“We don’t know why the price went down, but we have nothing else to depend on,” said Ms. Wang’s son-in-law, Jie Er, 32.

Recognizing that, environmental officials just outside Jinghong, the region’s major city, have been testing a plantation model that they hope will become the blueprint for a more sustainable and economically stable rubber industry.

On approximately 165 acres of land, workers have interspersed the rubber trees with cacao, coffee and macadamia trees, as well as high-value timber species. The mix, promoted as “environmentally friendly rubber,” is intended to decrease soil erosion, improve water quality and increase biodiversity, among other benefits.

Rubber plantations first appeared in this tropical region in the mid-1950s as state farms run by the centrally planned economy. Mile after mile, the uniform rows of rubber trees fan out across the valleys where Asian elephants and white-cheeked gibbons once roamed. From afar, they meld into an unnaturally even carpet of single-shade green, a stark contrast to patches of remaining natural forest.

The transition to a free-market economy combined with rising rubber prices led to the rapid expansion of plantations beginning in the late 1990s. These days, over a fifth of all land in the Xishuangbanna prefecture of Yunnan Province is devoted to rubber production, an area of cultivation that tripled in size between 2002 and 2010. Natural forest coverage, in turn, has fallen to less than 50 percent in 2003 from nearly 70 percent in the late 1970s, snuffing out wildlife in a corner of China renowned as one of its most biologically diverse.