International trade in medicinal plants: conservation issues and potential roles for botanic gardens

Alan Hamilton

WWF International, Panda House, Weyside Park, Godalming, Surrey GU7 1QJ, U.K.

Abstract

There is large-scale international trade in medicinal plants, used both for herbal medicine and for the manufacture of pharmaceutical drugs. There is also growing interest in obtaining samples of plant material, or traditional knowledge about plant uses, to explore for new commercial medical products. The scale of international trade in medicinal plants is difficult to assess, because of a paucity of reliable statistics and trade secrecy, but it is growing rapidly.

Conservation issues in international trade in medicinal plants for existing products mainly concern those plants which are harvested from the 'wild', which is the case for the great majority of species. Conservation issues arise if the trade threatens conservation of biodiversity or is not sustainable. Biodiversity may be threatened if the trade endangers survival of the species, erodes its genetic diversity or causes loss or degradation of important natural or semi-natural ecosystems. The international movement of plant samples (or traditional knowledge about the uses of plants) for analysis to discover possible new commercial products raises the issue of equitable distribution of rewards in the event of successful commercialisation. Following the Biodiversity Treaty, there is an urgent need for equitable partnerships to be developed between those involved in developing new commercial products from plants and those responsible for conservation of biodiversity (often in the South).

Botanic gardens have long been involved with both medicinal plants and plant movements, but not with conservation. Notable features of botanic gardens relevant to conservation include the fact that they are often major centres of expertise about plants, that they have collections of living plants and that sometimes they have been assigned legal roles concerning the movements of plants between countries (e.g. as scientific authorities for CITES). There is also the possibility of botanical gardens being involved in ex situ conservation of plants, as part of integrated conservation strategies aimed at particular plant species. Thus, botanical gardens have special opportunities and responsibilities in respect of conservation issues raised by the international trade in medicinal plants.

If existing trade in medicinal plants results in conservation problems, for example if plants are being over-harvested from wild populations, then potential solutions include the design and implementation of new methods of managing wild populations, or transferring the business to reliance on cultivated plants. Many botanic gardens, having skills in plant propagation and horticulture, are in a special position to assist with the process of introducing plants into cultivation, but they will generally need to work closely with other agencies better equipped to deal with other necessary aspects, including social and economic ones. Success in making harvesting of species sustainable must involve the social dimension.

Botanic gardens are being approached by commercial interests that are interested in developing new medical products, in order to supply plant material, or knowledge about the uses of plants, for testing the development of new products. Botanic gardens are attractive agencies for commercial firms to approach, because of their concentration of botanical expertise. Botanists, for example, may be contracted to collect plant material from the 'wild'. The living collections of botanic gardens may be sampled without the bother of mounting expeditions to, perhaps distant, climes. Botanic gardens, therefore, have a special responsibility to ensure that they only supply samples to commercial interests for evaluation of possible new products under agreements which are ethically just.

International trade in medicinal plants

It has been said that as many as 35 000-70 000 species of plants have been used at one time or another for medicinal purposes (Farnsworth & Soejarto 1991). By far the greater number of species is employed in herbal medicine and is used in unrefined or semi-processed form, often in mixtures which sometimes also contain non-botanical ingredients. A few species are the sources of defined compounds used in the pharmaceutical industry. The overall quantities of plants used medically, in one way or another, are large. Farnsworth and Soejarto (1991), quoting other papers by Farnsworth, state that approximately one-quarter of all prescriptions dispensed from community pharmacies in the USA contain one or more ingredients derived from higher plants. In many tropical and sub-tropical countries, as in Africa and South and East Asia, the majority of people resort to herbal medicine for the majority of their primary healthcare needs. There are also strong traditions of herbal medicine in parts of Europe, such as Germany, France and eastern Europe generally. The herbal sector is growing fast, increasing by 12-15% by value per year in the UK, USA and Italy (Abrahams 1992). According to a review of a recent consultancy report by McAlpine Thorpe and Warrier (1992), there are more than 2000 herbal medical companies in Europe and more than 220 in the USA; this review states that Germany is the largest market in the world for herbal medicines, with annual sales of $1.2 billion representing nearly 25% of the national pharmaceutical market. The USA is the next largest market with sales of $480 million.

