Chen S-L, Yu H, Luo H-M, Wu Q, Li C-F, Steinmetz A. Conservation and sustainable use of medicinal plants: problems, progress, and prospects. Chin Med. July 30, 2016;11:37. doi: 10.1186/s13020-016-0108-7.
Over 1300 medicinal plants are used in Europe, with 90% harvested from the wild. In the United States, about 118 of the top 150 prescription drugs come from, or are some derivative of, natural sources; in developing countries, about 25% of prescribed medicines come from wild plants. Worldwide, about one-tenth of all plants, between 50,000-80,000 flowering species, are used medicinally. However, an estimated 15,000 are threatened by overharvesting and habitat degradation. Concurrently, due to a rising demand, medicinal plants are being harvested in rising volumes, largely from wild populations. Distribution of medicinal plants is not uniform around the world. China and India have the largest numbers of medicinal species, with those in China, India, Kenya, Nepal, Tanzania, and Uganda at particular risk. Yet, only a few of the species suffering from genetic erosion and habitat destruction have been listed as threatened.
The authors conducted systematic literature searches of electronic databases to assess global trends, developments, and progress affecting conservation and sustainable use of medicinal plants. Their search considered articles in English or Chinese published between January 2000 and December 2014. Of 673 abstracts initially identified, 231 met inclusion criteria and full papers were retrieved for 106. Citations found in retrieved papers added another 25 papers, for a total of 131 reviewed. Of these, 42 concerned in situ conservation; 35, ex-situ conservation; 31, cultivation practices; 23, sustainable use; and 22, other relevant topics. Each of these strategies is described and its particular benefits assessed. For example, in situ conservation encompasses natural reserves where medicinal species may thrive without interference in their natural ecosystem and wild nurseries where specific species can be propagated and domesticated. Ex-situ conservation includes botanic gardens and seed banks.
Increased cultivation of wild species relieves pressure on wild populations and, with the use of Good Agricultural Practices (GAP) such as organic farming, helps ensure a consistent supply of high-quality medicinal plant products. Moreover, advances in genetic engineering have led to the possibility of large-scale syncretization of bioactive compounds and the development of superior plant populations using molecular marker-based approaches. Sustainable use demands sustainable harvest practices. Recent research indicates, for example, that the leaves of some plants may have the same effects as less sustainably harvested but traditionally used plant parts such as roots or whole plants.
The authors summarize seven original investigations into medicinal plant conservation and sustainable use in a table that describes factors contributing to the relative susceptibility of plants to collection pressures. The most susceptible species reproduce generatively, grow slowly, have little intraspecies diversity and small populations, along with a narrow range of distribution and specific and restricted habitat needs.
A large number of recommendations have been made for medicinal plant conservation and sustainable use but only a small portion have been widely implemented. Meanwhile, it is estimated that the current rate of plant extinction is 100-1000 times the expected natural extinction rate, with at least one major potential drug lost every two years. The authors suggest improved conservation strategies and resource management be combined with biotechnical approaches to advance sustainable cultivation, harvesting, and use of medicinal plants.