Town Socio-economic Status and Road Width Determine Street Tree Density and Diversity in Karachi, Pakistan

Abstract Despite being one of the largest and fastest growing cities of the world, little is known about the urban forest of Karachi. The city consists of eighteen towns. Each town has different socioeconomic status. Therefore, the present study investigates 1) the patterns and differences in the diversity and density of street tree communities across the towns of different socio-economic status, 2) the patterns and differences in the diversity and density of the communities of different road widths, 3) the factors that cause variation in different attributes of the community. The study revealed significant variation in the diversity and density of the tree community of different towns and road categories. The socioeconomic status of towns and different road categories demonstrated statistically significant influence in determining their tree density and species diversity. Statistically significant correlation was found between socioeconomic status and tree density per thousand inhabitants of towns. The study divulges recurring planting of one or few species that decrease the species diversity in many towns and streets. Conocarpus erectus revealed strong dominance on wide and medium width roads while it demonstrated co-dominance with Azadirachta indica on narrow roads. Overall, 62 species (30 native and 32 exotic) were recorded, which were very unevenly distributed in the streetscape of the city. The study also discusses the socioeconomic factors and role of civic agencies in planting trees.