Since the mid-1800s, cities like Adelaide, New York City, and Rome have seen a significant decline in their native wildlife. Adelaide has lost over a quarter of its mammal diversity, New York City has lost nearly half of its native plants, and Rome has seen at least 25 species of butterflies disappear. Urban environments can be tough for wildlife, yet some plants and animals manage to not only survive but also thrive in these bustling settings.
Certain species are naturally equipped to handle city life. For example, English ivy and rock pigeons are adept at climbing and roosting on vertical structures like trees and cliffs, so they find brick walls and high ledges in cities to be perfect substitutes. Similarly, raccoons, which are omnivores, can exploit a wide variety of food sources. This adaptability allows them to live in cities at densities ten times higher than in their natural woodland habitats.
Some animals adapt to the stresses of urban living by changing their behavior. Coyotes, for instance, often become more nocturnal when they move into cities, reducing their chances of encountering humans. However, not all species can easily adjust to urban environments. Over time, genetic changes can help some populations evolve into urban specialists. A fascinating example is New York City’s white-footed mice. DNA sequencing shows that these urban mice have over 30 significant genetic differences compared to their rural relatives. These changes likely involve genes related to disease resistance and toxin processing, which help them survive in crowded urban settings.
We usually think of evolution as a slow process, but it can happen quickly when a significant challenge arises. A rare trait that helps individuals cope with new conditions can become widespread surprisingly fast, especially in species that reproduce quickly. For example, after factories released large amounts of toxic PCBs into the Hudson River in the mid-20th century, it took just six decades for 99 percent of the local tomcod fish to develop a mutation that protects them from the toxin. Similarly, in Montpelier, France, urban weeds have evolved to produce heavier seeds in less than 12 years, increasing their chances of taking root in soil rather than landing on concrete.
As urban and rural populations continue to diverge both genetically and geographically, there is a possibility that some could split into distinct groups. This doesn’t mean that cities are inherently good for biodiversity, but they aren’t entirely devoid of life either. Instead, cities act as unintentional laboratories where the limits of life’s adaptability are tested.
Choose a species that thrives in urban environments and research how it has adapted to city life. Create a presentation to share your findings with the class, focusing on the species’ natural suitability, adaptability, and any evolutionary changes it has undergone.
Visit a local urban area and observe the wildlife present. Take notes on the species you see and their behaviors. Write a report discussing how these species might be adapting to urban challenges and compare your observations with examples from the article.
Participate in a class debate on the impact of urbanization on biodiversity. Prepare arguments for both sides: one supporting the idea that cities can foster biodiversity through adaptation and evolution, and the other highlighting the negative impacts on native species.
Engage in a simulation activity that demonstrates rapid evolution. Use a computer program or a classroom activity to model how genetic traits can spread quickly in response to urban challenges, similar to the tomcod fish or urban weeds mentioned in the article.
Write a short story or essay imagining the future of urban wildlife. Consider how species might continue to evolve and adapt to city life, and what new challenges or opportunities they might face. Use examples from the article to inspire your narrative.
Since the mid-1800s, Adelaide’s mammal diversity has fallen by more than a quarter, New York City has lost nearly half of its native plants, and at least 25 species of butterflies have disappeared from Rome. Our urban environments can be challenging for wildlife, but some plants and animals manage to survive – and even thrive – in these settings. Certain species are naturally suited to city life. For example, English ivy and rock pigeons can climb and roost on vertical structures like trees and cliffs, making brick walls and high ledges suitable substitutes. Additionally, omnivorous raccoons take advantage of a wide variety of food sources, allowing them to live ten times more densely in cities than in woodland habitats.
Natural adaptability can also help animals cope with the stresses of urban living; for instance, coyotes that move into cities often become more nocturnal to reduce their encounters with humans. However, most species cannot easily adapt to an urban lifestyle. Over several generations, genetic changes can enable some populations to evolve into urban specialists. New York City’s white-footed mice are one example: DNA sequencing indicates that these urban mice have genetic differences from their rural counterparts in over 30 significant ways. While the exact effects of these changes are still being studied, they appear to involve genes related to disease resistance and toxin processing, traits that likely aid their survival in crowded environments.
We typically think of evolution as a slow process, so the idea of evolving quickly enough to keep pace with urbanization might seem daunting. However, when a significant challenge arises suddenly, a rare trait that helps individuals cope can become the genetic norm surprisingly quickly, especially in species with rapid reproduction rates. For instance, after factories released large amounts of toxic PCBs into the Hudson River in the mid-20th century, it took just six decades for 99 percent of the local tomcod to develop a protective mutation that prevents the toxin from entering their cells. Similarly, in Montpelier, France, urban weeds have begun producing a higher proportion of heavy seeds in fewer than 12 years, increasing their chances of establishing in nearby soil rather than landing on concrete.
As urban and rural populations diverge both genetically and geographically, there is a possibility that some could split into distinct groups. This does not imply that cities are beneficial for biodiversity, but they are not entirely devoid of life either; rather, they function as unintentional laboratories where the limits of life’s adaptability are tested.
Species – A group of organisms that can interbreed and produce fertile offspring. – The Galápagos Islands are home to many unique species that have evolved in isolation.
Wildlife – Animals and plants that grow independently of people, usually in natural conditions. – Conservation efforts are crucial to protect the diverse wildlife found in the Amazon rainforest.
Adaptability – The ability of an organism to adjust to different conditions or environments. – The adaptability of certain bacteria allows them to survive in extreme environments like hot springs.
Evolution – The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth. – Charles Darwin’s theory of evolution explains how species adapt over time through natural selection.
Urban – Relating to or characteristic of a city or town. – Urban development often leads to habitat fragmentation, affecting local wildlife populations.
Biodiversity – The variety of life in the world or in a particular habitat or ecosystem. – The coral reefs are known for their high biodiversity, hosting thousands of marine species.
Genetic – Relating to genes or heredity. – Genetic diversity within a population can increase its resilience to environmental changes.
Environments – The surroundings or conditions in which an organism lives or operates. – Different environments, such as deserts and rainforests, support distinct ecosystems and species.
Habitats – The natural home or environment of an animal, plant, or other organism. – Wetlands serve as critical habitats for many bird species during their migratory journeys.
Challenges – Difficulties or obstacles that need to be overcome. – Climate change presents significant challenges to the survival of polar bear populations.
