Study: Growing cities threaten survival of more than 800 species

NEW HAVEN — A new Yale-led study predicts the next three decades of urban expansion will threaten the survival of more than 800 species and cause habitat loss for tens of thousands more.

By 2050, the planet could have up to 1.53 million square kilometers of urban land, according to an article about the study published in Proceedings of the National Academy of Sciences.

The growth most significantly would imperil biodiversity in the developing tropical regions of sub-Saharan Africa, South America, Mesoamerica and Southeast Asia, but projected city expansion in the American Northeast also would cause habitat loss for species such as the New England cottontail and the bog turtle.

By 2050, urban land could cover more than half of Connecticut, according to a map released by the researchers. The map, which illustrates projected urban growth around the globe, shows an almost continuous urban corridor between New York and Boston.

Karen Seto, a professor of geography and urbanization science at Yale School of the Environment, and Rohan Simkin, a Ph.D. student, two of the study’s co-authors, hope governments and other entities will use their work as a guide and urbanize in a way that protects biodiversity.

“There are these places where if cities grow they will actually impinge upon habitats,” said Seto.

Beatrix Potter might have been disappointed to learn the New England cottontail is projected to be among the mammal species most heavily impacted by urban expansion in the Northeast, according to the study.

The region’s only native rabbit species, the cottontail’s historic range already has decreased by about 86 percent, according to the Connecticut Department of Energy & Environmental Protection.

“In 2006, the U.S. Fish and Wildlife Service (USFWS) designated the New England cottontail as a candidate for threatened or endangered status due to the severe population decline and widespread habitat loss experienced since the 1960s,” the DEEP’s website says.

(Locals may mistake the New England cottontail for the eastern cottontail, which the DEEP says was introduced to the area in the 1800s and has become the dominant species. And, Beatrix Potter was the author of “The Tale of Peter Rabbit.”)

Growth in greater New York, an area encompassing much of Connecticut and New Jersey and part of Pennsylvania, could eliminate between 3 and 5.2 percent of the cottontail’s remaining habitat over the next 30 years, according to the study.

All told, the researchers predict the cottontail will lose 10 to 20 percent of its existing habitat by 2050, 90 percent due to urban expansion, according to Simkin, one of the study’s coauthors.

The critically-endangered bog turtle represents another critter whose plight may worsen as cities grow. With road mortality and illegal pet collection already threatening Connecticut’s turtle species, the bog turtle could lose more than 5 percent of its habitat to New York area urban expansion.

To evaluate which animals face habitat loss, the Yale researchers compared “data on where in the world you will find many, many thousands of species” with “data on where we expect cities to expand,” said Simkin.

They used information from the Map of Life, a web platform that assembles data on species distribution worldwide. Walter Jetz, director of the Yale Center for Biodiversity and Global Change, is the principal investigator for the Map of Life project and also a co-author on the urban expansion study.

Using three different socioeconomic scenarios, or “plausible alternative trends in the evolution of society and natural systems over the 21st century” which vary based on how humanity prioritizes sustainability and regulates land use, the study found urban land area is likely to double or triple by 2050, according to the PNAS article.

Those scenarios represent “business as usual,” said Seto, the YSE professor and another coauthor.

“If we do nothing and continue to develop the way we are, then the news is bad for habitat and species,” she said.

The study projects the Javan slow loris, a wide-eyed primate native to Indonesia, will lose up to 46 percent of its habitat. Urban growth would drive 28 percent of the loss.

Meanwhile, the pink-headed warbler, a Guatemalan bird species, could lose nearly a quarter of its habitat, half of that from urban expansion.

But Seto says not to despair.

“I think this is really a story of hope,” she said. “So many of the new cities of tomorrow have not been built.”