The Regional Conference for Africa on Conservation, Management and Utilisation of Plant Gums and Resins, hosted by Kenya Forestry Research Institute (KEFRI), was held in Nairobi, Kenya from 6 to 10 October 1997.
Coordinated by KEFRI, a number of international and bilateral agencies, namely: Association for International Development of Natural Gums (Aidgum), FAO, Promotion of Sustainable Forestry Management - (GTZ/KEFRI) and Third World Academy of Sciences (TWAS) collaborated by providing funds, sponsoring participants and /or by direct attendance.
The outcome of the Conference was substantial, with clear recommendations for action. We have pleasure in sharing it with all interested persons and institutions. We take this opportunity to acknowledge with thanks the contribution of all those who attended the Conference and their active participation in the discussions, which made this meeting a remarkable success. We thank all those who collaborated with, and supported the efforts of KEFRI in organising this Conference. We are grateful to all the members of the secretariat for their devoted service. Finally, we fully appreciate the contribution of J.O. Mugah, B.N. Chikamai and E. Casadei for reviewing and editing the Conference report.
No doubt, the perspectives on conservation, management and utilisation of plant gums and resins as they emerged from the discussions at the Conference and the light they threw on how to address aspects of production and quality control and the need for linkages will help national and international agencies in designing and implementing viable programmes. FAO is committed to pursue the outcome of the Conference and to support the implementation of its recommendations, in collaboration with partner agencies and countries.
Karl-Hermann Schmincke
Director
Forest Products Division
Forestry Department
PART I:Background to the Conference and Recommendations |
The role and value of plant gums and resins in Africa cannot be over-emphasised. The resources are found in hot and dry regions, where they are valuable in various ways. In countries bordering the Sahara, the plants have proved useful as windbreaks and shelter belts against desert encroachment and hence desertification. Their canopies intercept rain drops while the root systems are effective in reducing soil erosion, thereby stabilising soils. Species in the genus Acacia improve soils due to their ability to fix nitrogen. The foliage and pods are valuable dry season fodder while the stem has wide application in fencing, wood energy and construction. The environmental benefits of these plant resources in the region are therefore significant.
However, the most valued commodities in economic terms are the gums and resins. The most important of these are gum arabic, myrrh and frankincense. Gum arabic is a product of Acacia senegal, A. seyal and closely related species. Virtually all the gum arabic of commerce comes from Africa with Sudan accounting for up to 80% of the world production followed by Chad and Nigeria. About 12 other countries in the Sahel, stretching from Senegal/Mauritania in West Africa to Somalia in the Horn of Africa and southwards to Tanzania are also producers. Gum arabic has wide application in the food and pharmaceutical industries and in miscellaneous technical applications. In the food industry (foods and drinks), it is used as a thickening, stabilising, emulsifying and suspending agent. In the pharmaceutical industry, it is used as a binding agent in tablets and as a suspending and emulsifying agent in creams and lotions. Some of the technical applications are in the printing and textile industries where advantage is taken of its film-forming and sizing properties respectively.
Myrrh is produced by species in the genus Commiphora. The main source of true myrrh is C. myrrah found in Somalia, Ethiopia and Kenya. Myrrh, like resin is also produced by Commiphora habessinica, C. confusa, C. africana and C. incisa. Additionally, Commiphora holtiziana and C. pseudopaoli produce resins commercially referred to as opoponax , which are used as tick repellent. Frankincense on the other hand is produced by species in the genus Boswellia. The main source of frankincense from Africa is B. papyrifera found in Ethiopia, Sudan and Somalia. Boswellia neglecta from East and the Horn of Africa also produce commercial incense. The main uses of myrrh and frankincense are as sources of fragrances and pharmaceuticals.
1.2 The need for a regional conference
Over the years, and particularly in the recent past, there has been a decline in the use of the above-mentioned natural products in favour of synthetics. The latter are preferred because of their consistent quality and generally lower prices. The natural products are characterised by unreliability of supply accompanied by unpredictable prices and variable quality. Nevertheless, gums and resins remain products of choice if these constraints are addressed. Gum arabic, for example, has functional properties which synthetics cannot match. Additionally, growing health consciousness among consumers is favouring increased use of natural products.
Africa has enormous resources with the potential of producing these natural commodities on a sustainable basis. If properly developed, the resources will provide reliable supply and stabilise the market prices. What is required is a co-ordinated strategy on conservation and development of these resources. This would be in line with the Rio Convention on Biodiversity and Agenda 21. It was in recognition of the opportunities and challenges facing most of the producing African countries that led to the organisation of this Conference. The main objectives of the Conference were:
1.3 Outcome/Recommendations of the Conference
The Conference had two main sessions focusing on plant gums and resins. A workshop was held for each session to discuss pertinent issues and develop recommendations. Major issues on plant gums centred on gum arabic, the main product of commerce in Africa. Similarly, issues on resins focused on myrrh and frankincense. The outcome of the Conference is thus based on the three commodities with the last two being grouped under resins and is presented in the form of draft proposals with details of working groups under each session given as annexes.
