The Regional Impacts of Climate Change

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Six areas are most likely to be negatively affected by climate change: the area around the Great Wall lying southeast of the transition belt between crop agriculture and animal husbandry; the Huang-Hai Plains, where dryland crops like wheat, cotton, corn, and fruit trees are grown; the area north of Huaihe River-including east Shandong-that lies along the south edge of the temperate crop zone; the central and southern areas of Yunnan plateau; the middle and lower reaches of the Yangtze River; and the Loess plateau. Except for the Yunnan plateau, these areas would be at heightened risk of drought and would suffer potential increases in soil erosion. The Yunnan plateau, with generally abundant rainfall, would be subject to alternating drought and waterlogging, as well as to cold spells, and hence would also suffer yield losses (IPCC 1996, WG II, Section 13.6.3).

Studies for Japan indicate that the positive effects of CO₂ on rice yields generally would more than offset negative climatic effects in the central and northern areas. However, in southWest Japan, particularly in Kyushu, the effects on rice yields, on balance, would be negative (IPCC 1996, WG II, Section 13.6.3).

GISS-G1 and GFDL-A3 GCMs under 2xCO₂ equilibrium scenarios suggest that the production of spring wheat in Mongolia could be reduced significantly because of higher evapotranspiration. Adaptive measures-such as changing planting dates, using different varieties of spring wheat, or applying the ideal amount of nitrogen fertilizer at the optimum time-are potential responses that could modify these effects (Bayasgalan et al., 1996). Climate change is projected to have favorable impacts on agriculture in the northern areas of Siberia and to cause a general northward shift of crop zones. Grain production in the steppes of southWestern Siberia is projected to fall by about 20% as the result of a more arid climate. These projections could change substantially if market reforms succeed in improving the efficiency and productivity of agriculture (IPCC 1996, WG II, Section 13.6.5).

For mountain regions in China, climatic warming would, in general, increase agricultural productivity-partly as a result of reduced periods of low temperature and partly because of the expansion of arable lands. Studies using simple empirical indices show that a warming of 1�C in mean temperature in the mountain regions of southWest China would cause a 170-m shift in the upper boundary for growing grain. There is uncertainty, however, related to the expansion of crop areas because soil is a very important limiting factor for grain production. In addition, the specific crop varieties that are used in mountain agriculture may need to be altered to keep up with global warming. In Japan, for example, although current varieties of rice respond positively only to small temperature increments, late-maturing varieties are likely to adapt well under much warmer conditions. For such crop varieties, under a temperature rise of 3�C, most of the land below 500 m on Hokkaido and up to 600 m on Tohoku could become viable for agriculture (Yoshino et al., 1987).

Estimated net economic welfare impacts of climate change for three GCMs under 2xCO₂ equilibrium scenarios are shown in Table 10-8. According to the GFDL-A2 and UKMO-H3 GCMs, all countries/regions would experience negative impacts except the mainland of China. On the other hand, the GISS-G1 GCM estimated positive impacts for all countries except the Republic of Korea if no adaptation options were pursued. In China, climate change would occur against a steadily increasing demand for food, which is expected to continue through at least 2050. The increased annual cost of government investment only (excluding farmers' additional costs) in agriculture in response to climate change through 2050 was estimated at US$3.48 billion (17% of the cost of government investment in agriculture in 1990) (IPCC 1996, WG II, Section 13.6.3).