It’s well known that cities affect biodiversity by reducing the number and variety of species that live in urban habitats. But new research from the University of Washington shows that cities even cause organisms to undergo accelerated evolutionary changes and the potential impacts on the ecosystem are taking place not in the distant future – but now.
Marina Alberti, a professor of urban design and planning at the University of Washington, recently published a paper in which she argues that human-driven evolutionary changes could have serious implications for ecological as well as human well-being. And these changes are taking place now.
Humans in cities are causing organisms to undergo accelerated evolutionary changes “that have effects on ecosystem functions such as biodiversity, nutrient cycling, seed dispersal, detoxification, food production and ultimately on human health and well-being,” said Alberti.
Alberti systematically reviewed evidence of so-called human signatures – examples of human-caused trait changes – in fish, birds, mammals and plants, and their effects on ecosystem function. She cited shrinking salmon, earthworms with increased tolerance to metals, seeds of plants that disperse less effectively, a type of urban mouse that is a “critical host” for the ticks that carry Lyme disease, leading to spikes in human exposure to the illness, and European blackbirds that are becoming sedentary and have changed their migratory behaviour.
Urbanisation causes these changes in a variety of ways as it alters and breaks up natural vegetation patterns, increases the temperature in cities, and introduces toxic pollutants, noise and light. Human presence also changes the availability of food and water, which has a direct impact on the life cycle of many species.
While Alberti does not believe these evolutionary changes are leading to an ecological catastrophe, she insists that humans must become aware of the role we are playing: “We can drive urbanising ecosystems to collapse – or we can consciously steer them toward a resilient and sustainable future.”