Brief Summary of Examples for the United States

The preceding sections have discussed the advantages and disadvantages of cross-sectional as well as panel models. While a cross-sectional analysis of farmland values seems appealing as it can capture crop switching, it might also suffer from omitted variable bias, which is less of a concern in a panel data set. While some argue strongly for cross-sectional analysis to measure adaptation (Mendelsohn et al. 1994), others will argue strongly for a panel model (Desch nes and Greenstone 2007) to...

Measuring Food Security

Proper measurement of food security is of clear policy and humanitarian concern, primarily because such measures are used to both assess progress in a given region and to target assistance where needed. However, given the multiple interacting components of food security listed above, measurement of food security is both difficult and controversial. The most cited country- and global-level statistics on food security are those of FAO, who use a measure of undernourishment as a proxy for food...

Missing Pieces

Editors must inevitably choose to draw the line somewhere in order to balance the scope and focus of a book. The decisions made here reflect partly the expertise and interests of the authors involved, and partly our own biases on the most relevant and scientifically mature topics. However, we wish to point out many less mature topics that may prove important in the final analysis. For instructors who plan to use this book as a text, we encourage instructors planning to use this book as a text...

Cross Sectional Analysis

A cross-sectional analysis of a specific crop would incorporate how a farmer switches to other crop varieties of the same crop (e.g., corn varieties). The idea is to compare corn yields in Iowa with corn yields in warmer states like Arkansas. The problem is that there are other differences between Iowa and Arkansas besides differences in climate. For example, soil quality varies a great deal between states. A cross-sectional analysis would have to account for all covariates to correctly...

Genetic Variability

9.2.1.1 The Breeding Program Gene Pool The genetic constitution of wheat is both tetraploid (i.e., containing four sets of chromosomes, as in the case of Triticum turgidum or durum wheat) and hexaploid (i.e., containing six sets of chromosomes, as in the case of Triticum aestivum L. or bread wheat), and this presents both opportunities and difficulties for its improvement. Durum wheat is a fusion of two diploid species and its genetic constitution is denoted as AABB, whereas bread wheat...

Food Availability and Climate Change

The food availability dimension of food security encompasses issues of global and regional food supply, and asks the basic question can we physically produce enough food to feed our population There is a vast literature on past trends and future trajectories in the world's ability to feed itself which cannot be adequately summarized in the current chapter (Conway and Serageldin 1997 Dyson 1999), Nevertheless, any discussion of the effect of climate change on the global food supply must take...

Changes in Yield Quality at Elevated [COJ

Much of the focus on the effects of elevated CO2 on crops has been on harvestable yield quantity. However, yield quality is an important issue as well. The two most studied aspects of quality are protein and nitrogen concentration. A meta-analysis of crops grown in elevated CO2 found that protein content was reduced in grain (Taub et al. 2008). Barley, wheat, rice, potato and soybean all showed significant decreases for the non-legumes, the decrease was between 10 and 14 , whereas for soybean,...

References

Barnett T, Zwiers FW, Hegerl GC et al. (IDAG) (2005) Detecting and attributing external influences on the climate system a review of recent advances. J Clim 18 1291-1314 Bony SR, Colman VM, Kattsov RP, et al. How well do we understand and evaluate climate change feedback processes J Climate. 2006 19 3445-3482. Christensen JH, Christensen OB. A summary of the PRUDENCE model projections of changes in European climate by the end of this century. Climatic Change. 2007 81(1) 7-30. Christensen JH,...

Climate Models and Their Projections of Future Changes

Abstract This chapter describes global climate models and their output. The current approaches for analyzing their simulations, characterizing the range of likely future outcomes, and making projections relevant for impact analysis are described, specifically referring to the latest assessment report of the Intergovernmental Panel on Climate Change. We provide a summary of future projections of average temperature and precipitation changes at continental scales, together with a broad brush...

Investments in Crop Development

As climate change pushes regional climates outside of historical experience, development of crop varieties better suited to these new climates will be an important component of adaptation. Chapter 9 reviews the breeding challenges associated with developing crops for new climates. Throughout much of the world, these challenges will mostly be met by the private sector. In high-income countries, the private sector accounts for 55 of total agricultural R& D expenditures, and many companies are...

Advances In Global Change Research

Martin Beniston, University of Geneva, Switzerland B. Allen-Diaz, Department ESPM-Ecosystem Sciences, University of California, Berkeley, CA, USA. R.S. Bradley, Department of Geosciences, University of Massachusetts, Amherst, MA, USA. W. Cramer, Department of Global Change and Natural Systems, Potsdam Institute for Climate Impact Research, Potsdam, Germany. H.F. Diaz, Climate Diagnostics Center, Oceanic and Atmospheric Research, NOAA, Boulder, CO, USA. S. Erkman, Institute for communication and...

