09 April 2020 (online)
Scientists’ Warning: Climate change puts medicinal plants at risk
Stuttgart - Next time you reach for ginseng tea or frankincense oil take a moment to consider life without it. Although neither of these plants are immediately at risk, they are cited as some of many examples in a new research paper by Wendy L. Applequist and colleagues that lays bare the damaging effects of climate change on the world’s curative plant species: the pushing-back and extinction of medicinal plants. The appeal, Scientists’ Warning on Climate Change and Medicinal Plants, has recently been published in Planta Medica (Thieme, Stuttgart. 2019) and endorsed by many scholars.
Medicinal plants are the primary drugs for 70 to 95 percent of most developing country populations and their use in wealthier countries is growing. The annual global export trade value for herbal ingredients is estimated to be almost US$33 billion. But these medicinal plants are threatened. The paper’s authors catalogue a range of risks for medicinal plants which are directly and indirectly related to climate change. These are higher temperatures, drought and heavy rain, increased carbon dioxide and rising pest and disease levels. Human-driven dangers do also include overharvesting. The paper divides the effects on plants into two categories: decreased availability and extinction, and changes in plant quality or productivity. Especially the latter is a cause of concern for the researchers, as the plants can change their medicinal effect or even lose it altogether.
The populations most likely to suffer from these effects are local communities and indigenous tribes. The plant communities most at risk are alpine meadows and those in northern latitudes. When the climate changes in traditional habitats, plants try to adapt or migrate to neighbouring habitats. According to the authors, some might not be able to or fast enough to settle in new habitats. The authors cite published research that predicts a “complete loss of habitat” for Tylophora hirsuta in certain regions of Pakistan. The plant is used to treat asthma and urinary retention. In another example, the acute pressures on Boswellia, the source of frankincense resin, are listed as farm expansion, fire, overexploitation, wood-boring beetle infestations and grazing.
If effects of overharvesting for global consumer markets and climate change are combined, the threat grows exponentially. In one projection, that the authors cite, the extinction risk for a population of American ginseng due to harvesting is estimated at 8 percent over the next 70 years. The climate change extinction risk alone is 6 percent. Taken together, the risk rises to 65 percent.
If mankind continues to fail in sustainable climate change mitigation, the authors recommend growing plants in community gardens to maintain local access and training harvesters in sustainable practices and plant quality monitoring. Last resorts are the assisted migration of plants and off-site seed banking.
The authors’ appeal follows the tradition of the “World Scientists’ Warning to Humanity” published in 1992 and 2017 and several other studies that show the effects of climate change on individual aspects of human life.
- 1 Wendy L. Applequist et al.: Scientists’ Warning on Climate Change and Medicinal Plants. Planta Med 2020; 86 (01) 10-18