Kindeya Gebrehiwot, Bart Muys, Mitiku Haile and Ralph Mitloehner
Boswellia papyrifera is one of the most important multipurpose tree species in Central and eastern Africa. It is a drought-resistant species that continues to grow in marginal lands, produce incense, flower and grow leaves even in harsh and unpredictable biophysical conditions. The species is better known for its non-timber forest product, frankincense. Frankincense has been used for ritual and church ceremonies, traditional medicines, pharmaceutical, perfumery, adhesive, painting, food and other industries all over the world. In addition to this, the species has other numerous environmental, socio-economical, traditional and industrial benefits. However, recent reports indicate that the species is declining at an alarming rate and needs priority in conservation. In this paper the importance of B. papyrifera in general and its non-timber product, frankincense, in particular are described. The history and the contemporary use and trade of frankincense from B. papyrifera are reviewed. Techniques of harvesting, grading and sorting of frankincense are discussed. Finally, issues and concerns related to the population decline of B. papyrifera are highlighted.
Boswellia papyrifera (Del.) Hochst is one of those species with multiple economic and ecological benefits in Africa. It is found in Ethiopia, Nigeria, Cameroon, Central African Republic, Chad, Sudan, Uganda and Eritrea (Vollesen 1989). The species is widely known for its frankincense. Despite its multiple benefits, B. papyrifera is nowadays reported to be in plight conditions and needs priority in conservation (Marshall, 1998). Its population is degrading due to extensive farming, overgrazing, fire, poor incense harvesting practices, shifting cultivation, termite and other insect infestations (Oqbazghi 2001). This paper introduces and describes the species in general and its non-timber product (frankincense) in particular. The history and contemporary use and trade of frankincense from B. papyrifera are reviewed. Techniques of harvesting, grading and sorting of frankincense are presented. Finally, issues and concern related to the population decline of B. papyrifera are highlighted.
Boswellia papyrifera (Del.) Hochst belongs to a tropical family called Bruceraceae (Fitchl and Admasu 1994) which is distinguished by the presence of resin ducts in the bark (Groom 1981). B. papyrifera is a deciduous tree which can be as tall as 12 m, with a rounded crown and a straight regular bole. The bark is whitish to pale brown, peeling off in large flakes; slash red-brown and exuding a fragrant resin. The bark contains schizogenous olea-gum-resin pockets (Verghese 1988). Leaves are large, compound, arranged on long stalks with 11 to 29 leaflets which are narrowly ovate to oblong, waved or toothed along the margin. B. papyrifera is a monocious species with sweet scented flowers which are white to pink, arranged on long red flower stalks, in loose panicles at the end of branches. Fruits are obtetrahedral, which are red capsules about 2 cm long, usually containing three tapered seeds (Vollesen 1989). The tree and its flower are shown in Plate 1.
Plate 1. Boswellia papyrifera (Del.) Hochst in northern Ethiopia
Frankincense production: When the bark of the tree is incised, a white gum-oleo resin exudes. This emulsion of aromatic oils or resins later dries into globular, pear or club shaped tears, known as frankincense. Frankincense constitutes 3-8% volatile oil, 60-70% alcohol-soluble resin and 27-35% water soluble gum (Verghese, 1988).
Wood products: The wood and its branches are used mainly for fencing, making agricultural implements, household furniture, matchboxes, splints, particleboard, pencils, plywood, picture frames and veneer.
Traditional medicine: Various plant parts and products are utilised for traditional and medicinal purposes. The leaves and roots of the species are used against lymphadenopathy while the resin is used as a febrifuge (Fitchl and Admasu 1994). Frankincense was considered as a stimulant and was once used to treat leprosy in China (Tucker 1986). The bark is chewed to treat stomach disturbances. It is burnt as a mosquito repellent in the tropics and also chewed by lowlanders to quench thirst during hot days (Tilahun 1997).
Livestock feed and Bee fodder: The pink sweet smelling flowers of the species are frequently visited by honeybees for pollen and nectar. The long flowering period from October to February is helpful for bee colony maintenance (Fitchl and Admasu, 1994). Accordingly, Boswellia growing lowland areas are often known for their good quality honey. Leaves and seeds of the species are highly valued as fodder for goats, camels and other livestock. The succulent stem is also used as fodder during the dry season.
Environmental role: B. papyrifera grows in dry and rocky sites where other tree species often fail. In northern Ethiopia, B. papyrifera trees are found in steep slope with an average gradient range of 30-40%. The majority of the soils (60-80%) in northern Ethiopia (where Boswellia grows) are about 20 cm deep (Hurni 1988). In those sites, it provides plant cover and produces litter and hence protects the soil from erosion and provides shade.
