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 into account current realities and trends in global and regional supplies of food. We therefore highlight three particularly important characteristics of the global food supply.
The first is that on an average per capita basis, the world today produces more than enough food to meet caloric requirements, and that this success has been based mostly on yield gains over the last half century. Perhaps first popularized by Thomas Malthus in the early 1800s, the question of whether the world can produce enough food to feed a growing population has been a perennial concern. Thus far, technology has mostly precluded Malthusian doomsday predictions of population-driven food shortages. Through the first half of the last century, the need for increased food production was met by expansion of cropped area. But beginning in about the 1950s, when population and income growth were adding increasing pressure to global food markets, large-scale sustained investment in crop productivity greatly increased yields of crops throughout the developing world. This so-called Green Revolution allows the world today to produce 170% more cereals on just 8% more cropped area than 50 years ago (Panel (a), Fig. 2.3) - certainly an incredible achievement. Furthermore, on a global level this productivity growth has more than kept pace with the large observed increases in population, and global per capita cereal production currently stands at almost exactly 1 kg/person/day - or more than enough, on average, to feed everyone on the planet.
These global averages, however, hide large regional discrepancies, and the second important characteristic of the global food supply is that there are stark regional differences in the magnitude and source of agricultural productivity growth - differences that provide important insights into the challenge a changing climate might pose. Panels (a-c) in Fig. 2.3 show area, yield, and per-capita production trends by region
over the last half-century. While most regions in the developed and developing world enjoyed somewhere between a doubling and tripling of yield since 1960, allowing them to increase their per-capita production of cereals with only minimal expansion in cropped area, Africa stands out as the continent on which progress has been most difficult. African cereal yields have grown at less the half the Asian rate, and despite an 80% increase in the amount of cropped area on the continent, total cereal production has not kept pace with population growth. As a result, the African continent is the only region where per capita production of cereals has declined over the last half century.
The potential for reversing this decline and for further boosting productivity elsewhere in world is at once promising and troubling. The promise for Africa and other low productivity regions lies in the large gulf between observed yields and potential yields - the so-called "yield gap" - much of which is explained by low adoption of modern agricultural technology and inputs. In theory, developing appropriate agricultural technology for these regions and providing the proper incentives to use it could rapidly close these substantial yield gaps and quickly raise productivity. But elsewhere in the world, particularly in the high-input systems in much of North America, Europe, and parts of Asia, yield gaps are much smaller, and achieving the sustained increases in yield observed over the past 4 decades will likely be very difficult without further increases in yield potential ceilings (Cassman 1999).
Furthermore, expanding cropped area, which is the alternative to increasing yield, is either difficult or unappealing throughout much of the world, either because of urban encroachment on agricultural land or because of the environmental costs of bringing new land into production. The FAO, which periodically assesses trends in crop demand and supply, envisages a significant expansion of cropland area in Africa and Latin America but little growth elsewhere, mainly because so little land in Asia remains uncultivated (Bruinsma 2003). Overall, most global assessments project that (1) crop demand will grow considerably over the next few decades, given the additive pressures of population growth (estimated to peak at 9.1 billion mid-century), higher incomes resulting in shifting food preferences, and potential development of large-scale biofuel production and the additional crop demand it represents; (2) the rate of demand growth, however, will be slower than observed in the past few decades, as population begins to stabilize; (3) and based on existing land, water, and fertilizer resources, crop production should be able to keep pace with the decelerating demand growth, but only with a formidable and sustained investment in yield improving technologies, cropland expansion, and input use.
The third important feature of the global supply situation is that food is now a truly global commodity, and the movement of food across borders plays an increasingly important role in meeting regional food demand. As Fig. 2.4 shows, about 10% of world cereal production is traded internationally, with some regions (Oceania, North America) exporting substantial amounts of what they produce, and other regions (notably Africa) importing up to a third of what they consume. Such food trade can either buffer or exacerbate the effects of a local food supply shock. A country experiencing drought, for instance, might make up for production shortfalls through imports, but cereal
importing nations would pay higher food prices on the world market when large exporting countries suffer similar shortfalls. In the event that such shocks happen simultaneously, poor importing nations would need to import when prices are very high, greatly increasing their difficulties in bolstering local food supplies.
So how might climate change affect global and regional food supply? As the rest of this book will show, climate change will have potentially large effects on both agricultural yields and potential cropped area, with global trade acting as a potential buffer when countries trade and when climate shocks are not uniform across space. But agricultural production and food availability are just one part of the food security story, and we now turn to the less frequently discussed potential effects of climate change on access and utilization.
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