The wild giant pandas living in the Piankou Nature Reserve -- the largest panda reserve in Mianyang, Sichuan Province -- are facing hunger this winter owing to the rare blossoming of the arrow bamboo and the dieback that follows.

Seventy percent of the bamboo, a primary component of the pandas' diet, withers and dies after blooming. It takes approximately 10 years for the new plants to mature.

The periodic mass flowering and subsequent dieback are unusual in the plant kingdom, but a natural phenomenon for bamboos of all types.

"So far, in the Piankou Nature Reserve alone, all the arrow bamboo growing at an altitude above 2,700 meters has blossomed," said Huang Lishuang, director of the reserve's administration department. "According to the latest observations, the blossom area is spreading down to the 2,500-meter level. Both areas are major sources of the pandas' food."

The blossom zone now covers 20-25 percent of the panda habitat.

Li Zuobin, chief of the Mianyang Municipal Bureau of Forestry's Wildlife Protection Section, said that wild pandas in Mianyang account for one-quarter of the total number in China. In addition to providing safe habitat, Piankou Reserve is a corridor between five different groups of pandas and is essential to preserving genetic diversity in the species.

"Actually, the worst impact on the pandas is the isolation of their living space." stressed Li.

Li said that the arrow bamboo was blossoming in several panda habitat areas in two of the neighboring counties as well.

In two surveys conducted earlier this year, the main panda activity area at Piankou was in the bamboo forest at an altitude of 2,600-3,200 meters. A recent check shows that most of the animals have moved to an area below 2,700 meters, with only a small group left alive at the higher elevations. However, it is believed that as the bamboo continues to die back this winter, all the pandas will be forced to continue moving to lower areas, and possibly even out of the reserve.

"If that happens, the likelihood of injury to the pandas will soar," predicted Huang Lishuang. Humans inhabit the areas adjoining the reserve at the 1,600-meter level, which means the pandas are exposed to diseases and accidental poisonings as well as reduced food availability.

Experts say they cannot yet predict accurately just how severely the bamboo dieback in such a large area will affect the panda population.

The provincial Forestry Bureau has been encouraging local residents to report any sightings of wild pandas, and bureau staff regularly conduct patrols and surveys. They have now increased the frequency of patrols from once a quarter to once a month, focusing on the areas around the flowering bamboo.

If a sick or injured panda is found, a rescue team is dispatched immediately. They will treat and release the animal if possible, but if its condition is serious the animal will be captured and sent to the Wolong Giant Panda Protection and Research Center or Chengdu Research Base of Giant Panda Breeding.

"So far, we have not found any pandas suffering from hunger or illness." Li said.

"The blossoming of the arrow bamboos will not lead to the extinction of the giant panda," said Zhang Hemin, director of the Wolong center. "This is a natural phenomenon."

Zhang explained that in the long run, this type of phenomenon strengthens the species. Although the Piankou pandas are accustomed to eating arrow bamboo, there are scores of other varieties that are edible. The stronger animals will be able to adapt or travel to new food sources, ultimately strengthening the genetic makeup of their descendants.

Bamboo diebacks occurred in the Wolong center in 1983 and in the Minshan Mountains in 1975. Many pandas were lost in the Minshan Mountain dieback because several varieties of bamboo flowered simultaneously, and also because many stands had been removed and replaced by crops.

However, very few pandas were lost at Wolong in the 1980s, as other varieties of bamboo were available and the animals simply altered their eating habits.

Bamboo accounts for about 99 percent of the giant panda's diet. The plant's nutritional content is low, so the panda must spend about 57 percent of its day feeding in order to meet its nutritional requirements. Under normal conditions, bamboo is plentiful but large fluctuations in their food supply make them vulnerable.

(China.org.cn; Shanghai Morning Post, translated by Li Shen, December 16, 2004)