Cities are no longer the wildlife ‘deserts’ scientists once feared

Some species, such as peregrine falcons, have higher survival rates or better breeding success in cities than in rural areas. Some even prefer cityscapes. A Analysis 2017 out of 529 bird species worldwide, 66 were found only in urban areas, including not only classic urban birds like wild pigeons, but also a variety of species native to their regions, such as the Burrowing Owl and black and red finches. According to another meet again, diverse communities of native bee species persist in cities around the world, and in several cases more diverse and abundant native bee populations live in cities than in neighboring rural landscapes. In Australia, researchers recently identified 39 endangered “last chance” species that survive only in small patches of urban habitat, including trees, shrubs, a turtle, a snail and even orchids.

For centuries, urbanization has resulted in the massive elimination and fragmentation of natural vegetation. After the initial assault, a complex mosaic of new habitats composed of native, non-native and invasive plants emerged, dominated by buildings, roads and other impervious surfaces and contaminated with pollution.

Urban ecologists see them as a series of “filters” that make it difficult for many species to persist in cities, especially those with specific habitat needs. Myla Aronson, an urban ecologist at Rutgers University, pointed out, for example, that so-called ericaceous plants such as blueberries and rhododendrons, which require acidic soils, have disappeared from cities. A probable cause, she said, is that concrete has increased the alkalinity of urban environments.

As urbanization continues to pose a significant threat to species and ecosystems, cities are teeming with a “wonderfully diverse” array of unconventional habitats “which may provide important habitat or resources for native biodiversity.” wrote University of Melbourne scientists in 2018 article Conservation biology. These range from remnants of native ecosystems such as forests, wetlands and grasslands, to traditional urban green spaces such as parks, backyards and cemeteries, as well as golf courses, urban farms. and community gardens. Additionally, as cities invest in green infrastructure to mitigate environmental damage, wildlife increasingly occupies new niches, including green roofs and man-made wetlands, and colonizes old brownfields and wasteland. . And the positive roles that cities play in promoting biodiversity “can be enhanced by intentional design,” write the authors of the Biosciences article on the “fallacy of biological deserts”.

In recent years, urban ecologists have carved out a new niche for themselves in the field of conservation biology. A seminal article, published in 2014, analyzed 110 cities in a range of biogeographic regions with complete inventories of resident plant life and 54 with complete bird lists. According to to study, cities have retained most of their native biodiversity. However, Aronson, the lead author of the article, and his colleagues also found that plants and birds in the cities studied had become much less abundant, losing 75% and 92% of their pre-urban density, respectively.

Another foundation paper of Urban Conservation Biology, published two years later, was written by Australian scientists who discovered that cities are home to 30 percent of the country’s endangered plants and animals, including Carnaby’s black cockatoo, a large Gregarious cockatoo that lives only in southwest Australia, where large-scale agriculture has fragmented much of its habitat. In fact, they found that cities contained significantly more endangered species per square kilometer than non-urban areas. “Australian cities are important for the conservation of endangered species,” they wrote.

Scientists have describe several ways in which urban areas can benefit regional biodiversity. For example, cities can provide refuge from pressures such as competition or predation that native species face in the surrounding landscape. Higher prey density in cities has been linked to the success of several urban raptors, including Cooper’s Falcons, Peregrine Falcons, Northern Goshawks, and Mississippi Kites. The towns also serve as stopover sites where migrating birds can rest and refuel. Large urban parks, such as Highbanks Park in Columbus, Ohio, provide critical staging habitat for thrushes, warblers, and other migratory songbirds.

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