Course 2: Increase Food Production without Expanding Agricultural Land (Synthesis)
In addition to the demand-reduction measures addressed in Course 1, the world must boost the output of food on existing agricultural land. To approach the goal of net-zero expansion of agricultural land, under realistic scenarios, improvements in crop and pasture productivity must exceed historical rates of yield gains.
Assessing the Challenge of Agricultural Land Expansion
The single most important need for a sustainable food future is boosting the natural resource efficiency of agriculture, that is, producing more food per hectare, per animal, per kilogram of fertilizer, and per liter of water. Such productivity gains reduce both the need for additional land and the emissions from production processes. Without the large crop and livestock productivity gains built into our baseline (based roughly on trends since 1961), land conversion would be five times greater by 2050 and GHG emissions would be more than double the level projected in our baseline (Figure 9).
In some mitigation analyses, including reports by the Intergovernmental Panel on Climate Change (IPCC), agricultural productivity gains are barely mentioned, for reasons that are unclear. Even under our baseline projection, with its large increases in crop and livestock yields, we project that agricultural land will expand by 593 Mha to meet expected food demand. Unless projected growth in demand for food can be moderated, to avoid land expansion both crop yields and pasture-raised livestock yields will have to grow even faster between 2010 and 2050 than they grew in previous decades.
Arguments can be made for both pessimism and optimism:
- Studies have projected that farmers could achieve far higher yields than they do today. However, methods for estimating these “yield gaps” tend to exaggerate gap sizes and farmers can rarely achieve more than 80 percent of yield potential. The most comprehensive study suggests that fully closing realistic yield gaps is unlikely to be enough to meet all food needs.
- The massive yield gains of the 50 years from 1960 to 2010 were achieved in large part by doubling irrigated area and extending the use of scientifically bred seeds and commercial fertilizer to most of the world. Only limited further expansion of these technologies remains possible.
- Optimistically, farmers have so far continued to steadily boost yields by farming smarter in a variety of ways, and new technologies are opening up new potential.
Whatever the degree of optimism, the policy implications are the same: Going forward, the world needs to make even greater efforts to boost productivity than in the past to achieve a sustainable food future.
Figure 9 |
Improvements in crop and livestock productivity already built into the 2050 baseline close most of the land and GHG mitigation gaps that would otherwise exist without any productivity gains after 2010
- 33AnimalChange (2012), Figure 7. This analysis focused on efficiencies based on protein (kg of protein in output, e.g., meat, divided by kilograms of protein in feed). This analysis also noted that feed conversion efficiencies were not widely different in different regions for the reasons we discuss related to backyard systems.
- 34Herrero et al. (2013).
- 35Herrero et al. (2013), Figure 4. Systems are defined in this paper, and in the so-called Seres-Steinfeld system, by whether they are grazing only, mixed systems of grazing and feeds (a broad category that varies from only 10% feed to 90% feed), or entirely feed-based, and whether they are in arid, temperate, or humid zones.
- 36Atlin et al. (2017).
- 37NAS (2016).
- 38Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated.
- 39FAO (2011a). Preliminary results from the Global Land Degradation Information System (GLADIS) assessment.
- 40Williams and Fritschel (2012); Bunderson (2012); Pretty et al. (2006); Branca et al. (2011).
- 41Arslan et al. (2015).
- 42Reij et al. (2009); Stevens et al. (2014); Reij and Winterbottom (2015).
- 43Aune and Bationo (2008); Vanlauwe et al. (2010).
- 44Giller et al. (2015); Williams and Fritschel (2012); Bationo et al. (2007).
- 45To develop an estimate of fallow land, we deduct 80 Mha of cropland from the total estimate of rainfed cropland in Table 4.9 in Alexandratos and Bruinsma (2012) to come up with land that is not double-cropped, and deduct 160 Mha of land from harvested area (reflecting two crops per year on 80 hectares of land). The resulting difference between single-cropped cropland and harvested area suggests around 350 Mha of fallow land each year. FAO (2017a) indicates a 251 Mha difference between total arable land (including land devoted to permanent crops such as trees) and harvested area in 2009. These figures differ somewhat from the 299 Mha presented in Alexandratos and Bruinsma (2012), which adjusted arable land and harvested land in a couple of ways. However, assuming that roughly 150 Mha were double-cropped for reasons discussed above, that means 400 Mha were not harvested at all.
- 46Siebert et al. (2010).
- 47Porter et al. (2014).
- 48World Bank (2012).
- 49Porter et al. (2014).
- 50Craparo et al. (2015); Eitzinger et al. (2011); Ortiz et al. (2008); Teixeira et al. (2013).
- 51IPCC (2014); Semenov et al. (2012); Teixeira et al. (2013).
- 52World Bank (2012); Lobell et al. (2008).