Since the beginning of the 21st century, the net primary productivity (NPP) of grassland in the Three-Rivers Headwaters (TRH) region has changed significantly. In this study, NPP was assessed by the Carnegie-Ames-Stanford approach (CASA) model in TRH from 2000 to 2019. The abrupt changes of NPP and meteorological factors were analyzed by cumulative departure, MK test, and Pettitt test. The contributions of meteorological and human factors to changes in grassland NPP were quantitatively assessed using the scenario simulation method. The obtained results showed that: (1) From 2000 to 2019, the NPP of grasslands increased from 135.72 to 141.16 gC/m⁻²a⁻¹. However, the overall growth trend was not significant, and the proportion of significant growth was only 31.45%; (2) An abrupt increase in meteorological factors occurred around 2005, while an abrupt increase in NPP occurred around 2008, which showed that 2008 was the year when human factors, such as ecological projects and policies, began to show a significant impact on the growth of NPP; and (3) The contribution of human factors to the abrupt increase in NPP was significantly greater than the contribution of meteorological factors. The contribution of human factors exceeded 70% in 93.68% of the studied area, reaching 98% in general, while the contribution of meteorological factors was less than 2%. Among them, the human contributions to the Yangtze River Source, the Yellow River Source, and the Lancang River Source all exceeded 95%. The negative effects of meteorological factors on the growth of NPP in the abovementioned three regions were as high as 47.35%, 48.66%, and 36.91%, respectively. Human factors have contributed greatly to the increase in NPP in most of the source areas of the Yellow River, the eastern part of Tanggulashan County, the southeastern part of Zhiduo County, and the western part of Zaduo County at the source of the Yangtze River.

Ecosystem service connectivity (ESC) is the spatial and functional links among and within ecosystems that support unimpeded service flows, and that could play an important role in ecosystem stability enhancement and regional land planning. Understanding the relationships between landscape patterns and ESC is crucial to achieving certain sustainable development goals, but it has not yet received an adequate amount of attention. Here, we evaluated the changes and connectivity of five key types of ecosystem services from 2000 to 2020 and analyzed the correlations and spatial aggregations between the ESCs and landscape metrics in the wetlands of the Yellow River Delta, China. Various research methods, such as the InVEST model, spatial autocorrelation analysis, Spearman’s correlation, and self-organizing map, were applied. The results showed that water yield, water purification, and habitat quality showed high connectivity, but the overall ESC declined along with the restoration of the wetland area. Meanwhile, the High-High ESC cluster of water yield, water purification, and habitat quality had similar spatial distribution patterns, and both were dominated by tidal flats. Moreover, the ESC and landscape metrics showed significant correlations and spatial heterogeneity, and a potential connectivity between water yield and habitat quality was also found. These findings can assist decision-makers in developing effective ecosystem management strategies and provide a reference for future research on ecosystem service connectivity.