A preliminary study of oasis evolution in the Tarim Basin, Xinjiang, China

The causes of oasis evolution in the Tarim Basin of north-west China are discussed. Climate change and human activities play different roles in oasis evolution on different temporal scales. The impacts of climate change on oasis evolution are macroscopic and continuous, while the influences of human activities are local and disconnected. The climate of the Tarim Basin, since the late Pleistocene, has tended towards hyper aridity. The existence of oases has depended entirely on the runoff from thawed glaciers and snow, as well as orographic rainfall. Climate change on a geological scale led to variation of runoff flowing into oases. The alteration of water resources caused by climate change, therefore, was the fatal factor for oasis evolution in the Tarim Basin. Climate change was still the principal factor influencing the oasis evolution during historic times although human activities increasingly impacted oasis evolution in the Tarim Basin with the development of the settled human populations. In historic times, the socio-economic prosperity of oases and their expansion occurred largely during warm periods, while desertification and the deterioration of natural resources in oases mainly occurred during cool periods. Continuous trends of aridity brought about the damage of some ancient states in the oases of the Tarim Basin. Changes in oasis environments in modern times are mainly influenced by human activities in the Tarim Basin. Population growth and improvement of socio-economic conditions lead to the rapid expansion of cultivated land with reclamation and evident shrinkage of native vegetation. Irrational reclamation of land and utilization of natural resources in oases by humans have had increasingly destructive effects on oasis environments in modern times.