Page 104 - Climate Change and Food Systems

climate change and food systems: global assessments and implications for food security and trade
hydrological modelling (GHM). The latter models are rooted in the well-established science of watershed hydrology, whose basic principles
are virtually applicable anywhere. In contrast, GWUM has to consider various water use sectors under drastically contrasting socioeconomic and political contexts. In terms of data, GHM can make use of global land cover, soil, topology and long-term climate data available at fine spatial scales, while GWUM lacks consistent global water use data with adequate sub-national disaggregation, and data coverage remains poor even for OECD countries. Thus, few groups quantitatively model global water use (Hoff et al., 2010; Elliott et al., 2013). However, their use can be helpful for global policy dialogue on water issues.
While the literature on climate and hydrological impacts is growing, relatively little work has
been done to quantify the global food supply implications. Kummu et al. (2014) apply an
LPJmL vegetation and hydrology model and a historical climate-forcing dataset over the period 1977-2007 to quantify the effects of hydroclimatic variability on global “green” and “blue” water availability and demand in global agriculture,
food deficit and trade. The authors calculate the spatial variation in food production, green-blue water availability and the water requirements
to produce a reference diet (3000 kilocalories per capita per day, with 80 percent vegetal
food and 20 percent animal products) for each FPU. An FPU was considered water-scarce if its water availability was not sufficient to produce
the diet (i.e. assuming food self-sufficiency to estimate dependency on trade from elsewhere). The authors isolate the effect of interannual hydroclimatic variability from other factors that drive food production and find that 24 percent
of the world’s population lives in chronically water-scarce FPUs (i.e. water is scarce every year), while an additional 19 percent live under occasional water scarcity (water is scarce in some years). Among these 2.6 billion people altogether, 55 percent would have to rely on international trade to reach the reference diet, while for
24 percent domestic trade would be enough. For the remaining 21 percent of population exposed to some degree of water scarcity, local food storage and/or intermittent trade would
be enough to secure the reference diet over the occasional dry years.
In a recent review of water and climate change, Olmstead (2013) concluded that
the current literature offers little guidance on
the extent to which the prospect of climate change will alter: (a) the level and structure of water prices; (b) reliance on non-price water conservation mandates, incentives and other policies; (c) legal property rights regimes for water; (d) the allowable extent of and constraints on transferring and leasing water among users, within and across basins; and (e) investment
in water supply infrastructure. The author also concludes that a key for future progress in water climate modelling requires better representation of political economic institutional features into the market-driven economic models.
Computable general equilibrium models13
Computable general equilibrium (CGE) models are economy-wide models and encompass the economic interactions of a country’s producers, consumers, investors, government and trade partners. CGE models describe an initial equilibrium state in which, at the initial set of prices and quantities, all agents are satisfied and there is no momentum for change in supply or demand. Climate shocks lead to endogenous economic responses as price changes signal producers to readjust their production toward products whose relative prices are rising and to adjust their demands for intermediate and factor inputs accordingly. Price and income changes
13 CGE-based analyses falling outside of agriculture or focusing exclusively on climate mitigation are
not covered in this review. A good example of such analysis is given by van der Mensbrugghe and Rosen (2010), who used the ENVironmental Impact and Sustainability Applied General Equilibrium (ENVISAGE) model to develop a comprehensive CGE-based assessment for climate mitigation impacts.
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