Considerations on the impact of “source-sink” landscape pattern changes on urban thermal environment and cooling efficiency: a case study of Nanjing, China

The urban heat island effect caused by rapid urbanization has had a great impact on human health and ecological environment. The evolution of landscape patterns often affects regional thermal characteristics at the local scale. How to rationally allocate land cover types from the perspective of urban planning is a huge challenge. This paper takes Nanjing, a typical “stove city” in China, as an example to study the impact of landscape pattern changes on the urban thermal environment. Firstly, based on the “source” landscape “/sink” landscape identified by the “source-sink” landscape index, on this basis, the contributions of the “source-sink” landscape and its effects are calculated, and the temporal and spatial evolution laws are analyzed. Second, we study the cooling effect of different characteristic landscapes. The results show that the change of landscape pattern is closely related to the urban thermal environment, and the expansion of built-up areas is the main reason for the urban thermal environment. With the development of urbanization, the “source-sink” landscape structure in most districts and counties has aggravated the heat island effect, and the ratios of “sink” and “source” landscape contribution ratios with strong levels are concentrated in the suburban areas. The results of cooling efficiency research show that the cooling range of forest land is larger than that of water bodies. At the same time, we found that the cooling efficiency of the sink landscape is the highest when the area of the sink landscape is 0.18–0.9 hm 2 and the shape index is between 1 and 4. The research results can provide feasible and practical scientific suggestions for the planning and ecological construction of Nanjing.