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Modelling the future of Boswellia papyrifera population and its frankincense production
Journal of Arid Environments 105 (2014) 33e40
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Modelling the future of Boswellia papyrifera population and its frankincense production M. Lemenih a, *, B. Arts b, K.F. Wiersum b, F. Bongers a a Center for Ecosystem Studies, Forest Ecology and Forest Management Group, Wageningen University and Research Center, P.O. Box 47, 6700 AA Wageningen, The Netherlands b Forest and Nature Conservation Policy Group, Wageningen University and Research Center, PO Box 47, 6700 AA Wageningen, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 September 2013 Received in revised form 5 February 2014 Accepted 14 February 2014 Available online 19 March 2014
Sustainable production of the aromatic forest product frankincense is at stake due to rapid decline in its resource base. This affects livelihoods of thousands of citizens and several global industries. A system dynamic model approach is used to predict the future population of Boswellia papyrifera trees and its frankincense yield for three decades (2010e2040) in Metema and Abergelle districts in northern Ethiopia. Data from studies on the ecology, distribution, rate of deforestation and participatory future scenario development were put together and analysed using a model platform developed with STELLA. Four alternative scenarios namely Business As Usual (BAU); Low Intervention Scenario (LS), High Intervention Scenario (HS) and Stabilization Scenario (SS) were used. The model predicts 3%, 8% and 37% of the current stem population to exist in 2040 under BAU, LS, HS scenarios, respectively in Metema. Similarly, 11%, 13% and 46% stem density is predicted under BAU, LS and HS, respectively for Abergelle. Test of model sensitivity shows adult mortality is the most serious problem facing the resource. Immediate management intervention should focus on reducing adult tree mortality followed by reducing deforestation. Medium and long term interventions need to focus on how to improve recruitment and afforestation/reforestation of the species. Ó 2014 Elsevier Ltd. All rights reserved.
Keywords: Abergelle Deforestation Metema Reforestation Participatory future scenario
1. Introduction Dry tropical forests including woodlands cover over 40% of the global tropical forest areas (Mayaux et al., 2005). In Africa alone, these forests cover 17.3 M km2, and are home for half a billion people (Chidumayo and Gumbo, 2010). About 28 African countries host such vegetation types and in some of the countries they are the only forest resources. Although less diverse than the wet tropical forests, African dry forests also host considerable biological diversity of immense local, regional and international significances (Bongers and Tennigkeit, 2010; Murphy and Lugo, 1986; White, 1983). An important feature of the dry forests in East Africa in particular is their richness in plant species of the genera Acacia, Boswellia and Commiphora (Chikamai et al., 2009; Lemenih, 2005; Vollesen, 1989). Several of the species in these genera are renowned for being the sources of commercial gums and gum resins such as gum arabic, frankincense and myrrh; important export forest products for several countries in the Horn of Africa
* Corresponding author. Tel.: þ31 251 912066839; fax: þ31 251 116612877. E-mail address: [email protected] (M. Lemenih). http://dx.doi.org/10.1016/j.jaridenv.2014.02.006 0140-1963/Ó 2014 Elsevier Ltd. All rights reserved.
