Urban green space solutions in carbon neutral cities

Urban areas are major emitters of carbon dioxide into the atmosphere. Along with a growing concern of climate change, several cities worldwide are pursuing carbon neutrality by reducing their carbon emissions and aiming at maximizing the carbon sinks of their green space, i.e. vegetation and the soil beneath. However, it is still not know how effective these natural carbon sinks can actually be in different cities under the current and future climates. This is partly due the complex land use and microclimate present in urban areas. Particularly processes concerning urban soils are poorly understood.

CarboCity will answer to these needs by 1) quantifying carbon storages and flows in cities in different parts of the world, and 2) finding optimal practical planning solutions for maximising these storages in the future. Our cities under study (Helsinki, London, Minneapolis-Saint Paul, Beijing and São Paolo) are located in different climate regions, they have different vegetation types and manage their green areas differently. First, we will quantify the special characteristics of tree ecophysiology and decomposition of soil organic matter in urban green area and upscale these processes to a landscape-scale by combining traditional and new innovative methods from ground, air and space. In addition, we study for the first time the applicability of direct surface exchange observations of novel carbonyl sulphide (COS) in distinguishing the photosynthetic signal from the net exchange of carbon dioxide over mixed land use. We build the results into a general ecosystem-atmosphere exchange model and into an urban surface exchange model which is further developed and evaluated in this project to simulate the biogenic carbon exchange in heterogeneous microclimate and soil characteristics within a city.

The results of CarboCity provide us with detailed information on the processes and impact of urban green space in reducing carbon from the atmosphere, and means to maximize the natural carbon stocks in different cities. The results will directly benefit local stakeholders, urban planners and citizens by giving research-based knowledge about the effectiveness of different urban planning solutions in storing carbon from the atmosphere. The results support directly the carbon neutrality aims set by Finnish government as well as those of countries and cities around the world.