Assessment of net primary productivity in urban open green spaces using the CASA model under climate change scenarios: The case of Adana, Türkiye

Urban areas are major sources of carbon dioxide (CO₂) and other greenhouse gas emissions due to high population density, land-use transformation, and intensive human activities, whereas urban open green spaces support climate change mitigation through vegetation productivity and ecosystem services. This study assesses the spatial distribution of Net Primary Productivity (NPP) in urban open green spaces in the central districts and surrounding areas of Adana Province, Türkiye, and evaluates its potential changes under future climate scenarios projected for 2100. NPP was used as an indicator of ecosystem productivity and potential carbon uptake and was calculated using the Carnegie–Ames–Stanford Approach (CASA) model. Sentinel-2-derived Normalized Difference Vegetation Index (NDVI) and land-cover data for 2022 were used together with temperature, precipitation, and solar radiation inputs. For future projections, temperature and precipitation outputs from the HadGEM3-GC31-LL climate model within the Coupled Model Intercomparison Project Phase 6 (CMIP6) framework were incorporated under the Shared Socioeconomic Pathways (SSP) SSP2-4.5 and SSP5-8.5 scenarios. The resulting NPP raster datasets were integrated with urban open green space polygons in a GIS environment to calculate mean NPP values for urban green spaces and urban areas. In 2022, NPP ranged from 0 to 332 g C m⁻² yr⁻¹, while mean NPP was 61.18 g C m⁻² yr⁻¹ in urban open green spaces and 29.40 g C m⁻² yr⁻¹ in urban areas. By 2100, mean NPP in urban open green spaces decreased to 56.82 g C m⁻² yr⁻¹ under SSP2-4.5 and to 46.68 g C m⁻² yr⁻¹ under SSP5-8.5. These results indicate that high-emission climate conditions may substantially reduce ecosystem productivity and potential carbon uptake. Protecting high-productivity green spaces, increasing tree canopy cover, and strengthening ecological connectivity are therefore important for climate-resilient urban planning and maintaining ecosystem services in rapidly urbanizing areas.