Evaluating habitat isolation driven by future urban growth: A landscape connectivity perspective

Natural habitats in rapidly urbanizing regions face significant human disturbances due to urban development. However, the extent to which future urban growth will further isolate these habitats remains inadequately explored. To address this gap, we developed a comprehensive framework that integrates habitat isolation assessment with future urban growth models, using the Nanjing Metropolitan Area from 2020 to 2050 as a case study. We employed Morphological Spatial Pattern Analysis (MSPA) to delineate natural habitat patches and identified urban pixels causing isolation through an ecological network approach. The Isolation Effect Index (IEI) and the Isolation Degree Index (IDI) were used to quantify the isolation impacts of urban areas at the pixel scale and the degree of isolation for individual habitat patches. Utilizing the Patch-Generating Land Use Simulation (PLUS) model, we projected land use changes under five Shared Socioeconomic Pathways (SSPs) to analyze the dynamics of IEI and IDI from 2020 to 2050. Our findings reveal that urban pixels in the central area are hotspots for causing isolation, severely impacting surrounding natural habitats. Increases in habitat isolation are primarily driven by newly-added urban pixels, particularly from low expansion intensity, indicating that non-intensified urban expansion exacerbates habitat isolation. This study quantifies the habitat isolation caused by future urban growth, with the isolation mitigation strategies are both essential for understanding human impacts on natural habitats and improving ecological protection policies.