Urban Heat Dilemma: Why Birds Abandon Cities and How To Attract Them Back

Urbanization is one of the main drivers of global environmental change, affecting not only human well-being, but also biodiversity and ecosystem services.

One of the most noticeable effects of urbanization is the urban heat island (UHI) effect, which is the phenomenon of higher temperatures in urban areas compared to surrounding rural areas.

The UHI effect can have negative impacts on human health, air quality, energy consumption, and water availability.

But how does it affect the diversity and distribution of birds, which are important indicators of ecological health and provide many benefits to humans, such as pollination, pest control, and recreation?

How urban heat affects bird diversity

(Photo : LUIS ROBAYO/AFP via Getty Images)

A new study by researchers from Zhejiang University and the Cornell Lab of Ornithology has addressed this question by analyzing data from 336 cities across China.

The study, published in the journal Global Change Biology, used citizen science data from eBird, a global online platform where birdwatchers can report their observations of birds.

The study also used satellite imagery and climate data to measure the UHI intensity and other environmental variables in each city, and also identified which bird species are most sensitive or tolerant to urban heat, based on their traits and phylogenetic relationships. 

The results showed that urban heat reduces bird diversity by up to 15%, depending on the city and season.

For example, birds that are small-bodied, insectivorous, migratory, or belong to certain families, such as woodpeckers, nuthatches, and chickadees, are more sensitive than birds that are large-bodied, omnivorous, resident, or belong to other families, such as pigeons, starlings, and sparrows.

The study also found that urban heat affects bird diversity differently across regions and seasons.

For instance, urban heat has a stronger negative effect on bird diversity in North America than in Europe or Australia, and in summer than in winter.

According to the study, urban heat reduces bird diversity by altering the availability and quality of food and habitat resources for birds.

For example, urban heat can reduce insect abundance and diversity, which affects insectivorous birds. It can also increase water stress and evapotranspiration, which affects vegetation structure and composition, which in turn affects bird habitat suitability.

Furthermore, urban heat can increase the risk of heat stress and mortality for birds, especially during extreme heat events.

Also Read: Solutions to Urban Heat Differ Between Tropical and Drier Climes

How to protect urban birds from heat

The study provided practical recommendations for urban planners and managers who want to protect urban birds from heat.

The researchers suggested that the best way to mitigate the UHI effect is to increase the amount and quality of green spaces in cities, such as parks, gardens, green roofs, and street trees.

These green spaces can provide cooling benefits for both humans and birds by shading surfaces, reducing albedo (reflectivity), increasing evapotranspiration, and creating microclimates.

They can also provide food and habitat resources for birds by supporting native plants and insects.

Other strategies to reduce urban heat have also been suggested, such as increasing the albedo of roofs and pavements with light-colored or reflective materials; installing cool roofs or pavements that reflect or emit solar radiation; increasing the ventilation and air circulation in buildings; using renewable energy sources such as solar panels or wind turbines; and reducing greenhouse gas emissions from transportation and industry.

The researchers also emphasizesd the importance of involving citizens in urban bird conservation efforts, as they can contribute valuable data and observations through platforms like eBird.

Educating citizens about the value and beauty of urban birds can also increase their awareness and appreciation of these animals.

By implementing these strategies, it is possible to reduce urban heat and its negative impacts on bird diversity.

Related article: Heatwaves This Summer Are Worsening Due to Urban Heat Island Effect