Medicinal plant knowledge and its erosion among the Mien (Yao) in northern Thailand
Introduction
For thousands of years worldwide, plants have been used in traditional medicine, resulting in the development of a large body of local knowledge. This knowledge base arises primarily from trial-and-error experiences and is rarely embedded in complete and systematic theories of medicine (Bo et al., 2003). In many cases, local knowledge of medicinal plants remains poorly documented in the scientific literature. For example, in a study of herbs used for medicinal baths among the Red-headed Yao in China, only 5% of 110 species registered had been previously identified as having medicinal properties, and 79% were newly recorded for their use in medicinal baths (Li et al., 2006). Local knowledge of how medicinal plants are used may be a rich basis for the phytochemical, pharmacological, and clinical studies necessary to secure sustainable and rational use of these plants as a resource.
In addition to the limited documentation, much traditional medical plant knowledge is being lost before its incorporation into modern science. Environmental degradation and large changes in modern social and economic systems have affected medicinal plant use over the past few decades (Anyinam, 1995). A study of medicinal plants of the Zay in Ethiopia reported the use of 33 species, but the informants all agreed that more species had been used in the past. It was suggested that deforestation, degradation, and acculturation over many years caused the reduction (Giday et al., 2003). Likewise, in northwestern Yunnan in China, over-exploitation and deforestation are depleting the medicinal plants used by the Lisu (Ji et al., 2005).
The most serious threat to local medicinal plant knowledge, however, appears to be cultural change, particularly the influence of modernization and the western worldview (Voeks and Leony, 2004). Knowledge loss has possibly also been aggravated by the expansion of modern education, which has contributed to undermining traditional values among the young (Giday et al., 2003). For example, in the Velliangiri holy hills in India, young people lack interest in Malasar traditional knowledge, and many of them leave their home villages in search of emerging opportunities in more industrialized settings (Ragupathy et al., 2008). In Lençóis, Bahia, Brazil, young people sometimes understand how plants were used in the past, but they never actually employ them and are not likely ever to do so (Voeks and Leony, 2004).
In addition, the virtues of modern medicine lead to the abandonment of local medicinal practices in many villages. In the Velliangiri holy hills in India, modern health care facilities are thought to be a barrier to effective dissemination of traditional aboriginal knowledge (Ragupathy et al., 2008). Folk healers and their orally transmitted traditions may be more vulnerable to extinction than medicinal plants themselves (Anyinam, 1995) because many healers are aged and are dying with their knowledge left unrecorded (Cox, 2000). Among Red-headed Yao in southwest China, medicinal herb healers are old, and the younger generations have learned little from them (Long and Li, 2004). Among the Lisu in northwestern Yunnan, China, a treatment for birth control was lost because the only woman who held knowledge about this treatment kept it secret and passed away without revealing the information to anyone (Ji et al., 2005); a remedy against snakebite used by the Zay in Ethiopia met the same fate (Giday et al., 2003). As a result, traditional knowledge of medicinal plants, once embedded in tens of thousands of indigenous cultures, is rapidly disappearing. Bussmann and Sharon (2006), based on a study of medicinal plant knowledge in southern Ecuador, suggested that to avoid the loss of this intellectual heritage, which has evolved in traditional cultures over hundreds of years, and to keep it alive, it is necessary to document and describe traditional use of plants.
In the study of local knowledge of medicinal and other useful plants, many researchers have made the assumption that all plants mentioned as useful are also actually being used. But a few studies have teased apart what people say and what they do, and it turns out that the “local knowledge,” represented by what the informants tell the researcher, is not always equal to “local use,” which refers to which plants and which uses are actually practiced (Byg and Balslev, 2001). This gap between local knowledge and local use can be taken as the first sign of degradation of traditional ethnobotanical knowledge and can be used to measure loss of knowledge (Reyes-García et al., 2005).
