What Is Urban Biodiversity and Why Is It Important?
Cities are living ecosystems. Discover how the variety of life within them provides crucial benefits for the environment and our health, and how we can nurture it.
Urban biodiversity is the variety of life found within cities and other human-dense settlements. This includes the full spectrum of organisms and encompasses not just the number of species, but also their genetic diversity and the variety of habitats they occupy. These habitats range from remnants of original landscapes, like forest patches, to newly created green spaces such as parks and gardens. The concept recognizes that cities are not devoid of nature but are complex ecosystems at the intersection of the natural and constructed worlds.
The Importance of Life in the City
The living organisms within a city provide environmental services that make urban areas more habitable. Vegetation improves air quality by absorbing pollutants and producing oxygen, while green spaces help manage water. Permeable soils and plant roots soak up rainwater, which filters the water and reduces stormwater runoff, easing the burden on drainage systems and preventing flooding.
Urban nature also has a significant effect on local climate. Cities often experience a “heat island” effect, where temperatures are higher than in surrounding rural areas due to heat-absorbing pavement and buildings. Parks, street trees, and other green areas counteract this by providing shade and releasing water vapor through evapotranspiration, a process that lowers air temperatures.
Beyond these environmental functions, urban biodiversity offers benefits for human well-being. Access to green spaces encourages physical activity and contributes to better physical health. Spending time in natural environments can also improve mental health by reducing stress. The presence of nature in cities provides educational and recreational opportunities, from bird watching to learning about insects in a community garden.
Urban Habitats and Their Inhabitants
Nature in the city is found in a wide array of habitats, from large, planned areas to small, unexpected niches. The most recognizable urban habitats are intentionally cultivated areas like public parks, community gardens, and green roofs. These spaces can support a diverse array of life, including pollinators like bees and butterflies.
Accidental habitats also emerge in urban landscapes. Industrial brownfields, or abandoned commercial sites, can develop into unique ecosystems, hosting resilient plant and insect species. Even small spaces, such as cracks in a sidewalk or the surface of a brick wall, can become microhabitats for mosses, lichens, and hardy plants.
Many animal species have successfully adapted to city living. Some, like the raccoon and the eastern gray squirrel, are opportunistic, thriving on resources provided by human populations. Cities also host predators that have learned to navigate the built environment. Peregrine falcons use skyscrapers as nesting cliffs, while coyotes have become adept at moving through suburban and semi-urban areas.
Designing Cities for Nature
Urban planning and design can intentionally integrate nature into the fabric of a city by creating a network of functional green spaces. One strategy is developing green infrastructure, which includes elements like green roofs and living walls integrated directly into buildings. These features provide habitat for wildlife while also improving building insulation and managing stormwater.
Creating connections between green spaces is another design strategy. Wildlife corridors, which are continuous stretches of vegetation, allow animals to move safely between fragmented habitats like parks and nature reserves. These corridors can be as simple as a line of street trees or as complex as a vegetated land bridge built over a highway.
City governments contribute through policy and preservation efforts, such as protecting remnant ecosystems like native forests or wetlands from new construction. Some municipalities have enacted policies that require or encourage using native plant species in public landscaping. These plants are well-suited to the local climate and provide food and shelter for native insects and birds, helping to rebuild local food webs.
Fostering Biodiversity at Home
Individual actions can collectively contribute to a city’s ecosystem. Private yards, balconies, and even window boxes can be managed to support local wildlife. Planting native species is effective, as these plants are adapted to the regional climate and have co-evolved with local animals that depend on them for food and shelter.
Providing for the basic needs of wildlife can make a small space more hospitable. This includes offering a source of water, such as a bird bath or a shallow dish with pebbles for insects. Avoiding chemical pesticides is also beneficial, as these products can harm not only the target pests but also beneficial insects like pollinators and the birds that feed on them.
Residents can also become actively involved in monitoring and protecting local nature through citizen science. Many organizations run projects that rely on volunteers to collect data on local species, such as annual bird counts or butterfly surveys. This information helps scientists track the health of urban wildlife populations and provides data for conservation planning.