Desert ecosystems in China: Past, present, and future

As the largest ecosystem of China, the desert ecosystem and the desertification-prone region (DPR) occupies 44% of China's land area. The past, present, and the future of China's desert ecosystems were reviewed. Following desert ecosystem classifications adopted by most scholars and the criteria of DPR determinations proposed by United Nations Convention to Combat Desertification (UNCCD), the total area of desert ecosystems in China are presently 2.08 × 106 km2, and total area of DPR is 2.13 × 106 km2. The desert ecosystem developed during the Quaternary period in most regions of northeastern China, but this area is not currently classified as this ecosystem. At present, the xeric shrub, sandy, gravel, saline-alkaline, clay-based, and alpine-cold desert ecosystems are found in China, and their areas are 6.34%, 27.49%, 26.99%, 6.88%, 19.98%, and 12.31%, respectively, of the total desert ecosystem area. There were no great variations in the areas of the gravel and alpine-cold desert ecosystems in China throughout the Quaternary period to the present because of the control exerted by long-term climate change and the Qinghai-Tibet Plateau uplift. Close relationships exist between xeric shrub and clayed-based ecosystem development and drought events. The formation and development of the saline-alkaline desert ecosystem has been mainly controlled by variations in groundwater levels and human activities such as irrigation and dam building. Among all of the desert sub-ecosystems, the sandy ecosystem appears to be more sensitive to climate change, and its area in the Holocene Optimum was only 60% of that in the Last Glacial Maximum. Over the past half-century, the development of the sandy desert ecosystem has been consistent with trends of aeolian activity, achieving its maximum area in the late 1980s, and then decreasing from that time to the present. Due to the influence of both climate change and human activities in China, some desert sub-ecosystems have evolved into other types of desert ecosystems. In addition, considering the impact of human activities on soil and vegetation in desert ecosystems, at present only 0.10–0.35% of China's desert ecosystem area is associated with human activities. Data provided by World Climate Research Programme (WCRP) Coupled Model Intercomparison Project (CMIP) (Phase 6) indicates that the area of desert ecosystems may decrease by 9.30%, 13.40%, and 17.30% in 2050, 2070, and 2100, respectively.