Policy Impacts on Land Degradation: Evidence Revealed by Remote Sensing in Western Ordos, China

Abstract

This paper presents a multi-temporal monitoring and assessment of biomass dynamics in response to land cover change in Western Ordos, one of the most important dry areas in China, aiming to reveal the impacts of governmental land management policies on the biomass production of the rangeland ecosystem and on land degradation. Multi-temporal Landsat images (MSS 1978, 1979; TM 1987, 1989, 1991, 2006 and 2007; ETM+ 1999, 2001, 2002, 2004) were used in this research. An integrated processing algorithm, indicator differencing andthresholding and post-classification differencing, was applied to reveal the land biophysical change and rangeland degradation, and a relevant biomass estimation model was developed for the rangeland ecosystem based on other researchers' work. Meteorological data since the 1960s were incorporated in the analysis to avoid false signals of degradation, as could arise from normal climatic variability. The results show that to some extent land management policies have been instrumental in the protection and recovery of grasslands biomass production. On the other hand, in the non-controlled and weakly monitored zones land degradation, in the form of biomass loss due to desert extension, vegetation degradation, salinisation and water-table decline has continued. This could be attributed to a combination of both natural and human factors, such as lack of protection against strong winds, collective grazing in the permitted rotation areas and previously controlled zones, and over-pumping for agricultural and sand control activities. From this case study, it seems that the effectiveness and rationality of land use policy depend on whether it can coincide with the interests of the local people while conserving the environment. Where there is a conflict between economic viability and environmental sustainability, land degradation is inevitable.