Pigs: A Boon to Yunnan's Biological Diversity?
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|Zeng's team and their baby pig. Provided by Zeng Yangzhi.|
As environmentalists lament the rapid loss of forest landscapes in southwestern China's Yunnan Province, they may now have an unlikely ally in their efforts to preserve this biologically diverse region: pig geneticists. As of November 2005, a team of zoologists at Yunnan Agricultural University had bred the world's purest inbred line of pigs, an endeavor considered nearly impossible in scientific circles. The ancestry of the line can be traced to a single litter of piglets first identified in species-rich Yunnan in the 1980s.
Geneticists define "inbred line" mammals as having at least 20 generations of full-sibling or parent-offspring inbreeding, all sharing a common pair of ancestors. For decades, researchers around the world have attempted to create a pure line of pigs through more than 200 large-scale inbreeding experiments, but these failed due to severe inbreeding depression, which lowers a population's ability to survive and reproduce. The Yunnan team, however, led by Professor Zeng Yangzhi, was able to breed its line for 23 successive generations.
Their research is expected to have enormous implications for biomedical and clinical research, as pigs are considered ideal lab animals due to their close anatomical, physiological, and metabolic resemblance to humans. The inbred pig family, with nearly 900 members in 18 sublines, includes the world's smallest pig sub-line (and the most suitable variety for biomedical testing), weighing less than 30 kilograms at 18 months old. Currently, the most common lab animal in modern medical research is the guinea pig, actually an inbred line of mouse that helped to achieve major medical breakthroughs in the 20th century.
|Zeng found his foundation pigs in this village in the 1980s. Provided by Zeng Yangzhi.|
The potential boon for conservation efforts is that Yunnan's rich genetic diversity was instrumental in germinating this scientific success. In 1980, the Yunnan Agricultural University team found its first six foundation pigs in a mountainous Lagu minority village deep in the province. Remote and isolated, the village had never introduced male pigs from outside the area, and the households each take turns in selecting one boar annually to mate with all sows, including its own mother and sisters. The brood of piglets the team identified had been born from one sow-son relationship, sparking 26 years of breeding research.
Blessed with a favorable geographic location and unique landscapes, southwestern China boasts tremendous genetic diversity. The region has long been a paradise for flora and fauna, nurtured by warm temperatures and abundant precipitation brought over by Indian Ocean monsoons. Its complex topography, ranging from just over 1,000 meters in some valley floors to 6,740 meters at Meili Snow Mountain, allows for a wide range of life zones. In addition, three major river systems, the Lanqang (Mekong), Nu (Salween), and Jinsha (a tributary of Yangtze), traverse the region from north to south through precipitous valleys, serving as important conduits for the exchange of biological information.
Hou Mingming, a professor with the School of Environmental Science and Engineering at Yunnan's Kunming University of Science and Technology, has labeled the region a "golden cross" for biodiversity. Though its richness is not fully documented, southwestern China is believed to house more than 6,000 plant species and over 1,000 animal species. Researchers suspect that a large percentage of these species contain genes still unknown to science.
|Destroyed natural forests at Gezaxiang. Photo by Zhu Wenyu|
Genetic diversity provides scientists with options for developing new, more productive crop varieties, as well as potential ingredients for future medicines and pharmaceuticals. According to the BBC, three-quarters of the top 150 prescription drugs in the United States are laboratory versions of chemicals found in plants, fungi, bacteria, and vertebrates. The World Health Organization estimates that more than 60 percent of the world's population relies on plant-derived medicines for primary healthcare.
Yet far-reaching human activities are increasingly jeopardizing this hidden treasure. Residents of China's southwest have long faced extreme poverty, due in large part to the region's inaccessibility and complex topography. Though the Chinese central government talks increasingly about "green GDP" and "ecological compensation," local governments have far greater incentive to exploit the region's plentiful natural resources for immediate economic return. "In order to attract more enterprises to the region, local governments are selling mountains and rivers to paper-making companies and dam developers," said Professor Hou. "The modern machinery used in logging by paper companies has erased all the vegetation in the affected areas, without discrimination."
Debates abound on whether the ultimate goal of biodiversity conservation should be to preserve the sanctity of species as such, or to capitalize on their utility to humans. Tensions also run high between animal lovers and scientists engaged in potentially lifesaving medical research. Yet seeing the smiling faces of newly employed Yunnan residents, typing at their computers at the training center of one local paper company, one wonders whether Professor Zeng's pigs and similar medical incentives may be more effective in raising local awareness of the value of the region's resources than well-intentioned environmental campaigns. Growing recognition of the importance of Yunnan's genetic diversity can only be good news for the province's remaining plants and animals.