Employment generation: Frankincense collection offers off-farm employment for many rural farmers, both men and women. Men are mainly involved in tapping and collecting incense from the forest while women undertake sorting and grading of the same. For example, in northern Ethiopia, a tapper can collect about 10-15 quintals of incense per annum and receive a net income of US $ 100 to 150. Women accrue an average income of US$ 16 per month. About 31% of those involved in frankincense collection in northern Ethiopia are women (Tilahun 1997).
The use of frankincense has a long history in human civilisation (van Beek 1960). The natural oil content and pleasant smell of frankincense made it desirable to be used in temple rituals as incense, as a base for perfumes and as well as for medicinal properties since ancient times (Groom 1981). The first recorded mention was found on a 15th century B.C tomb in Egypt (Abercrombie 1985). Frankincense is mentioned 22 times in the Bible; 16 times for religious worship, twice as a tribute of honour, once as an article of merchandise, and 3 times as a product of the royal gardens of Solomon (Moldenke and Moldenke 1952). According to Tucker (1986) any frankincense use mentioned in the Old Testament of the Bible would have been from B. papyrifera. Frankincense was included in the gifts presented by the wise men to the infant Christ together with gold and myrrh (Mathew 2:11).
Detailed accounts on the history of frankincense trade can be found in Groom (1981). The frankincense trail depended much for its existence on the camel, domesticated by 1300 B.C. (Abercombie 1985). Through the use of the camel and improved land routes around 11th century B.C. frankincense was carried from Qana to Gaza. By sea it went straight from Qana to India. By 1000 B.C. frankincense had already made its impact on the ancient world including Babylon, Egypt, Rome, Greece and China. Frankincense was held by the Romans to be the incense par excellence and its high price reflected the enormous demand for it (Groom 1981). The principal route in those times led from Dhufar by sea to the port of Qana, then overland into northern Arabia for transhipment to Athens and Rome (Abercrombie 1985). Southern Arabia had shipped more than 3000 tonnes of incense each year to Greece, Rome and the Mediterranean world in the 2nd century A.D.
In the current international market, there is ambiguity in determining the demand and supply for frankincense as it is often aggregated as natural gums, resins and balsams. Besides, there also exists a great deal of unofficial trading across the borders of the producing countries. Somalia, Sudan and Ethiopia are by far the biggest producers of frankincense. The export from Ethiopia between 1995 and 1999 is shown in Figure 1. Indian frankincense is used domestically for making incense sticks, and an average of about 90 tonnes per annum have been exported between 1987-1993 (Coppen 1995). China was the largest market for frankincense, and it imported more than 1000 tonnes in 1984. In Europe and Latin America, about 500 tonnes of frankincense was used by the Orthodox and Roman Catholic churches in 1987. Similar quantities of higher quality frankincense are imported into North African countries and Saudi Arabia where its is used for chewing. Lower grade olibanum has been used for burning in the Middle East, although its use has declined in favour of other fragrance materials such as sandalwood. About 50 tonnes of frankincense per annum is used in Europe for the production of essential oils and extracts (Coppen 1995).
Figure 1. Frankincense export from Ethiopia between 1995 - 1999 in metric ton
Burning incense: Incense has been associated with religious ceremonies all over the world since time immemorial. Frankincense was introduced into church ceremonies at the beginning of Christianity (Abercombie 1985). Ever since, the hardened resin burns in the Roman Catholic, Greek Orthodox, Ethiopian Orthodox and Coptic Churches throughout the world.
Perfume industry: Frankincense has had an ancient use in cosmetics. Frankincense is employed by perfumers as an absolute (by alcohol extraction), oil, or resinoid (by hydrocarbon extraction). Both solvent extracts (resinoides and absolute) can be used as fixatives in perfumes. Oils are obtained from the crude resin by steam distillation and are then normally used whole for flavouring and fragrance applications (Coppen 1995). This oil from frankincense can take up to six hours to evaporate, making it an important ingredient in many perfumes.
Medicinal uses: Limited information exist on the industrial medicinal uses of B. papyrifera. Nevertheless, the traditional medicinal uses by the local people (reported in the previous sections) and experiences with other species of the genus (for example, B. serrata) highlight the potential use of B. papyrifera for industrial medicinal purposes as well. Boswellic acid (which constitutes about 50-70% of the oil) extracted from B. serrata in India is commercially used as an anti-arthritic and anti-inflammatory pharmacological agent (Anon 2000). Those extracts from B. serrata were found to be more beneficial, less toxic, and more potent than standard anti-inflammatory drugs.
Other industrial and household uses: Frankincense is also used in the fabrication of varnishes, adhesives, fumigation powders and pastilles. It gives flavour in food industries including bakery, milk products, different alcoholic and soft drinks. The distinctive flavour of frankincense also makes it highly valuable for chewing gum industries. About 500 tones of frankincense were imported into North African countries for chewing purposes in 1987 (Coppen 1995). Incense is also used as an ingredient for lotion, soaps, and ointment formulation, as addition to wound plasters, tooth paste and mouth water.
