Another side effect of China's swift economic rise is poking its head from under the surface of the Yangtze river.

While air pollution from cities like Beijing has spread across international borders and into headlines, the plight of one of the Yangtze River's inhabitants has been less visible.

The population of the Yangtze finless porpoise in the world's third largest waterway has declined rapidly over the last eight years, from 1800 to around 1200.

To put that in perspective: the population in the wild of that other cute and cuddly icon of conservation - the giant panda - has risen to 1600.

After extensive breeding efforts, it's believed that number has risen even further.

Chinese environmentalists are hoping they can give the so-called "river pig" the same chance as the giant panda, and save it from the fate of another Yangtze native which was declared functionally extinct in 2006 - the Baiji dolphin.

Dr Li Lifeng is head of the World Wide Fund for Nature's freshwater program and he says throughout history the porpoise was a common sight in the river.

"The local fisherman, when they paddled out for fishing, they could easily find two or three porpoises following their boats," Dr Li said.

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"Now it's not common in the central Yangtze."

Human impact

Dr Li says there are a number of factors contributing to the porpoise's decline.

Habitat loss, overfishing, congestion on the river and low water levels are combining to cause them serious harm.

He says the Three Gorges Dam is also having an indirect effect by changing the flow patterns and water temperature of the river.

Overfishing has taken away so much of the porpoises' food source that researchers have found starved dead bodies of the aquatic mammals in the river.

It's estimated between 50,000 and 70,000 fisherman exploit the Yangtze.

Dr Li says conservation efforts in China are "half-hearted" and that the country is financially able to give these fisherman an alternative livelihood to give the finless porpoise the same chance as the more famous panda.

"The porpoise is really on the top of the food chain in the fresh water ecosystem," he said.

"So from the conservation perspective it's a flagship species that can tell whether the river is healthy or not.

"If these kinds of flagship species are disappearing, it means the whole river system is in big trouble."