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Three subregions in north China appear to be especially sensitive to climate change because of potential increases in the soil moisture deficit:
The state and farmers can take steps to adapt agricultural production to the unfavorable impacts of possible climate change. Such strategies include allowing the sown acreage of grain to stabilize at a level of 0.8-0.9 ha per capita to attain the production target; strengthening irrigation capacity as one of the most beneficial means of maintaining agricultural production in the face of unfavorable climate change; and transforming medium- or low-yield farmland into high-yield farmland. To maintain the productivity of cultivated land, it is necessary to popularize a more optimal fertilizer mix and adopt the technique of subsoil application according to actual changes in soil conditions. It also is necessary to use and extend technology for agricultural adaptability-such as using superior species of crops, improving standardized cultural techniques under climatic variation, using dryland farming techniques, and developing feed crops instead of grain crops.
Forests in northern China have been seriously depleted over the past few centuries. Despite recent reforestation efforts, the forested area in the region is only 11.8% of the total land cover, which is lower than the mean value for China. Under the influence of projected climate change, the distribution pattern of many important tree species would be affected. For example, the present forests of Pinus tabulaeformis, a key temperate species widely distributed in northern China, will be reduced an additional 9.4% under a 2xCO2 equilibrium climate (Guo, 1995).
For the southern coast of Shangdong, estimated sea-level rise by the years
2030, 2050, and 2100 would be 1.1, 5.7, and 40.2 cm, respectively and, for the
coast of Liaoning-Tianjin, 13.1, 22.5, and 69.0 cm, respectively (Du et al.,
1996). Construction of dikes and seawalls is likely to be the most common adaptation
strategy in these areas; this practice has been used there throughout history
to combat sea encroachment (ESD-CAS, 1994).
| The Old Huanghe (Yellow River) delta, the Changjiang (Yangtze River) delta, and the Zhujiang (Pearl River) delta are major areas of economic activity in China. The metropolises of Tianjin, Shanghai, and Guangzhou (Canton) are located within these three deltas, respectively. The three deltas are located in regions with tectonic subsidence rates of about 2-3 mm/yr, 1-2 mm/yr, and 1-2 mm/yr, respectively (although hilly lands in the Zhujiang delta have a tectonic uplifting rate of 1 mm/yr). The Old Huanghe delta and the Changjiang delta have experienced severe land subsidence problems in the past as a result of groundwater extraction. Recent efforts to mitigate this problem have been successful in reducing the subsidence rate. It is estimated that these rates can be controlled within the range of 6-10 mm/yr for the Old Huanghe delta and 3-5 mm/yr for the Changjiang delta. In the Zhujiang delta, natural progradation of the coast and active land reclamation activities have resulted in a 0.5-1 mm/yr sea-level rise in the distributaries in the estuarine area-the same order of magnitude as the projected value due to climate change. This rate is expected to continue for some time. In the next 50 years, therefore, the expected eustatic sea-level rise due to climate change will not be a major factor in relative sea-level rise for the Old Huanghe and Changjiang deltas, although it may be for the Zhujiang delta. |
Integrated vulnerability to climate change for northern China, including the
vulnerability of forests, is summarized in Table 10-10.
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