An Assessment of Ecosystem Services Provided by Street Trees in Bangkok, Thailand

This study focuses on the analysis of ecosystem services provided by green spaces in Bangkok, Thailand, as a potential tool to address urban and environmental problems there. The analyses are divided into two parts for achieving two objectives, 1) estimating the magnitude of ecosystem services provided by public street trees, and 2) examining the relationship between stable isotopic data of tree leaves and the environmental quality of Bangkok's streets. The findings could be used to identify tree management issues and tree species with high potential to mitigate environmental problems through enhancement of the ecosystem service provision. A combination of field inventories, interviews with related stakeholders, stable isotopic analyses, remote sensing, geographic information, and computational models were used in this dissertation.For objective 1, the results indicate that citywide public street trees can provide environmental services, including reducing about sixty-five tons of air pollutants per year; reducing 2.11 million m3 of storm water runoff per year; reducing 13,000 tons of CO2 per year; saving 8.29 million kWh of electricity per year; and storing 70,000 tons of carbon throughout the trees' lifetime. The total annual monetary benefit of these services is about $4.34 million. Interviews with public officials indicate that they have a moderate understanding of the ecosystem services provided by street trees. Major challenges in tree management are lack of personnel, conflicts with street vendors, sidewalk damage, and overhead wire problems. According to the opinions of street vendors, Bangkok Metropolitan Administration (BMA) should increase tree maintenance to reduce damage risks, and to improve tree health conditions.Regarding the objective 2, the findings from studying the relationship of stable isotopic compositions of nitrogen in tree leaves, and factors such as air quality parameters could be useful in tracing air pollution levels, as well as determining which tree species can absorb high amounts of air pollutants. Tree species recommendations based on the two objective findings are: for reduced planting spaces (minimum width 1.2m), trees in the genus Lagerstroemia are highly recommended. For medium and broad sidewalk plantings (minimum width 1.8m), yellow poinciana (Peltophorum pterocarpum) and tamarind (Tamarindus indica) are the recommended species