A comprehensive inventory is not available for Canada yew in Ontario at this time. However, field data collected on yew as part of Ontario's forest ecosystem classification and monitoring programs may be used in the future to map its potential locations and abundance.
Factors Affecting Canada Yew
Deer and moose browsing can create local pressures on the Canada yew resource. However, the commercial harvest of Canada yew from the natural environment is potentially a more significant factor affecting the resource (Figure 3).
The commercial harvest of Canada yew began in Ontario in 2003. During that year, about 5,000 kilograms (kg) of foliage was harvested. Based on information volunteered by harvesting companies, the ministry estimates that about 320,000 kg of foliage was commercially harvested in Ontario in 2004, mostly from private land. In 2005, about 400,000 kg was harvested, primarily from public land. Demand seems to have stabilized or even decreased in 2006 in response to changes in world market conditions.
The Discovery of Paclitaxel in Canada Yew
In 1960, the United States Department of Agriculture and the National Cancer Institute started testing plants for chemicals that have the potential to fight cancer. Paclitaxel was identified as the active anti-cancer chemical in the bark of Pacific yew but the demand for paclitaxel was greater than the supply of Pacific yew. Paclitaxel continues to be difficult to produce by synthetic means.
To help overcome this shortage, all yew species were investigated as potential paclitaxel sources. This led to the discovery that Canada yew was a good source of paclitaxel as well as two other taxanes that can be used to synthesize paclitaxel. Given the high levels of taxanes in Canada yew, this species could become one of the most valuable natural sources of taxanes for the pharmaceutical industry.
For further details on paclitaxel's discovery, visit this website and this website.
Canada yew was not actively managed in Ontario until after the commercial harvest of yew began in 2003.
|Figure 3: Harvesting yew foliage. Photo by Dr. Tom Noland, Ontario Ministry of Natural Resources.|
The ministry currently has a voluntary system in place for managing the commercial harvest of Canada yew. Specifically, companies requesting the right to harvest yew on public land are asked to submit a business plan to the ministry. This plan must meet specific requirements in order for the company to receive a “Letter of Support” from the ministry to harvest yew on public land. Harvesters are encouraged to comply with the Canada yew sustainable harvesting guidelines developed in 2002 in Prince Edward Island by the Canadian Forest Service in partnership with Prince Edward Island's Department of Agriculture and Forestry. Details of these harvesting guidelines can be found on the Prince Edward Island’s Department of Agriculture and Forestry website. (www.gov.pe.ca/photos/original/af_hemlock0402.pdf)
To help landowners understand issues around harvesting Canada yew on private land, the ministry has produced a pamphlet entitled Harvesting Canada Yew – Information for Landowners. (See Information Sources).
Canada Yew Research
In Ontario, many factors influence the capacity for and interest in harvesting Canada yew from the wild. These factors include:
Cultivating Canada yew in a farm or nursery setting has the potential to provide an abundant supply of paclitaxel in a highly efficient manner.
Through the Ontario Forest Research Institute (OFRI), Ontario is directing its interests in Canada yew to research aimed at developing this shrub as a crop for Ontario farmers and nurseries and to select wild yew for their superior growth and paclitaxel content. These projects may lead the way to establishing Canada yew plantations in Ontario and across eastern Canada.
The ministry is also conducting research in partnership with Chatham Biotec (a Canada yew supply company) and the Canadian Forest Service to better determine what level of wild yew harvest is sustainable in Ontario. This research may result in some refinement to existing sustainable harvesting guidelines to better represent Ontario conditions.