Gum arabic-producing countries are facing problems in relation to commercialisation and ensuring added value to the product in relation to international markets. Most of the countries of the Africa region feel isolated and cannot readily access the technology, quality control and market opportunities available. These countries need further regional cooperation to exchange information, training, research and development opportunities.
Objective
To create a sub-regional network to enable countries to develop their system of sustainable production, marketing and improvement of their products to international standards. The network should promote the relationship between the primary producer, the processor and the end-user.
Inputs
Activities
1. Set up the network initially by Kenya as a follow-up to the Regional Conference
2. Organise workshop to set out the protocol for operation and seek support from various donors (such FAO, National Aid/Development Agencies, AIDGUM/AIPG, and the Private Sector to pursue the objectives defined).
3. Pursue priority objectives, namely:
4. Establish Information Systems
Expected Outputs
Time Frame
Annexes to the draft proposal based on outcome of working groups
Annex 1 A Basic Training Manual
Objective
To prepare a basic manual which sets out in an illustrative manner the various primary functions performed by farmers and extension workers in gum arabic production and primary quality control.
Inputs
Annex 2 Education and Training Programme
Objective
To provide education and training for the person involved in the chain of gum arabic production from planting, collecting, sorting, cleaning, storing, processing, quality control and end-use marketing.
Inputs
Annex 3 Quality Control
Objective
Develop national quality control systems for gum arabic from production (primary quality control) to end-product (certification of product).
Inputs
Annex 4 Resources Survey
Objective
To establish the production of gum arabic in the region, and identify the future market production opportunities by surveying the plant gum resources (resource map).
Inputs
1.3.2. Resins: Myrrh and Frankincense
Resins, just like gum arabic, are available in several African countries, and potential to utilise them as commodities of commerce exists. However, their utilisation is hampered by a number of factors relating to production, quality control and marketing. For instance, the resource type, their quantities and distribution are not clearly known.
Objectives
1. To identify ways of improving the production, marketing and quality of resins
2. To establish national/regional bodies which will co-ordinate resource surveys, production, marketing and quality control of resins
Inputs
Activities
1. Establish regional network centres
2. Establish information systems:-
3. Organise workshop(s) to set out the protocol for operation and seek financial support that will focus on research and development in:-
a) production
- Improve production methods in terms of extraction, handling of the product, cleaning, sorting and grading of the product, storage, packaging and pricing
- Conduct research on land tenure and property rights linked to the production of resins
- Issue on sustainability should be explored
b) marketing
- Conduct research on marketing in terms of where the product goes, in what form and for what use
- Determine the potential of the resin product
- Search for new markets
- Secure the base and research on consumer acceptance
c) quality control
- Identify simple methods which can be used to characterise resins in producer countries
- Set up standards between producers and users and establish regulations on quality and purity
Outputs
1. Formation of Regional Network Centres
2. Improved exchange of information among resin-producing countries through the formation of a database, establishment of a newsletter for the scientific community and production of a simple manual for the rural communities
3. Improvement and development of the resin industries, from the local communities to the end user, through conformity with international standards
Time Frame
Approximately 2-3 years to establish network
Conference PapersThe Conference comprised essentially three main thematic areas namely
PART II:Conference Papers |
MANAGEMENT AND ORGANISATION OF GUM
ARABIC INDUSTRY IN SUDAN
Sudan is the acknowledged world leader in gum arabic production. It contributes between 70 and 90% of the total world production. In 1995 alone it produced 51,564 tonnes comprising 45,564 tonnes of gum hashab (i.e., from A. senegal) and 6,000 tonnes from gum talha (i.e., A. seyal). This was in excess of the average world demand of 40,000 tonnes. Not only does it produce far more gum than any other country butt its gum is of the best quality and thus sets the standards by which gums from other sources are judged. This success is as a result of two main factors: ideal environmental conditions suitable for the growth of A. senegal and a long history of sound production practices. This paper outlines aspects of management and organisation of the gum arabic industry in the country.
Gum arabic from Sudan is a product of A. senegal and A. seyal. There is only one variety of A. senegal in Sudan, i.e., var; senegal which is the source of hashab. In the case of Acacia seyal, both varieties, i.e., var. seyal and fistula are found in the country with var. seyal being the main source of talha. Production of gum arabic is concentrated in he gum belt between latitudes 10o and 14o North spanning 12 states with an estimated area of 520,000 km2.
