Bird communities threatened by urbanization

A local ornithological expert conducted regular bird surveys over one year and recorded 126 bird species. Using remote sensing techniques, satellite pictures were processed to produce a map of different land-uses, from which urbanization intensity was measured based on the proportion of sealed surfaces and buildings in the landscape. The researchers analyzed how farmland bird communities changed along a gradient of urbanization using newly developed statistical analyses.

"We found that urban bird communities were impoverished subsets of rural communities, both in terms of species composition and the ecological functions they provide," says first author Gabriel Marcacci, PhD student in the Functional Agrobiodiversity group at the University of Göttingen. "Birds perform important roles in the environment, for instance controlling pests by eating insects, scavenging and removing carrion, or eating fruits and dispersing the seeds. But only bird species that are well adapted to urban environments such as pigeons or crows can thrive."

"The homogenization -- resulting from losing diversity through the exclusion of certain groups -- of farmland bird communities may disrupt important ecosystem functions and services in urban agroecosystems such as pest removal by insect-eating birds," explains Professor Catrin Westphal, head of the Functional Agrobiodiversity group. Urban communities were found to be more sensitive to species loss, endangering ecosystem resilience.

"Our study underscores urbanization as a serious threat to biological communities and ecosystem functioning that may affect food production systems," adds Professor Ingo Graß, head of the Department of Ecology of Tropical Agricultural Systems at the University of Hohenheim. Professor Teja Tscharntke concludes, "This concern is especially relevant for countries from the Global South where urban agriculture and ecosystem services play an increasingly important role for food security."