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Although about 35 species of Acacia, Boswellia and Commiphora have been identified as potential producers of gum and resins, currently they are collected only from few species. Gum arabic is collected from Acacia Senegal var. Senegal and var. kerensis, Acacia Seyal, var Seyale and var. fistula; frankincense from Boswellia papiphera, B. neglecta, B. rivae, B. microphilla, B. ogadensis; opoponax and myrrh from Commiphora myrrha, C. guidotti, C. erithraea.

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It is used as a suspending agent, emulsifier, adhesive, and binder in tablet and in demulcent syrups (Getachew and Wubalem, 2004), also in ayurvedic medicine and traditional therapies.

443 _{It is used as a thickening agent in printing pastes for the coloration of knitted cellulose fabrics.}

444 _{As a stabilizer in lotions and protective creams, where it increases viscosity, imparts spreading properties,}

and provides a protective coating and a smooth feel. It is used as an adhesive agent in blusher and as a foam stabilizer in liquid soaps (Whistler, 1993).

445 _{Food additives manufactures have tried to develop gum arabic substitutes as starches, corn-based, celluloses,}

but it seems that none has the functionality of gum arabic. It has comparative technical advantages over substitutes: products incorporating gum arabic retain flavour better and their shelf lives is also superior. Both Peopsi and Coca Cola contain gum from Acacia Senegal.

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In the intervention area all the 3 species of trees are found, but it has been chosen to analyse the value chain of frankincense from Boswellia and gum arabic from Acacia.

Boswellia is indigenous lowland tree species of Ethiopia. It is a deciduous tree that reaches to the height of 12 meters or more at maturity. It is usually dominant in on steep rocky slopes, lava flows or sandy valley, with altitudinal range at 950-1,800 m, where temperature is between 20-25° C and rainfall is less than 900 mm per annum. The ecological distribution of the species is confined to lowlands subjected to hot and arid conditions. Frankincense is the resin obtained from species of Boswellia trees: in particular the Ogaden (B. rivae, B. ogadensis and B. microphylla) and the Borena (B. neglecta) species are present in the eastern, south-eastern and southern parts of the country, respectively where this research focuses. A third topology of Boswellia in Ethiopia is the papyphera, found in the North and North-west, so not object of this research, even if it produces the most widely exported frankincense (90% of the overall export)446. Literaturespeaks mainly about Boswellia papyriphera, as this is the specie that produces the biggest quantity of gum in Ethiopia. Frankincense tress produces leaves with small showers of rain that start in April447. The leaves drop sometimes in November at the beginning of the dry season. Frankincense is classified in 5 grades and only the resins from grade 1 to grade 4 can be exported, while the grade 5 is just for internal use. Frankincense is traded internally and for exporting uses and it is available in different grades; it ranges in appearance from pale pieces or tears up to several centimetres in size to smaller pieces, and from powder and siftings to large, reddish brown or dark agglomerated masses448. Gum arabic is the dried exudates produced from the trunk and branches of the acacia Senegal tree and the acacia Seyal tree. Gum arabic is a pale white to orange brown solid which breaks with a glassy fracture. If properly stored, it stays unaltered for decades. Gum arabic is a complex polysaccaride with food, pharmaceutical and technical applications, whose uses are known since about 5,000 years. Gum from Senegal trees (hard gum) has major technical properties and different chemical composition than gum from Seyal trees (flaky gum). A.

446 _{In Ethiopia is possible to find also the Boswellia pirrotae.}

447 _{Among others: Tadesse W., Desalegn G., Alia R., Natural gum and resin bearing species of Ethiopia and}

their potential applications, Ethiopian Institute of Agricultural Research - Forestry Research Center, 2007; Gebremariam A. H., Bekele M., Ridgewell A., Small and Medium forest enterprises in Ethiopia International Institute for Environment and Development, 2009.