It is difficult to obtain precise information about the structure (Fig. 1) and scale of the international trade in medicinal plants. Anna Lewington, who recently carried out a short-term study on behalf of WWF of the importation of medicinal plants into Europe and attendant conservation problems, found trade statistics and customs records to be very inadequate, and the industry as a whole not particularly forthcoming about its activities (Lewington 1992a). A complication in some cases is that there can be no clear distinction between medicinal, food, spice and aromatic plants. The most recent report available to the general public dealing with European imports appears to be by the International Trade Centre, Geneva, in 1982. This report states that 8 countries then belonging to the EEC imported 80 738 tons of 'vegetation plant materials used in pharmacy' in 1980, the biggest importer being Germany with 31 452 tons, followed by France. Quantities will certainly be larger now, as it is widely acknowledged that the trade has grown. Lewington (1992a) estimates that 500, and possibly as many as 600, species of medicinal plants are traded through Hamburg, Germany, which lies at the heart of the import business in Europe. In 1980 India was the biggest exporter of medicinal plants to Europe (10 055 tons out of the 80 738 imported). Eastern Europe is another important source of supply.

Major international trade in medicinal plants is not only from developing to urban-industrial countries. For instance, there is major trade from the Himalayas, including Nepal, to India and beyond, mostly for use in herbal medicine (notably ayurvedic medicine). The volume of this trade is unknown, because it is believed that the greater part of it passes through unofficial channels. Unregulated harvesting of medicinal plants in the Himalayas is a cause for conservation concern.

The majority of conservation problems that result from existing trade in medicinal plants arise if the plants are 'wild' collected, as opposed to being cultivated. Lewington (1992a) reports that it is very difficult to determine the precise origin of medicinal plants currently imported into Europe, a complicating factor being that some species which are cultivated are also collected to some extent from the wild. Judging by Lewington (1992a) and various articles in Akerele et al. (1991), only a few species, required in large quantities, are cultivated to any significant extent. The great majority of species in international trade, certainly most of those which are used in herbal medicine, are harvested in the wild.

Case study: Prunus africana

Information has been compiled by WWF on conservation issues associated with international trade in Prunus africana for medicinal products (Lewington 1992b). Prunus africana is a large and widely distributed tree of wet montane forests in Africa. Extracts of the bark, marketed as Tadenon (France) and Pigenil (Italy), are used in several European countries to treat early stages of benign prostatic hypertrophy.

The use of this medicine first came to the attention of European industry from the earlier traditional employment of the bark in warm milk in South Africa to treat "old man's disease". Prunus africana is, in fact, a widely used medicinal plants in many parts of Africa. Today, bark, or extracts from the bark, are exported to Europe in significant quantities from Cameroon, Zaire (Kivu), Kenya and Madagascar. So far as can be determined, all harvesting is from uncultivated 'wild' trees growing in forests. It is difficult to establish the scale of the trade, but our information indicates that the total harvest of wet bark each year might be in the order of 1600-2000 tonnes. We estimate that the total value of the trade at the point of sale in European pharmacies as over $100 million a year, a figure which can be compared with the amount received by all those collectors who gain some income from the harvesting of the bark in Africa, estimated in total at less than $200 000 a year.

The manner of collection of Prunus bark, at least in Cameroon and Zaire, seems to be similar to the way many plants are harvested from the 'wild', all over the world for the international medicinal plant trade. Businessmen or their agents contract local villagers for collection of the plant material which is required; this material is then more or less indiscriminately harvested from surrounding areas. A variant, reported in the case of collection of medicinal plants in the Himalayas, is for merchants to bring in their own labourers to the collecting area from elsewhere. It is difficult for poor people to resist this chance of an income, however small it may be, even if they are aware that the long-term effects may be disadvantageous.

