Achieving sustainable irrigation water withdrawals: global impacts on food security and land use

Unsustainable water use challenges the capacity of water resources to ensure food security and continued growth of the economy. Adaptation policies targeting future water security can easily overlook its interaction with other sustainability metrics and unanticipated local responses to the larger-scale policy interventions. Using a global partial equilibrium grid-resolving model SIMPLE-G, and coupling it with the global Water Balance Model, we simulate the consequences of reducing unsustainable irrigation for food security, land use change, and terrestrial carbon. A variety of future (2050) scenarios are considered that interact irrigation productivity with two policy interventions— inter-basin water transfers and international commodity market integration. We find that pursuing sustainable irrigation may erode other development and environmental goals due to higher food prices and cropland expansion. This results in over 800 000 more undernourished people and 0.87 GtC additional emissions. Faster total factor productivity growth in irrigated sectors will encourage more aggressive irrigation water use in the basins where irrigation vulnerability is expected to be reduced by inter-basin water transfer. By allowing for a systematic comparison of these alternative adaptations to future irrigation vulnerability, the global gridded modeling approach offers unique insights into the multiscale nature of the water scarcity challenge

Heat stress on agricultural workers exacerbates crop impacts of climate change

The direct impacts of climate change on crop yields and human health are individually well-studied, but the interaction between the two have received little attention. Here we analyze the consequences of global warming for agricultural workers and the crops they cultivate using a global economic model (GTAP) with explicit treatment of the physiological impacts of heat stress on humans' ability to work. Based on two metrics of heat stress and two labor functions, combined with a meta-analysis of crop yields, we provide an analysis of climate, impacts both on agricultural labor force, as well as on staple crop yields, thereby accounting for the interacting effect of climate change on both land and labor. Here we analyze the two sets of impacts on staple crops, while also expanding the labor impacts to highlight the potential importance on non-staple crops. We find, worldwide, labor and yield impacts within staple grains are equally important at +3 ∘C warming, relative to the 1986–2005 baseline. Furthermore, the widely overlooked labor impacts are dominant in two of the most vulnerable regions: sub-Saharan Africa and Southeast Asia. In those regions, heat stress with 3 ∘C global warming could reduce labor capacity in agriculture by 30%–50%, increasing food prices and requiring much higher levels of employment in the farm sector. The global welfare loss at this level of warming could reach $136 billion, with crop prices rising by 5%, relative to baseline

SIMPLE: a Simplified International Model of agricultural Prices, Land use and the Environment

In this paper, we document the Simplified International Model of agricultural Prices, Land use and the Environment (SIMPLE). SIMPLE is a partial equilibrium model which is designed to better understand the competing forces that influence the global farm and food system and how these drivers influence long run agricultural land use, production, prices, GHG emissions and food consumption. SIMPLE has been developed under the principle that a model should be no more complex than is absolutely necessary to understand the basic forces at work. Therefore, unlike other global models which are generally more complex and disaggregated, SIMPLE is parsimonious and tractable. Indeed, our historical validation over the period 1961-2006 confirms that SIMPLE can be used to simulate the long run changes in the global farm and food system given exogenous shocks in a few key drivers of world agriculture. Equally important is that we demonstrated how SIMPLE can be used to assess the relative contribution of each of the individual drivers to the endogenous changes in world agriculture via the numerical and the analytical decomposition tools. With these tools at hand, SIMPLE offers a more robust analysis of both historical and future long run changes in the global farm and food system

Global food security in 2050: the role of agricultural productivity and climate change

In this paper, we examine how the complexities introduced by trends in agricultural productivity and climate change affect the future of global food security. We use a partial equilibrium model of global agriculture incorporating a food security module that links changes in the average dietary energy intake to shifts in the full caloric distribution, allowing us to compute changes in the incidence, headcount and average depth of malnutrition. After validating the model against an historical period, we implement a series of future scenarios to understand the impacts of key exogenous drivers on selected food security outcomes. Our results show improvements in global food security for the period 2006–2050. Despite growing population and increased biofuel demand, baseline income growth, coupled with projected increases in agricultural productivity lead to a 24 per cent rise in global average dietary energy intake. Consequently, the incidence of malnutrition falls by 84 per cent, lifting more than half a billion people out of extreme hunger. However, these results hinge heavily on agricultural productivity growth. Without such growth, there could be a substantial setback on food security improvements. Climate change adds uncertainty to these projections, depending critically on the crop yield impacts of increasing CO2 concentrations in the atmosphere

