Unravelling 25 years of urban green space change in a growing city: Linking NDVI-based urban green space dynamics to urbanization in Helsinki

Urban green spaces (UGSs) are facing increasing pressures from urbanization and rising urban populations, with these impacts varying across different regional contexts. Understanding local magnitudes, trajectories, and drivers of UGS dynamics therefore requires city-specific assessments. This study investigates changes in UGS cover and their associations with urban population dynamics, while also considering transformations in the built environment, in the city of Helsinki during 1999–2024. Multidecadal changes in UGS cover are detected using a Normalized Difference Vegetation Index (NDVI)-based classification and subsequently linked to urbanization processes using statistical and spatial methods. The findings indicate a slight overall decline in UGS cover between 1999 and 2024, which appears to be partly associated with population growth but more strongly linked to non-residential building development. In contrast, increases in residential building counts were found to be associated with UGS cover gains, indicating that greening measures are incorporated into new residential zones. However, UGS losses without pronounced population growth persist in areas of industrial and commercial development, as well as in small-scale infill development. Overall, the present study highlights how urbanization processes shape local UGS dynamics in growing cities at a fine spatial scale, thereby providing valuable insights for sustainable urban planning.