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280 | IAASTD Global Report

Figure 4-18. Land and water use today and in the future under different scenarios. Source: CA, 2007

Note: The dark gray bar represents the worst case scenario in which no productivity improvements occur in rainfed or irrigated agriculture. The 'rainfed scenario' assumes that most of future investments are targeted to upgrading rainfed agriculture. The medium-dark bar denotes the difference between optimistic and pessimistic yield assumptions and gives an indication of the risks involved in this scenario. The 'irrigation scenario' assumes a major drive in improvement of water productivity and expansion of irrigated areas. The 'trade scenario' assumes increased food trade from water abundant to water scarce areas. The 'Comprehensive Scenario' combines elements from all three scenarios depending on regional opportunities.

world has not been able to support its increasing popula­tion. The challenge is highly likely to persist towards 2050.
     At the global level, out of the total ice-free land area of 13.4 x 109 ha, only 4.9 x 109 ha are agricultural lands. The Food and Agriculture Organization Database (WRI, 1997; FAO, 2006c) has provided individual country assessments on quantity of arable land and other indicators for national and global assessments. Out of the agricultural lands, 3.2 x 109 ha are in developing countries, while 1.8 x 109 ha are in industrialized countries (FAO, 2003). Some (1.3 x 109 ha)

 

of this area has been classified as low productivity. About half of the potentially arable land is actually cultivated, while remaining lands are under permanent pastures, forests and woodland (Scherr, 1999). In the future, feeding an increasing population will remain a challenge, particularly as per capita land availability decreases and soil degradation continues.
     Population pressure and improper land use practices are expected to continue giving rise to soil degradation, mani­festing itself through processes such as erosion, desertifica­tion, salinization, fertility loss. Especially in regions with low

Table 4-12. Comparison of recent global water use forecasts.

Author

Projection period

Increase in rain-fed cereal production

Increase in irrigated yield

Increase in irrigated harvested area

Increase in cereal trade

Increase in agricultural water withdrawals

 

 

annual growth rate

annual growth rate

annual growth rate

annual growth rate

annual growth rate

Shiklomanov 2000

1995-2025

 

 

0.74%

 

0.68%

Seckleret al. 2000

1995-2025

0.19%

1.13%

0.95%

0.64%

0.56%

Rosegrant et al. 2002

1995-2025

1.14%

1.14%

0.36%

2.41%

 

Faures et al. 2002

1995-2030

1.10%

1.00%

0.95%

2.08%

0.43%

Alcamo et al. 2005

2000-2050

 

 

0.06%-0.18%

1.85%-2.44%

0.40%-1.22%

Fraiture et al. 2007

2000-2050

0.63%-1.03%

0.58%-1.15%

0%-0.56%

0.98%-2.01%

0.10%-0.90%

Source: adapted from CA, 2007.

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