including Ethiopia, Sudan, Eritrea, Somalia and Kenya (Chikamai, 2002; Chikamai and Cascade, 2005; FAO, 1995). In Ethiopia alone, dry forests and woodlands cover ca. 55 M ha (WBISPP, 2004). The vast Combretum e Terminalia broadleaved deciduous woodlands in the western and north-western lowlands of the country are the home for the frankincense tree species Boswellia papyrifera. Those in the east, southeast, along the rift valley, in the south and southwest host diverse Acacia, Boswellia and Commiphora species. Frankincense from B. papyrifera in particular has been produced and traded since antiquity (Bard et al., 2000; Butzer, 1981), and still today produce to feed domestic and international markets for fragrance (Lemenih, 2005; Ogbazghi, 2005). Despite their economic and ecological importance, dry forests and woodlands in Africa in general and those in Ethiopia in particular are rapidly declining and degrading (Bongers and Tennigkeit, 2010; Chidumayo and Gumbo, 2010; Lemenih and Kassa, 2011). With these changes, biodiversity of the forests and woodlands and their ecosystem services are severely threatened (Chidumayo and Gumbo, 2010; Eshete et al., 2011). In Ethiopia the current status of the resource shows a worrying trend (Abiyu et al., 2010; Eshete et al., 2011; Groenendijk et al., 2012; Lemenih et al., 2012a,b). Most of the Boswellia natural
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stands are characterized by a lack of recruitment (complete hindrance of recruitment) through natural regeneration, high rate of deforestation and widespread encroachment by expanding cropland and very high adult mortality; hence a declining population (Abiyu et al., 2010; Eshete et al., 2012a; Groenendijk et al., 2012; Lemenih et al., 2012a,b; Tolera et al., 2013). There is no forest management plan put in place in major producing areas, tapping is uncontrolled and enrichment planting is also absent. Promoting sustainable frankincense production requires the balance between economic and ecological uses of the woodlands and comparative analysis of the short term rural development demand from alternative land uses on the one hand and the long term ecological and economic benefits from the woodlands on the other (Dejene et al., 2013). Some studies are showing that managing the Boswellia woodlands for frankincense and other nontimber forest products can offer competitive financial return with alternative agricultural land uses (Dejene et al., 2013; Tilahun et al., 2007), yet the woodlands are considered generally as having low economic potential, one of the factors leading to their wide spread conversion and use for resettlement programs (Dejene et al., 2013; Lemenih et al., 2012a). Given all the challenges that the woodlands and the frankincense trees are facing there is serious doubt of long term prospect for a sustained supply of frankincense and other ecosystem services from the woodlands and the species. One way to explore and predict potential future threats facing Boswellia resources and the production of the fragrance frankincense is by means of modelling. Modelling future trends under sets of scenarios provide good information on how various courses of action may affect the future of a resource in question. Thus, it significantly contributes to the understanding of the potential impacts associated with various threats and enhances early decision making process to minimize consequences. Therefore, the model outputs could play an important role in facilitating the identification and planning of management strategies that could reverse the trend and promote improved management of the resource. In this study, a system dynamic simulation modeling approach is employed to compose data and assumptions generated from our own research and a number of parallel studies from an integrated project (Eshete, 2011; Mengistu, 2011; Woldeamanuel, 2011; Lemenih, unpublished; Atkilt, unpublished) to predict the future of Boswellia population and its frankincense production in the northern lowlands of Ethiopia (Sections 2.2e2.5). Modeling approach to vegetation study is a useful approach to investigate the
long term consequences of different scenarios of changes on vegetation (Pausas, 1999), thereby assisting the designing of effective management strategies (Garedew et al., 2012). System dynamics modeling in particular differs from other modeling system in its use of feedback loops, and stocks and flows (Costanza and Voinov, 2001) to provide a basis for better understanding of socioeconomic and environmental interactions (Garedew et al., 2012). It is a concept that considers dynamic interactions between various elements of the studied system to understand their behavior over time, build models, identify how information feedback governs the behavior of the system and develop strategies for better management of the system (Doerr, 1996). Since it involves various alternative scenarios, most of which are developed through stakeholder participation or expert assumptions, simulation models are not a forecasting instrument but a planning and analysis tool. The model structure developed for this study included submodels representing components of forest ecosystem dynamics: recruitment (separating between planting and natural regeneration), mortality (death and deforestation separately) as well as frankincense production. Four main scenarios were constructed together with local stakeholders using a participatory stakeholder scenario development process. The objective was to employ scenario modelling technique to simulate and examine the future population of B. papyrifera and the production of frankincense under various plausible assumptions and conditions likely to prevail in affecting management and conservation of the frankincense woodlands in Ethiopia. 