Human activities challenge carbon storage in the Yangtze River Delta, China

Under the increasing disturbance of human activities, the Yangtze River Delta (YRD) region of China is experiencing a large loss of natural vegetation, progressively transforming it into an emerging ecologically fragile region. To achieve human-environment synergies, monitoring the spatiotemporal changes of ecological environment and examining their anthropogenic mechanisms are critical, which is nevertheless largely limited in the YRD region until now. In this study, we track spatiotemporal patterns of net primary productivity (NPP) dynamics and evaluate the influences of human activity-dominated land cover changes in the YRD region based on remotely sensed data. We find that overall, the region showing a significant increasing trend in NPP occupies a substantial proportion of the YRD region (43.6 %), while significant decreases are observed only in limited proportions (4.6 %). Using the optimal model selection method to identify the relative importance of climate and human activity, we find that the effect of land cover change, as an anthropogenic factor, cannot be ignored, despite precipitation and minimum temperature being the dominant explanatory factors. Among several land cover changes, we find that the major change is the urbanization in the YRD region, and it generally causes NPP decreases. In addition, we also find that NPP increases happening on the cropland and forest expansion may conceal the loss of ecologically-beneficial natural vegetation. Our comprehensive assessment suggests the urgent needs on natural vegetation conservation in the YRD region to achieve the co-benefits of ecosystem functions and carbon storage.