Modeling the Impact of [CO2 on Crop Production and Global Food Supply

The response of crop yields to elevated CO2 is a key parameter in projections of the effects of climate change on global crop yields, world food supply and risk of hunger in the future (e.g., Parry et al. 1999, 2004). Inclusion of the direct effects of elevated CO2 in a recent assessment substantially improved estimated world cereal prices and reduced the risk of hunger for 500 million people by 2080 (Parry et al. 2005). Process-based crop models with deterministic equations of underlying...

Why Read This Book

Springer Science + Business Media B.V. 2010 Erratum to DOI 10.1007 978-90-481-2953-9_1 2nd Indented line, 4th line should read Theory alone cannot refute either of these extreme positions, as there are no obvious reasons why the pace of climate change caused by human activity should or should not match the pace with which we are able to adapt food production systems. The online version of the original chapter can be found under DOI 10.1007 978-90-481-2953-9_1

Different Models Different Votes

From a pragmatic standpoint, in view of the increasing attention and activities in the area of adaptation, simple ensemble means and ranges have the desirable property of being easy to interpret so that non-experts handling multi-model projections can straightforwardly appreciate what they are dealt. The need remains though to alert users to some shortcomings of these multi-model ensembles. They have been called ensemble of opportunity for very important reasons they are not intended to be a...

Pending Issues in Applications of Ecophysiological Models 4331 Model Selection and Accuracy

One can imagine a well-structured process whereby a suite of potential models to be used in climate change research are tested for accuracy, considering the target crop(s) and production region. The best model or subset of models would then be used to estimate impacts. In practice, this process is seldom fully executed. The Fourth Assessment Report of the IPCC (Easterling et al. 2007) noted that previous calls by the Third Assessment Report (TAR) to enhance crop model inter-comparison studies...

Building Local Knowledge

Public-sector involvement in information provision to farmers has long been a cornerstone of agricultural development strategies, with large proven benefits to agricultural output in both rich and poor countries (Birkhaeuser et al. 1991 Alston 2000). These strategies can involve educating farmers about the availability of new technology and how to use it, providing information on improved farm management techniques such as optimal input use, or providing forecast information about likely short-...

Broader Economic Adjustments to Climate Change

Even if individual farmers do not successfully perceive and adapt to climate change, market forces will tend to favor those farmers and regions that are more successful in the new climate. These market-mediated responses can range from individual farmers taking over their neighbor's land, to entire regions shifting into and out of production of different crops. Most studies of market effects to date have focused on the latter mechanism, namely markets adjusting through international trade. All...

Making Markets Work for the Poor

Developing improved agricultural technology will almost certainly be necessary for adapting agriculture to climate change, but it is unlikely to be sufficient. Current adoption of improved cereal varieties differs widely across Africa, with estimates ranging from 0 adoption of improved millet varieties across much of the continent, to 80 adoption of improved maize varieties in parts of East and Southern Africa (Maredia et al. 2000 World Bank 2008). To adapt to climate change, farmers need...

Final Thoughts

In pursuing the above scientific questions or the many others we have undoubtedly ignored, and in presenting and communicating the results, we should never lose sight of how difficult it is to predict the future. Models will always be simplifications of reality, and predictions should always be treated with humility and caution. But as discussed in Chapter 1, models provide valuable insight by synthesizing our knowledge of the world and translating it into probabilities of outcomes we care...

Global and Regional Assessments

Abstract The main conclusions from recent global and regional assessments are reviewed, with an emphasis on China, India, Africa, and the United States. Most studies have provided primarily best-guess point estimates, often supplemented with a few sensitivity analyses, but without a comprehensive measure of uncertainties. Although some useful lessons have been learned, most existing estimates of food security risks leave much to be desired. We explore these estimates, some of their strengths...

Environment

Environmental factors such as temperature, solar radiation, and CO2 directly affect plant processes, and models can use the current value of a factor, such as from a daily weather record, with minimal modification. The effects of these factors have been discussed individually in relation to specific processes, but their roles are summarized in Table 4.2. It is constructive to compare responses across processes. The CSM-Cropsim-CERES-Wheat model specifies nine temperature responses affecting...

Panel Analysis

A panel analysis recognizes that there are fundamental differences between spatial units of the analysis (e.g., countries) and that it is a difficult task to account for all these differences explicitly in a model. If these influences impact yields in an additive fashion and if they are time invariant, one can use fixed effects to capture them. In defense of the first assumption, the large majority of regression models use a linear specification and hence all factors are assumed to have an...

