Beyond Yields: Mapping the Many Impacts of Climate on Food Security

Rising temperatures and changing precipitation patterns are increasingly putting food and nutritional security at risk across the world. Popular narratives have stressed the importance of climate impacts on crop yields and food supplies. However, a growing body of evidence supports a more complicated situation, in which climate variability may influence each of the four dimensions of food security—availability, accessibility, utilization, and stability. The implication is that efforts to protect food security from climate change must look beyond agriculture and rural populations—these efforts should address livelihoods and health and consider the unique vulnerabilities of urban areas as well.

One established concern about climate change and food security emphasizes the implications of changing temperatures and precipitation for crop yields and food supplies. These impacts are indeed very important, and there is rigorous evidence of such impacts. For example, one study of historical maize trials in Africa found that excessive temperatures were associated with large reductions in maize yields, on the order of 1–1.7 percent per degree-day over 30°C. Likewise, a meta-analysis of published studies suggests that, without meaningful adaptation, 2°C of local warming will lead to production losses for wheat, rice, and maize across the world. Climate change represents an important challenge to the gains in agricultural production that have occurred over recent decades.

However, climate change may also affect food security through other channels. For one, well-documented climate impacts on economic activity have the potential to reduce incomes and therefore diminish households’ ability to purchase food. Such impacts will also leave households more vulnerable to rising food prices. Attention to this economic channel is particularly important since these “demand-side” forces are already a leading cause of food insecurity globally. In addition to this economic channel, changes in temperature and precipitation are correlated with changes in health, which influences individuals’ ability to fully utilize the food they have. For example, temperature- and precipitation-induced increases in diarrheal illnesses and other diseases may reduce individuals’ ability to fully metabolize the food they consume, thereby increasing rates of malnutrition. Finally, climatic variability has been linked to changes in human migration patterns, including the out-migration of working-age household members in some contexts. Although migration often helps households adapt to climate shocks by increasing household incomes, it may also lead to changes in labor allocation that diminish food security among the household members that remain in the origin. For example, if one family member leaves a farm for employment elsewhere, this can increase household income via remittances, but decrease the amount of labor available on the farm and ultimately reduce household level food security.

With these potential impacts in mind, the research community has renewed its efforts to empirically evaluate the relationship between climate variability and food security. Much of this research has involved the integration of large-scale household survey data on demographics and health with detailed historical records of temperature and precipitation. Using these data, researchers can apply statistical techniques to isolate the effects of climatic variability on a range of health and nutritional outcomes. Our reading of, and contribution to, this emerging body of research point to at least four important conclusions.

First, climate impacts on food security are meaningfully large. For example, a recent study found that exposure to abnormally high temperatures in the past year were associated with an over 8 percentage point increase in the probability of wasting—or extremely low weight for age—among children under five years old in sub-Saharan Africa. Likewise, another study from Ethiopia showed that a 1°C increase in temperatures during a child’s prenatal period is associated with an approximately 16 percent increase in the odds that the child becomes stunted—with low height for age—in subsequent years. Importantly, when climate shocks impact children in this manner, they may also have effects for years, if not decades, to come. Children who experience malnutrition in early life tend to experience worse health and socioeconomic outcomes over their lifetime, representing an important, costly challenge to human and economic development.

Second, the effects of drought and heatwaves rightly receive the most attention, but other forms of climate variability are also important. There is evidence that both exceptionally low and high levels of precipitation can adversely affect food security, albeit sometimes through different mechanisms. For instance, drought may destroy crops, reduce local food supplies, and increase food prices, while high levels of precipitation may increase the prevalence of malnutrition-increasing diseases. It is also important to think carefully about context, since the most salient forms of climate shocks will vary from place to place. For example, studies of rice production and nutritional outcomes from Indonesia each suggest that the timing of precipitation matters more for food security than the levels of precipitation. There, delays in the onset of the monsoon season are associated with significant reductions in rice production and increases in both acute and chronic malnutrition among children. Likewise, evidence from Bangladesh shows that exposure to flooding is better predictive of outcomes than precipitation in general.

