Recent Research Shows Decline in Bird Species Diversity as Urban Temperatures Rise

A recent scientific study, published in the journal “Science of the Total Environment,” conducted by researchers from Cornell’s Lab of Ornithology and Zhejiang University, has unveiled a significant correlation between the urban heat island effect and the diversity of bird species in 336 Chinese cities. This effect is causing avian populations to migrate from urban centers to suburban areas.

The urban heat island effect occurs when urban environments become isolated “islands” of higher temperatures due to the scarcity of green vegetation and the abundance of heat-absorbing surfaces like asphalt, concrete, and steel, explained Frank La Sorte, a senior research associate at the Lab of Ornithology and one of the paper’s authors.

The study analyzed data from the breeding and non-breeding seasons of various bird species in 2001, 2011, and 2019. It observed a considerable decrease in bird species diversity in areas with higher heat island effects.

Surprisingly, the decline in species diversity was evident not only during the breeding season but also during the typically cooler non-breeding season. Researchers had initially expected the urban heat island effect to reduce bird diversity in cities during the summer breeding season while increasing it in the winter non-breeding season, making this finding unexpected.

Quantifying their results, the study indicated that for every one-degree Celsius increase in temperature between urban and suburban areas, there were, on average, 0.291 fewer bird species during the non-breeding season and 0.132 fewer species during the breeding season, as noted by La Sorte.

The expansion of urban areas, in terms of both size and population density, may have far-reaching consequences on bird diversity worldwide. As urban areas become hotter, birds face greater challenges in maintaining their normal body temperatures, leading to increased physiological stress. In the long term, this could result in declining bird populations, according to La Sorte.

While the study focused on China, a highly urbanized country, its findings are relevant to metropolitan areas globally that feature structures promoting heat absorption and retention.

“As global temperatures continue to rise, these effects are likely to intensify as urban temperatures increase,” added La Sorte.