The average Australian city is home to 32 threatened species, according to a study recently published in the journal Global Ecology and Biogeography.

“The finding was surprising because we generally write off cities as ‘lost causes’ when it comes to conservation,” says Pia Lentini, a research fellow at the University of Melbourne’s School of Biosciences and a member of the study team. “We tend to imagine that threatened species are only found in far away national parks or remote areas.”

Not so, Lentini and her colleagues found. In fact their study, the first continent-scale analysis of threatened species and cities, suggests that urban areas are disproportionately rich in threatened species compared to non-urban areas.

The researchers compiled data on the distribution of Australia’s 1,643 land-dwelling threatened species, including 1,215 plants and 428 animals. They compared these maps to the locations of Australia’s 99 cities that have more than 10,000 residents.

They found that 503 threatened species, or 30 percent of the total, have distributions that overlap with urban areas. This includes 25 percent of listed plants and 46 percent of listed animals – species like the koala, grey-headed flying fox, swift parrot, Carnaby’s black cockatoo, green and gold bell frog, and lots of orchids.

Some species are heavily dependent on urban habitat, in fact. For 51 of the species, at least 30 percent of their range falls within urban areas. And eight threatened species, all plants, are entirely confined to cities. For example, the Nielsen Park she-oak is found only within metropolitan Sydney, and the fringed spider-orchid only in a rapidly developing part of Melbourne.

Each Australian city contains a different suite of threatened species. About half of the species, or 258, are found in only one city each. But all 99 of the cities are known or likely to be home to at least one threatened animal, and 88 of them are known or likely to harbor threatened plants. Sydney contains the most threatened species, with 124 found there.

Even more striking, the researchers found that acre for acre, urban areas contain more threatened species than do non-urban areas, leading them to dub cities “hotspots” for threatened species.

As an extra test of this finding, the researchers also created “dummy” cities equivalent in area and in the same bioregion as each of the 99 real cities. True cities contain more threatened species than dummy cities, they found.

In some ways this is no surprise. Cities tend to be located in areas of high biodiversity, because humans just like other living things know a promising patch of habitat when they see one. And once urbanization gets going, of course, it tends to put the squeeze on wild plants and animals.

But the findings also suggest that with a little more care and consideration cities could make a major contribution to conservation. Urban areas commonly contain patches of native habitat interspersed with development, after all. Moreover, landscapes planted and maintained by humans can help certain species through lean times of the year.

Even so, policymakers often consider urban habitat degraded and insignificant, the researchers note, and therefore permit development that further erodes habitat for threatened species, bit by little bit. So the assumption that cities don’t matter not only means missed opportunities for conservation, but paradoxically, could itself be a threat to endangered species survival. – Sarah DeWeerdt | January 5, 2016

Source: Ives C.D. et al. “Cities are hotspots for threatened species.” Global Ecology and Biogeography DOI: 10.1111/geb.12404

Header image: Carnaby’s black cockatoo (Calyptorhynchus latirostris), photographed in a suburb of Perth, Australia. The endangered bird relies on an introduced pine plantation in Perth for food. Credit: Ralph Green via Flickr.