When severe sandstorms swept Beijing at the beginning of this century, the importance of the land degradation issue was lifted to an unprecedented level since land degradation was seen as threatening the ‘national ecological security’. To stop the underlying ‘ecological crisis’, a large-scale ‘ecological construction’ programme was carried out. This thesis focuses on exploring ecological resettlement, a policy measure in the programme, in the pastoral context of western China. The aim is to understand environmentalisation through drawing out the politics of the formulation, implementation and effects of ecological resettlement at and across different scales. By combining insights from political ecology, environmental governance, migration, and pastoralism studies, with fieldwork, interviews, analysis of policy documents, and statistical analysis, this book provides a nuanced approach to exploring the human-environment relationship. The analysis exposes in a developmental context how the central state made grassland degradation governable, how and why the local state put emphasis more on short-term-effective solutions rather than on environmental sustainability, and how and why the pastoral households prioritised social, economic and cultural considerations over environmental concerns when making migration decisions. The study draws attention to the significant impact of ecological resettlement on Mongolian pastoralism. While further fragmented rangelands obstructed mobile pastoralism, new social arrangements enabled migrant households to remain involved with pastoralism.