Page 247 - Climate Change and Food Systems

chapter 7: grain rain production trends in russia, ukraine and kazakhstan in the context of climate change and international trade
figure 4
Climate change impacts on the factors limiting agriculture: growing degree days
base 10 ˚C (GDD) and Thornthwaite’s aridity index (Aridity), for the current (1970-2000) climate (A) and projections for the 2020s (B) and 2050s (C). The projections combine mean GDD and aridity computed for five CMIP-3 GCM projections under the
IPCC SRES A1FI scenario
by precipitation levels (322 mm for agricultural lands in Kazakhstan, 507 mm for the Russian Federation and 547 mm for Ukraine) than by temperatures (Figure 4A). Droughts regularly occur in this region (Table 6). Over the last three decades, the frequency of drought in the main agricultural regions of the Russian Federation has increased (Gruza et al., 1999; Spinoni et al., 2013). On these lands, a longer and warmer growing season may affect soil moisture, decreasing yields and leading to higher incidence of drought (Alcamo et al., 2007; Figure 4B, 4C). Limited land availability and soil fertility outside
of Chernozem areas (Stolbovoi and McCallum, 2002) make it highly unlikely that the shift of agriculture to the boreal forest zone will ever compensate for crop losses caused by increasing aridity in the current zone of intensive agriculture. Decreasing availability of soil moisture is especially important for the main grain-growing regions of the Russian Federation and Ukraine, which in
the past have been subjected to droughts every third year on average (Khomyakov et al., 2005). Without expansion of agricultural lands, increased temperatures combined with minor changes in precipitation, which are projected by the majority of GCMs for the steppe regions of the Russian Federation, Ukraine and Kazakhstan (Figure 4)
will lead to a 6-9 percent reduction in grain production on average (Alcamo et al., 2007).
These simulations do not take into account
any effects on yields from higher aerial CO2 concentrations. “Carbon fertilization” directly affects yields by increasing photosynthetic production (Smith et al., 2000). Higher CO2 concentrations may also indirectly affect yields
in water-deficit conditions by decreasing plants’ water requirements. Both direct and indirect effects are significantly more pronounced for C3 plants, such as wheat. The earlier laboratory studies demonstrated a very high carbon fertilization effect, with 19 to 31 percent increased wheat yield under a 550 ppm CO2 concentration (Long et al., 2006). On average, across several species and under unstressed conditions, recent data analyses find that, compared with current atmospheric CO2 concentrations, crop yields would increase at
550 ppm CO2, in the range of 10-20 percent for C3 crops and 0-10 percent for C4 crops (IPCC 2007). However, the results obtained for the Russian Federation with physically explicit models based on these data – e.g., by Sirotenko et al. (1997) – are likely to overestimate the related increase in global yields (Ainsworth, 2008). The Free Air-Enrichment Experiments (FACE) suggest that outside the highly artificial conditions of a
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