Reader’s opinion|Sinks are also affected by other types of green areas and vegetation, and especially the soil’s ability to bind and store carbon.
Hanna Wesslin presented in his opinion piece (HS 8.8.)that Helsinki’s carbon sinks are mainly based on forests (97 percent), and other types of green areas are only of minor importance (3 percent). In his writing, he referred to a report in which yard areas and street trees had been ignored and only the growth of trees in park environments had been taken into account.
However, the carbon sinks of cities are not only focused on forests and tree growth, but the sinks are also affected by other types of green areas and vegetation, and especially the ability of the soil to bind and store carbon.
The multidisciplinary CO-Carbon project has produced information on the carbon sequestration of different types of vegetation in cities and utilized process-based models that take into account the variation of vegetation and the effect of surrounding conditions, such as temperature, on carbon sinks. According to these peer-reviewed calculations, 56 percent of carbon sequestration in Helsinki takes place in places other than forests, i.e. in parks, yards and street areas, which is clearly more than in Helsinki’s own calculations.
The differences in the evaluation of carbon sinks highlight the need to systematize and develop even more reliable calculation methods, so that the multiple benefits of urban nature can be comprehensively evaluated.
Leena Järvi
professor of urban meteorology, University of Helsinki
Liisa Kulmala
head of the carbon cycle group, Finnish Meteorological Institute
Ranja Hautamäki
professor of landscape architecture, Aalto University
The CO-Carbon project
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