Management of the Acacia senegal for gum production falls into either of two systems: hashab owner or hashab renter. Hashab owners are either small or large-holder farmers. The former make up the majority of gum producers across the gum belt. They own small holdings "gum orchards" which are part of the A. senegal rotation system and practise gum production in one of three ways:
Large-holder farmers include traditional hashab owners, sheiks, well-to-do families and mechanised scheme owners. They depend on hiring labour and on share-cropping for production.
Collection of gum is carried out by daily payment or share-cropping of the produce. The latter is more prevalent in the dry areas and Darfur region. It is an arrangement where two thirds of the produce goes to the owner and one third to the collector of the gum. Sometimes a 50:50 sharing arrangement is undertaken. This applies when the hashab plantations are remotely located or the owner is not providing food or water to the workers.
Hashab renter system includes those renting forest administration plantations and property owners. The two prominent groups of the first category are the resident local entrepreneurs and financially capable migrants from Kordofan known as "Kardafa". There are also the individual camel owners who associate themselves with a handful of workers. All three groups rent hashab plantations, support the organisation of the labour groups (who they usually draw from their places of origin) and act as guarantors to the improved labourers at the village shops. A form of liability is demanded by local shops to extend the credit support. The local entrepreneur, when not a merchant, and the migrant organises from Kordofan are often figures known to the shop-owners, whilst the camel owner would be given credit against the value of the camel.
a) Overview
One of the greatest strengths of the present Sudanese gum arabic industry is the consistency it offers end-users in terms of both quality and price a the point of export. This is due, in large measure, to the fact that production of gum arabic is actively controlled from beginning to end by a single body, the Gum Arabic Company (GAC).
The GAC's activities begin at the start of each gum collection season, usually around September/October, when it announces the export price (FOB Port Sudan) to be set for the coming year. The level at which it is to be set is decided as a result of market intelligence gained through a network of overseas agents and other sources, which enables estimates to be made of likely demand for gum arabic, and the anticipated availability of gum from the resource. Likely production levels can be predicted quite accurately from such factors as rainfall (which is not only necessary for the trees but important for the farmer/collector and his family) and market prices for the farmer's other crops (which will affect his willingness to collect gum).
Using the export price (in US$) and he appropriate exchange rate as a starting point, the total estimated costs (at Port Sudan) of cleaning, handling and preparing the gum for export are deducted to give a Port Sudan procurement price. From this are deducted the costs of up-country cleaning, handling and transport to Port Sudan to arrive at the basic floor price which is set for the gum auctions at origin. Costs at Port Sudan include those incurred as a result of cleaning, quality control, storage, weight losses, fumigation, transport and loading, export duty, insurance and other financial charges, and GAC profits. Those incurred before arrival at Port Sudan include various fees and commissions, cleaning, packing, handling and transport costs, the cost represented by gum weight loss en route to Port Sudan, and merchants' profits.
At the up-country markets the collectors, or small village traders to whom they have sold gum, bring sacks of gum for auction and sell to the highest bidder. The bidders are other, larger traders who, if successful, clean and sort the gum and then sell it on the GAC. the GAC, in turn, re-clean and grade the gum at their warehouses in Port Sudan and prepare it for export. If the bidding at auction does not reach the guaranteed floor price (set by the GAC at the start of the season), then the GAC intervenes to buy the gum themselves.
b) Production Methods
Hashab is collected from A. senegal by tapping while talha is from natural exudation. Tapping begins when the trees are just starting to shed their leaves, usually about the end of October or beginning of November although the exact timing depends on the rains. Older methods of tapping involved making small incisions into the tree with an axe. To avoid the damage that this could do to the tree, methods were developed which use a specially designed tool, a 'sunki'. Through promotion by the extension services the method has largely replaced the older ones. The sunki has a metal head fixed to a long wooden handle. The pointed end of the head is pushed tangentially into the stem or branch so as to penetrate just below the bark, and then pulled up so as to strip a small length of bark longitudinally from the wood. Damage to the wood should be minimal. Several branches are treated in a similar manner at one tapping and in the course of a day one person can tap about 100 trees. In subsequent years, other branches or the reverse side of the previously treated branch are tapped.
For trees which have been planted from seed, tapping starts at age 4-5 years; for those planted as seedlings, tapping can start in the third year.
