China’s panda habitat is increasing, but is still smaller today than it was when the species was first listed as endangered. Binbin Li

Panda habitats are smaller than they were when the bears were first declared to be endangered almost 30 years ago, meaning the animals are still at risk even as conservation efforts have increased their numbers.

Although pandas are now considered slightly more stable, with their classification from the International Union for Conservation of Nature moving from endangered to vulnerable as their adult population increased, their habitat could have a significant influence on the species. In many cases where animals have gone extinct in the past, human encroachment on habitat has played a role in a species’ downfall. According to an article in the journal Nature Ecology & Evolution, data show that “panda habitat covered less area and was more fragmented in 2013, the most recent year for which data is available, than in 1988 when the species was listed as endangered.”

“The extent and connectivity of a species’ habitat is also a major factor in determining its risk of extinction,” Stuart L. Pimm explained in a statement from Duke University.

The scientists who worked on the habitat analysis found that it has been increasing, although a small amount — less than a half of 1 percent between 2001 and 2013. But that came after a period of decline; the habitat had decreased almost 5 percent between 1976 and 2001, according to the article.

“Habitat recovery has not offset previous habitat loss,” the paper says.

But the overall habitat size is not the entire picture — there is a difference between a continuous habitat and one that is fragmented. Between 1976 and 2001, the average “patch size” of the panda habitat went down by almost a quarter, and increased less than 2 percent between 2001 and 2013.

As a result, both the sizes of the entire panda habitat and the average habitat patch are lower now than they were when the panda was first listed as endangered in 1988.

“The conservation status of the iconic giant panda is a barometer of global conservation efforts,” according to the article. “Our results show a more complicated picture that warns against complacency.”

The scientists wrote that commercial logging, which continued until 1999, has been the biggest driver of panda habitat loss, with other factors like expanding infrastructure in China playing additional roles. For example, more roads were built and pandas tend to stay away from them, which reduces the area where they can roam.

On the other side of things, establishing nature reserves has been the biggest driver of habitat preservation.

“Currently, pandas are facing great threats and challenges from habitat fragmentation, population isolation, infrastructure development, tourism, and climate change,” the researchers wrote. “Additional measures could contribute to the long-term survival of the panda and prevent having to upgrade its conservation status to ‘endangered’ again.”

Among those suggested measures are making mandatory preservation of certain habitat areas and corridors — the land that connects isolated panda populations to one another — and potentially having state control of certain areas to prevent “human disturbance” and deforestation. The authors also recommend building road tunnels over surface roads where possible.

“Banning commercial logging in natural forests, establishing nature reserves and helping residents in the reserve change behaviors that damaged habitat has been beneficial,” Michigan State University’s Jianguo Liu, an article co-author, said in the Duke statement. “But conservation is a dynamic process with humans and nature in a constant push and pull to survive and thrive, so new solutions always are in demand.”