An economic evaluation of medicinal tree cultivation: Prunus africana in Cameroon

Wild populations of the Afromontane forest tree Prunus africana (Rosaceae), known as the African Cherry or Red Stinkwood (sometimes called Pygeum africanum) are currently the sole source of bark and bark extract exported from Africa and Madagascar to Europe. This trade has taken place for nearly 30 years, for production of at least 19 different herbal preparations sold by 23 companies based primarily in Europe, but also in North and South America. These are used to treat benign prostatic hypertrophy (BPH), a common disease in older men. This account provides an interesting case-study of a medicinal species which is in transition from wild harvest to cultivated sources of supply. It also illustrates the ‘ecological footprint’ of Europe on African forests, and upon a medicinal resource within them. Bark exploitation has caused serious damage to wild populations of Prunus africana, including trees inside forests of high conservation value in Madagascar and Cameroon. Because of the difficulty of implementing and enforcing conservation measures or developing local institutions to do so, sustainable bark harvesting of remaining wild stocks by local communities is considered unlikely in Cameroon and in Madagascar. For these reasons, cultivation has been suggested as an alternative source of bark production. This study investigated the economic feasibility of different planting systems (enrichment planting, small-scale farming and plantations) for Prunus africana cultivation. As part of this process, we investigated Prunus Africana bark production and growth rates, finding statistically significant correlations between bark thickness, diameter at breast height (dbh) and tree height. Prunus africana showed rapid growth, reaching 14m high and 37cm dbh in 18 years. Results of a comparison between the flow of costs and benefits from small-scale production of Prunus africana and Eucalyptus camaldulensis show that Eucalyptus camaldulensis cultivation is 30% more profitable than Prunus Africana production. But there are reasons why farmers might rather invest in Prunus africana instead of, or in addition to, Eucalyptus trees: Prunus africana is highly valued as an ingredient in many local medicinal treatments, it is used in making tools such as hoes and axes, and it is a good source of poles and firewood. Moreover, farmers and field observation indicated that with the possible exception of maize, crop yield is not much affected by the presence of Prunus africana in the fields. This contrasts with the depressive effect of Eucalyptus trees on crop yields. In North West Province, Cameroon, at least 3,500 farmers are already planting Prunus africana. Bark price is affected by moisture content, distance from the factory and the monopoly, which the company has had on export of bark and bark extract. This study determined bark moisture content to be 42-50%. In rural Cameroon, intermediaries only pay 70 FCFA (0.14 US$) per kg of Prunus africana bark, equivalent to about US$ 142 per ton of fresh bark. At the factory gate, bark sells for 104-270 FCFA francs per kg (in 1994, 1 US$ = 490 CFA), depending on bark moisture content and quality, equivalent to US$ 212 - 551 per ton. Higher prices were paid for bark in Cameroon in 1994, when an Italian company paid 250 FCFA francs/kg, regardless of bark moisture content (US$510 per ton of fresh bark). In Kenya, the price paid to the exporter was considerably higher (11 French francs (US$ 2) per kg). This is equivalent to a price of US$ 2,000 per ton of fresh bark. By comparison, the price for fresh bark of the black wattle, Acacia mearnsii, which is cultivated for its tannin- rich bark, was US$ 94 per ton. On the basis of this study, we recommend clarification of Cameroon forestry law to enable farmers to sell bark from Prunus africana trees they cultivate, that information on the best methods for Prunus africana cultivation from seed be provided to farmers, more competitive bark prices that reflect the international market value of this product, and the initiation of an out-grower scheme with the involvement of the pharmaceutical company that buys the bark and has a monopoly on the export of bark extract.

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