Page 146 - Climate Change and Food Systems

climate change and food systems: global assessments and implications for food security and trade
7 and 8) but, as shown for wheat in Figure 7, the magnitude of yield losses, ranging from
0 to 10 percent, is not as severe as for other world regions. Nevertheless, there are areas
in Europe where the impacts of CC can have significant negative yield effects, as can partly be seen in southern Europe (Figure 8a). Increased temperatures and drier conditions can reduce rainfed wheat yields in those areas by up to
30 percent, as reported for southern Spain and the central regions of France. Projections for regions
in Italy and Greece are also negative and yields
are expected to decrease by 10 to 20 percent.
On the other hand, beneficial effects of CC are expected in central, eastern and northern Europe, where wheat yields in most areas are likely to increase by 10 to 30 percent. Similar geographical patterns of projected yield reductions and gains can be observed for potato (Figure 8d) and grass (Figure 8g), with expected increases in northern Europe (just for potatoes), central and eastern Europe (for potatoes and grass) and reductions in western and southern Europe.
Effects of climate variables and CO2.
When the fertilization effect of CO2 is added to
the projections, net impacts become positive at European scale, as shown for wheat in Figure 7. Ewert et al. (2005), for example, projected increases in wheat yields of 9 to 14 percent (EU15+2) by 2050, assuming a relative yield increase of 0.08 percent per unit ppm increase
in CO2 concentration. Simulations at country
scale (Supit et al., 2012) support those findings (Figure 9a-c). However, there are areas in
southern Spain (Iglesias and Minguez, 1997; Iglesias et al., 2011), France (Hermans et al.,
2010) and Italy (Tubiello et al., 2000; Farina et al., 2010; Ferrise et al., 2011) where elevated CO2 concentration cannot compensate for the yield reductions caused by CC (see Figure 8b, e, h). Projections for rainfed maize show higher variability and are more dependent on the CC scenario under consideration. Degree and spatial patterns of yield changes (Figure 9d-f) differ strongly according to choice of climate model and the resultant climate
projection. While the average yield projections
for rainfed maize, based on the output from
three different climate models, indicate either no significant change or yield reduction in most parts of western, central and eastern Europe, they
show increases in southern Europe (Figure 9d). Yield projections based on GCM mpi_echam5 are positive for southern and western Europe and for Poland (Figure 9e). On the other hand, projections based on GCM ipsl_cm4 (Figure 9h) turn sharply negative for nearly all of Europe, showing yield declines of more than 30 percent for Spain, France and southeastern Europe. Exceptions are Italy
and the United Kingdom, where yields are likely to increase by 10 to 20 percent. It is important to keep in mind that for mid-century projections, as presented in Figures 8 and 9, the effect of climate model uncertainty exceeds the uncertainty of emissions scenarios (SRES A1 and B1).
Effects of climate variables, CO2 and technology
A sharp increase in crop yields can be observed when also taking the effects of technical improvements into consideration (see Figure 7 and Figure 8c, f, i). According to a study on European wheat yields conducted by Ewert et al. (2005), which incorporates the effects of technology development, wheat yields (in EU15+2) are likely
to increase between 37 and 100 percent around 2050, depending on the scenario-specific pace of progress in agrotechnology development (Figure 7). Ewert et al. (2005) define the latter as comprising improvements in crop management (e.g. improved machinery, pesticides, knowledge of farmers)
and plant breeding. The results of Hermans et al. (2010) indicate that incorporation of technological progress clearly overrules the influence of all other factors (Figure 8c, f, i).
Finally, we present results from regional impact studies, to illustrate similarities and discrepancies in impact projections for some main commodities (Table 1).
The regional CC impact projections for wheat underline the general picture drawn for Europe: Higher yields are reported for regions in
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