Disease and Food Utilization

Food utilization also concerns the ability of individuals to make use of the nutrients available to them, and is thus closely linked to both the overall safety of the food and to the individual's health. While not all unhealthy people are necessarily food insecure, health status can be a primary contributing factor to food security. Of particular concern in poor countries are the strong feedbacks between malnutrition and disease, in which undernutrition leads to increased infection and a higher...

Basic Estimation of Climate Change Impacts

Prior to any climate change impact study, it is important that a model has been thoroughly evaluated for the crop or production system of interest. Once the evaluation is acceptable, simulating a future climate change scenario is no more difficult than simulating a crop under current or historic conditions. One needs an accurate estimate of the future weather conditions and data for the additional crop, soil and management inputs. The model is simply run with the future weather data and if...

The Importance of Time Scales

Two main types of interventions are often discussed as ways to reduce the impacts of climate change on society mitigation and adaptation. Mitigation is a reduction in greenhouse gas emissions, which leads (eventually) to a reduction in climate change. Adaptation refers to changes made to a system impacted by climate, in this case some aspect of the food economy, that improve the outcome of climate change relative to no adaptation. Adaptations can include both changes that either reduce negative...

Overview of Book

This book is organized to cover the major topics that, in our opinion, are needed to address this interdisciplinary subject. Part 1 of the book includes essential background information on food security and trends in the climate system. Chapter 2 presents an overview of food security and the potential ways that it can be influenced by climate changes. Chapter 3 presents an overview of climate models and how they are used to assess uncertainties in the future of climate. Part 2 delves into the...

Crop Responses to Climate Time Series Models

Abstract Time series of annual crop production levels, at scales ranging from experimental trials to regional production totals, are widely available and represent a useful opportunity to understand crop responses to weather variations. This chapter discusses the main techniques of building models from time series and the tradeoffs involved in the many decisions required in the process. A worked example using United States maize production is used to illustrate key concepts.

Temperature and Precipitation Projections by Region

Chapter 11 of the IPCC latest report by Working Group 1 describes in detail model projections for a set of subcontinental regions that have been traditionally used by the climate change community since they were proposed by Giorgi and Francisco (2000). The chapter also analyzes the processes relevant to each region's climate and the ability of models to capture them, thus gauging the reliability of future projections. It also considers the consistency of future projections with changes already...

Food Utilization and Climate Change

Even if climate change were to have minimal impacts on the supply of food or on the ability of households to access it, it could still affect food security through its effects on the utilization of food. The utilization component of food security is perhaps its murkiest and least well-studied aspect, but generally relates to the nutritional aspects of food consumption. Supposing availability and access issues are taken care of, achieving proper food utilization requires satisfactory answers to...

Climate Change and Food Security

Adapting Agriculture to a Warmer World Editors David Lobell Stanford University CA, USA Marshall Burke Stanford University CA, USA ISBN 978-90-481-2951-5 (HB) e-ISBN 978-90-481-2953-9 ISBN 978-90-481-2952-2 (PB) DOI 10.1007 978-90-481-2953-9 Springer Dordrecht Heidelberg London New York Library of Congress Control Number 2009928835 Springer Science+Business Media B.V. 2010 No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means,...

Breeding Strategies to Adapt Crops to a Changing Climate

Turner, and T.M. Chattha Abstract Climate change is expected to reduce global crop productivity, although the impact will vary region to region. At many locations, particularly those at lower latitudes, the environment will become drier and hotter, which will reduce crop yields and potentially change the incidence of insect pests and diseases. These climatic changes are also expected to alter the nutritional properties and processing quality of crop products. This chapter...

Utilizing GCM Projections

Given that there is no easy alternative to producing future projections based on GCMs, we now delve deeper into the way uncertainty manifests itself in GCM projections, and what the attempts are at reducing it or at least characterizing and quantifying it in robust ways. Figure 3.2 shows changes along the twentieth and twenty-first centuries in global temperature from the climate models (21 of them) used in IPCC AR4 that performed their simulations under the emissions scenario SRES A1B (the set...

Crop Responses to Climate and Weather Cross Section and Panel Models

Abstract Crop choices vary by climate, e.g., Florida specializes in citrus crops while Iowa specializes in corn and soybeans. The advantage of a cross-sectional analysis is that it incorporates how farmers adapt to existing difference in average climate conditions across space. A potential downfall is omitted variable bias. A panel analysis can overcome omitted variable bias by including fixed effects to capture all additive time-invariant influences, yet does not account for the same set of...

