Many plant and fungal species synthesize chemical compounds of interest to the pharmaceutical industry. This group of compounds includes complex acids, lactones and anthocyanins, all useful in the construction of anti-viral vaccines (Macy 1990). Worldwide, more than 120 prescribed drugs are derived from 95 plant species. Approximately three-quarters of these drugs have been selected, based on ethnobotanical uses (Farnsworth 1988; Joyce 1991). While modern technology has enabled pharmaceutical manufacturers to synthesize analogs of natural chemical compounds, recent discoveries (such as the anticarcinogen taxol) are renewing interest in the chemical composition of forest plants (Thomas and Schumann 1993).
Medicinal plants used for herbal and alternative health products are marketed primarily through small botanical or herb buying houses. Buying houses process and package the plant material for the final processors or the retail market. These buying houses typically publish buying and selling catalogues that list the types and quantities of plant materials they purchase and sell. Such companies also provide guidelines on proper collection and shipping methods (Thomas and Schumann 1993).
Typically, roots, barks, leaves and flowers are collected separately for use as medicinal or pharmaceutical products. The harvester thus must use a variety of hand tools, such as shovels, rakes, axes, knives, and chainsaws. Bark, for example, is removed by stripping with a sharp knife.
A survey of industry participants and Forest Service staff has revealed a current total of 26 plants harvested for medicinal and pharmaceutical purposes in British Columbia. Table 8 summarizes this information on the basis of species, plant part used and product use. The plants listed in Table 8 may have commercial potential either as medicinals, pharmaceuticals or foods. Practically no information is available to characterize commercial harvesting of medicinal and pharmaceutical plants in British Columbia, with the exception of cascara and western yew. All of the plants in Table 8 are generally harvested on a personal scale. The following sections summarize available information on harvesting of cascara bark and western yew bark.
Table 8. Summary of medicinal and pharmaceutical products harvested in British Columbia.
“Extract of cascara sagrada” from cascara bark (Rhamnus purshiana) is recognized as a useful tonic laxative by doctors and has been prescribed since about 1877. Cascara bark was first commercially harvested in Oregon and Washington for eastern pharmaceutical manufacturers. Overharvesting of cascara bark, however, soon depleted these Oregon and Washington resources (Davidson 1949).
By 1915, as the cascara bark resource of Oregon and Washington was declining, eastern pharmaceutical manufacturers selected British Columbia for new supplies (Davidson 1949). Since the 1960s, however, the demand for cascara bark has diminished because alternative drugs have been developed. In recent years, Campbell River and Chilliwack forest districts have reported enquiries about cascara bark harvesting, but neither district confirms active commercial harvesting of cascara bark.
The Cascara Bark Regulation was created in 1958 to ensure the long-term conservation of cascara trees. This regulation controlled the activities of cascara bark harvesters and purchasers. The Cascara Bark Regulation was repealed by Regulation #13281 in 1981. The Forest Act now provides for the development of a new cascara bark regulation under section 158(j). Under this section, the Lieutenant-Governor-in-Council may make regulations respecting “harvesting of cascara bark from Crown land.”
Western yew bark
Taxol was isolated from the bark of the western yew tree (Taxus brevifolia) as early as 1971. Since 1971, taxol has been used as an anti-tumor drug in clinical trials run by the United States National Cancer Institute. Taxol has been hailed as one of the most significant advances in cancer therapy in recent history. It acts on tumor cells ostensibly by interfering with the functioning of microtubules during mitosis. Since 1990, clinical trials using taxol have succeeded in treating advanced ovarian and breast cancers (Chabner 1991).
Since 1991, the National Cancer Institute has required about 20 to 30 kilograms of taxol to treat more than 21,000 cases of ovarian cancer each year. To supply this amount of taxol would require 330,000 kilograms of dry bark or roughly the bark from 36,000 trees. Concerns about the scarcity of taxol and the ecological impact of harvesting prompted extensive investigations into alternative sources, including semisynthesis, cell culture production and chemical synthesis. Although the taxol molecule is structurally complex it was successfully synthesized in early 1993 (Nicolaou et al. 1994). Initial estimates are that the time lag between laboratory synthesis and commercial production may be less than two years. It therefore appears that harvest of western yew bark harvest may be curtailed in the future (Schlosser and Blatner 1993).
The high demand for western yew bark as a raw material for taxol led to concern that its harvest should be controlled in a sustainable manner. The Vancouver forest region therefore developed an information package describing interim provincial procedures (July 1991) for the harvest of western yew bark. These interim provincial procedures were based on the repealed Cascara Bark Regulation. Harvest of western yew bark was to be authorized only in areas already approved for timber harvesting.
Further interim instructions were established to ensure that the western yew species was not over exploited. Specific guidelines were developed for western yew bark harvesting, the shipping of western yew bark and keeping records on harvest volumes and locations for the western yew bark register. No requirement was established for harvesters to obtain permits or pay stumpage for harvesting western yew bark.
Table 9 presents a summary of the volume of western yew bark harvested between 1991 and 1993 in the Vancouver, Nelson and Kamloops forest regions. In 1993, the total volume of yew bark harvested in British Columbia had almost tripled to about 35,000 kilograms (dry weight).
Table 9. Western yew bark register: summary of 1991, 1992 and 1993 harvest data by Ministry of Forests regions.
These interim procedures were designed to govern the provincial harvesting of western yew bark until policy was formulated. In 1993, the Timber Harvesting Branch finally developed policy for the harvest and collection of western yew bark. The policy states that the Ministry of Forests supports and promotes “the orderly harvesting of bark from the western yew tree, to provide a source of the drug taxol.” The policy addresses the issue of sustainable harvest in respect of the survival and genetic diversity of the western yew.
The western yew bark policy generally endorses the conditions prescribed for harvest in the original 1991 information package. The specific guidelines for harvesting, shipping (of bark or wood), and keeping records of harvest volumes and locations are reiterated. The policy does however, expand the previously designated yew bark harvesting areas to include:
Inspection of western yew bark harvesting operations is not yet a formal requirement. The policy recommends that informal inspections should be implemented to ensure that western yew bark harvesting is performed in a sustainable manner.
Since 1991, no export permits have been granted for exporting western yew bark to the United States. In 1992, Towers Phytochemicals, a Vancouver company, began buying western yew bark for a proposed processing facility. Since Towers Phytochemicals did not process yew needles and boughs, the provincial government permitted limited 1992 export of needles and boughs for taxol extraction. Despite the authorization, there were no exports of yew needles or boughs in 1992. Under current policy there will be no authorizations for exporting bark, needles or boughs to the United States. Towers Phytochemicals claims and buys all the western yew material, leaving no surplus for export.
Harvesting in other jurisdictions
U.S. Pacific Northwest
The western yew is distributed throughout forested zones of Washington, Oregon, Idaho and Montana. During 1992, approximately 730 tonnes (dry weight) of yew bark were harvested from this region. The majority of the product was collected from U.S. Forest Service lands scheduled for timber harvest (Schlosser and Blatner 1993).
Hauser Northwest Inc. is the principal purchaser of western yew bark in the region. The company chips the bark, dries it and then delivers it to a chemical manufacturing plant in Boulder, Colorado. Hauser Northwest Inc. estimates that $5.6 million (U.S.) in total was paid to about 1,500 harvesters in the U.S. Pacific Northwest. Although this industry has contributed to many rural economies in the Pacific Northwest, it is expected to decline in the future because of the recently successful laboratory synthesis of taxol (Schlosser and Blatner 1993).