2. Material and methods 2.1. Study sites The study was conducted in two woodland areas dominated by B. papyrifera trees: Abergelle in the north and Metema in the northwest. Both woodlands are known for having a high frankincense production and a long history of marketing of the product. However, there are several differences between the two sites in biophysical, socio-economic and livelihood conditions (Table 1). Abergelle is both one of the oldest and the main gum/resin production areas in Ethiopia. The production of this resource forms an important means for cash earning by local communities. This cash earning supplements the mainly subsistence-oriented mixed farming practices (Lemenih et al., 2012a). Metema was traditionally
Table 1 Major biophysical and socio-economic land-use conditions in the two study districts Metema and Abergelle, northern Ethiopia. Site attribute
Abergelle
Metema
Location Area and population Climate conditions
13 110 and 13 150 N and 37 430 and 38 070 3000 km2 with the population of 113,526 inhabitants; Semi-arid; rainfall is uni-modal and very erratic with mean annual rainfall of ca. 800 mm. Mean Annual Temperature of 22 C; Range between 1400 and 1650 m a.s.l. Homogenous, Tigre ethnic group
12 390 and 12 450 N, and 36 170 and 36 480 E 3995 km2 with population of 83,193 inhabitants; Semi-arid to sub-humid; rainfall is uni-modal with Mean Annual Rainfall of ca. 965 mm; Mean Temperature 28 C;
Altitude Ethnic composition
Main livelihoods
Original natural vegetation
History of gum-resin production
Mixed subsistence farming. Prevalent food insecurity stimulates alternative income earning Combretum-Terminalia woodlands and wooded grasslands. B. papyrifera and some Acacia spp. predominate; Woodlands cover only small portion of the district Probably the oldest commercial production region in Ethiopia (since 1940s). Systematic resin production through tapping mainly in concession areas allotted to commercial firms
Range between 549 and 600 m a.s.l. Heterogeneous, with Amhara (80%), Tigre (10%), Oromo (5%) and Gumuz (2%). Increasing importance of immigrants Traditional hunting-gathering being replaced by mixed subsistence farming. Quick expansion of commercial farming of oilseed and cotton. Combretum-Terminalia woodlands and wooded grassland. More diverse and higher in stature than in Abergelle. B. papyrifera is the main species. Woodland cover large part of the district Systematic commercial production started recently (1980’s), and has gradually intensified
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sparsely inhabited by people that practice shifting cultivation supplemented by hunting and gathering (Mekonnen, 2004). However, in recent decades, high population migration from highland to lowland is intensifying the mixed crop-livestock production system that is negatively affecting the woodlands (Lemenih et al., 2012a, 2007). Migration to Metema from the highlands has intensified since the latee1960s/earlye1970s, and it has changed significantly the demographic and ethnic composition of the district (Lemenih et al., 2007). The range use of the woodlands in Metema is also increasing. The woodlands are extensively used as rangelands by resettled local people for grazing and by seasonally migrating cattle herders from the surrounding highlands (transhumance). According to a study by Tegegne et al. (2009), 60.3 per cent of the total cattle population in three nearby highland districts (Chilga, Dembia and Gondar Zuria) trekked to Metema for 6e8 months each year while the highlands were used for cultivating food crops. Unlike in Abergelle, the climate and the soil conditions in Metema are also suitable for the intensive cultivation of various crops, such as cotton, sesame, sorghum, finger millet, maize and tef, and the area has recently been opened up for the cultivation of most of these cash crops. 2.2. Approaches and methods of data collection The study employed a system dynamics modeling technique, which is based on building a stock- and-flow model using STELLA (version 8), a software package specifically designed for dynamic systems modelling. STELLA is one of the most versatile graphical programming language used widely by ecological, economic and biological system modelers (e.g. Costanza and Voinov, 2001; Costanza et al., 1998; Hannon and Ruth, 1994). The purpose of the model in this study was to predict the population of B. papyrifera and its frankincense production over the next 30 years (i.e. by 2040) under four alternative future scenarios that take into consideration the main drivers affecting the species on one hand and possible management interventions to improve or reverse the drivers threatening the species on the other, the latter as perceived by local stakeholders that participated in the future scenario development process. The four scenarios considered in the model process were developed through a participatory process by engaging stakeholders at each locality (see Section 2.5). The structure of the model is shown in Fig. 1. The main components of the model are: i) recruitment into the standing population of B. papyrifera mainly from two means namely from natural regeneration and artificial
Fig. 1. Model components for the quantitative projection of B. papyrifera population and its gum-resin production in northern Ethiopia.
