Expansion of Irrigation Infrastructure

Irrigation was discussed above (Section 8.4.3) as a possible autonomous adaptation, but in many cases major public investments will be needed to provide farmers access to water. Some of these investments would undoubtedly happen even without climate change. For example, as part of its recent outlook assessment, the FAO projected changes in irrigated area for 93 developing countries notwithstanding climate change (Faures et al. 2002). Overall an additional 40 Mha in irrigated area was anticipated by 2030, an increase of 20% over 1997-1999 levels. An increase in the cropping intensity (number of crops per year) on these lands is also anticipated, which results in a 33% increase in the effective area of crops harvested from irrigated land. A regional breakdown of these projections (Table 8.2) shows that most of the expansion in absolute terms is expected in Asia, with Africa anticipated to remain with only roughly 2% of cropland area under irrigation.

The additional irrigated areas will reduce impacts of climate change relative to no expansion, and in that sense will represent an adaptation. But as with most other planned adaptations, these investments also accrue benefits in the current climate, and some level of investment would therefore occur even without concern for climate change. Partitioning out the additional investments needed or benefits occurring because of climate change can therefore be difficult. This is similar to the questions of additionality that plague funding of mitigation projects, and will certainly be a challenge for evaluating pledges of adaptation funding in the future.

Nonetheless, it is clear that only irrigation beyond this baseline amount can truly be considered an explicit response to the added pressures of climate change. What will such investments cost? A recent review of project costs by the African

Table 8.2 One study's projection of increases in irrigated area for developing countries, without adaptation to climate change (Faures et al. 2002)

Increase

Irrigated area in 1997-1999 Irrigated area in 2030 1999-2030

Table 8.2 One study's projection of increases in irrigated area for developing countries, without adaptation to climate change (Faures et al. 2002)

Increase

Irrigated area in 1997-1999 Irrigated area in 2030 1999-2030

As % of total

As % of total

Region

Mha

crop area

Mha

crop area

Mha

%

All developing countries

202

21

242

22

40

20

Sub-Saharan Africa

5.3

2

6.8

2

1.5

28

Near-East/North Africa

26

30

33

35

7

27

Latin America and

18

9

22

9

4

22

Carribbean

South Asia

81

39

95

44

14

17

East and Southeast Asia

71

31

85

36

14

20

Development Bank and the International Water Management Institute (Inocencio et al. 2007) puts the average cost of new irrigation projects at roughly $8,200/ha in developing countries, with higher costs in Sub-Saharan Africa ($14,500) relative to other regions (ranging from $3,400 in South Asia to $8,800 in the Middle East and North Africa). Much of this difference can be attributed to the smaller size of most irrigation projects in Africa, which increases per area costs.

Applying these costs to the expected rates of expansion in Table 8.2 yields a total cost of roughly $300 billion over the 30-year period. If doubling the anticipated rate is considered as a target for adaptation, then the cost would be roughly $10 billion per year. Doubling rates in Sub-Saharan Africa would cost roughly $650 million per year assuming past costs, although several strategies for cost reduction have been identified (Inocencio et al. 2007). These are of course extremely crude estimates, but they raise important questions about the opportunity costs of such investments, particularly given the dismal past performance of most large-scale irrigation projects in Africa (World Bank 2008). Potentially more cost-effective solutions include the rehabilitation of existing systems, investments in rainwater harvesting approaches (discussed in Section 8.4.3), and investments in smaller-scale irrigation systems for high-value crops.

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