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crops depend, at least partly, on animal pollinators (usually insects) for yield and/or quality, and pollinator-dependent crops contribute 35 per cent of the global crop production volume (Klein et al. 2007). Reducing negative impacts can to some degree be achieved in high-yield agricultural systems. There is some evidence that organic farming could be an alternative as it may support greater local species richness and higher densities of natural organisms compared with conventional farms (Bengtsson, Ahnström and Weibull 2005; Tuck et al. 2014). However, organic farming could also lead to lower yields and thus increased land use (Clark and Tilman 2017). The role of organic farming cannot be really assessed in this chapter as, at present, the issue of organic farming is hardly addressed in scenario studies. In fact, the same goes for strategies to preserve sufficient genetic diversity. While there is some evidence that it is important to maintain diversity as a buffer against all kinds of environmental variability, again this is not really addressed in scenario studies. Such diversity can be encouraged by rotating crops, intercropping and varying crop varieties.
Preventing land degradation The loss of soil organic carbon and other forms of soil degradation can significantly impact crop yields and the nutritional values of food produced (Godfray et al. 2010; Lal 2015; Rojas et al. 2016). Therefore, maintaining soil health, through the management of soil organic carbon and preventing land degradation, is important. The recently published Global Land Outlook is one of the few studies that discuss land degradation in the context of different scenarios, but it only discusses trend scenarios and not pathways towards achieving the land degradation neutrality target (United Nations Convention to Combat Desertification [UNCCD] 2017; van der Esch et al. 2017). Land restoration and protection targets are projected to increase tree cover by 4 million km2
in 2050
compared to the area in 2000 and increase forest carbon stocks by 50Gt over the same time period (Wolff et al. 2018). However, due to the limited scenarios literature, it is hard to assess the role of avoiding land degradation in achieving the SDGs.
Agricultural demand-side measures To limit cropland expansion, it is also possible to reduce the food demand that would occur in baseline projections. Reductions in demand could come from reduced food consumption, reduced waste or reduced feed/fuel uses of crops.
Dietary change Changes in diet are considered an effective measure for reducing land-use impacts of agriculture. Diet changes resulting in less meat consumption would reduce crop use as animal feed, which in turn would reduce demand for land, since direct human consumption of crops requires less land (Stehfest et al. 2009). In particular, a reduction in beef consumption would have the most direct positive impact on environmental indicators, as ruminants have the lowest feed and protein conversion rates of all livestock (Béné et al. 2015). This implies that reduction of meat consumption to levels consistent with health recommendations in high-income countries could lead to positive impacts in terms of reducing agricultural land-use and increasing human health (Stehfest et
al. 2009) – as on average current consumption of beef is above this level. Strong reductions in land area for food production as a result of dietary shifts towards more plant-based diets have been reported by Foley et al. (2011) and Stehfest et al. (2009). Such a shift would also lead to health benefits, according to these studies. Land-efficiency gains can also be gained by eating different meat. Meat from non-ruminant livestock (e.g. pigs) has a lower impact than beef, and the land footprint of their diets can be improved by shifting to more efficient (higher- yielding) fodder crops (Béné et al. 2015; van Zanten et al. 2018). Thus, diets based on lower shares of ruminants would reduce land demand. In the case of bivalves, aquaculture may even remove nutrient run-off into estuaries through filtration, a potential synergy.
More recent scenarios in the literature have also focused on dietary change, including the SSP1 scenarios (see Popp et al. 2017), and the ‘consumption change’ pathway from Roads from Rio+20 (van Vuuren et al. 2015; van Vuuren et al. 2018) and others (Bajželj et al. 2014; Tilman and Clark 2014). The dietary change ranges from modest shifts towards non-ruminants (the SSP1 scenario) to complete elimination of meat (Tilman and Clark’s Vegetarian scenario). Several of these scenarios limit the expansion of cropland area, but these also include enhanced yields, suggesting that dietary change alone is not enough to limit cropland expansion given a growing population. Note that, in addition to changes in yield and diet, these scenarios also have limited expansion of bioenergy cropland (60 and 140 million ha in 2050 in the SSP1 scenario of the IMAGE and GCAM models, respectively). In the end, this means that a combination of yield improvement, diet change and control of bioenergy expansion offers the most likely situation in which expansion of agricultural area can be avoided.
Waste and loss reduction Global agricultural production in 2010 (about 3,900 kcal of food crops per person per day) was more than enough food to feed the world, yet more than 800 million people were undernourished (Alexandratos and Bruinsma 2012; Kummu et al. 2012). One reason is that 25-40 per cent of food produced is wasted, either through supply-chain waste or end-consumption waste (Godfray et al. 2010; Kummu et al. 2012). Reducing food waste and loss is one way of reducing hunger, while limiting cropland expansion. The amount of food wasted today is enough to feed several hundred million people a year (West et al. 2014), with some studies showing that if half of this waste were redistributed to consumers an extra billion people could be fed (Kummu et al. 2012). Similarly, Bajželj et al. (2014) show that cutting food waste in half would reduce cropland area by 14 per cent. Muller et al. (2017) show that, in addition to reducing land demand, dietary change and waste reduction can result in reduced fertilizer and water use. Bijl et al. (2017) show that, although significant improvement can be achieved through yield increase, the improvement is less than expected – mostly because meat is, on average, wasted less than other agricultural products. Several of the scenarios that look into waste reduction also report limited cropland expansion (consumption change from van Vuuren et al. 2015 and some scenarios of Bajželj et al. 2014). Each of these scenarios also assumes enhanced yields leading to the conclusion that waste reduction alone is not enough to limit cropland expansion given an increasing population.
518 Outlooks and Pathways to a Healthy Planet with Healthy People
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