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Improving yield


In the SSP2 baseline (Fricko et al. 2017), between 2010 and 2050, per capita demand for food, feed and energy crops increases by 60 per cent. In the same period, global average aggregate food, feed and energy crop yields (mean tons of agricultural products per hectare) also increases (by around 1.0 per cent per year). As a result, the net effect in SSP2 is an increase in cropland area of about 15 per cent in 2050 (230 million ha) (Figure 22.3). This is in line with the FAO projection for yield improvements and agricultural area expansion through 2050 (Alexandratos and Bruinsma 2012). To limit cropland expansion, yield growth would need to increase from around 1.0 to 1.4 per cent per year. It is thus useful to look into the evidence on the question whether fast yield improvements are possible in the future. First, similar yield improvement rates have been achieved historically (Alexandratos and Bruinsma 2012). Moreover, several scenarios indeed show high future yield increase (Figure 22.3). There is also a large yield gap between the most- and least-productive regions (Global Yield Gap and Water Productivity Atlas 2018),


Figure 22.3: Percentage change in non-energy crop production versus the percentage change in non- energy cropland area from 2010 to 2030 and 2050


125


and transfer of best practices from the leaders to the laggards might raise global average yields (Neumann et al. 2010; Foley et al. 2011). Finally, new methods to improve yields might also provide further potential (including genetically modified organisms [GMOs]). On the other hand, the easy yield gains may already have been achieved (Slade, Bauen and Gross 2014). Moreover, over the past decades yield increases have coincided with significant increases in environmental pressure such as nitrogen pollution as a result of nitrogen fertilization (Lassaletta et al. 2016). Projections of future fertilizer use are uncertain, but it is clear that increasing global production levels would require greater fertilizer use (Alexandratos and Bruinsma 2012). For instance, yield increase could lead to 15-70 per cent increase in nitrogen losses to the environment, leading to further pollution of water and soil (Sutton and Bleeker 2013; Lassaletta et al. 2016). Sustained yield improvements may also be reliant on increased irrigation, impacting water resources (Neumann et al. 2010). It is also possible that in the future organic farming coupled with reduced food waste and diet change could considerably reduce the environmental footprint of agriculture (Muller et al. 2017). However, one might question whether such measures would lead to similar yield levels as through conventional agriculture (Leifeld 2016), or the scalability of existing experiences in both alternative production and food waste reduction methods (Schneider et al. 2014). For pasture area, the intensification of livestock production could limit the increase in pasture area, and possibly lead to a decrease.


100 75 50 25 -50 Period


2010–2030 2010–2050


-25 0


Average Annual Yield Change (% per year)


1.6 1.2


0.8 0.4 0.0


Each marker is a model-scenario-year combination. Colour indicates the annual percentage change in yield over the same time period. Yellow is close to historical trends (about 1 per cent per year between 1960 and today from Alexandratos and Bruinsma 2012); blue indicates yield growth faster than historical trends; red indicates yield growth slower than historical trends. For the SSPs, yield is the global average yield for cereal crops. For the Bajželj et al. (2014) scenarios, yield is the global average yield for wheat and data are referenced with respect to 2009.


Sources: SSPs (Popp et al. 2017) and Bajželj et al. (2014). Pathways toward Sustainable Development 517 25 Change in cropland area (%) 50


Reducing environmental pressures associated with agriculture High-yield agricultural systems are usually associated with high levels of nitrogen loss as reported in the previous section. There is evidence, however, that the negative impact of high- yield agriculture on nitrogen loss could be limited by improving nitrogen-use efficiency (Lassaletta et al. 2016; Bouwman et al. 2017). This can be shown by the large variation in application rates, with excess application in some regions leading to significant environmental impact, especially in China (Zhang et al. 2016; Cui et al. 2018). In fact, rapidly increasing global nitrogen-use efficiency from the current 40 per cent to close to 70 per cent may lead to a sharp decline in excess nitrogen to 50 Tg N/year, with the added benefit of potentially leading to stabilization of total nitrogen inputs in global crop production (Zhang et al. 2015). Mogollon et al. (2018) present similar findings but emphasize that this can only happen in optimistic sustainability scenarios (limited increase in demand and high efficiencies). The relationship of crop yield to nitrogen application means there are diminishing returns to higher nitrogen application in regions with high fertilizer application rates and more potential for increased production in regions with low application rates. This means there is room globally to optimize nitrogen application. The trade-off in this case would be an increase in international trade of agricultural commodities.


It is also important to reduce other environmental pressures – such as high levels of water consumption (see Section 22.3.3), the negative impacts of use of herbicides and pesticides, and eutrophication of inland and coastal waters due to excess nutrient use in food production and sewage water discharge. Scientific evidence shows that it is important to maintain agricultural sustainability to ensure services such as natural pest control, pollination and fertility (Oerke 2006; de Vries et al. 2013; Garibaldi et al. 2017). For instance, except for cereals (which are not insect-pollinated), many important global food


22


Change in agricultural production (%)


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