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Table 2 Major threats to B. papyrifera and frankincense yield in the two study districts considered for model development. Current threats and management practices
Region Metema
Abergelle
Competing land use pressure (deforestation and conversion) Current reforestation and afforestation Protection of the standing stock Production intensity Adult mortality Recruitment Fire and grazing intensity
Very high
Low
Non-existent
Non-existent
Very poor High and no control Exceptionally high Non-existent High
Moderate High and no control Exceptionally high Non-existent Low
Sources: Eshete, unpublished.
2011;
Mengistu,
2011;
Woldeamanual,
2012;
Lemenih,
planting, and ii) mortality, which refers to loss of B. papyrifera from the standing population as a result of annual deforestation (ha/yr, which is also translated into Boswellia stem removal per ha and year based on its average stem density in the forest) and natural adult death (stem/ha/yr). The third component of the model is frankincense yield per year, which predicts change in total yield as a result of change in standing population of Boswellia, given a standard mean yield production per tree per year. The fourth component, which represents the stock at the centre of the model, is the current stem density of Boswellia. Recruitment adds to this stock, while mortality reduces from this stock. So the stock is the beginning of the dynamics either increased when recruitment is higher than mortality or declines when mortality is higher than recruitment. These model components were selected based on threats identified for the woodlands from parallel studies within the same project coupled with participatory problem analysis (Eshete, 2011; Mengistu, 2011; Woldeamanuel, 2011; Lemenih et al., unpublished) (Table 2). Moreover, some of the quantitative data inputs and assumptions used in the model were generated from these parallel studies. The procedures employed by the parallel studies to generate the quantitative data are described in Sections 2.3e2.5.
2.3. Model input: stand density, recruitment, mortality and yield estimate In Metema, 12 plots of 1.6e2.0 ha each were established. In these plots complete census of population took place in 2007, 2008 and 2009 with the first census result of a total of 4370 trees with >1 cm DBH and 2228 smaller individuals (seedlings and saplings) (Eshete et al., 2012a, 2011; Groenendijk et al., 2012). Identity of all species within the plot were recorded and the stem density of B. papyrifera per ha also determined. In the subsequent years (2008 and 2009) survival was assessed for all individuals. A similar study was carried out in Abergelle on six plots of 1.2e2.0 ha in size. What is found for both woodlands is the high rate of adult mortality and complete absence of recruitment in the current populations (Eshete, 2011; Groenendijk et al., 2012). Adult Boswellia tree mortality is huge taking place at the annual rate of 7% in both woodlands (Eshete, 2011). These two factors, mortality and lack of recruitment, are critical degradative factors threatening the future of Boswellia tree population and frankincense production (Table 2). Causes for the high rate of adult mortality are not known for sure but insect attack and windfall are assumed to be the direct causes. Increased fire frequency, and human and livestock population pressure are also blamed for this (Eshete, 2011; Lemenih et al., 2007).
