How does urbanization on a global scale affect relationships between species?

Writing / Irene Vega

The researchers in this study collected information on studies of trophic interactions (how some species feed on others) from more than 800 study sites around the world, with the aim of studying how urbanization influences interactions between species. In particular, they examined how insects feed on the leaves of more than 500 tree species (known as herbivory) and how insectivorous birds prey on insects in areas subject to different levels of urbanization.

The study reveals that, in regions close to the equator, birds hunt fewer caterpillars in cities than in natural areas. On the other hand, at higher latitudes, birds hunt more in urban areas than in rural areas. “This difference is related to temperature: cities are generally warmer than the countryside, and in high latitudes, this additional warmth allows some animals to survive cold winters that they would not normally survive,” he explains. Juan Antonio Hernández Agüero, doctor in Natural Resources Conservation from the Rey Juan Carlos University (URJC) and main author of the study.

Currently, Hernández Agüero is a member of the Institute for Environmental Studies (IVM) at the Vrije Universiteit in Amsterdam and, together with the rest of the authors, has linked these findings to environmental changes caused by urbanization. “In this sense, cities, with their elevated temperatures, can serve as models to study the effects of climate change, since they experience conditions similar to those projected for the future due to global warming,” he points out. Louis Cayuela, professor of Ecology at the URJC.

These results, published in the journal Global Ecology and Biogeography, could be key to anticipating how climate change will affect the relationships between herbivores and predators, with important consequences for pest control and agriculture.

Image: Periclista albida on an oak leaf in Amsterdam (Netherlands). Author: Velin Velichkov