Data Quality and Regression Bias

The example of US maize yields represents perhaps the most accurate long (50+ years) time series available on both crop yield and climate anywhere in the world. In many countries of prime interest for food security, the quality of data can be considerably worse. The crop production database of the Food and Agriculture Organization of the United Nations (FAO), for instance, contains an enormous wealth of information but much of it is visibly suspect. Reported yields are often identical for 3 or...

Expanding Irrigated and Total Cropped Area

In addition to changing their crop mix, farmers could also change how much land they farm or the way in which they farm what they have. Introducing irrigation into currently rainfed systems is an often cited adaptation option, and will indeed likely be critical for some regions. As mentioned, irrigation not only alleviates water stress but could expand the opportunities for switching planting dates and varieties, as well as increasing returns on investments in fertilizer and other inputs. Large...

Crop Yield Responses to Elevated [CO2

The direct effects of elevated CO2 on photosynthesis and stomatal conductance lead to changes in crop growth, carbon allocation, biomass accumulation and ultimately seed yield. It is well established that stimulation of seed yield by elevated CO2 is lower in magnitude than stimulation of photosynthesis and above-ground biomass, suggesting that feedbacks constrain the potential benefits of elevated CO2 (Long et al. 2004). For example, in soybean, night-time foliar respiration is stimulated by...

Formal Statistical Approach

The Tebaldi and Lobell (2008) paper is meant to be a methodological study. As the title suggests it proposes an approach towards a formal and rigorous quantification of the uncertainties that, from multiple sources, affect the estimates of climate change impacts in the agricultural sector. A Bayesian hierarchical model is used to synthesize the joint projections of temperature and precipitation change from a multi-model ensemble, for a given SRES scenario. The output of this step of the...

Summary of Current Projections

Both temperature and precipitation output from all GCMs' twentieth century simulations have been found to be satisfactory representations of current climate in terms of mean geographical patterns, if analyzed at large scales (Raisanen 2007 Randall et al. 2007). Trend patterns are consistent with observations for those models that are forced by all known sources volcanic eruptions, solar irradiance, greenhouse gases and aerosols (Barnett et al. 2005). Projected future warming patterns are robust...

Summary

This chapter has provided a glimpse into results from global and regional assessments conducted over the past decades. The key points are summarized below Global assessments have generally concluded small changes in global prices for a doubling of CO2, with gains in developed countries balancing losses in the tropics. Yet these conclusions have been based on a relatively small number of models, and the sources and magnitudes of uncertainty have not been well quantified. Projections for CO2...

Projecting Impacts of Climate Change with Time Series Models

Once a model has been calibrated with time series data, it can be used to predict yield responses to any hypothetical amount of climate change. (Chapter 3 describes approaches for downscaling climate projections for input into crop models.) For example, temperature and precipitation changes from climate model simulations can be used to generate new values of the relevant predictor variables, which the regression model then translates to yields. There are, however, three extremely important...

Further Look at Growing Season Length

In Tebaldi et al. (2006) growing season was defined in terms of thermal characteristics. Obviously, though, moisture and precipitation changes will influence greatly the ability of cultivating crops in areas where structures for irrigation are absent, or water resources are subject to competing demands. In this section we modify the definition of growing season by including conditions that are related to the available moisture. In addition to requiring mean temperature to be above 5 C we...

Food Security and Adaptation to Climate Change What Do We Know

Abstract The potential for agricultural systems to adapt to climate change is at once both promising and poorly understood. This chapter reviews possible producer and consumer responses to a changing climate, the ability of these responses to offset otherwise negative impacts on food security, and the role of public and private institutions in investing in adaptation where individual responses are insufficient. Accumulated evidence suggests that wealthier societies and households will be better...

Measuring Uncertainties

The conclusions outlined above represent, in most cases, a relatively broad consensus among researchers. However, it is important to emphasize that all global and most regional assessments to date can best be characterized as best-guess, usually supplemented with some simple sensitivity tests such as impacts with and without CO2 fertilization or adaptation. Yet a consensus among best guesses does not imply that we fully understand the risks associated with climate change, even at global scales...

Crop Management

Besides planting per se, most crop management can be simulated by modifying the levels of certain environmental factors, especially those associated with inputs. Planting is a special case because the selection of the cultivar, planting date, and spatial arrangement (e.g., density and row spacing) set the stage for simulating the crop in the environment. Cultivar selection is especially important and is discussed separately below. The planting date provides a starting date for simulating plant...