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Furthermore, at both sites tapping experiment to assess frankincense production per tree and year was also conducted. In both places 25 trees of different diameter categories were marked and tapped during 2008 and 2009 tapping seasons (Eshete et al., 2012a). Incense tears produced during each cycle of collection were gathered, weighted and annual yield was obtained to provide estimate of average production per tree/yr. 2.4. Model input: deforestation rates in the studied districts Rate of deforestation of the woodlands, hence loss of B. papyrifera population was assessed using multi-temporal satellite images from 1985 and 2010. Both Landsat and SPOT satellite images were used for the assessment. Supervised classification using ERDAS Imagine 9.1 software was conducted to identify major land cover/land use in the districts and detect changes. First scenes covering the area are identified and important bands are collected. Then, triple images of bands 4, 3, 2 in Landsat and 3, 2, 1 in SPOT are stacked to one image as layers. After identifying images that cover the entire Metema and Abergelle districts, their mosaic was created and clipped to the district boundaries. Pseudocolor combination (bands 4, 3, and 2 as Red, Green, and Blue layers in Landsat and 3-21 in SPOT images), which is good in vegetation identification, was employed for the land use/land cover classification. The images where corrected geometrically, colour enhanced and classified. To assist the supervised image classification, training areas that represent separate land use/cover types existing in the district were entered as signatures to the software. Combinations of prior field knowledge, field observations, ancillary data from Google Earth and unsupervised image classifications were used in defining the training area (Alemu et al., 2012). Finally the supervised image classification was run for each site in an iterative approach until land use/cover classification of acceptable accuracy level was obtained for the two periods (Rogan and Chen, 2004). Change detection and rate of changes of different land use/land cover were assessed, and areas converted from one cover or use to the other was computed. ERDAS Imagine version 9.1was used for image classification, while ArcGIS version 9.3 was used for mapping and area estimation. For Metema district in 2010 land use/land cover map showed 42.2% cropland, 46.5% woodland and shrubland, 7% grassland and 9.7% bare land. In 1985, however, cropland cover was 24.1%, woodland and shrubland was 58.6%, grassland was 10.3% and bare land was 7% (Table 3). It is clear from these figures that cropland has increased significantly while woodlands and shrublands decreased. Based on this, the average deforestation rate in Metema for the past four decades is estimated at 1796.42 ha/yr. On the contrary in Abergelle there has been no detectable deforestation since the 1970s. Absence of detectable woodlands deforestation in Abergelle is attributed to stringent local institutions that control forest clearance and conversion to other forms of use or cover. This is
verified during the interviews and participatory stakeholder workshop. 2.5. Scenario construction: stakeholder engagement and future scenario definition The alternative future scenarios used in the study were developed by engaging stakeholders that comprise local communities, Development Agents and experts of Office of Agriculture at district level. Two levels of engagement were conducted. First interviews (household survey, key informant and focus group discussions) were conducted to collect major drivers of Boswellia woodland change and the perception of the interviewees on how the woodland will develop over the 30 years to come. This was followed by local level workshops one per site to present the findings from the interview and to develop the alternative scenarios together. In Metema five key informants and 4 group discussions were held, while in Abergelle 20 household heads were interviewed. In Metema 34 individuals participated in the workshop, while in Abergelle 36 participants involved. The workshops were facilitated by the researchers assisted by local experts. The workshops had two major sessions: a morning session was dedicated to presentation of the key findings from the questionnaire survey and discussion on it. An afternoon session was dedicated to jointly define the alternative scenarios. For both sites four alterative future scenarios were developed. The first was Business As Usual (BAU, here after), which refers to no management intervention to reverse the current trend of woodland degradation. The second scenario was called Low Intervention Scenario (LS, here after), which refers to the least management intervention that are probable to have. The third was called High Intervention Scenario (HS, hereafter), which referred to the best possible management intervention likely to be exercised to manage the woodlands. The last and fourth scenario was called stabilizing scenario (SS, hereafter), was added by the researchers to indicate the maximum conditions that are expected to maintain the current Boswellia population, which is supposed to indicate the utmost efforts needed to stabilize the population at its current state compared to what the stakeholders indicated as likely possible both in LS and HS. Since the two sites vary in terms of institutional and local efforts to stop degradation and restore the woodlands (Table 2), the definitions of data inputs for the various components of the model also varied. In Metema participants of the scenario workshop expected the probable reduction in deforestation of the woodlands by 30% and 70% under the LS and HS, respectively (Table 4). On the other hand, afforestation/reforestation rate was estimated to be equal to 50 ha/yr and 100 ha/yr for the LS and HS respectively. In addition in the case of HS, enrichment planting was expected to replace 2.1% of the 7% adult mortality, which was equal to 4 stem/ha/yr (Table 4). The SS assumes replacement of the deforestation rate through
Table 3 Land use/land cover change in Metema district between 1985 and 2010. Land cover/land use type
Cover extent (in ha and %) 1985
1995
Cropland/settlement Woodlands Shrub lands Grassland Water body Bare land
91,889.7 108,333.5 114,570.9 39,300.9 444.5 26,137.7
Total
380,677.3 (100)
Source: Alemu et al., 2012.