Fig 1 Movements of plant materials traded internationally for medicinal purposes. Note: Some categories are not mutually exclusive. Note that the connections between exporting and importing countries are relatively few and that importers, who may also be pharmaceutical or herbal medical companies, have a central position of potential control.

Conservation issues associated with Prunus collection are that the bark is being harvested unsustainably, that it is causing degradation and in some cases loss of an important ecosystem (wet montane forest - vital for catchment protection in Africa) and that it is almost certainly eroding genetic diversity within Prunus africana. There is no threat to survival of the species as such (as seems often to be the case with collection of medicinal plants traded internationally). The Prunus issue first came to the attention of WWF in Cameroon, where indiscriminate harvesting has destroyed many trees in a small remnant montane forest on West Africa's second highest mountain, Mt Kilum. According to local sources, the harvesting has also been indirectly responsible for triggering total forest loss, associated with the sudden injection of a heavy dose of materialistic values, undermining local traditions which afforded some protection to the forests.

Conservation issues relating to trade in medicinal plants for existing products

Trade in medicinal plants for established products can be considered to result in conservation issues if the trade:

Conservation issues and the development of new products

There seems to be an increasing interest by natural product chemists and the pharmaceutical industry in exploring the plant world for possible new medical products. Plants have contributed much to modern Western medicine, in a number of different ways (Hollman 1991): (1) purified compounds from plants are used directly as medicines (e.g. morphine from the opium poppy Papaver somniferum), (2) compounds are extracted from plants and then used in a modified form (e.g. steroid drugs from Dioscorea), (3) an active principle in the plant has provided the stimulus to produce new medicines by total synthesis (e.g. the synthetic drug Intal developed from investigations based on Ammi visnaga), and (4) the mode of action of a plant medicine has been copied to provide a better synthetic drug (muscle relaxants from curare). New biotechnologies will open up new ways in which plants can contribute to advances in medicine.

Strategies for choosing which plants to investigate in the search for new medical products include the random selection of plants based on taxonomic affinity, or the pursuit of leads based on ethnobotanical knowledge. The use of plants in folk medicine has led to the discovery of the majority of major drugs used in Western medicine with an origin in plants (Hollman 1991). Traditional knowledge, accumulated through years of experience, can be regarded as the product of a natural screening process.

The search for new medical products based on plants often involves the movement of plant samples or information about plants between countries, and thus is a type of plant trade (see Fig 2). Differences with trade for products which already exist are: (1) the amount of material involved is generally very much smaller; (2) the transfer of material or information may only occur once or, perhaps only a few times (an initial sample for screening; larger quantities for product development); (3) there is a high chance that no commercial products will result and (4), if commercial success does eventually result, then profits may be very large (due to a monopoly position protected by patenting during early years of marketing of a new pharmaceutical drug).

The sizes of samples required for initial screening are generally small, but sometimes larger quantities are needed for follow-up testing; this can result in serious depletion of plant populations. An example is the collection of Dioscorea deltoides, allegedly for German pharmaceutical firms, in the Khasi and nearby hills in India in the 1980s, allegedly resulting in local near-extinction. This plant is traditionally used in the area as a female contraceptive, so that, ironically, it is possible that advances in the development of contraceptive drugs in Europe have been instrumental in removing the availability of a traditionally used means of contraception from another part of the world.

The most pressing conservation issue in the discovery and commercialisation of new plant-derived or plant-inspired products (including medicines) is the question of how to create equitable partnerships, in order to return a proportion of profits deriving from commercialisation back to the country of origin of the species, plant material or knowledge about the species.

Medicinal plants: the historical role of botanic gardens

A botanic garden has been defined as 'a garden containing scientifically ordered and maintained collections of plants, usually documented and labelled, and open to the public for the purposes of recreation, education and research' (Botanic Gardens Conservation Secretariat (BGCI) 1989). Botanic gardens have a long history of involvement with medicinal plants and with movements of plants around the globe, but not with conservation. According to Heywood (1991), the first botanic gardens in the western tradition, at Pisa, Padua and Florence in Italy, were medicinal plant gardens attached to medical faculties or schools. There is also a long link between medicine and the garden in Asia. At the famous cultural site of Sigiriya in Sri Lanka, dating from the fifth century AD, excavation has revealed the well preserved remains of very extensive, formally laid out, pleasure gardens, and historic records indicate that there was once also a garden for medicinal plants.