Third, climate-induced food insecurity is a pressing problem in the developing world, but it is a risk everywhere. Many of the world’s poorest countries are disproportionately dependent on agriculture, lack resources to mitigate climate impacts on food systems and population health, and suffer from high baseline levels of food insecurity. Unsurprisingly, recent evidence suggests food security in these places—including Mali (ranked #184/189 on the Human Development Index), Burkina Faso (ranked #182), Ethiopia (#173), and Nepal (#142)—is routinely disrupted by weather shocks. However, populations in wealthier countries are also susceptible to the nutritional impacts of climate variability. This is evident in the above-mentioned research from Indonesia, as well as evidence from many middle-income countries in sub-Saharan Africa. Likewise, cold spells in the United States have led to increased food insecurity among low-income populations, who face critical tradeoffs between the costs of energy and food. Recent events in Texas demonstrate how cold shocks may also limit access to water with which to clean and prepare food.

Fourth, not only rural populations are at risk—urban populations are at risk, too. Many accounts emphasize the vulnerability of rural populations to climate change, due largely to their dependence on agriculture and high rates of poverty. However, recent studies demonstrate that urban populations—which are growing rapidly across many regions of the world—also face significant impacts. In Indonesia, for example, the effects of delays in the monsoon season on child stunting were concentrated in urban areas, and evidence from sub-Saharan Africa shows that high temperatures have indistinguishable impacts on wasting across rural and urban areas. In our view, the salient question is not so much whether rural or urban residents are more or less vulnerable, but instead how—and why—the sources of vulnerability differ for these populations. For example, since rural populations are more dependent on agricultural production for food and income, they are more likely to be affected by climate’s direct impacts on agriculture. In contrast, urban populations may be most vulnerable to increases in food prices that stem from climate-related disruptions to agriculture, or to the health effects of heat stress or flooding. More evidence about these mechanisms is needed, but there is already a clear basis for focusing on both rural and urban populations.

Climate change poses a real and important threat to global food security, but in a manner that is more complicated than often portrayed. This complexity represents a challenge for policymaking, but we raise a number of preliminary points and questions for consideration. First, stemming climate impacts on food and nutritional security will require a focus beyond food supply to consider how changes to income and health may also undermine food security. This suggests a need for integrated approaches that link agriculture, livelihoods, and health. Second, we underline the need to build resilience in both rural and urban areas—an observation the CSIS Global Food Security Program has made before—which differ more in their sources than levels of vulnerability. Finally, investments in data collection and dissemination have allowed scientists to rapidly develop a foundation of empirical evidence on this topic. Continued efforts to innovate on this front will assist with the improvement of monitoring and forecasting.

In our view, the salient question is not so much whether rural or urban residents are more or less vulnerable, but instead how—and why—the sources of vulnerability differ for these populations.

What does this mean for policymakers? 2021 is undoubtedly a year for climate action, with both the UN Climate Change Conference (COP26) and the UN Food Systems Summit on the horizon. COP 26 presents an opportunity for policymakers to redouble their focus on food security in the context of the negotiations. The evidence discussed above suggests that member states should be agnostic as to whether climate-sensitive investments in food security have rural or urban designations. In a similar way, as the UN Food Systems Summit identifies “game-changing solutions,” it should consider the many urban-focused initiatives being proposed alongside those focused on rural issues, such as agricultural production and landscape regeneration. Finally, the U.S. government should break out of traditional, narrow thinking about the impacts of climate on agriculture, acknowledge the diversity of impacts as we and others have outlined, and take appropriately multi-sectoral approaches to build communities’ resilience via the next U.S. Global Food Security Strategy. As our understanding of the pathways by which climate is impacting food systems is growing, efforts to improve food security in the years ahead must adapt accordingly.

Brian Thiede is an assistant professor of rural sociology and demography at The Pennsylvania State University. Christian Man is the policy action lead for the Just Rural Transition and an adjunct fellow (non-resident) with the CSIS Global Food Security Program.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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Christian Man
Adjunct Fellow (Non-resident), Global Food Security Program

Brian Thiede

Assistant Professor, Pennsylvania State University