Green in the City: Estimating the Ecosystem Services Provided by Urban and Peri-Urban Forests of Tbilisi Municipality, Georgia

Abstract

Green spaces play a significant role in providing essential natural services to cities. This study aims to estimate Tbilisi’s green cover and identify the surface cover classes, volumes, and values of ecosystem services. The study area embraces the territory of Tbilisi municipality in its legal/administrative boundaries, which is equal to 502 sq. km. We use the i-Tree Canopy program (v.7.1) to identify the surface cover classes and quantify and price the ecosystem services provided by Tbilisi’s urban and peri-urban forests. The analysis includes the identification and distribution of the surface classes of the territory of Tbilisi, which is presented as follows: grass/herbaceous (38.71% +/− 1.36%), various impervious surfaces (approx. 21.18%), soil/bare ground (8.61% +/− 0.78%), trees/shrubs (28.55% +/− 1.26%), and water (2.95% +/− 0.47) surfaces. Analysis revealed the volumes of the removal of atmospheric pollutants, the annual removal of atmospheric carbon, and the total carbon stock fixed in the trees and shrub vegetation and provided the monetary values, expressed in US Dollars rounded per sq. km, of stored and sequestered carbon and pollution removal on the studies territory. The results showed that the annual removal of air pollutants (CO, NO2, O3, SO2, PM2.5 and PM10) totals 1227 tons or 2.444 t/sq.km. The average annual carbon sequestration by trees and other vegetation is 43.72 thousand tons (87.09 t/sq.km), with an approximate value of 8.22 million USD. The trees are storing 1097.9 kilotons of carbon (2187.95 t/sq.km) with its CO2 equivalent of 4025 kilotons. The estimated value of this service equals 206.4 million USD. This type of analysis of surface covers and ecosystem services has been performed in Tbilisi for the first time. The study revealed the significant magnitude and the great potential of “green benefits” provided by the urban vegetation to the city. It gives additional arguments for better utilization of this knowledge for advanced planning of the urban green infrastructure of Tbilisi for strengthening its sustainable and resilient development.