After this superficial injury, ears of gum form o the exposed surfaces and are left too dry and harden. After 5 weeks the first collections of gum are made, with further collections from the same trees at approximately 15-day intervals until the end of February, making five or six collections in total. The land tenure system and respect for local tradition generally ensures that the people who carry out the tapping also reap the rewards of collecting the gum. However, after the bulk of the gum has been harvested, the odd tears of gum which continue to be produced by the tree can be collected by any other person. Trees in wadis or elsewhere, where the leaves had not been shed earlier, may be tapped and subsequently harvested at a later date than the others.
As far as possible, the tears are picked by hand from the stems and branches where they have formed, and not by knocking to the ground where they can pick up dirt. They are placed in an open basket by the collector, the use of plastic sacks is discouraged since they have been found to increase the risk of moisture retention and mould formation.
At present, little cleaning or sorting is undertake by the producer (collector) of the gum. Since he is paid at the auction according to the weight of gum rather than on quality criteria (within limits, since his gum would not be accepted for auction if it were grossly contaminated), there is no great incentive for him to spend time cleaning and sorting it. Some degree of cleaning and sorting may be undertaken by small village traders to whom the producer sells him gum, but it is usually undertaken by the large traders after it has been sold att auction and prior to them selling it to the GAC. If the GAC intervenes to buy the gum at auction because it has not reached the floor price, then the company undertakes the cleaning and sorting at its own warehouses in the regional centres in the gum belt.
Cleaning and sorting is done by hand, usually by women, who sort it on the ground into piles of whole tears and smaller pieces, separating any excessively dark gum and removing pieces of bark and other foreign matter. Gum sorted in this way by the trader is sold on to the GAC and bagged and transported to its warehouses at Port Sudan as 'Selected' and 'Cleaned' gum, distinct from 'Natural' gum. Unlike some other countries, separation of mixtures of gum from different botanical sources (such as A. senegal and A. seyal) is not necessary because it is kept quite separate during its collection.
On arrival at the GAC dept at Port Sudan, every consignment of gum hashab is re-cleaned, sorted and graded in preparation for export. Until 1991 this operation was carried out manually. Since then, it has been mechanised using a system of conveyor belts and shaking and sieving machines. The traders' bags of cleaned gum are upturned onto an inclined moving belt which takes the gum up to the shakers and sieves; a person is present at the start of the belt to remove any lumps that are very large. After separation of the dust and under-sized pieces by sieving, the remaining lumps of gum pass on a belt between lines of women who give them a final inspection - any remaining foreign mater (such as stones) or dark coloured pieces are removed by hand. At the end of the conveyor belt the gum is bagged and weighed ready for export or it is transferred to the kibbling machine for further processing.
The outputs from the cleaning and sorting operations are graded and sold according to eh following main designations; export prices for 1994/95 are also indicated (per tonne, FOB Port Sudan):
Hand Picked Selected (HPS) US$4850 Cleaned US$4200 Siftings na Dust US$2760 Red na
HPS gum is in the form of clean, whole tears (but not the very largest) which have been carefully selected and which fetch a premium price. Cleaned gum is the gum which is bagged at the end of the conveyor belt, and may comprise whole or broken lumps. Siftings are the smaller pieces of sieved gum, and dust is the fine material which passes through he finest sieve. Red gum is the dark gum removed by hand from he other lumps. Exported gum is packaged in new 50-kg jute bags.
c) Monitoring and Quality Control
The intrinsically high quality of Sudanese gum arabic (hashab), combined with an efficient, long-established system of collection and post-harvest handling, means that the problems of quality control are no as great in Sudan as they are for some other countries. A well-organised extension service ensures that the people who tap the trees and collect the gum do it in the correct manner (for example, no mixing of gum from different botanical sources, picking the gum from the tree rather than off the ground, placing it in baskets rather than closed bags) and these aspects play an important part inn determining the quality of the gum which arrives at the market for auction. Traders who purchase the gum (or the GAC) will also do so only if it matches their own visual criteria for cleanliness and this, too, instills in the producer a sense of quality consciousness (although not, perhaps, as great as iff there were a financial incentive to produce high quality gum). In turn, the traders who clean and sort the gum before selling it on to the GAC know that they will be penalised if, during the re-cleaning, the gum is found to be below the expected quality.
During the course of the last few years a more rigorous system for quality control and certification has been put in place at the GAC's cleaning and processing facility att Port Sudan. A purpose-built laboratory was established in early 1992 and equipped with new equipment. The laboratory is small, but clean and air-conditioned and a well-stocked chemical store.
All gum is sampled when it arrives at Port Sudan, in a proper, statistical manner, each of 21 bags out of every 400 are emptied and sub-sampled by quartering; the combined sub-samples are further sampled to give a representative 1-kg sample. Half of this sample is ground to a powder to provide the material for analysis; i.e. loss on drying and optical rotation. The latter parameter is sufficient to identify any gum talha in a mixture with gum hashab. he bags of up-country gum are each labelled with a number which identifies the trader, so any problem brought to light by the quality control measures can be discussed and resolved with the trader concerned.
