Study on the ecosystem services of urban forests: implications for climate change mitigation in the case of Adama City of Oromiya Regional Sate, Ethiopia

This study was conducted to explore the ecosystem services of urban forests in Adama city, central Ethiopia. Attempts were made to quantify the carbon storage and sequestration, air pollution removal and hydrological benefits of urban trees. The urban forest structure and composition of the city was surveyed and analyzed. The i-Tree Eco Model was employed to analyze the ecosystem services based on the current urban forests structure of the city. The result revealed that the urban trees of the Adama city stored a total of 116,000 tons of carbon. The tree species identified with higher CO2 sequestration per year were Melia azedarach (15%), Eucalyptusglobulus (8%), Carica papaya (7%), and Delonix regia (6%). In addition, 22%, 12%, 10% and 4% of carbon were stored by Eucalyptus globulus, Melia azedarach, Carica papaya and Delonix regia tree species respectively. Moreover, trees and shrubs species in the city removed about 188 thousand tons of air pollutants caused by O-3, CO, NO2, PM2.5 and SO2 per year. In Adama, 35% of the urban trees' volatile organic compaound emissions were from Eucalyptus cinerea and Eucalyptus globulus. The monetary value of Adama urban forest in terms of carbon storage, carbon sequestration, and pollution removal was estimated to 43,781, 3,121 yr(-1) and 320,915,596 USD yr(-1), respectively. It was concluded that significant quantity of CO2 and air pollutants were found being removed by the exotic tree and shrub species. However, every plant species found in the city does not mean ecologically important due their VOC emitting nature. Thus, the results of the study are valuable in increasing the awareness of the decision making bodies, the public and any stakeholders of the eco-benefits of urban trees in the mitigation of climate changes.