Anthropogenic Activities Drive the Spatiotemporal Changes of Wetland Area in Tianjin, China

Countries and regions worldwide face varying degrees of wetland degradation risks due to economic development and climate changes. As a coastal megacity and economic powerhouse in northern China, Tianjin once boasted abundant wetland resources but has experienced significant ecosystem alteration. This study systematically investigated spatiotemporal dynamics and driving force of Tianjin wetlands (1990‒2020) using multi-source remote sensing data and statistical models (Partial Least Squares Structural Equation Modeling, PLS-SEM; Geographically Weighted Regression, GWR). Key findings reveal: (1) A net wetland loss of 655.64 km² with alternating phases of wetland loss and recovery; (2) The roles of climatic and soil factors have undergone a fundamental shift—transitioning from positive facilitation to significant suppression (path coefficients: 0.495 to −0.414 and 0.018 to −0.104, respectively), whereas the negative driving effects of urbanization have persisted throughout and shown intensifying trends (path coefficients: −0.330 to −0.372). Furthermore, urbanization indirectly exacerbates wetland degradation through its impacts on soil composition and topographic patterns, collectively establishing it as the central determinant of wetland area dynamics; (3) Urbanization dominates the dynamic changes in Tianjin wetland area through three mechanisms: direct encroachment, indirect ecological disturbances, and spatial reconfiguration; (4) Within the urban development axis and belts demarcated by Tianjin’s Urban Master Plan, paddy fields and tidal flats wetlands have decreased by 70.82% and 99.33% respectively, with 43.11% and 64.88% of these wetlands respectively converted to built-up land. Conversely, three protected regions achieved a countervailing 21.84% wetland increase. These findings underscore anthropogenic urbanization processes and coupled ecological governance as the principal drivers of spatiotemporal wetland evolution. Our quantitative framework advances understanding of human-wetland interactions and provides a methodological basis for sustainable wetland management in rapidly urbanizing coastal regions globally.