Assessment of ecosystem services and perceived benefits of street trees : a case study of Coyoacan, Mexico City

Mexico City, one of the biggest and most polluted cities in the world, is facing a gradual disappearance of its green areas, especially the loss of street trees. In the current situation, street trees are subject to constant removal, poor management and vandalism, and few studies have been done about their role and effectiveness in air pollution removal and carbon sequestration. For this study, the ecosystem services of street trees were quantified using the software i-Tree Eco along with a social survey of how people perceived them. The study site is Coyoacan, one of the greenest districts in Mexico City, comprised of 95 neighbourhoods, of which 12 were sampled. A random stratified sample was carried out to estimate the number of street trees in Coyoacan and the number of street units (blocks) to be sampled in each of the 12 neighbourhoods, in order to reach a sample size of 500 trees. The surveys were performed following a pass-by method. In general street trees provide important quantities of ecosystem services at the district level; but the predominance of small trees produces lower ecosystem service values compared to other cities with similar populations. The situation can be improved if the survival and healthy growth of those small trees can be guaranteed through better management practices. At the neighbourhood level we encountered an uneven distribution in the number of street trees and in the proportion of large trees over small trees, affecting the quantity of ecosystem services which a neighbourhood receives. These findings suggest that to increase the provision of ecosystem services at a city or district level, resources should be directed at a local level, looking to provide equality in the distribution of ecosystem services among neighbourhoods rather than allocating resources through random tree plantations across the city. Finally, people show high appreciation for trees and knowledge about a wide range of benefits, suggesting a tree caring culture that can be strengthened through social involvement programs for the care and management of street trees.Forestry, Faculty ofGraduat