Spatio-temporal changes in oases in the Heihe River Basin of China: 1963–2013

Artificial oases have flourished as human activities have intensified. Changes in oases in the Heihe River Basin are typical for the arid areas of China. Based on images from 14 separate periods during 1963–2013 that were compiled from multi-sensors, data on the boundaries of oases were extracted using the methods of object-oriented image segmentation and Normalized Difference Vegetation Index thresholds as well as visual interpretation. Based on extracted data, the spatio-temporal changes in oases were analyzed using models i.e. grid transformed model for rate of change. The drivers were analyzed based on data from Statistics Yearbooks and field surveys. The results show that from 1963 to 2013 sprawl dominated oasis evolution and occurred not only in the surroundings but also in interior patches. Oasis evolution patterns of “unchanged,” “expanding,” “shrinking” and “oscillating” were observed. The development exhibited three stages, the unstable (1963–1980), the steady development (1980–2002) and the rapid expansion (2002–2013), which correspond to the Planned Economy Period, the Commodity Economy Period and the Market-oriented Economy Period, respectively, in China. Oasis expansion was mainly determined by the human instincts for survival and for human well-being and was governed by population growth, agricultural policies and economic development.