During mechanical cleaning a sample of gum is taken every hour for analysis (optical rotation and acid-insoluble matter). Finally, during bagging a sample is taken for analysis: loss on drying, optical rotation, acid-insoluble matter and total ash are determined and the details are recorded on a Certificate of Analysis. This is presented with each batch of kibbled, HPS or cleaned gum that is exported. A sample of each export batch (identical to the sample analysed for certification) is kept for reference for one season.
_____________________________________________
1 State Minister, Ministry of Agriculture and Forestry, Sudan
PRODUCTION AND MARKETS OF GUM ARABIC
FROM FRENCH SPEAKING WEST
AFRICAN COUNTRIES
About 30% of the world production of gum arabic comes from the French speaking west African countries (FSWACs). The main producers are Chad, Niger, Burkina Faso, Mali, Senegal and Mauritania with some exports recorded for Cameroon and Central African Republic. The main sources of gum arabic are Acacia senegal (hard gum) and A. seyal (flaky gum). Additionally, commercial gum arabic includes some gum from Acacia leata, A. polyacantha and A. dudgeoni. Europe is the major destination of exported gum arabic from FSWACs though USA has emerged as an important destination in the last 2-3 years.
Table 1 provides 7-year annual average production data (1980-1994) of gum arabic (by botanic source) from six FSWACs. Since very little of the gum produced is consumed domestically (except perhaps Senegal), export levels are also a good indicator of domestic production. Table 2 gives the export levels of gum arabic from FSWACs. There was an upward trend in the production of gum arabic over the 6 year period (1991-1996). The production reached a peak level of more than 9400 tons (about 30% of the world production) in 1996. Chad is the main producer of gum arabic and in 1995, it became the second most important producer after Sudan.
Gum arabic of commerce from Chad is produced from both Acacia senegal and A. seyal. Over the last 2-3 years, increasing amounts of gum arabic from Chad has been coming from A. seyal. Cameroon and the Republic of Central Africa (RCA) have recorded significant quantities of exported gum arabic. Cameroon is said to export flaky gum, i.e., from Acacia seyal. It is believed that most of the gum from Cameroon and RCA originate from Chad and Sudan respectively.
Based on the 7-year annual averages (Table 1), production in the other FSWACs was in the following descending order: Senegal, Mali, Mauritania, Niger and Burkina Faso. However, production data over the 6 year period (1991-1996) have revealed lower annual averages. Official records show that most of the gum arabic from Senegal and Mauritania is from Acacia senegal while Mali exports both A. senegal and A. seyal gum. It is believed that most of the gum arabic from Senegal are re-exports from Mali and Mauritania. It is also said that about 200 tonnes/year of gum arabic in Senegal is used in the local food and pharmaceutical industries.
Table 1: Summary of gum arabic data for five French Speaking West
African countries,
showing botanical source, production, imports into EC, and main European markets
| Country Main botanical Source |
Annual production |
Annual imports to EC and main European Markets |
||
| Chad | A. senegal A. seyal |
3,500 1,500 |
EC France UK |
3,500 2,800 600 |
| Mali | A. senegal A. seyal |
500 | EC France |
140 45 |
| Mauritiania | A. senegal | 400 | EC | 180 |
| Niger | A. senegal A. seyal |
300 | EC France |
150 115 |
| Burkina Faso | A. senegal A seyal |
200-300 | ||
| Senegal | A. senegal | 700 | EC France UK |
450 300 130 |
Table 2: Export of gum arabic from FSWA countries (in tons)
1991 |
1992 |
1993 |
1994 |
1995 |
1996* |
|
| Chad | 2188 | 2450 | 3696 | 4662 | 7021 | 7315 |
| R.C.A. | 74 | 78 | 33 | 119 | 126 | 639 |
| Senegal | 262 | 261 | 459 | 362 | 662 | 213 |
| Mauritania | 32 | 48 | 55 | 166 | 258 | 256 |
| Cameroon | 95 | 647 | 841 | 1031 | 161 | 560 |
| Niger | 27 | 155 | 228 | 240 | 110 | 242 |
| Mali | 112 | 31 | 77 | 249 | 295 | 229 |
| R.C.I. | 0 | 0 | 26 | 50 | 15 | 20 |
| TOTAL FSWAC | 2790 | 3670 | 5415 | 6879 | 8648 | 9474 |
| TOTAL World | 37089 | 31764 | 27348 | 41789 | 38568 | 32590 |
| %/World | 7.52 | 11.55 | 19.8 | 16.46 | 22.42 | 29.07 |
Production of gum arabic in Niger is far below the 1980s level when it was among the five top producing countries in the world. It produces both A. senegal and A. seyal gum. Also a significant amount of gum arabic - a mixture of hard and flaky gums comes from Burkina Faso. One development in Niger is the production of a specialised product under the trade 'clean sifted Niger gum'. The product is a mixture of 60% flaky gum and 40% hard gum destined to satisfy the demand of a limited number of importers in the industrialised countries. Burkina Faso has been excluded from the wide marketing circuit of gum arabic. It has contributed though in a discontinuous and indirect ways (with border countries such as Mali and Niger acting as go betweens) to supplying the world market.