When Adaptation in Agriculture Is Not Enough

Even if all of the above adaptation measures are taken (perhaps a big if), food systems may still not be fully shielded from the negative effects of a changing climate. As a result, a final set of planned adaptations might involve strengthening social safety nets to deal with climate-related shocks to food systems when they inevitably occur. The expansion of insurance products to farmers (explored above) would be a primary means for smoothing producer income in the face of climate induced...

Introduction

Roughly a billion people around the world live their lives in chronic hunger, and humanity's inability to offer them sustained livelihood improvements has been one of its most obdurate shortcomings. Although rapid improvements in agricultural productivity and economic growth over the second half of the twentieth century brought food security to broad swaths of the developing world, other regions did not share in that success and remain no better off today - and in some cases worse off - than...

Climate Effects on Food Security An Overview

Abstract There are roughly 1 billion food insecure people in the world today, each having this status because food is unavailable to them, because it is unaffordable, or because they are too unhealthy to make use of it - or some combination of the three. Assessing the potential effects of climate change on food security requires understanding the underlying determinants of these three aspects of food security -availability, access, and utilization - and how climate change might affect each....

Farmer Adaptations and Their Potential Gains

Supposing for now that a climate signal is detected, and that the need for a change in management is perceived, farmers must then decide how to respond. This response will depend on the choices they see themselves having and the perceived costs and benefits associated with each choice. Various potential adaptations are listed in Table 8.1, each of which we now explore in turn. Table 8.1 Potential farmer adaptations to climate, and some reasons why they might or might not help Table 8.1...

Direct Effects of Elevated [CO2 on Plant Physiology

There are two direct, instantaneous effects of elevated CO2 on C3 plants an increase in photosynthetic carbon gain and a decrease in stomatal conductance of CO2 and water vapor. Any stimulation of crop yield by elevated CO2 is principally determined by those two fundamental responses (Farquhar et al. 1978 Drake et al. 1997 Long 1999 Long et al. 2004 Ainsworth and Rogers 2007). An immediate rise in CO2 increases the net photosynthetic carbon gain in C3 plants because ribulose-1,5-bisphosphate...

Breeding Strategies to Improve Productivity and End Use Quality Under Moisture Deficit and Higher Temperature

A basic breeding scheme for a self-pollinated crop such as wheat is outlined in Fig. 9.1. This scheme represents either a modified bulk or selected bulk selection strategy. In a modified bulk strategy individual plants identified in the early generations are grown as individual plots in the following generation. These progeny are usually derived from three-way or top crosses (involving three parents) or simple crosses between two parents, and individual plants are usually selected from the...

The Strength and Limits of Models

In order to provide quantitative measures of climate change impacts, we will rely heavily on numerical models of various pieces of the puzzle, including climate, agricultural, and economic systems (Fig. 1.1). Models are needed because it is rarely possible to perform controlled experiments where one or two factors are changed while others are held constant, particularly for the time scales and spatial scales of interest. One cannot measure, for example, global crop production with climate...

Adapting to Climate Change Some Difficulties 831 Signal Detection

Adaptation at the farmer level requires three basic steps detecting a shift in one's external environment, determining that it would favor a change in behavior, and undertaking that change (Hanemann 2000 Kandlikar and Risbey 2000). Thus the first step in adapting to climate change requires detecting the signal of climate change in the noise of climate variability. Given the amplitude of climate variability in many regions, this might be no small task. Figure 8.1 illustrates this detection...

Conclusion

Ecophysiological models are widely used to simulate potential impacts of climate change on agricultural systems because they reflect the best-available information on how plants respond to environmental factors and crop management. Nonetheless, use of the models involves numerous assumptions whose net effects are difficult to quantify. Results from ecophysiological models are also sensitive to the quality of inputs for cultivar traits, soil conditions, weather, and management. Researchers...

An Illustrative Example

Graph A of Fig. 6.1 displays crop yields in Lesotho in light grey squares and South Africa in black triangles for the years 1961-2000. The x-axis displays average temperature during the growing season, while the y-axis displays log yields (note that this variable can be negative as the log of 1 is 0, so any yield less than 1 ton ha is a negative number). Lesotho is colder than South Africa as all grey squares lie to the left of the black triangles. Average yields are also lower is Lesotho than...

Where and How Numerous Are the Food Insecure

Progress in reducing the number of food insecure over the last half century is at once both promising and discomforting. As Fig. 2.2 shows, since 1970 there has been a general decline in both the number of global food insecure and their percentage of the total population, as calculated using the FAO undernourishment measure described above. These reductions were driven primarily by large gains in East and Southeast Asia, where decades of strong economic growth liberated hundreds of millions...

