An evaluation of the ecosystem services provided by urban trees: The role of Krasiński Gardens in air quality and human health in Warsaw (Poland)

Trees remove air pollution by the interception of particulate matter on plant surfaces and the absorption of gaseous pollutants through leaf stomata. However, to date, we have rather few empirical studies on the magnitude and value of the effects of trees on air quality and human health, especially especially within the climatic conditions of Central Europe. To investigate the significance of urban trees from the point of view of air pollution removal, an i-Tree Eco model was implemented. The results indicate that the 932 trees in Krasiński Gardens (Warsaw, Poland) absorb 267.12 kg of pollutants per year: 149.9 kg of O₃, 94.4 kg of NO₂, 11.8 kg of SO₂ and 10.9 kg of PM_2.5. That makes an average removal per tree (calculated by summarizing the values of all of the pollutants) of 0.287 kg/year. Furthermore, health values were used to estimate their pollution removal services in monetary terms. The total benefit of air purification by trees in Krasiński Gardens is estimated at 26250 PLN/year with an average value per tree of: 28 PLN. Although PM_2.5 removal is the lowest among the four air pollutants analysed, accounting for only 4% of the total mass reduction, it provides 69% of the total economic value. The benefit associated with absorption of O₃ provided 28% of the value, with the absorption of NO₂ and SO₂ at just 3%. The results also show that large tree species (with a crown diameter of 14-15m) can provide around 10 times higher benefits, than small ones (5-6m).