Cities can be part of the solution in sustaining species

Within the next 30 years, the global urban human population is projected to increase by 2.5 billion, which will accelerate urban spread. Much of this expansion is predicted in biodiversity hot spots -- areas rich with species that are at high risk for destruction due to human activity -- imperiling a wide variety of animals and plants, many of which are already threatened by extinction.

Urban land expansion is projected to result in up to 1.53 million square kilometers of new urbanized area, directly threatening 855 species, according to the findings of a study published in Proceedings of the National Academy of Sciences. The U.S. National Science Foundation-supported work is co-authored by Yale University scientists Karen Seto, Rohan Simkin and colleagues.

The study identified hotspot cities whose growth is predicted to have large impacts on species' habitats. Many of these cities are in equatorial regions where urban growth coincides with biodiverse habitats. The cities that pose the greatest threat are predominately located in the developing tropical regions of sub-Saharan Africa, South America, Mesoamerica and Southeast Asia.

Focusing efforts on minimizing impacts on habitats in these regions can help conserve species, the co-authors say.

The study relied on data from Yale's Map of Life -- species distribution data used to monitor, research and create policies that protect species worldwide. It also used a recently developed suite of land-use projections to assess future habitat loss from urban land expansion for more than 30,000 terrestrial species worldwide. The scientists found that urban land expansion is a significant driver of habitat loss for about one-third of these species.

The largest impacts are not from the world's largest cities, but from urban areas that host myriad endemic species and where rapid urban expansion can destroy habitats.