XINING - Every summer, Tibetan antelopes in China's remote northwest follow a certain pattern of migration that is key to the endangered species' survival.

Normally, around 30,000 pregnant gazelles migrate, some travel for thousands of miles, in June and July to the heart of Hoh Xil nature reserve on the eastern edge of Qinghai-Tibetan plateau to deliver calves.

Scientists have not been able to explain why the gazelles favor this place to give birth. But there are worrying signs that this pattern might change before they even have another calf -- due to climate change.

In recent months, melting glaciers and excessive rainfall caused several lakes in Hoh Xil to overflow, forming new rivers. Deep and wide river channels that scarred the grasslands prevented some pregnant antelopes from reaching their "comfort zones" for delivery this year, said Tseten, a senior official of the Hoh Xil nature reserve administration.

"Climate change has come too fast and is too big," Tseten said.

At Drolnai Lake, pregnant antelopes can not cross the newly-formed rivers to reach the southern bank of the lake, where many gazelles have gathered to deliver calves over the past few decades, said Zhao Xinlu, a nature reserve official in charge of the Drolnai area.

Around 3,000 antelopes that were stranded on their way to Dronlnai Lake, had to deliver their calves near Khuse Lake this year, even though the site had not previously been favored by pregnant antelopes, Zhao added.

Hoh Xil, dubbed "no man's land" for its remoteness, is home to 70,000 Tibetan antelopes. The plateau galleze was once near extinction due to rampant hunting of the animal for its fur and buckhorn. The illegal trade in antelope products was stemmed around 1999 amid intensified government crackdowns.

This time the threat comes from the nature, Tseten said.

The survival rate of Tibetan antelopes is already low at around 30 percent, he said, adding that the figure might plunge as more pregnant antelopes are forced to deliver in unfamiliar environments.

Zhao pointed to the snow-capped mountains afar for evidence.

"Look, about 15 years ago, these peaks were fully snow covered. But now, we only see snow on the tip of the mountains," he said.

Melting snow is the prime source of the lakes in Hol Kil region.

Researches have found with alarming results that glaciers are also melting fast on the Qinghai-Tibetan plateau.

Satellite pictures of the glaciers on the plateau show that most of them have shrunk over past decades, some for as much as 12.9 percent, said Cheng Haining, senior engineer with the Qinghai provincial surveying and mapping bureau.

He said about 5.3 percent, or 70 square kilometers, of the glaciers in the Yangtze headwaters in Qinghai had melted away over the past three decades. Two small glaciers had even disappeared.

"The melting is closely linked to the climate change," Chen said, adding that data collected by three meteorological stations over the past 50 years show a continued rise in the average temperature in the area.

Xiao Penghu, the natural reserve administration's deputy chief, said a melting glacier was like "a sword hanging over the heads of Tibetan antelopes."

He said the climate change now causes lakes to swell and rivers overflow but in the long run, after most glaciers melt away, the lakes and rivers will dry out -- a "disastrous" consequence for the ecology of the region.

"The fate of Tibetan antelopes are in our hands, because our actions set the pace of the global warming," said Tseten, calling for people around the world to unite to fight climate change.

"And in the long run, the fate of these gazelles are connected with the fate of human beings," he added. "Once the global warming wiped them out, we would eventually be wiped out as well."