The European Community (EC) is the major regional market for gum arabic from FSWACs (Table 3). France is the leading importer within the EC which in 1996 accounted for 54% of the total imports from FSWACs. UK is the second largest importer though in 1996 the total amount imported fell below the 6-year annual averages. Imports into Germany have shown a general increase over the last 4 years. Belgium-Lux and Italy are other emerging markets in the EC.
Outside the EC, USA is the single most important trading partner. In 1996 alone, it accounted for 33% of the total imports from FSWACs. Chad is the main supplier of gum arabic to USA. It appears that this increase is the result of two main factors namely the TCP project by FAO which raised the awareness of the potential and value of gum arabic in Chad. This was followed by improvements in the production and quality of locally produced gum arabic. At about the same time a workshop was held by USAID in 1994 in N'Djanena which offered USA with opportunities of a ready source of good quality gum arabic. In addition to USA, small quantities of gum arabic have been exported to South Korea, Sweden, India and Pakistan though in a sporadic manner.
Table 3: Countries where FSWAC raw gum arabic is exporting (in tons)
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
6-year annual average |
|
| France | 1739 |
2107 |
3505 |
4741 |
4483 |
5431 |
3668 |
| U.S.A. | 0 |
18 |
60 |
341 |
1415 |
2425 |
710 |
| Germany | 37 |
49 |
827 |
432 |
1139 |
705 |
532 |
| U.K. | 1008 |
1476 |
894 |
1103 |
1396 |
880 |
1126 |
| Belgium-Lux | 0 |
0 |
0 |
39 |
49 |
66 |
26 |
| Italy | 0 |
0 |
3 |
0 |
0 |
38 |
- |
_____________________________________________
1Applications Techniques Forestieres, France
RECENT ADVANCES ON CLASSIFICATION AND STATUS OF THE MAIN GUM-RESIN PRODUCING SPECIES IN THE FAMILY BURSERACEAE
FRANCIS N. GACHATHI |
Burseraceae is a family of 17 genera with some 560 species which are widespread in the tropics especially in Africa, Malaysia and South America. These are trees or shrubs characterised by aromatic resins from the bark used even in Biblical times for frankincense, myrrh and perfumes. The main resin-producing species are found in the genera Boswellia and Commiphora which are common in the hot drylands. Despite their early recognition, classification and nomenclature of members of the two genera, and particularly those of Commiphora have remained unstable. They have been described by botanists as taxonomically difficult, frustrating or confusing. This is largely because of the nature of the plants themselves, appearing leafless and in a drought-dormant condition for much of the year. This has led to the practice of describing species from inadequate and often sterile material. As a result ,some species have been described by different botanists under different names. Also, sterile plants from other genera have been described as species of either Boswellia or Commiphora. For example, six plants described by Engler (the chief worker on the genus Commiphora) as new species of Commiphora belonged in fact to other genera and in other families. Several plants within the two genera therefore have been known, simultaneously or successively, by two or more different names. This instability of plant names is a real disadvantage as all information about plants and their products is communicated by name. Recent taxonomic revisions of the family Burseraceae have resulted in the union of two or more species previously considered distinct, splitting what was considered previously to be one species into two or more species or outright rejection of wrong names brought about by mis-identification. Most names of the members of the family Burseraceae are therefore marred by numerous synonyms, subspecies, varieties, long descriptions and additional notes. The aim of this paper is to survey the recent advances on classification and look at the status of the main resin-producing species in the family Burseraceae with particular reference to the region of Tropical East Africa.
Production of gum resins from members of the family Burseraceae is of economic importance in some tropical countries. Although substantial quantities especially of frankincense and myrrh from the genera Boswellia and Commiphora are harvested annually for sale, little is known about the status of the main gum resin-producing species within the family. Recent classifications place the family Burseraceae Kunth in the Order Sapindales Bentham and Hooker. This is a natural group consisting of 15 families characterised by their woody habit, compound or cleft leaves, two whorls of stamens, a well-developed nectary-disk and a syncarpous ovary with a limited number (1-2) of ovules in each locule (Cronquest, 1981).
