Liu and other scientists are worried that the expansion of rubber plantations to feed China's voracious tyre industry, the world's largest, will destroy the ecosystem of Xishuangbanna. The province is home to China's richest variety of flora and fauna.

Three decades ago, jungles and high mountain forests covered about 70 percent of Xishuangbanna, tucked between China's borders with Laos and Myanmar. By 2003, that proportion had shrunk to less than 50 percent.

"With rubber prices rising like crazy, any tree that can be cut down has been cut down to make way for rubber," said Liu, a professor at the Xishuangbanna Tropical Botanical Garden, run by the Chinese Academy of Science.

Rainforests have been reduced to patches of protected zones in Xishuangbanna, one of the top rubber producing regions in China, as double-digit economic growth has caused increasing encroachment on China's last remnants of uncultivated land.

The official figure for Yunnan Province's rubber acreage is 334,000 hectares, about 43 percent of the country's total acreage, but the real figure may be much higher.

China consumed 2.35 million tonnes of natural rubber in 2007. About 70 percent of that was imported from abroad, mainly from Thailand, Malaysia and Indonesia, Southeast Asian countries that are also facing deforestation from expanding rubber plantations.

China has seen natural rubber imports nearly double since 2000 thanks to fast-growing domestic auto sales and as it becomes the top tyre maker and exporter in the world.

China produced 330 million units of tyres in 2007 and shipped nearly half abroad. Global tyre heavyweights, such as Goodyear, Continental AG Michelin and Bridgestone, are either setting up or expanding their plants in China.

To feed the demand, China is seeking to expand its natural rubber output which is expected to grow by 30 percent to 780,000 tonnes by 2010, the China Rubber Industry Association forecasts.

But available land suitable for growing rubber is very limited as the trees need to be planted in sub-tropical or tropical climates, weather conditions found only in small parts of southern China.

RUBBER PLANTATIONS SHRINK FORESTS

In the years between 1976 to 2003, about 67 percent of the region's rainforest areas were lost to rubber plantations, according to a 2006 paper by researchers with the Chinese Academy of Sciences and a scientist at the University of Puerto Rico.

Scientists say that both state-owned and private plantations are responsible for shrinking forests.

State-owned Yunnan Natural Rubber Industrial Co, the province's top producer, denies the allegation. The company says its rubber plantations are only expanding into previously deserted farmland, or regrown forests.

"We've used almost all possible land to grow rubber here, and now we'll need to grow rubber overseas," said Yin Shiming, head of Yunnan Rubber's production division.

Yunnan Rubber currently has rubber acreage of more than 1,333 hectares in neighbouring Laos and Myanmar, which will start producing rubber in six or seven years.

It plans to expand the acreage to 33,333 hectares in the next few years, replacing poppy opium fields. High prices have made rubber more appealing to farmers who profit little from growing opium as most of the profits go to the processors.

In Xishuangbanna, rows of graceful, grey-green rubber trees are visible everywhere.

Rubber saplings grow next to banana trees in fields. They even appear on patches of land around farmers' houses, displacing bamboo, once the distinguishing feature of the local landscape.

Little by little, local farmers are encroaching on protected forest zones, researchers said.