(24.1) (28.5) (30.1) (10.3) (0.1) (6.9)
160,699.4 63,423.1 93,076.7 26,651.25 198.99 36,627.93
Average rate of change (1985e2010 in ha/yr)
2010 (30.8) (19.4) (30.9) (10.6) (0.08) (8.3)
380,677.3 (100)
160,699.4 63,423.09 93,076.65 26,651.25 198.99 36,627.93
(42.21) (16.66) (24.45) (7.00) (0.05) (9.62)
380,677.3 (100)
þ2752.39 1796.42 859.77 505.99 9.82 þ419.61 0
M. Lemenih et al. / Journal of Arid Environments 105 (2014) 33e40
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Table 4 Data inputs for the model simulation for Metema and Abergelle. Model variables
Status 2010 Average Boswellia stem density (stem/ha) Total area of woodlands in the district (ha) Initial total Boswellia population Current recruitment (No. stems/yr/ha) Frankincense yield (kg/ha/yr) Initial frankincense potential in the district in tons/yr Adult tree mortality (%) Annual deforestation rate (ha/yr)
Sites Abergelle
192 270,000 51,840,000 0 76.8 20,736 7 1796.42
281 150,000 42.150,000 0 112.4 16,860 7 0
Scenarios BAU Adult tree mortality rate (%) Annual deforestation (ha/yr) Natural recruitment (No. of stem/ha/yr) Reforestation plantation (ha/yr) Planted seedling survival rate (% of total planted) Enrichment planting (stem/ha)
Data source
Metema
7 2656.2 0 0
Field survey Secondary source Field survey Field survey Field survey Field survey Field survey Field survey
LS
HS
SS
BAU
LS
HS
SS
7 925 0 50 50 0
7 555 0 100 50 4
7 2656.2 0 444a 50 13.4
7 0 0 0 0
7 0 0 75 50 0
7 0 0 150 50 6.9
7 0 0 150 50 18.9
Field survey Field survey Field survey Based on participatory workshop Based on participatory workshop Based on participatory workshop
Reforestation practices assumed initial stocking of 1600 seedlings/ha. Enrichment planting was considered in the high case scenario to be 35% replacement of current adult death and in the stabilizing scenario is 100% replacement. a Because of 1600 stems/ha in plantation the planted area is lower than the deforested area. Enrichment planting also reduces the area needed for planting.
reforestation at 1600 stem/ha planting rate and 50% survival. The equivalent area that should be annually afforested is 444 ha. In the case of Abergelle, a reforestation rate of 75 ha/yr for the LS, and 150 ha in the HS were suggested (Table 4). In all cases it was assumed that a planted seedling needs about 10 years to produce incense and thus a 10 year time lag was considered for planted Boswellia trees to offer frankincense. Table 4 summarizes input data obtained both from the parallel studies and the participatory scenario workshops.
