亚洲精品无播放在线播放,精品国精品自拍自在线,免费国产污网站在线观看不要卡,97色欧美视频在线观看,久久精品本无码一本,国产精品高清视亚洲一区二区,全部无码特级毛片免费播放

Scientists are divided over whether to declare the Yangtze River's white-flag dolphin extinct after ending a 38-day search that found no trace of the animal.

 

Wang Ding, vice director of the hydrobiology institute of the Chinese Academy of Sciences and head of the research team, insisted it was still too early to say whether or not the dolphin, also known as baiji, is extinct, even though none were found along the 3,400-km expedition route.

 

"A species are only said to be extinct after human beings fail to find any in the wild for 50 years according to the standards of the International Union for the Conservation of Nature," Wang said.

 

"The expedition only covered the main section of the Yangtze River and the scientists only searched for the dolphins eight hours a day, which means some dolphins might have been missed," added Wang, who headed a 25-strong team of scientists from China, the United States, Britain, Japan, Germany and Switzerland.

 

But non-Chinese scientists were emphatic in their assessments.

 

August Pfluger, co-head of the expedition and chief of Swiss-based baiji.org, an environmental group dedicated to saving the dolphins, said, "We have to accept the fact that the baiji is extinct."

 

"I think we may never see the white-flag dolphin again," said Bob Pitman, a scientist with the National Oceanic and Atmospheric Administration of the United States who has observed more than 70 kinds of dolphins in the field.

 

The non-Chinese scientists also reached the general consensus that even if there were a few specimens of the rare fish left, the species' chances of survival were "virtually nil".

 

The white-flag dolphin, unique to China's Yangtze River, is listed as one of the 12 most endangered species in the world. Its population dropped to below 150 in the early 1990s from around 400 a decade earlier.

 

Before the search, scientists estimated there would be no more than 50 dolphins in the river, a prediction that appears wildly optimistic with hindsight.

 

If the white-flag dolphin is extinct, it will be the first cetacean to vanish as a result of human activity as it is on the top of food chain in Yangtze River and has no natural enemy, according to Wang.

 

The mammals share the river with ships, towboats and fishing vessels, as the Yangtze has developed into China's busiest waterway. The research team's monitoring results show that there are 12 vessels per km on the river.

 

"If the Yangtze River can not support the white-flag dolphin at present, maybe it can not support human beings in the future," Wang Ding said.

 

"We must learn a lesson from it," he added.

 

(Xinhua News Agency December 14, 2006)