Despite the fact that sub-Saharan Africa in 2012 contains much of the world’s unutilized and underutilized arable land, a significant and growing share of Africa’s farm households live in densely populated areas. Based on two alternative spatial databases capable of estimating populations at the level of one square kilometer and distinguishing between arable and non-arable land, we find that in at least five of the 10 countries analyzed, 25 percent of the rural population resides in areas exceeding 500 persons per square kilometer, estimated by secondary sources as an indicative maximum carrying capacity for areas of rain-fed agriculture in the region. The apparent paradox of a large proportion of Africa’s rural population living in densely populated conditions amidst a situation of massive unutilized land is resolved when the unit of observation is changed from land units to people.

A review of nationally representative farm surveys shows a tendency of (1) declining mean farm size over time within densely populated smallholder farming areas; (2) great disparities in landholding size within smallholder farming areas, leading to highly concentrated and skewed patterns of farm production and marketed surplus; (3) half or more of rural farm households are either buyers of grain or go hungry because they are too poor to afford to buy food; most households in this category control less than one hectare of land; and (4) a high proportion of farmers in densely populated areas perceive that it is not possible for them to acquire more land through customary land allocation procedures, even in areas where a significant portion of land appears to be unutilized.

Ironically, there has been little recognition of the potential challenges associated with increasingly densely populated and land-constrained areas of rural Africa, despite the fact that a sizeable and increasing share of its rural population live in such areas. Inadequate access to land and inability to exploit available unutilized land are issues that almost never feature in national development plans or poverty reduction strategies. In fact, since the rise of world food prices after the mid-2000s, many African governments have made concerted efforts to transfer land out of customary tenure systems (where the majority of rural people reside) to the state or to private individuals who, it is argued, can more effectively exploit the productive potential of the land to meet national food security objectives. Such efforts have nurtured the growth of a relatively well-capitalized class of “emergent” African farmers. The growing focus on how best to exploit unutilized land in Africa has arguably diverted attention from the more central and enduring challenge of implementing agricultural development strategies that effectively address the continent’s massive rural poverty and food insecurity problems, which require recognizing the growing land constraints faced by much of its still agrarian-based population. The final section of the paper considers research and policy options for addressing these problems.

This paper was prepared for Stanford University’s Global Food Policy and Food Security Symposium Series, hosted by the Center on Food Security and the Environment, and supported by the Bill and Melinda Gates Foundation.

Food policy makers are increasingly faced with the question of how to adapt to climate change. The increased attention on climate adaptation is partly related to the fact that greenhouse gas emissions and climate change show little sign of slowing, partly because of prospects for large sums of money devoted to adaptation, and partly because of well publicized recent weather events that have affected agricultural regions and rattled global food markets. A common and reasonable reaction from the food policy and agricultural community has been to argue that climate variations have always been a challenge to agriculture, and that climate change just makes addressing these variations more important. A logical conclusion from this perspective is to emphasize activities that help build resilience to unpredictable weather events, as well as to focus on the types of weather variables that exhibit a lot of year-to-year variability and cause the bulk of farmers’ concerns in current climate.

However reasonable as a starting point, this perspective is misguided and risks taking a challenging problem and making it even harder. Anthropogenic global warming (AGW) is fundamentally different from the natural variations driven by internal dynamics in the climate system. Indeed, predicting the course of climate change is less like predicting the weather next week than it is like predicting that summer will be warmer than winter. Progress in climate science has shown that the most indelible hallmarks of AGW will be increased occurrence and severity of high temperature and heavy rainfall extremes in all regions, and increased frequency and severity of drought in sub-tropical regions. Changes in the timing and amount of seasonal rainfall also appear likely in some regions, but at a much smaller pace relative to natural variability. In all of these cases, predictions from climate science are most robust at broader spatial scales, with considerable uncertainty in predicting changes for any single country.

Meanwhile, progress in crop science has shown that most crops show fairly rapid declines in productivity as temperatures rise above critical thresholds, with as much as 10 percent yield loss for +1°C of warming in some locations. Both sub-Saharan Africa and South Asia appear particularly prone to productivity losses from climate change, in part because major staples in these regions are often already grown well above their optimum temperature.

