Urbanisation is affecting the genetic makeup of species that are crucial to the ecosystem health and success, says a study.
The findings open new opportunities for advancing our understanding of the role of humans in Earth's evolution, said lead author Marina Alberti from University of Washington.
"By explicitly linking urban development to heritable traits that affect ecosystem function, we can begin to map the implications of human-induced trait changes for ecological and human well being," Alberti noted.
Rapid urbanisation poses new challenges for species, some of which will adapt or relocate while others go extinct, the researchers said.
With this study, they sought to learn whether signs of human-caused change could be detected across species in urban ecosystems worldwide, and to what extent humans and our cities and societies might be speeding up these changes.
They analysed 1,600 observations of phenotypic change — alterations to species' observable traits such as size, development or behaviour — across multiple regions and ecosystems worldwide.
They also assessed the relative impact of several human-caused "urban disturbances," including the acidification and pollution of lake habitats, the relocation of animals, heat and effluents associated with a power plant, long-term harvesting of certain medicinal plants — even the apparent effects of global warming on the reproductive patterns of birds.
"We found a clear urban signal of phenotypic change — and greater phenotypic change in urbanising systems compared to natural and non-urban anthropogenic, or human-created systems," Alberti said.
"The significance of these changes is that they affect the functioning of ecosystems," Alberti said.
"They may inhibit the ability of seeds to disperse, cause exposure to infectious diseases, or even change the migratory patterns of some species," Alberti noted.
The findings were published in the journal Proceedings of the National Academy of Sciences.