Assessing environmental benefits of urban forests and associated economic values of carbon dioxide reduction in te Mohafazat of Beirut

Abstract

An urban forest is a forest or a collection of trees that grow within a city, town or a suburb. Urban forests have many benefits and values for the urban environment and for people. These include among others; filtering the air, regulating surface water runoff, reducing urban heat island effects, providing humans with recreational zones, creating habitats for various animal species and regulating the climate. Quantifying the environment and the economic benefits of urban forests is expected to provide incentives for planners and decision-makers to conserve existing urban trees and boost their extent. Accordingly, the aim of this work was to investigate the environmental and economic benefits of urban forests in Lebanon. The specific objectives were to 1) map the land-cover/land-use of the Mohafazat of Beirut, 2) quantify the current environmental (i.e., removal rate of air pollutants) and direct economic (social cost of CO2 removed) benefits of existing tree cover, 3) develop scenarios for urban tree cover increase and assess resulting environmental and economic benefits in the Mohafazat Beirut, and 4) investigate the most appropriate tree species for use in urban setting. In this work, the vegetation cover of the Mohafazat of Beirut was initially mapped using satellite remote sensing data (i.e.., the use of Normalized Difference Vegetation Index of SENTINEL-2A image). More specifically, the tree cover was estimated for a baseline year (i.e., 2000) and target year (i.e., 2018) by sampling landcover/land-use using random points generated over high resolution satellite images. i-tree application was employed in the sampling process. Consequently, environmental benefits (i.e., air pollutants removal) and economic benefits (i.e., social price of CO2 removed) were calculated for the years 2000 and 2018. Different future scenarios of environmental and economic benefits of urban forests were developed. In this context, vacant lots in the Mohafazat of Beirut were mapped using very high spatial resolution satellite imagery to assess possibilities of expanding urban forests. Finally, a list of tree species for use in future plantation activities in urban settings was developed. Overall, this study is expected to shed light on the value of tree covers in urban settings, mainly in the Mohafazat of Beirut, in attempt to influence policy developers and decision-makers in undertaking necessary measures not only in order to protect the existing vegetation cover within cities but also to intensify it.