Despite the Concrete, Cities Still Retain High Numbers of Native Birds and Plants
The concrete jungles that are the world's urban centers are, indeed, not the best environment for wildlife to thrive. But according to new research, cities do still retain high numbers of native species and are far from ecologically barren environments.
The results of the largest analysis to date on the effects of urbanization on bird and plant species worldwide revealed much more diversity than expected.
"We were able to build the largest database to date from the largest number of cities, more than 140 on every continent except Antarctica," said urban ecologist Paige Warren of the University of Massachusetts Amherst.
Warren and her collaborators, which included a 24-member research group at University of California Santa Barbara's National Center for Ecological Analysis and Synthesis (NCEAS), reported their findings in Proceedings of the Royal Society B.
The study is of scientific value because of its scope, Warren said, noting that's more global in scale than past studies, which have focused primarily on Europe and North America.
"For the first time, we were able to include cities in South America, in the tropics and in developing countries. This gives us more confidence in our generalizations about what is going on," she said.
"Looking at what drives the number of species found, we see that human factors are more influential than region or where the city is located, for example," Warren added. "Not surprisingly, greater proportions of intact vegetation in cities, as found in older cities, preserve plant species. These results highlight the importance of including remnant vegetation and restoring natural areas in the design of cities."
The value of urban green space is underscored by the study, at it not only contributes to plant diversity, but it also acts as a refuge for native species and migrating birds.
Data on birds was compiled by the working group in 54 cities around the world, and for plants in 110 cities.
On average, the majority of urban bird and plant species are native to the area, noting that cities in the study support 36 threatened bird populations and 65 threatened plant species.
However, cities are not metropolises for birds and plantlife; they supported 92 percent fewer bird species and 75 percent fewer native plant species than similar but undeveloped lands.
The most common city birds were the rock pigeon, house sparrow, starling and barn swallow, occurring in more than 80 percent of the cities included in the study. For plants, 11 species including annual meadow grass occur in more than 90 percent of cities, the researchers report.
"While urbanization has caused cities to lose large numbers of plants and animals, the good news is that cities still retain endemic native species, which opens the door for new policies on regional and global biodiversity conservation," said lead study author Myla F.J. Aronson of Rutgers University.