LEDD issues in cropland: China and Zhang Jiachong

Editor's note 30 Apr 2012: Text source D111.

In the last 15 years, land use in the source region of the Yangtze River has changed noticeably. This has resulted in a number of negative effects on the environment (Pan 2005), discussed below.

Soil and water loss

Soil loss area in the source region of the Yangtze River is 10.63×104km², which is 31.17 percent of the soil loss area in Qihai province. Within this figure, the anthropogenic soil and water loss area reaches 930 km². Serous soil loss causes the sediment loading to increase in the upper reaches of the Yangtze River. The mean sediment discharge per year in Qinghai reaches up to 1232×104 t. The average soil erosion loss is 650 t/km² per annum.

Land desertification

The area of land desertification in the source region of the Yangtze River is 3328.03 km², which is 84.58 percent of all land desertification in the upper reaches of the Yangtze River. The yearly rate of increase in desertification is more than 0.9 percent.

Degradation of wetlands

The middle dry plateau vegetation is a succession from swampy, wet meadow vegetation. The peat bog land has become dry and exposed. As a result, the function of maintaining the watershed has been reduced. In addition, due to the degeneration of wetland areas, the natural environment on which many living organisms depend is being lost and thus, poses a threat to biodiversity. Because wetlands are regarded as the land use type with the highest ecosystem services value, the loss of wetlands in the source region of the Yangtze River is a serious issue.

Loss of vegetation cover

The forage yield and vegetation cover of grassland has been reduced and as a result, the carrying capacity in terms of livestock has also been reduced. Following this, there is often an infestation of mice, which accelerates the process of grassland degeneration. As a result, degeneration of grassland significantly affects livestock production and this has an associated impact in restricting local economic development.

Decline in the availability of cropland

The land in the Yangtze River delta has experienced long-term development and utilisation by humans   (Peng and Gao 2004). The form and structure of land use has been continuously evolving. With recent rapid economic development, the degree of intensification of land use is increasing. Currently, land use in the Yangtze River delta faces the following issues:

• The area of available cultivated land has been reduced.
• The quality of the cultivated land has also been reduced.

The main reasons for this reduction are: (a) because the economy is developing so quickly in the delta, more construction land is needed; (b) local farmers change their land use in response to the need for income growth; (c) Some cultivated lands are used for eco-tourism and afforestation; (d) population increases but the area of cultivated land decreases. For example, the density of the population was 20 people/ha in 1985, but has risen to 26 people/ha in 2000. Three waste products (waste gas, waste water and industrial residue) have also increased significantly and have resulted in the pollution of cultivated lands. In addition, large amounts of chemical fertilizers and pesticides have been used so that soil quality is declining. For example, in 1982 around the Taihu Lake, nitrogen application rates per year amounted to 395kg/ha for cultivated land but rose to 520kg/ha in the 1990s. Other issues are low utilization efficiency of land for construction and irrational land use structures including the increase in cropland and the loss of forest and grassland.

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