Linking neighborhood canopy coverage to city-scale biogenic CO2 uptake in Paris, France

Cities are major sources of anthropogenic carbon dioxide (CO₂) emissions. Reducing these emissions is not enough to make urban areas carbon neutral without biogenic sinks offsetting a portion of the remaining emissions. Urban vegetation provides a CO₂ sink that contributes to the net CO₂ balance of a city. CO₂ uptake of a neighborhood is strongly dependent on the number of trees, i.e. the canopy coverage. The current EU Nature Restoration Law recommends that each city should have a canopy coverage of 30% to get the multiple benefits of urban vegetation. However, this limit value is rarely reached at a neighborhood level, where most of the benefits take place.  

In this study, we utilized urban land surface model SUEWS (the Surface Urban Energy and Water balance Scheme) in greater Paris area, France, to examine the variability of biogenic CO₂ fluxes across the city with different canopy coverages. SUEWS simulates joint energy, water, and CO₂ exchanges on local neighborhood scale with meteorological forcing and vegetation-specific parameterizations. The study period was from March 2024 to June 2025, corresponding to the availability of eddy covariance (EC) measurements from an urban forest Vincennes located in eastern Paris, which were used to evaluate the model. The meteorological input was from ERA5 data. First, we tested the effect of choosing different sets of biogenic CO₂ parameters (Park trees, street trees, forest) for modelling CO₂ and heat fluxes. We then upscaled the results by modelling CO₂ in the greater Paris area with a 500 m x 500 m resolution. Results of CO₂ uptake were also compared to canopy coverage of the grids to see the effect of urban vegetation offsetting the CO₂ emissions on a neighborhood scale.