## 4 Discussion
From 2001 to 2015, the cultivated area in the Tarim River Basin (hyper-arid and arid zones) in southern Xinjiang increased by 51.6% (Table S5), where natural grassland was the primary source for farmland reclamation [43]. The increased cultivated land is mainly planted with high water consumption cotton. From 2001 to 2015, the cotton sown area increased by 2.6 times (Table S5). Decreasing natural land cover and increasing artificial land were also observed in the Aksu River Basin [71]. The increase in agricultural water use in this area significantly shifted the ecological water use [39; 71]. However, ecological water transfer projects, subject to certain limitations, could protect the survival of existing vegetation rather than facilitating the restoration of naturalvegetation effectively [68]. ET (\(p<0.05\)), GPP, and LAI presented a decreasing trend in the semi-arid zone that may be caused by the increasing trend of grazing intensity. Human activities contributed to more than 76% of the ecosystem changes. In the effective statistical area of this region based on grassland, grazing was the primary human activity. In recent decades, the grazing intensity has increased [16; 41]. Grassland degradation in Xinjiang due to overgrazing has become a common phenomenon [40; 41; 59], especially in the Ili River Valley, which has the most severe degradation of high-quality grassland [59]. From 2001 to 2015, the number of livestock in the Ili region (semi-arid zone) increased by 5.6% (Table S5). In many grazing areas, LAI decreased due to the consumption of grass by livestock. The reduction in plant transpiration leads to lower ET, which causes an evident decline in grassland productivity [40]. High-intensity grazing seriously inhibits grass growth, which reduces plant transpiration and promotes the production of surface runoff, resulting in a sharp decrease in ET [40]. Grazing at a high intensity can adversely affect grassland and possibly aggravate desertification process [64; 72]. The area of dry sub-humid and humid zones in Xinjiang accounts for only about 4% of the area of the entire Xinjiang region. Human activities, with a weakened effect on the ecosystem indicators, are still a dominant factor. Alpine meadow is the primary land cover type, and grassland degradation still affects sub-humid and humid zones. Xinjiang is a typical fragile and vulnerable ecological area [8; 26]. As the ecological environment in Xinjiang is very fragile, the frequency and intensity of sandstorms are increasing with the continuous expansion of the desert areas [72]. Human activities dominate the changes in the ecosystem process of Xinjiang (Figure 11). In hyper-arid and arid zones, LAI and GPP increased significantly, while ET also increased, indicating that the greening of vegetation comes at the cost of higher water consumption [16]. Given the limited water resources in this area, adjusting the structure of agricultural oasis, improving the water use efficiency, and developing water-saving and eco-agriculture are possible solutions [73; 74; 75]. For example, planting drought-resistant and salt-tolerant plants such as Chinese wolfberry (_Lycium barbarum_ L.) and sea buckthorn (_Hippocampae thannoides_ L.) can not only improve soil structure and facilitate wind break sand fixation but also increase farm income and achieve the sustainable development of oasis agriculture [74; 75]. The semi-arid zone climate has the most significant positive effect on LAI. As human activities have led to grassland degradation, we should pay attention to protecting natural vegetation and grassland. Protective measures, such as reducing livestock density and implementing fenced grazing, should be implemented in pastoral areas to mitigate the impact of grazing on grassland degradation [40; 41; 72]. In dry sub-humid and humid zones, the effect of human activities is relatively small due to the high altitude. However, we still need to pay attention to protecting natural vegetation.