 14 percent of their land value by the year 2020, 20 percent by 2060 and 53 percent by 2100. Losses to small farms will be slightly less than losses to large farms and irrigated farms.
In a summary of the findings from the African and South American analyses, Mendelsohn (2009) drew these general conclusions: Farmers in tropical and subtropical regions are found to suffer damage from even marginal changes in climate, and these damages are greater than those experienced by famers in temperate climates. Rainfall will benefit farmers in semi-arid places, but increased rainfall in very wet places can be harmful. Farmers using irrigation are less vulnerable than are dryland farmers, although
this relationship could change in the future if
fresh water supplies diminish. Perhaps the most important finding is that small farmers may be less vulnerable to the effects of climate change than are large and specialized commercial farmers because they are able to exercise considerable flexibility in adapting their crop and livestock production as climate conditions change.
4.2 Water-climate pathway models
The IPCC and Stern Review conclude that the impacts of climate change on humanity will be
felt ‘mainly through water’, via shifts in rainfall and extreme events (droughts, flooding), and their effects on hydrological systems (Bates et al., 2008; Stern, 2006). Consequently, the vast majority of
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