With less than 500 adult specimens, the Taxus mairei (family coniferous tree Taxaceae present in three districts of Nepal) is highly threatened. This type of yew has been part of traditional Nepalese medicine for years and is one of the main sources for the production of Taxol, a drug used to treat cancer. According to estimates, a ton of leaves of T. mairei can produce about 550 grams of 10-DAB-III, the natural organic compound that is used as a chemical intermediate to prepare paclitaxel (marketed as Taxol).
The high commercial value of this tree has generated a trade around its leaves; However the T. mairei It is found only in the wild in three districts of Nepal, and as their numbers decline, it is increasingly necessary to implement a responsible and sustainable conservation plan.
Yews to fight cancer
Paclitaxel (marketed as Taxol) is one of the most effective and most widely used drugs in the treatment of cancer that has been produced for the past 50 years. This anti-cancer drug was first found in the cortex of the Taxus brevifolia (Pacific yew). All yew species can be used to make Taxol. Besides of T. mairei, there are also two other yew species in Nepal: the T. wallichiana and the T. contarta.
T. mairei is present in the Nepalese districts of Sindhuli, Kavreplanchok and Makwanpur and also in China, Vietnam, Indonesia, Myanmar and in the Indian state of Meghalaya. During an interview, Kumar Paudel, the co-founder of the Greenhood Nepal organization, gave more details about the presence of the T. mairei in the wild:
There are less than 500 mature T. mairei trees (more than 30 cm diameter at breast height (dbh). If we include saplings (less than 10 cm dbh) and poles (10-30 cm dbh) then the total number is around 2000 in Nepal.
Fewer than 500 adult specimens (with a normal diameter (dn) greater than 30 cm) of the species remain T. mairei. If we consider still small (dn less than 10 cm) and medium (dn between 10 and 30 cm) individuals, the total number of trees is around 2000 in Nepal.
Using a study by Kumar Paudel and Reshu Bashyal of Greenhood Nepal, an organization founded by the Conservation Leadership Program and the Kate Stokes Memorial Award, an estimate was made of the total number of T. mairei and sustainable guidelines were developed to assist leaf collectors in their work.
Did you know that yew trees produce a chemical that is used to treat cancer? @bashyalreshu and @kmrpaudel are working with me and @verissimodiogo through @CLPawards to look at the impact of this trade in Nepal #EndWildlifeTrade # IWT18 pic.twitter.com/uHr0XTdbz8
– Amy Hinsley (@orchiddelirium) October 11, 2018
Did you know that yews produce a substance that is used to treat cancer? Reshu Bashyal and Kumar Paudel are working with me and Diogo Verissimo, with the support of the Conservation Leaders Program, to analyze the impact of this activity in Nepal.
A growing business
According to this study, Nepal exports an average of 25 kg of 10-DAB-III per year, which requires about 45 454 kg of leaves. Leaves are collected by local communities, dried and sold to nurseries or local merchants at rates ranging from 50 to 240 Nepalese rupees per kg (0.43 to 2.05 USD / kg). This is a considerable increase from the price of leaves in 2002, which was between 10 and 30 Nepalese rupees per kg (0.08 to 0.26 USD / kg).
Given the importance of yew leaves, the nursery sector has experienced remarkable growth and the demand for young yew specimens has increased throughout the country. In nurseries, sprouts are generally prepared from cuttings. However, if thousands of trees are grown in this way, they will be of the same genus and have the same genetics as the tree from which they came. Since yews are dioecious species (they have both male and female individuals), it is necessary to have specimens of both sexes within a short distance for fertilization to take place. Therefore, it is necessary to cultivate them in a nursery artificially and then plant them in their natural habitat to conserve them.
Yew trees in danger
Yews in Nepal have been used for multiple purposes for generations. The branches and leaves make beds for cattle or offerings for the gods. Wood is used to make beams as well as furniture or agricultural tools. Indigenous communities also use yews to make traditional recipes against fever, cough, asthma, or indigestion.
However, in the absence of specific guidelines or methods for collecting yew leaves, local communities rely solely on their experience. Sometimes trees are completely stripped of their leaves. In recent years, many trees have been felled to meet the strong demand for leaves.
In turn, the species T. mairei It is located at a lower altitude than other yew species, which confronts it with contact with human activity and with threats such as the destruction of its habitat, grazing, forest fires and illegal deforestation.
I think this opportunity is crucial for us as the harvesting communities to use this harvesting guidelines to ensure future viability of Taxus mairei along to educate them about more about it. Thank you Kate Stokes memorial award. #weareclp https://t.co/n8e4pTxxlq
– Sabitri Rai (@RaiSabitri) August 23, 2019
The team is reviewing the Yews (Nepali) crop guide and the community engagement program funded by the Conservation Leaders Program and the Kate Stokes Memorial award.
It seems essential to me that the collecting communities use these collection guidelines to guarantee the subsistence of the Taxus mairei and learn more about this tree. Thanks to the Kate Stokes Memorial Award.
If done properly, the growing trend in the cultivation of T. mairei It will constitute an important step for the conservation of wild specimens of this species.