Cities in the tropics lose more bird species than at high latitudes, eBird data show

Researchers analyzed data on more than 10 thousand bird species and found that urbanization weakens the latitudinal biodiversity gradient, the pattern in which species numbers usually decline from the equator toward the poles, reports science.mail.ru science.mail.ruscience.mail.ruscience.mail.ruOpen source ↗. They compared urban and natural areas of one square kilometer at the same latitudes.

On average, cities held a third fewer bird species than natural areas. The difference depended strongly on region: in Singapore and Quito, urban areas had 42% fewer species than natural ones, while in Reykjavik and Fairbanks the gap was only 12%.

In the tropics, birds are more often adapted to narrow ecological conditions. When buildings and asphalt replace natural habitat, such specialized species disappear, and generalists such as crows and Canada geese take their place. Tropical communities therefore lose more species to urbanization.

The analysis used observations from millions of bird watchers on the eBird platform, which allowed urban, suburban and natural areas worldwide to be compared in fine detail.

Greener cities hold more bird species than less green settlements at the same latitude science.mail.ruscience.mail.ruscience.mail.ruOpen source ↗. The authors say the preservation of green space should be considered in urban planning.