The family Burseraceae consists of 17 genera and about 600 species which are widespread in the tropics but especially well represented in tropical America, Malaysia and north-eastern Africa. The largest genera include Bursera, the type genus confined to tropical America with a centre of greatest diversity in Mexico and Commiphora which is widely spread in the less humid parts of tropical Africa and Madagascar with fewer species in west Africa, Iran, Pakistan, India, Sri Lanka and Brazil (Gillett, 1991).
Diagnostic features
The family Burseraceae is composed of trees and shrubs with prominent vertical resin ducts in the bark. The leaves, which are compound, are spirally arranged and crowded at twig-tips. The flowers are rather small and are either solitary or inflorescences usually at the twig-ends, regular with parts in threes to fives, bisexual or more often unisexual, the plants often dioecious. The sepals are fused and are either imbricate or valvate, petals free, also valvate or imbricate. The stamens are equal to or double the number of petals and usually in two whorls. The ovary is superior with three to five carpels and two to five locules. The fruit is usually a drupe, sometimes a capsule. Seeds are without endosperm.
Classification and chief genera
Burseraceae can be conveniently divided into three tribes as follows:
Protieae. Drupe with two to five free or adhering but not fused parts: six genera, including Protium and Tetragastris.
Burserae. Drupe with endocarp completely fused, exocarp dehiscing by valves: five genera, including Boswellia, Bursera and Commiphora.
Canariae. Drupe with completely fused endocarp: six genera, including Canarium, Dacryodes, Haplolobus and Santiria.
Of the three tribes, Burserae is of economic importance as far as gum resins are concerned. Frankincense comes from Boswellia, myrrh from Commiphora, while varnish is obtained from Bursera.
The most recent work on Burseraceae in East Africa is that of Gillett, (1991) "Flora of Tropical East Africa (FTEA)". Within the flora area, the family is represented by three genera: Canarium with 2 species, Boswellia with 4, and Commiphora with 66. Canarium schweinfurthii Engl. which is a tall tree attaining 40 m with a straight cylindrical trunk and compound leaves is found in Uganda and northern Tanzania around Lake Victoria. Canarium madagascariense Engl. ,which differs from C. schweifurthii in its fewer leaflets seems to be approaching extinction. It has only been collected twice since 1949 in west Usambara, Tanzania (Gillett, 1991). Boswellia and Commiphora, which produce frankincense and myrrh respectively are well adapted to the hot drylands usually below 2000 m, becoming most numerous in north-eastern Kenya and extending into Somalia and Ethiopia.
Problems associated with identification of Boswellia and Commiphora species
Despite their early recognition, classification and nomenclature of members of the two genera, Boswellia and Commiphora in tropical East Africa have remained unstable. They have been described by various botanists as taxonomically difficult, frustrating or simply confusing. This is largely because of the nature of the plants themselves, appearing leafless and in drought-dormant condition for much of the year and the difficulty of obtaining complete specimens showing both male and female flowers, leaves, fruits and bark, the useful characters in identifying members of these groups. The flowers and fruits are seldom produced with the leaves and are therefore difficult to identify. The situation is worsened further by the fact that Commiphora is a gregarious genus and where one species is found, several others are likely to occur as well (Beenje, 1994). This has led to the practice of describing species from inadequate and often sterile material. As a result some species have been described by different botanists under different names. Also, sterile plants from other genera have been described as species of either Boswellia or Commiphora. For example, six plants described by Engler (the chief worker on the genus Commiphora) as new species of Commiphora belonged in fact to other genera and were in other families: two to Lannea and two to Sclerocarya (Anacardiaceae), one to Platycelyphium (Papilionaceae) and one to Combretum (Gillett, 1973).
Even today sterile plants of Lannea continue to be mistaken for Commiphora. In Lannea, the bark is tough like string and nearly always some of the hairs are stellate. Such bark does not occur in Commiphora and neither do such hairs. Also, sterile specimens of Boswellia neglecta S. Moore Rae readily confused with Lannea alata Engl. which often occurs together with it and may be distinguished by its narrowly winged leaf-rachis. Several plants within the two genera therefore have been known, simultaneously or successively, by two or more different names. Recent classifications separate the two genera using the fruit as follows:
Boswellia: Fruit a (2)3(4-5) - valved pseudocapsule, releasing 1 - seeded nutlets on dehiscence; calyx-lobes and petals 5, stamens 10; leaves pinnate; true spines absent.
