Taxus wallichiana Zucc.

Taxaceae

Throughout its range in the eastern Himalayas this species is threatened by exploitation for traditional and modern medicines as well as the conversion of its habitat for agriculture and harvesting for fodder and firewood. 

Description

Taxonomic notes

Taxus wallichiana is usually considered to be a wide ranging species that occurs from Afghanistan eastwards through the Himalayas into southwestern China. Disjunct subpopulations in Vietnam, Indonesia and the Philippines are also sometimes identified as this species. Detailed morphological and molecular analyses of Himalayan and Chinese subpopulations over the last decade indicate that subpopulations in the western Himalayas represent a distinct species (T. contorta Griff.). In the eastern Himalayas two species are present: T. wallichiana and T. mairei. Subpopulations in southern Vietnam have been re-identified as T. mairei while those in the Philippines and Indonesia are the subject of ongoing research.

Distribution

Tauxs wallichiana's revised distribution is as follows: Nepal: eastern part of Baglung district along the South of the Dhaulagiri and Annapurna range to East Nepal; Bhutan: entire northern part of the country; India: NE India including Nagaland and Manipur, mostly above 1900 m; Myanmar: northern parts of Sagaing division, Kachin and Shan states; China: South and Southeast Tibet (from the eastern border of Sikkim) to Southwest and West Yunnan.

Taxus wallichiana was collected in 1931 from northeast Thailand but no recent collections have been made and it is uncertain if it still occurs there. It may also occur in Lao PDR.

Although this species has a wide range, subpopulations within that range are often disjunct and isolated. Over the last 25 years there has been a major decline due to over-exploitation for Taxol production.

Habitat and Ecology

Taxus wallichiana is usually a small to large understorey or lower canopy tree in montane, temperate or warm temperate forest. In open situations on rocky slopes and cliffs it may form a large, broadly spreading shrub. In the Himalayas it usually occurs on south facing slopes in areas with high summer rainfall. Elevation ranges from 1900 to 2700 (3300) metres above sea-level and soils are usually acidic to neutral. It has a very long life-span and may sprout from stumps. It may occur in pure stands of limited extent or be scattered in the understorey of Quercus, Tsuga, Abies and Picea mixed conifer forests.

Human Uses

The wood of Himalayan Yew is durable and strong and is used for door frames, furniture, candlesticks and knife handles. In Bhutan, especially in the East, people use the wood for making milk and water containers. It is also used for gates and fences. The wood is also burnt as incense in Nepal and parts of Tibet. In other areas the wood is used as fuel. Foliage may be used as fodder. The alkaloid compounds (taxanes) of the bark and leaves are a source for the anti-cancer drug paclitaxel (Taxol®) which has become a major reason for exploitation in recent years. Traditional medicine has made use of young shoots and leaves and sometimes of inner bark for a long time in various potions, tinctures, and pastes. The fleshy aril around the seed is consumed by local inhabitants as jams. The inner bark also produces a red dye, often used in religious ceremonies by Brahmins of Nepal.

Conservation Status

Global Status and Rationale

Endangered A2acd

In the major parts of its range (India, Nepal, and SW China) declines of 50-90% have been recorded after recent exploitation for Taxol production or other more traditional medicinal uses. This decline has been compounded in some areas by increasing deforestation and agricultural expansion associated with rising rural populations. The overall level of decline is likely to be in excess of 50% - almost all of this has taken place in the last 25–30 years (within a single generation).

Proposed National Status and Rationale - Bhutan

Vulnerable A2acd
Taxus is relatively rare in Bhutan. Exploitation has been lower than in in India, Nepal and China and rates of deforestation are also much lower than in surrounding areas. Poor regeneration due to overgrazing of seedlings and saplings has been reported. Taxus is listed as a protected species under the government's Forest and Nature Conservation Rules. The most recent National Redlist lists Taxus as Near Threatened (Dorji 2010)

Proposed National Status and Rationale - China

Endangered A2acd
Declines of up to 80% have been recorded from Yunnan where the major part of the Chinese subpopulation occurs.. This has principally been caused by exploitation for Taxol production over the last two decades rather than for traditional uses. The most recent national redlist assessment (Wang and Xie 2004) of Vulnerable was based on a wider distribution and a different species concept.

Proposed National Status and Rationale - India

Critically Endangered A2acd
In northeast India Taxus has been heavily exploited for its traditional uses and has also been effected by deforestation. Declines of up to 90% have been reported from some areas. In northwestern India similar declines have occurred but these subpopulations should be assessed as Taxus contorta. No official National Redlist has been undertaken based on recent research.

Proposed National Status and Rationale - Myanmar

Data Deficient DD
There is little information available concerning the current distribution and status of T. wallichiana in Myanmar but it is likely that it has been exploited at least for traditional medicines. Some historical herbarium records come from areas that have recently been logged, especially in the Kachin state.

Proposed National Status and Rationale - Nepal

Endangered A2acd
Subpopulations in central and eastern Nepal have been severely impacted by overexploitation for traditional and modern medicines as well as by deforestation and agricultural expansion. No official national assessment has beeen carried out although several unoffficial assessments that have included all Taxus subpopulations in Nepal have listed it as Endangered.

Conservation Actions

Taxus wallichiana is listed under CITES Appendix II and international trade is thereby regulated. It occurs in several protected areas, e.g. the Sagarmatha National Park in Nepal and Gaoligong National Nature Reserve in Yunnan. In Nepal government forestry regulations regulate the harvesting and prohibit the felling of all Taxus species. As in China plantations are being established and programmes are being developed to encourage its protection and cultivation in community forests as well as on private land. Similar measures are in place in Bhutan.