City heat linked to bird diversity declines


A study in China has found that the heat-retaining buildings and paved surfaces of cities are linked to a loss in bird diversity.

The research, conducted by scientists at Zhejiang University and the Cornell Lab of Ornithology and published in Science of the Total Environment, looked at 336 cities in China and found a direct link between heat-retaining features and a lack of avian diversity. The authors of the paper also suggest that it is likely that the patterns documented in the study are occurring in other large cities across the globe that have abundant asphalt, steel, and concrete with little green vegetation.

"The heat-retention characteristic of cities is a well-known phenomenon called the urban heat island effect," said Frank La Sorte at the Cornell Lab. "Our findings document, for the first time, the direct relationship between bird diversity and the urban heat island effect across multiple seasons.

"The heat island effect is not unique to Chinese cities and it is likely that the patterns documented in this study are occurring in other large cities across the globe that have abundant asphalt, steel, and concrete with little green vegetation."

Tree Sparrow is a common species in many Chinese cities (Ian Dickey).

Study authors said birds move to cooler suburban areas, decreasing diversity in the city during the breeding and non-breeding seasons, but the trend is especially strong during the non-breeding season. Lower bird species diversity also persists regardless of the city's size or where it's located.

The study authors used data from an ongoing bird diversity study in China. Then they determined the surface urban heat island intensity for each city compared to its suburbs. The impact of the urban island effect was documented after controlling for each city's unique environmental and ecological setting. Scientists expected their models to show an increase in diversity during the nonbreeding season and a decrease in diversity during the breeding season. However, diversity loss was even more pronounced during the nonbreeding season.

The urban heat island effect on bird diversity remained consistently negative during both the breeding and non-breeding seasons in the southern, northern, and north-western regions of China. Results for the Qinghai-Tibet Plateau region were quite different, however, with the heat island effect having a positive relationship with the number of species. The scientists suggest that adaptations to the alpine environment may have increased tolerance to extreme temperatures, enabling local birds to thrive in the region's urban environments.



Cai, Z, Chen, Y, La Sorte, F A, & Wu, J. 2023. The surface urban heat island effect decreases bird diversity in Chinese cities. Science of The Total Environment. DOI: https://doi.org/10.1016/j.scitotenv.2023.166200

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