Where Do Climate Change Projections Come from

Humans are conducting an unprecedented, deliberate yet uncontrolled experiment using our planet as its subject. Human-induced emissions of greenhouse gases and other pollutants, together with changes in land use, like deforestation, are altering our climate system properties in ways that are already detectable (Hegerl et al. 2007). The experiment is continuing, with future emissions projected to steadily raise the greenhouse gas concentrations in the atmosphere. This is because greenhouse gases...

Change in Components of Yield at Elevated [CO2

The consistent stimulation of economic yield at elevated CO2 can involve larger seed or grain size, more seeds per pod, ear or panicle, and or more reproductive structures per plant. The yield benefit for most C3 crops resulted from increased above-ground dry matter production supporting more reproductive structures (Table 7.1). In the FACE experiments with rice, tiller, panicle and spikelet numbers per area increased significantly (Kim et al. 2003 Yang et al. 2006). Those increases in dry...

Overview of Ecophysiological Models

A simulation using a basic model might start with a set of initial conditions specifying where the crop is grown, the initial status of water and nutrients in the soils, and the parameters needed to represent the physiological characteristics of the crop. Fig. 4.1 Flow diagram for a hypothetical ecophysiological model with a daily time step Fig. 4.1 Flow diagram for a hypothetical ecophysiological model with a daily time step For an annual crop, the model loops through a series of subroutines...

Crop Responses to Elevated Ozone

Tropospheric ozone concentrations ( O3 ) have more than doubled over land in the Northern Hemisphere since pre-industrial times (Akimoto 2003 Vingarzan 2004). Ozone is a dynamic secondary pollutant formed from the photochemical oxidation of methane, carbon monoxide, and volatile organic compounds in the presence of nitrogen oxides. Hot, sunny weather favors formation of ozone in the troposphere, and high concentrations can occur across large areas, far from industrial sources (Ashmore 2005)....

Global Assessments

The first major studies of global agricultural impacts began roughly 20 years ago, as agriculture was one of the first sectors for which impacts of climate change were thought to be important (Kane et al. 1992 Rosenzweig and Iglesias 1994 Rosenzweig and Parry 1994). Then, as now, these efforts focused on linking three basic modeling pieces that had been previously developed and applied independently (1) models of climate response to higher CO2 (2) models of crop yield responses to climate...

Two Examples One Model One Vote and a Formal Bayesian Model

Here we explore two examples of analyses based on multi-model ensembles. We refer to the related papers for details on the actual results, aiming simply at juxtaposing two approaches that could be seen as spanning the methodology range of multi-model analysis. We present first the approach from Lobell et al. (2008), which sought to rank 12 food-insecure regions in the developing world according to metrics of vulnerability in order to inform the prioritization of adaptation measures. The...

Food Availability

Efforts to better quantify and reduce uncertainties related to processes already represented in crop models are perhaps the most critical need for anticipating effects on food availability. A primary means for achieving this will be more experimental studies that manipulate temperature, CO2, soil moisture, and ozone, both separately and in combination, and for a range of crops of importance to the food insecure. The experiments will be particularly useful in tropical systems where they have...

Food Access

As the bulk of poor and hungry populations are in rural areas and have close ties to food production, their incomes could be significantly impacted by both local and global scale yield impacts. Many economic assessments to date have considered GDP growth as independent of agricultural impacts, but this is clearly not the case, particularly in the poorest of countries. Future work should more explicitly consider effects on income and resulting impacts on food security. Critical questions in this...

Food Security Definition Measurement and Recent Progress

Although an earlier study counted at least 30 definitions of the term food security (Maxwell and Smith 1992), the benchmark understanding of the term is roughly that of FAO (FAO 2001) Food security is a situation that exists when all people at all times have physical, social, and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life. Under this definition, food security consists of having, on an individual...

Worked Example US Maize Yields

To help guide the discussion and illustrate the time series modeling process, we will use a dataset for US maize yields from 1950-2005. The United States Department of Agriculture (USDA) has recorded average yields for each county since early in the twentieth century, and in many cases since the late 1800s. In addition, the United States has arguably the most complete weather records of any country for the twentieth century. Here we have averaged yields over all counties east of the 100 W...

Diversify Income

On-farm adaptations are not the only possibility for bolstering food security in the face of a changing climate. Recall from Chapter 2 that while many rural poor lean heavily on agricultural activities for income generation, off-farm income can also play an important role in economic livelihoods. To the extent that non-agricultural income sources are less climate-sensitive than farm activities, further diversification of incomes out of agriculture might seem a promising adaptation strategy in...

