Future climate impacts on carbon sequestration dynamics across urban ecosystem types in Finnish cities

Urban ecosystems have the potential to provide carbon (C) sequestration; however, the specifics of urban C sequestration and its behaviour under future climate change are poorly quantified. Here, we explore the C sequestration behaviour of five urban ecosystem types (lawn, mesic meadow, dry meadow, park and forest) and two irrigated types (irrigated park and lawn) in Finnish cities under climate change. Our focus was on the role of meteorological drivers and we wanted to understand how weather conditions influence regional differences in the C sequestration of the urban ecosystem types. We utilized the JSBACH model forced with simulated meteorological data between 2006 and 2100 from the CORDEX initiative, downscaled data from the CanESM2, MIROC5 and CNRM-CM5 climate models. The findings indicate that, overall, urban ecosystems with trees exhibit a higher net ecosystem production (NEP) and demonstrate more stable C sequestration in the face of future climate change. In contrast, different grassland systems are smaller C sinks and can become C sources under different climate projections. Irrigated versions of park and lawn had lower C sequestration than their non-irrigated counterparts through the simulation period. We found that changes in annual precipitation and incoming radiation were the predominant climatic drivers of NEP, while changes in temperature had a mixed or weak effect. These findings highlight the importance of long-term planning, management of urban ecosystems, and understanding of the trade-offs between various ecosystem types and services associated with these urban green spaces in future climates.