Here we record local medicinal plant knowledge and how it is transferred among the Mien (sometimes called “Yao”), an ethnic group with a population of over seven million in China, Vietnam, Laos, Thailand, France, and the United States (Long and Li, 2004). The Mien originated in southern China and has migrated to other parts of Southeast Asia since the mid-19th century with the expansion of the opium trade. The Mien and other groups were relegated from the Manchu state (Perve, 2006); because of civil war and communist terrorists in their Chinese home territory in the beginning of 20th century, they moved into northern Thailand, where they settled in the high mountains of Nan, Phayao, Chiang Rai provinces, and elsewhere. In 2003, there were 45,571 Mien in Thailand, distributed between 178 villages (Perve, 2006). Residing in the mountains, the Mien have limited access to western healthcare; consequently, they have accumulated a rich experience related to preventing and treating diseases with herbal remedies, and they have developed a distinctive traditional medicine. The Mien healer is accomplished in both medical practice and drug making. Therefore, since ancestral times, Mien healers have undertaken the tasks of diagnosis and drug gathering, processing, and distribution. Their traditional knowledge has been transferred from one generation to the next, based on oral transmission and lifestyle. However, because cultural systems are dynamic (Cunningham, 2001), the skills are fragile and easily forgotten. Some elderly Miens with knowledge of medicinal plants complain that it is difficult to find younger people with an interest in learning skills concerning local healthcare. Mien knowledge of traditional medicinal plants may therefore be decreasing.
When documenting the local knowledge of medicinal plants among the Mien, we compared what informants told us that they knew with the actual use of medicinal plants in the communities. We based our work on the assumption that the gap between knowledge and actual uses of plants can be used to study erosion of ethnobotanical knowledge (Reyes-García et al., 2005). We also observed the relationship between the practice of plant uses and the age and educational level of the informant, and in particular we asked whether incongruities indicate erosion of knowledge and how such erosion occurs.
Section snippets
Study area and socio-economic setting
Between March 2007 and March 2008, we worked in two Mien villages, Huai Labaoya (18°54′30.68″N, 100°40′05.92″E) and Samoon Mai (18°54′41.44″N, 100°39′52.97″E), located in western Nan province, 200 m above sea level and 23–24 km away from Nan city. They are surrounded by mountains that are mostly deforested and turned into cultivated land. There are 95 households and 645 people in Huai Labaoya, and 96 households and 845 people in Samoon Mai. In these villages, most villagers practice highland
Results
Fifty medicinal plant species were recorded, belonging to 41 families and 49 genera. Of those 50 medicinal plant species, 74% were said to be “easy to find,” whereas 16% and 10% were defined as “difficult” and “very difficult to find,” respectively. However, none of the informants used all of the recorded plant species. The ways to use each medicinal plant are listed in Table 1, ranked by their use values.
Medicinal plant knowledge and its trends of erosion
Two significant findings stand out from this work. First, we found that informants knew many more useful plants than they actually used. Of all of the use-reports, 21% referred to plants the informants knew about but had never actually used. For instance, 84% of the informants knew that Eleusine indica could be used to prevent abortion; they had heard about it from their predecessors, but they had never used it and they were not likely to do so. The remaining 79% of the use-reports were derived
Conclusions
Discrepancies between medicinal plant knowledge and the actual use of the plants as demonstrated in this study suggest that the medicinal plant knowledge in the studied Mien communities is undergoing inter-generational erosion. The erosion in particular may be attributable to disruption of the learning process and the interference of acculturation, especially the expansion of modern education and accessibility to modern medicine. These factors contribute to a lack of appreciation of traditional
Acknowledgments
We are thankful to all informants at Huai Labaoya and Samoon Mai for sharing their knowledge of medicinal plants with us and also permitting us to publish our findings. We would also like to thank The Royal Golden Jubilee Program of the Commission on Higher Education of Thailand for funding Kamonnate Srithi's PhD study. We thank Anders Barfod for reading the manuscript.
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