The expansion of European power around the world from the fifteenth century onwards was followed by a wave of creation of botanic gardens and arboreta in the tropics and subtropics. These gardens were established principally for economic evaluation of plants for the benefit of the colonial powers. Heywood (1991) states that medicinal plants were given little emphasis by these gardens and arboreta, but nevertheless they did play important roles in introducing tea, coffee and Cola to new areas (all these species can be considered medicinal plants) and also introductions of quinine. The first potential crop tried out at Hakgala Botanic Garden in Sri Lanka was quinine (in 1861), soon followed by tea (in 1865). The latter was successful, and was followed by development of a major industry.

Many plants, both those which had been previously domesticated and those which had not, were transported around the globe and tried out in botanic gardens or arboreta in the colonies. For example, the Germans established a botanic garden at Amani in the East Usambara (Tanzania) in 1902, planting about 900 species, nearly all exotics and nearly all woody. The Royal Botanic Gardens Kew at one time had a policy of facilitating the movement of plants around the British Empire.

Fig 2 Movements of plants, plant materials and knowledge of uses about plants, involving international transfer, for use in the search for new medical products. Note that botanist, ethnobotanist and those responsible for collections of plants, plant material and

From a modern conservation perspective, the historical role of botanic gardens in facilitating plant movements can be seen to have had some unfortunate consequences, both as regards natural ecosystems and mental attitudes:

How can botanic gardens contribute to conservation of medicinal plants in international trade?

Table 1 summarises some desirable conservation activities to combat conservation problems arising from the international trade in medicinal plants. Some of these activities are suitable for botanic gardens which have a number of special features which give them certain advantages and also convey on them certain responsibilities in this area. The ability of botanic gardens to become involved in conservation of medicinal plants depends partly on their available resources, which vary greatly from garden to garden.

If medicinal plants are being over-harvested from the 'wild', then it is possible that collection is not only not sustainable, but also that the genetic diversity of the species is being eroded and that natural ecosystems are being degraded. Except where there is a strong sense of community solidarity, it is likely to be often difficult to develop sustainable harvesting based on community control alone, given that collection of 'wild' medicinal plants for sale is often undertaken essentially competitively. The successful implementation of ways of harvesting 'wild' plants sustainably is generally likely to involve agencies such as forest departments, probably usually working closely with local people. Encouragement of cultivation is often likely to be useful, in order to take the pressure off wild stocks, thus helping to conserve genetic diversity and perhaps being a more reliable source of income for village people. Clearly botanic gardens, with their expertise in gardening and other botanical disciplines, can often play useful roles in helping to select and develop varieties for cultivation, and in undertaking research on techniques for propagation and cultivation. Where the aim is to produce sustainability in supply of plant material for the manufacture of medicines (as will often be the case), then assessments of whether sustainability has been achieved through the introduction of cultivation must consider both the social and ecological dimensions. If over-harvesting of plant material from the 'wild' by a poor rural community is replaced by cultivation by rich farmers, then it cannot be said that sustainability has been achieved, in terms of the total socio-ecological system.

Botanic gardens can also have a role to play in the conservation of genetic diversity within species of medicinal plants. In general, genetic diversity should be conserved through conservation of a network of in situ populations which together reasonably cover the total genetic diversity of the species. Usually these populations will be on land owned by other organisations or private individuals, not botanical gardens. However, botanical gardens may have a role to play in helping to develop back-up facilities for ex situ conservation of threatened medicinal plants. This could be through providing expertise to land-holding agencies or individuals for the development of small nurseries at each in situ site, so as to propagate the species and reintroduce them into nature where populations are low. Possibly, botanic gardens could also assist through the development of germplasm banks such as seed collections, though medicinal plants are not high on the list of ex situ conservation programmes of this type at present.

