China's fiercely protected giant panda had a smaller habitat in 2013 than when it was declared endangered more than 20 years earlier, researchers said Monday.

What living space they had was much more fragmented, and often in areas under threat from earthquakes, road construction, tourism or global warming, they wrote in the journal Nature Ecology & Evolution.

Last year, the International Union for the Conservation of Nature (IUCN) moved the giant panda from the "endangered" to the less-threatened "vulnerable" category on its species Red List.

But the iconic black-and-white bear is not out of the woods yet, according to the new study.

"We are not arguing with the IUCN assessment that the panda is less threatened now than in the past," study co-author Stuart Pimm of Duke University in Durham, North Carolina, told AFP.

"There is much good news about the panda -- its numbers are up, much more of its habitat is protected, deforestation has stopped," he said by email.

But "while there is some good news, there is also bad news: the panda habitat is much more fragmented than in the past and small fragments may not hold viable populations of pandas."

The panda's conservation status is a barometer of global conservation efforts, according to the study's authors.

The IUCN's assessment, they added, was based "solely" on population numbers, "while ignoring emerging threats".

"Our results show a more complicated picture that warns against complacency" in conservation efforts, the team wrote.

- High risk -

The researchers used satellite data collected over four decades to evaluate the giant panda habitat from 1976 to 2013.

Suitable panda living space decreased by nearly five percent until 2001, but increased by 0.4 percent from then to 2013, they found.

Initial losses have not been offset.

Compared with 1988, when the IUCN listed the panda as "rare" -- equivalent to "endangered" in a later update of the Red List categories -- its habitat in 2013 was 1.7 percent smaller, the authors said.

Commercial logging was the most harmful activity to panda habitat, the team said, but the creation of nature reserves "significantly" slowed the loss of living space.

The first reserves were created in the 1960s, and 67 were established by 2013.

Yet there are many remaining risks, including that giant pandas live in one of the most tectonically active regions of China.

"In the past, pandas had a much larger range across China, so while earthquakes are natural events, their impacts may now be disproportionately severe," the authors wrote.

Road construction is another driver of habitat loss and fragmentation, while tourism has increased throughout the panda's range.

And climate change risks altering the distribution of bamboo, the panda's main food source, the team said.

"The panda population is divided into 30 isolated groups across the six mountain regions comprising their range," they added. Of these, 18 groups had 10 or fewer individual animals.

"They face a high risk of local extinction".

The researchers argued for the expansion of nature reserves and the building of "corridors" to connect isolated populations.

source: AFP