Increasing vegetation cover masks ecological degradation during urban expansion

Abstract Urban vegetation cover is widely used as an indicator of environmental condition, yet vegetation gains may not necessarily reflect improvements in ecological functionality. Urban expansion can simultaneously alter connectivity, hydrological processes, landscape structure, and the spatial organization of anthropogenic pressure, generating ecological degradation that remains undetected by land-cover metrics alone. Here, we investigated long-term ecological transformation in São José dos Campos, southeastern Brazil, using remote sensing, spatial statistics, and spatial regression analyses to reconstruct land-cover trajectories, fragmentation patterns, hydrological functionality, connectivity dynamics, and urban-conversion pathways between 1985 and 2024. To integrate these dimensions, we developed a spatially explicit Natural Capital Index (NCI-BR) that combines vegetation integrity, vegetation condition, hydrological regulation, fragmentation resistance, connectivity persistence, and anthropogenic pressure into a unified framework for assessing ecological functionality in urban landscapes. Native vegetation increased at the municipal scale during the study period, yet fragmentation, ecological disconnection, hydrological alteration, and anthropogenic pressure remained strongly concentrated along urban-expansion fronts and peri-urban transition zones. The results revealed a persistent territorial asymmetry, with preserved and connected ecological corridors contrasting sharply with fragmented and highly urbanized landscapes. Spatial regression analyses further showed that urban expansion behaved as a spatially dependent process propagating preferentially through previously transformed anthropogenic corridors. Rather than relying on vegetation extent alone, the proposed framework reveals how ecological functionality is reorganized into spatially coherent territorial gradients during long-term urban expansion, providing a more comprehensive basis for evaluating urban natural capital and ecological resilience.