Techniques of tapping and harvesting of frankincense remained virtually the same since ancient times (See Groom 1981). Tapping of B. papyrifera in Ethiopia is carried out by shaving a very thin (1 mm deep and an area of 2.5 cm2) layer of the bark with a scalpel-like tool called mengaff (Plate 2). A tree could be tapped 8-12 times during the dry periods of the year (S Plate 3). The first 3-4 tapping are undertaken at an interval of 21-30 days while the interval becomes shorter, approx. 10- 15 days, at a later stage when the average daily temperature reaches above 25°C. At every tapping, a white emulsion exudes which dries and hardens into globular, pear or club shaped tears on exposure to air (Verghese 1988). One to three kg of frankincense is collected from a tree per year (Coppen 1995). The amount might vary depending on the diameter of the tree, site productivity and season. The species can continue producing incense up to the age of 50-60 years (Tilahun 1997).
Plate 2. Tapping and harvesting of frankincense in northern Ethiopia
Plate 3. Tapped Boswellia papyrifera in Tigray, northern Ethiopia.
Collected frankincense is then sorted and graded in accordance to size, colour and purity. In Ethiopia, there are five grades of frankincense from B. papyrifera which are sorted as:
a. First grade: white granule greater than 6 mm in diameter
b. Second grade: white granules, 4 - 6 mm diameter
c. Third grade: white granules, 2 - 4 mm diameter
d. Fourth grade: brown or black colour with any size
e. Fifth grade: powder with less than 2 mm diameter and bark with no size limit
The decline in the population of B. papyrifera in eastern Africa has become an ecological concern (Tilahun 1997; Marshall 1998; Oqbazghi 2001). In northern Ethiopia, more than 177,438 ha of B. papyrifera forests were destroyed in the last 20 years. Besides, the existing population consists of mainly matured trees which highlight the problems in natural regeneration, for instance more than 76% of the existing Boswellia trees in northern Ethiopia are greater than 30 cm. In Eritrea frankincense export dropped from 2000 tons in 1974 to 400 tons in 1998 (Oqbazghi 2001). In addition, B. papyrifera is listed by TRAFFIC (wildlife trade monitoring program of WWF and IUCN) among the species which are endangered and need priority in conservation (Marshall 1998). The decline in the population of B. papyrifera and lack of regeneration is related to the following factors in one way or another.
i. Extensive farming: In many B. papyrifera growing areas, there has been increased population pressure. This has resulted in the conversion of Boswellia woodlands to agricultural lands.
ii. Grazing: Unregulated overgrazing has damaged natural regeneration of B. papyrifera. Seeds and seedlings of B. papyrifera are highly preferred by goats and other livestock.
iii. Improper incense tapping practices: It is not uncommon to see over-tapping and use of inappropriate tapping methods by unskilled labourers. There is little supervision during tapping. More accessible trees are often tapped continuously with no resting periods. Seeds from un-tapped stands had high germination rates (94% and 80%) compared to seeds from tapped stands (14% and 16%) in Eritrea (Oqbazghi 2001). Some period (e.g. 3 to 5 years) is necessary for wound healing in northern Ethiopia. Oqbazghi (2001) has advised a healing period of between 4-14 years in order to attain the full potential for viable seed production in Eritrea. Murphy and Shiva (1977) indicated that the original thickness of B. serrata Roxb was regained three years after tapping.
iv. Termite and other insect infestation: Significant amounts of seeds are damaged by insects. About 17.5% and between 20 and 25% of the bulk seeds were attacked by insects in Ethiopia and Eritrea, respectively (Tilahun 1997; Oqbazghi 2001).
v. Wind damage: As the roots of B. papyrifera are shallow, substantial damage up-rooting is also caused by wind.
vi. Lack of silvicultural knowledge: Limited studies were undertaken on the silviculture of B. papyrifera (Tilahun 1996; Oqbazghi 2001). A number of nurseries in Ethiopia are attempting to raise seedlings of B. papyrifera for plantation. However, success is so far limited. For example, in the year 1999 and 2000, only 4.5% and 8.7%, respectivel, of those planted in northern Ethiopia survived, respectively. The low survival rate can be attributed to the lack of silvicultural knowledge of the species which include time of seed collection, nursery practices, choice of appropriate planting sites and post planting care.
Boswellia papyrifera is an important tree species from economical and ecological perspectives. If the resource could be sustained, farmers in rural areas of Africa could benefit from frankincense collection and accrue additional income in order to maintain household food security. Nevertheless, efforts should now concentrate on saving this important tree species from extinction. Efforts that promote natural regeneration should be strengthened. Concomitantly, natural regeneration and silvicultural studies on alternative methods of propagation, seed collection, nursery practices, choice of appropriate planting sites and post planting care are important. Marketing studies are also important in order to sustain the export sales of frankincense and income generation. Tapping improvements and strict regulations are required to minimise damage to trees and seedlings during incense harvesting
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