448 _{Boswellia resins (frankincense) contain the so-called α- and β-boswellic acids: 3α-hydroxy-olean-12-en-24-}

oic acid and 3α-hydroxy-urs-12-en-24-oic acid, respectively. The non volatile-constituents include numerous triterpenoids of the lupine, oleanolic and ursolic acid types, either as the free acids, acetyl esters or ketones.

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Senegal comprises about 70 % and A. Seyal about 15–25% of the species that contribute up to 95% of the total gum entering international trade449.

Acacia Senegal is a deciduous shrub or tree up to 15 m high, crown variable, flat to rounded; bark yellowish-brown to purplish-black, rough or smooth, scaly (Dagnew 2006). A. Senegal thrives on dry rocky hills, in low-lying dry savannas. This hardy species survives many adverse conditions, and seems to be favoured by low rainfall and absence of frost. It ranges from warm temperate thorn through tropical thorn to tropical dry forest life zones. It is very drought resistant. It grows on sites with annual rainfall mainly between 300-400 mm, and 5- 11 month dry periods. It tolerates high daily temperatures (temperatures of up to 45°C or more), dry wind and sandstorms. Acacia Senegal prefers coarse-textured soils such as fossil dunes, but it also grows on slightly loamy sands and skeletal soils. It tolerates high daily temperatures and a long dry season. It is available from 600 m to 1,700 m in altitude.

Acacia Senegal enrich the soil with nitrogen and so restoring soil fertility. Its wood is also an excellent slow-burning fuel wood giving intense heat and little smoke; it is also used for charcoal making. It has an important role in arid and semi-arid agro-forestry systems: it is browsed by livestock, mainly camels and goats, and it is reputed to fatten livestock and enrich milk.

Acacia Seyal is a deciduous and indigenous tree of the savannah woodland and the semi-arid lowland forest, in between 700-1800 meter of altitude, commonly found in the rock hillsides or in the drier parts of Acacia thickets. It is flat topped or umbrella shaped, small to medium sized tree to 17 m. It has a shining greenish white or greyish white bark. It has strong white thorns to 8 cm long. The milky white pears of prickles, straight bifurcated, are mostly swollen at the base450.

Yields of gum arabic from individual trees are very variable: from 250 grams of gum per tree per season to 1 kilo (Dagnew, 2006). The demand of the Sebansa gum (from Senegal type) is higher than Wacho gum (Seyal type), because of its better quality; therefore also the price is very different: gum from Sebansa price is 70-80% higher than gum from Wacho price451. The gum from Sebansa tree is more white and shining, than that one from Wacho tree: the last one is less brilliant. Sebansa gum is shaped in stones, while Wacho gum is in the shape of sticks.

449 _{The remaining 5%, which is relatively low quality, is mainly contrinuted by Acacia Polyacantha and A.}

Drepanolobium. In Ethiopia it is possible to find also A. Sieberiana, but just for internal consumption.

450 _{Tadesse W., Desalegn G., Alia R., Natural gum and resin bearing species of Ethiopia and their potential} applications, Ethiopian Institute of Agricultural Research - Forestry Research Center, No. 16 (3) 2007. 451 _{Acacia Senegal comprises about 70 % and Acacia Seyal about 15–25% of the species that contribute up to}

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An acacia tree, when planted, takes 5-7 years before producing gum Arabic and 15-20 years for its productivity to start to decline. The average gum yield per tree per season is around 300 grams but production can vary from less than 200 grams to exceptionally 1 kilo. Resins and gum exude from cracks in the bark of wild trees. It is not possible to collect immediately after the crack the resins and the gum, as not yet properly dried. To collect gum from Sebansa and Wacho trees it is necessary to wait for 3 weeks, while is possible to perform every 2 weeks collection from Dunkhal tree to collect white and black resins, in order to give the time to resins to come out and get dried. In the target area, resins and gum are collected in the natural forest/bush lands, from naturally oozing and without forcing the exudation from the trees.