Unraveling the impact of national strategy on urban blue-green space and growth dynamics: A spatiotemporal analysis in Beijing-Tianjin-Hebei (BTH) region

Urban blue-green spaces (UBGS) play a vital role in providing ecological services and enhancing human well-being in high-density cities. In this study, the spatiotemporal dynamics and drivers of UBGS in the Beijing-Tianjin-Hebei (BTH) region, a key economic and ecological hub in China, were examined using Landsat satellite data from 2010 to 2023 to analyze UBGS changes within urban areas. Subsequently, the relationship between UBGS changes and economic and population growth were assessed. Our results reveal a general increase in Urban Green Spaces (UGS) and Urban Blue Spaces (UBS) across BTH cities, with significant UGS quality improvements, especially in Beijing, Shijiazhuang, and Tianjin. Here, over 25% of the area experienced a significant increase in NDVI (Normalized Difference Vegetation Index) values, reflecting improved vegetation health. Landscape pattern analysis indicated UGS became more contiguous, with increased connectivity and structural integrity, as the aggregation index rose by 6.7% and the largest patch index by 239.2%. The BTH Coordinated Development strategy has helped reduce population pressures, supporting economic and environmental balance. Our findings offer valuable insights into sustainable urban development and UBGS conservation, relevant for urbanizing regions worldwide.