Highlights
- We developed a new index to measure the shade efficiency of urban trees.
- The shade efficiency of urban trees can be greatly reduced by shade from buildings.
- Other tree canopies also block or weaken a tree’s shade potential.
- Optimizing the layout of buildings and trees can enhance the shade potential of trees.
Abstract
Urban trees provide important cooling effects and lower the human health risks associated with UV radiation through shading. However, maximizing the shade potential of trees to improve the benefits to the health and sustainability of cities is not well studied. To explore whether optimizing the spatial pattern of buildings and trees could improve the shading capacity of trees, we sampled 65 neighborhoods in Beijing, China, and used ground-based light detecting and ranging (LiDAR) data and the solar radiation tool in ArcGIS™ to describe the shade pattern. We chose eight landscape metrics to quantify the landscape pattern of buildings and trees. We found that 56.4 % of potential tree shade in Beijing’s neighborhoods was lost to building shade, and we proposed a new concept of shade efficiency of trees (SET) to quantify this inhibition effect of buildings on trees. In addition, trees also weaken each other’s shade potential, as the shade provided by a unit area of trees declines sharply with increasing tree cover. Optimizing the spatial pattern of buildings and trees could ease those inhibition or weakening effects, and enhance the shading capacity of trees.