Approaches to climate adaptation should recognize these realities, and should not equate anticipating climate changes with the considerably harder task of predicting next year’s weather. Predicting and building resilience to climate variability still remain important goals for agricultural development, but adaptation efforts should balance these activities with those focused more on the specific threats presented by climate change. Heat tolerant crop varieties and strategies to deal with heavy rainfall provide two examples of important needs. Similarly, balance is needed between the local-scale efforts that attract most of adaptation investment currently, and regional and global networks to develop needed technologies. Given the greater certainty of climate changes at broader scales, as well as the positive track record of international networks for crop breeding, investments in these global systems are very likely to deliver substantial adaptation benefits. Finally, given the downward pressures that climate change will exert on smallholder farm productivity in sub-Saharan Africa, and the critical role productivity gains play in catalyzing an escape from poverty, speeding the pace of investment in African agriculture can also be viewed as a good bet for climate adaptation.

Climate change will lead to massive conflicts, according to claims of such prominent sources as Sir Nicholas Stern and the US National Security Agency - claims repeated by the media. Efforts to tease a specific climate change signal from historical records of civil conflict have proved inconclusive, however: they postulate that farmers will become fighters when resources become critically scarce; but they have been unable to illuminate what specific mechanisms may be involved. Yet the potential for climate change to cause significant civil conflict seems intuitively obvious, and the need for better understanding remains urgent. My research focuses on sub-Saharan Africa, the most conflict-prone region in the world; and it asks what factors make some countries erupt in civil conflict, while others do not. I find that drops in agricultural exports diminish government capacity as tax revenues shrink, leading to an increase in the risk of civil conflict. Thus, government capacity to provide security and services is likely to become weak just at the time when climate change is increasing the need for both. How governments respond will determine the risk of civil conflict, but this research shows that their capacity to respond will, in fact, also be affected. The implications of these conclusions apply beyond sub-Saharan Africa, and begin to move the debate from questions around if climate change will cause conflict to more productive discussions of how climate change may affect conflict risk.

Seeds of Sustainability is a groundbreaking analysis of agricultural development and transitions toward more sustainable management in one region. An invaluable resource for researchers, policymakers, and students alike, it examines new approaches to make agricultural landscapes healthier for both the environment and people.

The Yaqui Valley is the birthplace of the Green Revolution and one of the most intensive agricultural regions of the world, using irrigation, fertilizers, and other technologies to produce some of the highest yields of wheat anywhere. It also faces resource limitations, threats to human health, and rapidly changing economic conditions. In short, the Yaqui Valley represents the challenge of modern agriculture: how to maintain livelihoods and increase food production while protecting the environment.

Renowned scientist Pamela Matson and colleagues from leading institutions in the U.S. and Mexico spent fifteen years in the Yaqui Valley in Sonora, Mexico addressing this challenge. Seeds of Sustainability represents the culmination of their research, providing unparalleled information about the causes and consequences of current agricultural methods. Even more importantly, it shows how knowledge can translate into better practices, not just in the Yaqui Valley, but throughout the world.

Promotion of smallholder irrigation is cited as a strategy for enhancing income generation and food security for sub-Saharan Africa’s poor farmers, but what makes this technology a successful poverty alleviation tool? In the short run, the technology should pave the way for increased consumption, asset accumulation, and reduced persistent poverty among users. Over the longer run, it should lead to institutional feedbacks that support sustained economic development and nutritional improvements. Our conceptual model and review of case studies reveal the importance of three sub-components of irrigation technology—access, distribution, and use—and the ways in which the design of the technology itself can either bridge, or succumb to, institutional gaps. These critical features are illustrated in an experimental evaluation of a solar-powered drip irrigation project in rural northern Benin, which provides a controlled study of technology impacts in the Sudano-Sahel. The combined evidence highlights the technical and institutional requirements for project success and points to two important areas of research in the scale-up of any small-scale irrigation strategy: the risk behavior of water users, and the evolution of institutions that either support or obstruct project replication over space and time.