Direct Effects of Rising Atmospheric Carbon Dioxide and Ozone on Crop Yields

McGrath Abstract Rising atmospheric carbon dioxide concentration ( CO2 ) in this century will alter crop yield quantity and quality. It is important to understand the magnitude of the expected changes and the mechanisms involved in crop responses to elevated CO2 in order to adapt our food systems to the committed change in atmospheric CO2 and to accurately model future food supply. Free-Air CO2 Enrichment (FACE) allows for crops to be grown in their...

Climate Variable Selection

The above example used average growing season temperature, which is indeed a very common measure of growing season weather. However, there are many other defensible variables to use in place of or in addition to this value. We distinguish here between two main choices variable type and temporal scale. Variable type decisions involve, for instance, whether to include a term related to temperature, one for precipitation, and or one for solar radiation or some other meteorological variable....

Food Utilization

Despite recent evidence that higher atmospheric CO2 will tend to lower protein and micronutrient concentrations (see Chapter 7), there is much we don't know about the eventual health consequences of these changes. Will they be less or more important than associated changes in calorie consumption, and how do the two interact What management options exist to minimize the reductions in protein or micronutrient levels in crops 2. Climate change will very likely influence the exposure and infection...

Measuring Progress in Adaptation

Given the importance of climate adaptation to the future of agriculture, it is imperative that we improve our understanding of how and how fast management and technologies adaptations will proceed. In particular, understanding the pace and impact of autonomous adaptation will be necessary for identifying the scope and type of needed planned adaptations. The recent and ongoing changes in climate may offer some insight into what farmers are actually doing in response. However, how will we...

Cultivar Characteristics

Cultivar characteristics usually are embodied in a set of parameters, sometimes termed genetic coefficients, that are thought characteristic of the species. These can characterize differences in phenology through parameters for phase durations, response to photoperiod, and, if appropriate, vernalization requirements. Parameters may also be defined for seed growth characteristics, seed composition, relative leaf size, or other traits. Cultivar parameters are estimated by adjusting the parameters...

United States of America

The United States dominates international trade of several agricultural commodities. It is the leading exporter of maize, soybeans, and wheat flour, and therefore production of these crops in the United States has an important influence on food prices throughout the world and thus on food security. The United States is also one of the most extensively studied regions in terms of climate change impacts. An early analysis based on crop models indicated that some Northern regions would gain from...

Cognitive Biases

Once a farmer is convinced that the climate has changed, he or she must decide whether and how to respond. Most humans exhibit a considerable bias towards maintaining old ways, even in new environments, with the thought that what worked in the past should continue to work in the future. A clear example of this from the business world is that very few firms survive for long periods of time the economy evolves largely by new firms replacing old ones rather than firms themselves adapting...

Contents

3 2 Climate Effects on Food Security An 13 3 Climate Models and Their Projections of Future Changes 31 4 Crop Response to Climate Ecophysiological Models 59 Jeffrey W. White and Gerrit Hoogenboom 5 Crop Responses to Climate Time-Series Models 85 6 Crop Responses to Climate and Weather 7 Direct Effects of Rising Atmospheric Carbon Dioxide Elizabeth A. Ainsworth and Justin M. McGrath 8 Food Security and Adaptation to Climate Change 9 Breeding Strategies to Adapt Crops to a Changing Climate 155...

Reducing Uncertainties

Uncertainty in future climate stems mainly from scenario and model uncertainty, and both of these for the most part are not intrinsic to the system. In principle, we are free to choose a scenario for future emissions through our actions. Model uncertainty is different, as there is a 'true' climate system, so the uncertainty does not reflect a choice but our incomplete understanding of the system and our inability in describing it in a numerical model. For the decision relevance that climate...

Functional Forms

Functional form refers to the type of relationship specified between a predictor variable, X, and a yield response variable, Y. The form could be a polynomial relationship, such as Eqs. (5.1) and (5.2), or an exponential relationship such as Eq. (5.3). Several other classes of equations could also be used, such as regression trees, neural networks, or Mitscherlich equations. The most common forms used for modeling yield responses to weather are the linear model of Eq. (5.1) and the quadratic...

Adaptation

Production practices undoubtedly will evolve in response to climate change. However, they will also evolve with technological developments, environmental regulation, market conditions and other factors. Thus, while there is value in considering how possible adaptations in crop management might affect the impact of climate change, one must keep in mind that climate change is only one process among many that will affect future agricultural systems. Simulating the simplest adaptations mainly...

