Dynamic changes in urban form and function affect Carbon Dioxide Fluxes in a Mediterranean city.

Global carbon dioxide (CO₂) concentrations continue to rise at an accelerating rate, prompting universal efforts to mitigate emissions. Urban areas play a significant role in this increase, as their substantial anthropogenic sources often surpass the capacity of natural sinks. Urban emissions vary in response to the need for the combustion of fossil fuels for building heating or cooling, vehicular traffic, and commercial/industrial activities. The emissions also vary spatially depending on urban land cover (LC) and land use (LU), generating particular emission patterns across the city. The surface exchange of CO₂ has been monitored since 2016 in the city center of Heraklion, Greece using the Eddy Covariance (EC) approach. During this period, two major incidents occurred that altered the transportation behavior of the residents and the LC/LU of the city center. In January 2018, the municipality of Heraklion imposed traffic regulations and started a long reconstruction project, close to the flux tower’s location. In addition, COVID-19 spread mitigation measures implemented by the Greek government in 2020, changed the commuting patterns of citizens. Results show a reduction in CO₂ emissions throughout these eight years likely caused by the shift in land use, vehicle traffic, and commuting patterns. The reduction amounts to ~ 35% when comparing the monthly medians of June 2017 and 2022. The period during the COVID-19 restrictions exhibits an even larger reduction, showing sudden drops in measured CO₂ fluxes.