Abstract:
Objective Vegetation is an important component of terrestrial ecosystems and a key regulator of the climate system. The Yangtze River Basin is an important economic center and key ecological zone in China. Its vegetation status is crucial to maintaining China’s ecological security and supporting regional coordinated development across the country. There is still a lack of comprehensive and consistent understanding of the spatial differences, driving factors, and relative contributions of vegetation coverage changes in the Yangtze River Basin. Researching the impact of climate change and human activities on the spatiotemporal changes in vegetation coverage in the Yangtze River Basin has important practical significance for developing ecological protection and restoration strategies for the Yangtze River Basin in accordance with local and temporal conditions, and for scientifically coordinating the synergistic relationship between natural restoration and artificial restoration.
Methods Based on long-term time series data on meteorology, normalized difference vegetation index (NDVI), and land use/cover, the spatiotemporal dynamics of vegetation coverage and influencing factors of NDVI in the Yangtze River Basin from 2000 to 2022 are studied using methods such as Sen’s Slope, Mann-Kendall significance test, partial correlation analysis, and the relative contributions of climate change and human activities to vegetation coverage changes are quantified using residual analysis.
Results From 2000 to 2022, the overall vegetation coverage in the Yangtze River Basin has been good, with an average NDVI value of 0.741. The NDVI in most regions is above 0.5, roughly showing a spatial distribution pattern of “high in the middle and low in the east and west”. Affected by factors such as climate change and human activities, the NDVI has a fluctuating upward trend, with a slope of 0.001,9/a, less than the national vegetation greenness increase rate of 0.002,4. The spatial distribution pattern shows the characteristic that “NDVI has increased significantly in most regions in the middle reaches, while decreased in the urbanized regions in the upper and lower reaches”. The areas of regions where climate change has a positive and negative effect on the change of NDVI in the Yangtze River Basin account for 78.33% and 21.67%, respectively. From a single factor perspective, the regions where rising temperature and increased precipitation have a positive effect on NDVI account for 68.42% and 71.89% of the total land area of the Yangtze River Basin, respectively. Overall, the center of the regions where precipitation and NDVI are significantly positively correlated has shifted westward relative to temperature. The contribution of human activities to the trend of NDVI changes in the Yangtze River Basin reaches 64.90%, while the contribution of climate factors to the trend of NDVI changes reaches 35.10%. Except for the region above Shigu in the Jinsha River, the Mintuo River, and the subarctic zone of the Qinghai − Tibet Plateau, the driving effect of human activities on NDVI is greater than that of climate change in most regions.
Conclusion In the implementation of future ecological projects, it is necessary to properly handle the relationship between natural restoration and artificial restoration. In regions of the Yangtze River Basin where ecological damage is relatively light and self-recovery capacity is relatively strong, we should actively adopt nature-based solutions and focus on natural restoration. We should strictly implement closed protection and expand the proportion of natural recovery regions. Human activities have both positive and negative effects on the trend of NDVI changes, with the area of regions with positive effect from human activities greater than that of regions with negative effect. In the future, in regions where the damaged ecosystem is difficult to rely on natural conditions for short-term recovery and where the water and heat conditions are good, we must focus on the coordinated improvement of the “ecological − economic − social” benefits and carry out ecological engineering construction sustainably. Moreover, the implementation of ecological projects must respect the zonal distribution laws of the natural environment, the laws of ecosystem succession, etc., adhere to the principles of quality first and stability first, and scientifically evaluate the planting suitability of regional zonal vegetation.