Regional Assessments

In addition to estimates of regional yield changes that have been developed in the process of global assessments (e.g., Fig. 10.2), there is also a growing wealth of studies focused on particular regions. Indeed, the literature is too vast to provide an exhaustive review. 2 However, higher emissions scenarios can actually reduce near-term impacts since the CO2 fertilization effect responds instantly to higher CO2 levels while the climate system takes several decades to respond. Fig. 10.3 Yield...

One Model One Vote

It should be obvious then that future scenario analysis based on a single GCM would be a dangerously narrow view of what could be possibly in store. The IPCC report's future projections chapters, for global and regional projections (Meehl et al. 2007b Christensen et al. 2007), have in fact adopted a multimodel approach. For the most part the results in the report consist of simple descriptive statistics of climate change across the ensemble. Maps of ensemble means, accompanied by measures of...

Switching Planting Date

Perhaps the simplest farmer adaptations have to do with changes in on-farm management, which include decisions about what crops to grow and when and how to grow them. One of the more straightforward of these possible adaptations is the option to shift when in the year crops are planted. Current decisions about when to plant are made based on a number of factors, including available soil moisture, the expected timing of temperature extremes, and the demands of multi-cropped systems. Year-to-year...

Food Access and Climate Change

If Thomas Malthus is the customary jumping-off point for discussions of food availability, economist Amartya Sen dominates introductory paragraphs in discussions of food access. Recalling the definition above, food access refers to the ability of an individual to acquire food, either through its production or its purchase. Sen referred to these means of food acquisition as entitlements, and he won the Nobel Prize in part for showing how famines were a result of households or entire regions...

Experimental Approaches for Investigating Crop Production in Elevated [CO2

Several technologies have been used to study the effects of elevated CO2 on crop productivity, including controlled environmental chambers, greenhouses, open-top chambers (OTC), and Free-Air CO2 Enrichment (FACE Long et al. 2004). In controlled environmental chambers and greenhouses, plants are typically grown in pots, with lighting, nutrients and water supplied by the researcher in specified amounts. There are practical advantages to using controlled environments, including precise control of...

Switching Varieties or Crops

A second possible farmer adaptation to climate change is to switch varieties or crops to something better suited to the new climates they face. A farmer currently growing maize might switch to a faster-maturing maize variety if drought becomes more common, or might choose to grow a potentially more drought-tolerant crop like sorghum. But such decisions will not be made on the basis of climate alone. Different varieties and crops have different input requirements and costs associated with their...

Farmer Adaptation to Climate Dealing with Variability

The explicit focus of this book is on climate change - i.e. the potential shifts in the longer-run mean and extremes of temperature, precipitation, and other meteorological variables in a given area. And while longer-run climate exerts significant influence on agricultural decision-making, affecting what crops farmers grow and when and where they grow them, the actual amount of food produced in a given year depends on the specific realization of meteorological variables in that year....

Expansion of Irrigation Infrastructure

Irrigation was discussed above (Section 8.4.3) as a possible autonomous adaptation, but in many cases major public investments will be needed to provide farmers access to water. Some of these investments would undoubtedly happen even without climate change. For example, as part of its recent outlook assessment, the FAO projected changes in irrigated area for 93 developing countries notwithstanding climate change (Faures et al. 2002). Overall an additional 40 Mha in irrigated area was...

Changes in Yield Quantity at Elevated [CO2

Rice Grown Growth Chamber Picture

The large number of experiments in controlled environments has allowed yield dose response curves to be calculated for the major C3 food crops, soybean, wheat and rice. In Fig. 7.2, the ratio of yield at elevated CO2 relative to ambient CO2 was calculated from all available studies of soybean, wheat and rice grown to maturity at elevated CO2 in controlled environments and open-top chambers (for original references, see Ainsworth et al. 2002 for soybean, Amthor 2001 for wheat, Ainsworth 2008 for...

Breeding Wheat for Adaptation to Moisture Stress and Increased Temperature

The first step in breeding crops with improved response to water and temperature stress is identification of genetic variability governing the plant response. This response may be environment specific and its genetic control is likely to be complex. Soil type and associated water holding capacity and infiltration rates, crop management practices, timing of water stress during the plant growth cycle, temperature and biotic constraints will all influence plant response to drought. Determination...

Trend Removal

Figure 5.1a shows average yields over the study period. The most obvious feature of this time series, and time series of yields for most crops in most regions, is the highly significant positive trend with time. This trend results largely from improvements in technology, such as adoption of modern hybrid cultivars and increased use of fertilizer. Given that so much of yield variation between years in different parts of the record occurs because of technology differences, the effect of climate...