Land degradation monitoring in West MuUs, China

This paper presents a study on land degradation monitoring focused in the west part of the MuUs Sandy Land in Ordos, one of the important dry areas in China, aiming to understand land degradation distribution in space and time and the role of anthropogenic action in such land surface processes at local level. Multi-temporal Landsat images (MSS 1978, 1979; TM 1987, 1989, 1991 and 2007; ETM+ 1999 and 2001) and SPOT images (HRVIR 2005 and HRG 2006) were used in this assessment. A combined processing algorithm: indicator differencing-and-thresholding and post-classification differencing was proposed. Meteorological data since 1960s were incorporated in the analysis to avoid the false alarm of the land degradation signal — change due to temporary fluctuation in climate. The results show that although local people and government agencies have undertaken widespread activities to combat desertification, for example, planting first herbs, shrubs and then trees in a network way in the degraded grassland, deserts and other sandy land in the study area, land degradation has still taken place, especially, in the non-controlled zones. Grassland patches in the marginal areas are being engulfed by deserts, which are extending mainly to southeast at an average rate of 11-21m/year; grassland degradation and reactivation of sand dunes caused by overgrazing and cultivation around water points/settlements and in the permitted rotation zones were also observed; and water-table has regionally declined due to over-pumping for agriculture, sand-control activity, and in particular, coal mining and oil and gas exploitation. Some aquifer has been locally destroyed due to land subsidence caused by unsustainable mining activity. For this case area, land degradation is produced by human activity, mainly overgrazing, land reclamation and overuse of the groundwater for agriculture and exploitation of oil, gas and coal mines, and intensified and extended by the general aridity of the area and dominant strong wind from northwest; the causes leading to land degradation in the recent three decades are multiple, but the underlying causes are culture and unreasonable land use policies. Under the “social capitalism system” there is indigenously the institutional deficiency with which the land property cannot be clearly defined. These factors exacerbate the negative impacts of policies and lead to land degradation. However, land degradation is not absolute and can be mitigated and even restored with the implementation of rational policies.