**3. The green revolution**

Increasing food supplies, together with improved medical care, made possible the explosive growth of world population from 2.5 billion in 1950 to 7 billion today.

Much of the spectacular improvement in agricultural production is rightly attributed to development of high-yield strains of the major cereal crops, rice, maize, and wheat (Evenson & Gollin, 2003). Dwarf varieties allowed plants to bear more fruit without collapsing, enabling mechanized application of fertilizer (Figure 2), as well as pesticides and herbicides, greatly enhancing the productivity of land while reducing farm labor (Freebairn, 1995). A great increase in irrigation (Figure 3) further improved productivity and brought addidtional, mostly marginal, lands under cultivation (Figure 4). Notably, however, irrigated area per person has been constant within a few percent since 1960 (EPI, 2011b).

The level of fossil fuel dependence differs significantly between developed and developing countries. Although total primary fossil energy input into farm production is comparable between developed countries and developing countries, as illustrated in Figure 5, developed countries use more than four times the energy per capita (8.0 gigajoules/capita/year) than developing countries (1.7 GJ/capita/year). Moreover, Figure 5 further reveals very different distribution of energy use across agricultural inputs. For developing countries, nitrogen fertilizer accounts for more than half the energy inputs, with fuel and irrigation forming the next largest inputs. By contrast, in developed countries, fuel and machinery account for more than half the inputs, with nitrogen accounting for about one quarter.

Primarily as a consequence of this disparity, the farm inputs alone in developed countries average about 2 units of fossil fuel energy inputs for every unit of food energy, whereas in developing countries, the ratio is less than 1 to 2 (Giampietro, 2004, Table 10.7). These figures illustrate the heavy fossil fuel dependence of industrial agriculture.

Fig. 2. Global fertilizer use, 2009 (EPI, 20011c).

Fossil Fuel and Food Security 283

Pimentel et al. (2008) have assembled case studies of cultivation of a variety of crops in both developed and developing countries. In general, their data indicate that developed countries achieve much higher yields with much less human labor, with the difference coming from fossil energy. Consequently, developed country production is more expensive and less energy efficient. In most cases the output energy is less than the input, whereas the opposite is true in developing countries (with the few exceptions probably coming from animal energy—which is provided by forage unavailable for human consumption). To cite an extreme example, apple production in the United States achieves 9 times the yield per hectare, but with overall energy

The fossil fuel dependence of the food system in developed countries, however, is much larger still, because farm production accounts only for about 20% of the total system inputs. Indeed, the largest single contribution comes from food preservation and preparation in the home, with additional substantial contributions from transportation and food processing (Figure 6).

Fig. 6. Distribution of energy inputs in the U.S. food system (Heller & Keoleian, 2000, p. 41).

The Intergovernmental Panel on Climate Change (IPCC, 2007) has summarized the evidence for climate change, its likely impacts, and possible mitigation and adaptation measures. Heattrapping by so-called greenhouse gases, most importantly carbon dioxide (CO2), is warming the global climate (IPCC, 2007, p. 2). Most emissions (57%) of these gases come from fossil fuel burning, with an additional 17% contribution from deforestation, decay of organic matter, and peat (IPCC, 2007, p. 5). Deforestation is largely driven by expanding populations bringing additional land under cultivation. A breakdown of emissions by sector attributes nearly 14% to agriculture and another 17% to forestry, although these figures do not include other post-farm contributions from the food system. Agriculture accounts for roughly 50% of methane emissions (mostly from rice paddies and ruminant animals) and 70% of nitrous oxide

Climate change will have significant impact on agricultural productivity and consequently

emissions (mostly associated with nitrogen fertilizer) (IPCC, 1996, pp. 49-53).

Successive input sectors appear clockwise from the top.

**4. Climate change** 

on food security (Table 1).

efficiency of 40% compared to India and nearly 100 times the economic cost.

Fig. 3. Global irrigated area, 1950-2008 (EPI, 2011b).

Fig. 4. Global agricultural area, 1961-2009 (FAO, 2011a).

Fig. 5. Distribution of farm energy inputs in developing countries (left) and in developed countries (right) (Giampietro, 2004, Table 10.2). The areas are proportional to total energy use: 8 EJ/year and 10 EJ/year, respectively. Successive input sectors appear clockwise from the top.

Fig. 3. Global irrigated area, 1950-2008 (EPI, 2011b).

Fig. 4. Global agricultural area, 1961-2009 (FAO, 2011a).

Fig. 5. Distribution of farm energy inputs in developing countries (left) and in developed countries (right) (Giampietro, 2004, Table 10.2). The areas are proportional to total energy use: 8 EJ/year and 10 EJ/year, respectively. Successive input sectors appear clockwise from the top. Pimentel et al. (2008) have assembled case studies of cultivation of a variety of crops in both developed and developing countries. In general, their data indicate that developed countries achieve much higher yields with much less human labor, with the difference coming from fossil energy. Consequently, developed country production is more expensive and less energy efficient. In most cases the output energy is less than the input, whereas the opposite is true in developing countries (with the few exceptions probably coming from animal energy—which is provided by forage unavailable for human consumption). To cite an extreme example, apple production in the United States achieves 9 times the yield per hectare, but with overall energy efficiency of 40% compared to India and nearly 100 times the economic cost.

The fossil fuel dependence of the food system in developed countries, however, is much larger still, because farm production accounts only for about 20% of the total system inputs. Indeed, the largest single contribution comes from food preservation and preparation in the home, with additional substantial contributions from transportation and food processing (Figure 6).

Fig. 6. Distribution of energy inputs in the U.S. food system (Heller & Keoleian, 2000, p. 41). Successive input sectors appear clockwise from the top.
