XISHUANGBANNA, China: On a map on the ecologist Liu Wenjie's computer, the subtropical southern tip of Yunnan Province is slowly turning from green to red.
Rubber plantations, shown in red on Liu's computer screen, have supplanted nearly all the low-lying forest in the prefecture of Xishuangbanna and are now starting to encroach on the highlands.
Liu and other scientists are worried that the expansion of rubber plantations to feed China's voracious tire industry, the world's largest, will destroy the ecosystem of Xishuangbanna. Yunnan 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, which is managed by the Chinese Academy of Science.
Rain forests 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, or 825,000 acres, which is about 43 percent of the country's total acreage. The real figure may be much higher.
China consumed 2.35 million tons 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 as it has become the top tire maker and exporter in the world.
China ships nearly half of its production abroad. Global tire heavyweights, including Goodyear, Continental, 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 tons by 2010, the China Rubber Industry Association forecasts.
But available land suitable for growing rubber is very limited, since the trees need to be planted in subtropical or tropical climates. Those conditions are found only in small parts of southern China.
In the years between 1976 and 2003, about 67 percent of the region's rain forests 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.
The state-owned Yunnan Natural Rubber Industrial, 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 neighboring 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 since most of the profits go to the processors.
In Xishuangbanna, rows of graceful, gray-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.
"The shrinking rain forests pose an obstacle for the reproduction of elephants, as well as other animals and plants," Liu said.
Besides endangered Asian elephants, tigers, peacocks and monkeys live in the rain forest.
"Bird species richness has also decreased with the conversion of the tropical rain forest into rubber plantations," the 2006 research paper said.
Even Yunnan Rubber acknowledges the impact on biodiversity of expanding rubber acreage
"Rubber plantations are man-made forests, and it's true there is not as much biodiversity here," Yin said.
Its plantations have adopted environmental protection measures, like allowing weeds to grow in empty spaces between rows of rubber trees, he said.
Yunnan Rubber has also researched ways to make its rubber trees mature faster as a way to raise output without expanding acreage. Rubber trees are normally ready to be tapped after seven years.
Scientists said that it was not too late to save the forests. But unchecked expansion of rubber plantations remains possible as long as rubber prices keep rising and the government does not intervene.
Rubber prices have almost tripled over the last decade and are now around 20,000 yuan, or about $2,800, a ton.
"Natural products will continue to get more expensive, there's no doubt about it," Liu said.