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Risks, Impacts, and Adaptation Menus for Study Countries
Table 3.15 Uzbekistan: Effect of Climate Change on Crop Yield 2040–50 Relative to Current Yields under Medium Impact Scenario, No Irrigation Water Constraints % change Irrigated/Rainfed Irrigated
Rainfed
Crop
Desert and Steppe East
Desert and Steppe West
Highlands South
Piedmont zone East
Piedmont zone SW
Alfalfa
3
2
3
22
1
Apples
–8
–5
–9
–1
–8
Cotton
–6
–5
0
–2
–6
Potatoes
–6
–4
–7
2
–7
Tomatoes
–5
–6
0
–1
–7
Winter wheat
2
–2
–1
13
–4
Spring wheat
–10
–5
–13
5
–12
12
15
12
43
–1
Grassland
Note: Results are average changes in crop yield, assuming no adaptation and no irrigation water constraints and no effect of carbon dioxide fertilization, under medium impact scenario. Declines in yield are shown in shades of orange, with darkest representing biggest declines; increases are shaded green, with darkest representing the biggest increases.
Yields of apples, potatoes, and tomatoes are forecast to decline about 1–9 percent under the medium impact scenario. Grassland and alfalfa yields, on the other hand, are expected to show increased yields throughout Uzbekistan, grassland yields jumping by up to 43 percent, and alfalfa yields increasing 1–22 percent. Some adaptation issues might arise with regard to the relative viability of winter wheat, which may see lower yields in some areas where a winter freeze is less frequent, and also for spring wheat, which has a wider growing area but requires more irrigation and provides a different quality yield. Aggregate yield data for Uzbekistan are only available as an average for the two types; however, in general, yields for winter wheat are about 10 percent higher so a switch from winter to spring wheat would result in overall yield losses as well as an altered crop rotation. Yields could be reduced much more severely, however, under the high impact climate change scenario, which forecasts higher temperatures and lower precipitation and soil moisture in virtually all regions of Uzbekistan. Table 3.16 provides a summary of yield results for the high-impact scenario if no adaptation measures are taken, and illustrates that wheat (especially spring wheat) and apples in particular could suffer large yield losses in all three AEZs. As with the three other countries, water resource management implications of the high impact scenario are similarly severe because climate change both increases irrigation water demand and, in the high impact scenario, decreases overall water supply. For example, by 2040 forecast irrigation water demand during the summer months increases 25 percent in 2050 relative to historical conditions, while overall water availability declines by an average 30–40 percent, as illustrated in figure 3.8. This is especially critical in Uzbekistan because nearly all crops are irrigated and irrigation demand accounts for more than 90 percent of water withdrawals. The net effect of rising demands and falling supply is a Looking Beyond the Horizon • http://dx.doi.org/10.1596/978-0-8213-9768-8