October 28, 2011 - No Comments
In many areas, and particularly our forestry areas, bark is harvested from a range of tree species growing in our natural forests and woodlands, with sometimes devastating effects. We therefore need to take an alternative look at the practice of bark harvesting for traditional medicine.
by Coert Geldenhuys, forest ecologist
|Medicinal products at the Durban muthi market: Various types of Ocotea bullata bark products – bags from the forest, pieces of bark in different sizes and extracts in bottles.|
|Devastating commercial bark harvesting in Umzimkulu forests, southern KwaZulu-Natal: Third bark stripping from Ocotea bullata using a ladder made of small trees of Podocarpus henkelli – both nationally protected tree species.||O. bullata trees cut to collect more bark.||Traditional harvesting of bark of Rhus chirindensis in Magoebaskloof forests, Limpopo.|
|Response of tree species to experimental harvesting in the forest: Good edge growth of Ocotea bullata in Southern Cape.||Partial sheet growth in Curtisia dentata in Southern Cape.||Sheet and edge growth in Pterocarpus angolensis in Miombo woodland, Malawi.|
|Response of tree species to wild harvesting of bark for traditional medicine: Edge growth and aerial roots of Anthocleista grandiflora in Magoebaskloof, Limpopo.||Sheet growth after total bark removal from this Prunus africana, with added experimental strip removal in Umzimkulu forests, KwaZulu-Natal.||No recovery after large strip removed from Rapanea melanophloeos in Newlands, Cape Peninsula.|
The active compounds of many medicines that we buy from the pharmacy are obtained from plants: leaves, flowers, stems, roots or bark. Also, many teas that we drink come from the leaves or bark of trees.
The bark of Prunus africana, for example, a nationally and internationally protected tree species, is widely harvested all over Africa and sold in pharmaceutical shops worldwide for the treatment of prostate cancer. For many people in South Africa, plant parts are the only affordable medicine for their primary health care.
The trade in plants for traditional medicine is a major informal industry. We need to distinguish between rural subsistence use performed by traditional health practitioners, and commercial trade between rural areas and the urban ‘muthi’ markets. Plant material for the commercial trade is collected by harvesters who may have very little knowledge of the species and good practices.
Bark studies in natural forests in southern KwaZulu-Natal, in the Southern Cape and the Cape Peninsula, were done within the project Commercial Products from the Wild (www.cpwild.co.za) initiated as a collaboration between the Department of Forest and Wood Science at Stellenbosch University, the Institute of Natural Resources at KwaZulu-Natal University, the post-graduate School of Agriculture and Rural Development at University of Pretoria, and several independent scientists, with funds from the Department of Science and Technology. The studies were not concerned with what the bark is used for, but focused on understanding the basis for better and sustainable harvesting practices and developing rural institutions through which bark harvesting could be managed in a participatory approach. The bark studies were later expanded to include both natural forests and deciduous woodlands in Malawi and Zambia, with funds from the British Development Fund for International Development (DfID). These studies eventually covered more than 20 important tree species used for their bark in traditional healing.
A survey in 13 natural forests in the Umzimkulu district recorded 95 tree species with bark harvested from 36 species, and of the 7 281 recorded stems, 6.1% were harvested. The major impact was on a few target species, such as Red stinkwood (Prunus africana) (70% of 10 recorded stems), Black stinkwood (O. bullata) (57% of 359 recorded stems), Assegai (Curtisia dentata) (60% of 50 recorded stems), and Cape beech (Rapanea melanophloeos) (39% of 124 recorded stems).
The varied response to debarking shown by species in all the studies showed the need to manage different species differently for sustainable bark use for traditional medicine:
- Degree of ring-barking (percent of bark removed from around the stem) caused a more severe decline in tree health (crown condition) than the percent of total bark removed from the main stem (if not ring-barked).
- Bark regrowth on the wound is either by edge growth (from the edge of the wound towards the middle of the wound), or sheet growth (on the wood in the wound), or both. Wound recovery through edge growth is very fast in some species (such as Prunus africana, Ocotea bullata, Ilex mitis, Pterocarpus angolensis and Albizia adianthifolia), but very slow in others (particularly Rapanea melanophloeos and Parinari curatellifolia).