Botanic gardens have a major responsibility for ensuring that arrangements are equitable in cases where they have some involvement in providing plant samples or information about plants to commercial interests for investigation for new products. Botanic gardens are therefore in the front-line of implementing the principles of the Biodiversity Treaty discussed in Brazil in June 1992. The Biodiversity Treaty will presumably eventually result in new national legislation concerning the exploitation of plant diversity and the requirements for rewards from commercialisation. Botanists and ethnobotanists, including those associated with botanic gardens, will have to observe this legislation, but they have the additional responsibility, in any case, to ensure that their behaviour is ethical. Unfortunately there is little experience of suitable agreements between suppliers of plant material or information about plants and commercial interests. As far as I know, there are no cases in which such agreements have been followed by the successful commercialisation of new products, and then by the actual return of just rewards to sources. It is doubtful whether any very strict conservation guidelines can be written at the present time, given the lack of practical experience, but WWF, through Dr Anthony Cunningham, is in the process of preparing general guidelines for botanists and ethnobotanists to indicate the parameters of the issue and to assist them in arriving at fair arrangements. We hope to have these guidelines ready by the end of December 1992.

Table 1: Necessary activities for the conservation of medicinal plants


                                                                        
Objective               Activity                        Desired Result      


Sustainable harvesting  Assessment of impact of         Sustainability in   
of a non-cultivated     present harvesting on wild      harvesting,         
plant                   populations of the species and  considering both    
                        on biodiversity more widely.    the biological and  
                                                        social              
                        Determination of related        environments.       
                        social structures and                               
                        economics.                                          
                                                                            
                        Evaluation of methods to                            
                        achieve sustainable                                 
                        harvesting: methods of                              
                        harvesting, other methods of                        
                        managing the species or the                         
                        wider environment, social                           
                        structures, economics.                              
                                                                            
                        Implementation of changes,                          
                        initially on a trial basis,                         
                        through appropriate social                          
                        groups (e.g. those currently                        
                        involved, land management                           
                        authorities).                                       

In situ conservation    Mapping and monitoring of       Network of          
of germplasm of a       plant populations.              protected           
medicinal plant                                         populations, with   
species                 Assessment of patterns of       active management   
                        genetic diversity.              where necessary.    
                                                                            
                        Identification of management                        
                        authorities.                                        
                                                                            
                        Determination of management                         
                        needs to maintain viable                            
                        populations.                                        
                                                                            
                        Raising public/institutional                        
                        awareness of desirability of                        
                        this objective.                                     
                                                                            
                        Help to develop and enforce                         
                        CITES regulations.                                  

Ex situ conservation    Scientific sampling of          Adequate sample of  
of germplasm of a       targeted populations.           genetic diversity   
medicinal plant                                         maintained ex       
species                 Determination of methods for    situ.               
                        maintenance of collections,     Material available  
                        and sometimes multiplication.   for                 
                                                        reintroductions     
                                                        and commercial      
                                                        cultivation if      
                                                        required.           

Transfer of commercial  Identification of good          Cultivation         
supply to cultivation   cultivars.                      replaces wild       
of a species                                            collection.         
                        Determination of techniques     Wild populations    
                        for propagation, cultivation,   less threatened.    
                        harvesting, storage and         Reliable income to  
                        marketing.                      rural communities.  
                                                                            
                        Determination of suitable                           
                        growers.                                            
                                                                            
                        Determination of methods for                        
                        introducing new technology to                       
                        potential growers.                                  

Development of new      Collection of plant material    New medicines for   
medicines from plants   or ethnobotanical knowledge.    human benefit.      
                        Supply of plant material or     Fair returns to     
                        knowledge of plant uses for     sources for         
                        commercial evaluation under     conservation and    
                        ethically fair agreements.      development, if     
                                                        commercialisation   
                                                        is successful.      


References

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