Landscape modification for ambient environmental improvement in central business districts - A case from Beijing

Hundreds of large central business district (CBD) developments are in planning or development in China and other developing countries. Poor environmental performance in these large projects is thought to result from a lack of understanding of basic engineering requirements, especially transport-related. Large energy demand and air pollution are the obvious consequences. While many studies have focused on functional, symbolic and aesthetic requirements of these developments, environmental engineering has in general been neglected. In this study, a typical large-scale planned CBD in Beijing was investigated just several years after its completion and occupancy. The current transportation requirements of the development were measured. It was found that the road traffic provision exceeded demand. Redesign of road infrastructure and urban greening were evaluated for their contribution to alleviating heat stress in summer, providing a comfortable walking and living environment. Reducing the under-used road infrastructure, without affecting the traffic flow, would allow more space for urban vegetation. In particular, the thermal environment for pedestrians in the whole area could be substantially improved through the redesign of ground-level space. Using ENVI-met microclimate fluid dynamic model to measure the impact of greater green landscape area, it was found that the median air temperature (T_a) could be reduced by as much as 0.5°C. The environmental advantages increase with time, as the tree canopies grow. In the micro-scaled simulation (300×600m), the T_a was reduced by 1°C. That is to say, urban summer T_a mitigation could be achieved if such effective modification schemes were expanded from the micro-scale urban community to the whole city. This research provides support for the use of urban landscape greening as a means to improve environmental conditions and energy demands in large-scale commercial urban development. Reducing redundant road infrastructure and improving the walking environment with urban greening could potentially suppress motorized traffic demand growth and contribute to a more sustainable urban environment.