Global food security in 2050: the role of agricultural productivity and climate change

In this paper, we examine how the complexities introduced by trends in agricultural productivity and climate change affect the future of global food security. We use a partial equilibrium model of global agriculture incorporating a food security module that links changes in the average dietary energy intake to shifts in the full caloric distribution, allowing us to compute changes in the incidence, headcount and average depth of malnutrition. After validating the model against an historical period, we implement a series of future scenarios to understand the impacts of key exogenous drivers on selected food security outcomes. Our results show improvements in global food security for the period 2006–2050. Despite growing population and increased biofuel demand, baseline income growth, coupled with projected increases in agricultural productivity lead to a 24 per cent rise in global average dietary energy intake. Consequently, the incidence of malnutrition falls by 84 per cent, lifting more than half a billion people out of extreme hunger. However, these results hinge heavily on agricultural productivity growth. Without such growth, there could be a substantial setback on food security improvements. Climate change adds uncertainty to these projections, depending critically on the crop yield impacts of increasing CO2 concentrations in the atmosphere

The role of international trade in managing food security risks from climate change

Abstract International trade plays an important role in facilitating global food security in the face of a changing climate. In considering this issue, it is useful to distinguish between two different time scales: inter-annual and inter-decadal. Interannual adjustments in international trade can play an important role in shifting supplies from food surplus regions to regions facing food deficits which emerge as a consequence of extreme weather events, civil strife, and/or other disruptions The first section of the paper explores the evidence on increased inter-annual supply side volatility, as well as historical and prospective analyses of adaptation to such volatility and the role international trade can play in mitigating the adverse impacts on food security. In the long run, we expect that the fundamental patterns of comparative advantage will be altered by the changing climate as well as availability of technology and endowments (water for irrigation, labor force, capital stock). In a freely functioning global economy, long run trade patterns will respond to this evolving comparative advantage. However, historical food trade has not been free of obstacles, with both tariff and non-tariff barriers often limiting the adjustment of trade to the changing economic landscape. This section of the paper capitalizes on a newly available library of climate impact results in order to characterize the tails (both optimistic and pessimistic) of this distribution. We then explore the potential for a more freely functioning global trading system to deliver improved long run food security in 2050

Bursting the Bubble: A Long Run Perspective on Crop Commodity Prices

Contrary to the opinions expressed by many commentators, the recent price spike in agricultural commodities is a transitory phenomenon. Using projections from SIMPLE “ a global model of the farm and food system “ we argue that, in the long run, food prices will most likely resume their historical downward trend. We begin with an evaluation of the historical period 1961 to 2006 wherein the growth in agricultural productivity outpaced that of global crop demand, the latter being fueled by rising population and incomes. As a consequence, we observed a historical decline in global crop prices, which the SIMPLE model faithfully reproduces. Moving forward to 2051, we establish a set of projections in global crop prices given expected developments in population, incomes, agricultural productivity and biofuel use. We project that global crop prices will continue their long run decline in the coming decades, albeit at a slower pace. However, we recognize that, under some circumstances, global crop prices could still increase by mid-century. To formally assess the likelihood of future price changes, we conduct Monte Carlo simulations given distributions in the growth rates of both drivers and economic responses. Results show that 72% of the realizations produce price declines from 2006 to 2051

Looking back to move forward on model validation: insights from a global model of agricultural land use

Global agricultural models are becoming indispensable in the debate over climate change impacts and mitigation policies. Therefore, it is becoming increasingly important to validate these models and identify critical areas for improvement. In this letter, we illustrate both the opportunities and the challenges in undertaking such model validation, using the SIMPLE model of global agriculture. We look back at the long run historical period 1961–2006 and, using a few key historical drivers—population, incomes and total factor productivity—we find that SIMPLE is able to accurately reproduce historical changes in cropland use, crop price, crop production and average crop yields at the global scale. Equally important is our investigation into how the specific assumptions embedded in many agricultural models will likely influence these results. We find that those global models which are largely biophysical—thereby ignoring the price responsiveness of demand and supply—are likely to understate changes in crop production, while failing to capture the changes in cropland use and crop price. Likewise, global models which incorporate economic responses, but do so based on limited time series estimates of these responses, are likely to understate land use change and overstate price changes