# The Contributions of Climate and Human Activities to Water Use Efficiency in China's Drylands
## 5 Conclusions  
This study represents the first comprehensive temporal and spatial analysis of the impacts of climate change and human activities on WUE in China's drylands, revealing how these factors collectively influence GPP and ET. The interactions among WUE, GPP, and ET are illustrated in Figure 9. Through an exhaustive analysis of data from 2001 to 2020, we found a significant increasing trend in GPP across China's drylands, while WUE demonstrated fluctuating declines. The interannual variability in WUE was primarily attributed to the dual influences of climate change and human activities, with Solra and Prec identified as key climatic drivers. Human activities, especially in the eastern regions, significantly contributed to the reduction in WUE, while geomorphological and soil conditions were the main factors affecting spatial variability in WUE. Our research underscores the need to pay attention to the potential risk of vegetation degradation against the backdrop of global warming and increasing humidity in drylands, particularly in the Tibetan Plateau. Continuous monitoring and research into the dynamics of WUE in China's drylands are thus crucial. Our findings highlight the delicate balance between ecosystem productivity and water usage, emphasizing the need for ongoing research and monitoring efforts to effectively address environmental challenges in these regions.  
Future studies should focus on the interaction between WUE and GPP and its long-term impact on ecosystem health. This is vital for optimizing future ecological engineering projects in China's drylands. This study not only provides new insights into understanding and managing the water resources and ecosystems of China's drylands but also offers a reference for the ecological restoration and sustainable management of similar arid regions globally.  
**Author Contributions:** Methodology, K.T.; Investigation, K.T.; Writing--original draft, K.T.; Writing--review & editing, J.G., L.H., Q.J. and L.W.; Funding acquisition, J.G. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the the Development Program of the Ningxia Hui Autonomous Region [2023 BEG02049], the National Key Research and Development Program [2022 YFF1300404], Development Program of the Ningxia Hui Autonomous Region [2021 BEG02005].  
**Data Availability Statement:** Publicly available datasets were analyzed in this study. This data can be found here: [[[https://lpdaac.usgs.gov/](https://lpdaac.usgs.gov/)]([https://lpdaac.usgs.gov/](https://lpdaac.usgs.gov/)), [[https://www.ecmwf.int/](https://www.ecmwf.int/)]([https://www.ecmwf.int/](https://www.ecmwf.int/)), [[https://zenodo.org/](https://zenodo.org/)]([https://zenodo.org/](https://zenodo.org/)), [[https://www.resdc.cn/](https://www.resdc.cn/)]([https://www.resdc.cn/](https://www.resdc.cn/)), [[https://www.gscloud.cn](https://www.gscloud.cn)]([https://www.gscloud.cn](https://www.gscloud.cn))].  
**Acknowledgments:** The authors are grateful to the anonymous reviewers for their constructive comments that helped us improve this manuscript.  
**Conflicts of Interest:** The authors declare no conflict of interest.