- Fungal and insect infestations are particularly important in species that show no to slow wound recovery. Insect pinholes on the wood surface become entry points for fungi into the wood to weaken the stem to a point that the tree either dies or snaps. Termites form superficial soil tunnels on the wood surface of some woodland species but did not threaten tree health; the soil may even prevent the wood from drying out. The experimental use of tree seal on the wound in the Southern Cape showed very poor positive to no to negative effects.
- Some species produced excessive gum exudates, or showed severe bark lift on the edges of the wound, or cracks in the wood on the exposed part of the wound.
- Several species produced vegetative regrowth, either through stem sprouts (around the wound), coppice shoots at the base of the stem, or root suckers. The degree of vegetative regrowth is an important decision for tree management for bark production.
Bark harvesting in trees of species in which the wounds recover rapidly, could be done through narrow, vertical strips in a way that would facilitate easy and rapid bark recovery. Trees of species in which the wounds do not recover easily could be cut in a selection system, to use all bark on the stem and branches. For example, Rapanea melanophloeos often regenerates in dense stands on the forest margin. Selective felling of such stems for bark use could thin the stand and facilitate better growth of the remaining stems. Species with the ability to develop coppice regrowth have a better chance to survive than species that do not have that ability.
For example, Ocotea bullata developed good coppice regrowth, but the coppices died if the tree died. However, if the tree was cut before it died, the coppice shoots grew fast (3 to 4.5 m in height in 18 months) and ensured the survival of the tree. In general, it would be better to cut a few selected trees, harvest all the bark up to the smaller branches, and possibly also use the wood, and then manage tree recovery through coppice management (using some cut branches to protect the coppicing shoots against browsing from livestock and antelope), or seedling regeneration.
Bark use for traditional medicine affects the livelihoods of many people and requires management of the natural forests within and around about every forestry estate in South Africa. Bark harvesting from natural forests without a licence is illegal under Section 7 of the National Forests Act (1998), but provision is made for licensing resource harvesting for commercial purposes; users can apply for exemption for domestic and cultural uses. The reality is that current control mechanisms and law enforcement are not effective in many areas. The challenge is to support traditional subsistence bark use and control sustainable levels for commercial bark use – a basic approach towards sustainable resource use: adaptive management incorporating current ecological knowledge into participatory forest management with a bark user group in an area, and monitoring of resource use impacts.
Forestry estate managers could sustainably manage this perceived illegal bark-stripping from natural forests and woodlands in and around their plantations along the following general guidelines:
- Assess the status of bark stripping within the natural tree stands, large and small, on the estate. Sometimes this is visible from the road through a forest, but often bark is removed on the side of a tree away from the road. Look out for entry points from a nearby village.
- Do not create an awareness of bark harvesting in areas where there is no bark use or where harvesting is small with very little effect on the trees and/or forest.
- Develop a good relationship and communication with bark harvesters from neighbouring villages where bark use is more severe, to support traditional bark use and to involve those traditional practitioners to manage commercial use of bark from the forests. The best approach would be to assist the bark harvesters to develop an association through which the negotiations and participatory licensed bark management could be done. The constitution of such an association should ensure (1) to train, uplift, educate and develop its members with the objective of increasing their business skills and profits and to enhance their harvesting skills with the express purpose of protecting the environment and the long-term sustainability of targeted species of medicinal plants. (2) that all members sign an agreement between themselves and the association which binds them to a set of standards, rules, objectives or laws.
- Consider the development of alternative resources for future rural medical care currently based on tree bark: bark from old trees, on a small scale and as part of a sustainable forest management system; from planted trees in forest rehabilitation plantings adjacent to the forest or within suitable sites within the village; and harvesting leaves and young bark from short-rotation coppice stands in suitable sites outside the forest.
Protecting forests and species is not enough to ensure their survival in rural areas. Appropriate resource management, with involvement of potential resource users and training of all stakeholders, is essential to develop shared responsibility in sustainable bark use from natural areas for traditional primary health care.
Published in August 2011