Commiphora: Fruit a dehiscent drupe, splitting into 2(-4) valves disclosing a 1(-2)-seeded stone which is usually surrounded (at least at the base) by a red or orange, fleshy pseudoaril. Calyx-lobes and petals 4, stamens 8 (rarely 4). Leaves simple, 1-3-foliate, or pinnate; spines often present.
The species of Boswellia producing frankincense
The genus Boswellia Roxb. ex Colebr. is composed of 20 or so species extending from Ivory Coast to India and south to N.E. Tanzania and N. Madagascar but most numerous in N.E. tropical Africa. These are unarmed shrubs or small to medium-sized trees exuding a watery aromatic substance from the bark which slowly hardens to a resin on exposure. In tropical East Africa, the genus Boswellia is represented by four species: B. papyrifera, B. rivae, B. neglecta and B. microphylla. These are easily distinguished by the number, shape and size of their leaflets.
True frankincense is obtained from B. carteri Birdw, and some other species growing in northern Somalia, Dhofar and Hadhramaut. In tropical East Africa, the main species producing frankincense is B. papyrifora, found in Ethipia, Sudan and Somalia and B. neglecta S. Moore (B. hilderbrandtii Engl.) which is abundant in dry bushland of northern Kenya. The latter grows on basement complex or lava and red sandy soils at altitude 200-1300 m with less than 600 mm of annual rainfall.
The species of Commiphora producing myrrh
The genus Commiphora Jacq. comprises about 190 species, common in the drylands. These are generally small to medium-sized dioecious trees with outer bark often peeling in papery flakes or scrolls exposing the green or bluish under bark. The leaves are compound, spirally arranged and usually clustered at the ends of the short and spiny - tipped shoots.
In East Africa the genus Commiphora is represented by about 66 species. This is a taxonomically difficult group and classification of the different groups is made possible by first treating the entire group into 14 sections by use of combined characters and then applying a delimiting key to each section. These sections are as follows: Rosratae (1), Abyssinicae (13), Commiphora (3), Coriaceae (1), Campestres (7), Africanae (7), Latifoliolatae (10), Pedunculatae (1), Arillopsidium (8), Ugogenses (1), Hildebrandtianae (4), Hemprichia (6), Ciliattae (1) and Opobalsameae (2) species. The different species are distinguished by their resin and colour of the bark as well as details of spines and leaves which are not always available.
Several species of Commiphora produce gum resins which are used locally, particularly by the Islamic communities. The chief Commiphora gum of economic importance is myrrh, produced by C. myrrha (C. myrrha var. molmol). This is an important article of commerce in N.E. Kenya which is locally known as Molmol (Somali). Other species producing myrrh but of less value include C. habessinica (C. madagascariensis), C. schimperi (C. buraensis), C. africana (C. pilosa) and C. confusa. These species are quite abundant in northern Kenya. Gum resins from C. holtiziana spp. holtziana (C. caerurea) and C. pseudopaoli (C. paolii) are known as opoponax and are used as tick repellent. These are of commercial value especially in the USA where they are used on domestic animals. The same resins are used against snake bite. There are also other species such as C. incisa(C. candidula), C. campestris var. camppestris(C. scheffleri) which produce gums that are locally chewed.
Over the last few years, it has been increasingly evident that the production of frankincense and myrrh from Boswellia and Commiphora genera of Burseraceae is gaining in economic importance particularly for some tropical African countries. Although substantial quantities of these products are harvested annually, little is officially known about the status of the trees themselves. Recent classifications such as "An Integrated Systems of Flowering Plants" by Arthur Cronquist (1981) and "The Flora of Tropical East Africa" by Jan Gillett (1991) have greatly contributed to the understanding of the members of the family Burseraceae. These are natural classifications with high level of productivity and all the groups which they delimit are natural. Useful aromatic resins for instance occur in the tribe Burserae where frankincense and myrrh are restricted to the two genera, Boswellia and Commiphora respectively. Also, gum resins commercially known as opoponax used as tick repellent occur within Section Hemprichia of Commiphora. It is therefore possible to predict with some degree of accuracy which group contains what product by investigating a single species and hence restrict the areas of investigation within the family.
Beentje, H.J. 1994. Kenya Trees, Shrubs and Lianas. National Museums of Kenya, Nairobi, 722pp.
Cronquest, 1981. An integrated system of classification of flowering plants (with a new foreword by Armen Takhtajan). Columbia University Press, New York.
Gillett, J.B. 1991. Flora of Tropical East Africa - Burseraceae. A.A. Balkema, Rotterdam, Brookfield. 94 pp.
Gillett, J.B. 1973. Commiphora Jacq. (Burseraceae) - Englerian species which disappear. Kew Bull. Vol. 28(1), 25-28.