interventions such as reforestation and afforestation constant. Identifying which variable affect most will help to identify where management intervention should put priority and focus on. The sensitivity analysis was conducted by using a range of assumption in adult mortality such as 25% reduction in mortality, 50% reduction in mortality and 100% reduction in mortality while keeping all other factors at BAU. For deforestation zero rate i.e. no deforestation was used keeping all other factors at BAU. 3. Results
2.6. Data combination and model analysis The data and information generated from the above processes where combined together to define the alternative scenarios and fed into the model. The reference scenario, the BAU, serves to reflect what will happen to the resource if there is no intervention and current disturbances continue for three decades to come. The two other alternative scenarios, LS and HS, represent the ‘least and best’ interventions that local stakeholders perceived as practicable for interventions on these woodlands given the political and socioeconomic conditions of their respective districts. These interventions include actions to reduce deforestation, reforestation of deforested areas and replacement of adult death through enrichment planting. The data were fed into the model developed using STELLA software. The simulation time frame considered was three decades with the reference year being 2010. Some of the assumptions in the simulation include all threats and management interventions remain similar over the simulation period. This means adult mortality, deforestation rate, enrichment planting, reforestation and frankincense yield per tree per year are constant at the rate defined at the beginning of the simulation. 2.7. Sensitivity analysis The variables that drive change in B. papyrifera populations are not expected to have an equal effect. We conducted a sensitivity analysis of the model predictions to identify which of the factor(s) most strongly determine the population size of B. papyrifera. We used different ranges of mortality and deforestation rate reductions based on expert guess of the researchers, while keeping other
3.1. Predictions of Boswellia population and frankincense yield under the four scenarios The projection for B. papyrifera stem population and the subsequent volume of frankincense expected under the four scenarios for Metema showed a continuous and alarmingly decline for both (Fig. 2). After 30 years only 3% of the current stem density of B. papyrifera will be expected to remain under the BAU scenario, while 8% and 37% will be expected under LS and HS respectively (Fig. 2). The fact that expected stem density and frankincense yield are declining rapidly with widening gap under all the scenarios with respect to the SS implies that many more efforts are needed than those already considered as ‘possible interventions’ by the stakeholders to conserve the resources and sustain incense production. Whether such high efforts are likely to take place is yet to be seen. The projection for Abergelle also shows a considerable decline in stem density and frankincense yield under all the three scenarios (Fig. 3). Compared to the estimated potential current stem number of 42,150,000 Boswellia and 16,860 ton of frankincense yield in the district only 11% (4,778,439), 13.1% (5,538,419) and 33% (13,952,943) stems will be expected under BAU, LS and HS, respectively (Fig. 3). Similar trend of frankincense yield were predicted under the respective scenarios (Fig. 3). 3.2. Sensitivity of the model The sensitivity analysis shows that the population of Boswellia is very sensitive to the reduction in the rate of adult mortality. If
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Fig. 2. Simulated per cent of B. papyrifera stem (left) and frankincene yield (right) in Metema district under four alternative scenarios between 2010 and 2040 (BAU ¼ Business As Usual; LS ¼ Low intervention Scenario; HS ¼ High intervention Scenario; SS ¼ Stabilizing Scenario. It is assumed that ten years is needed for a planted Boswellia plant to start producing incense).
Fig. 3. Simulated per cent B. papyrifera stem (left) and frankincense yield (right) in Abergelle district under four alternative scenarios between 2010 and 2040 (BAU ¼ Business as usual; LS ¼ Low intervention Scenario; HS ¼ High intervention Scenario and SS ¼ Stabilizing Scenario. The jumps in the yield figure at around 10 years indicate additional new frankincense production from Boswellia trees established by planting. 10 years is considered as time lap for incense production.
mortality is completely avoided (100% reversal of adult mortality) the population of the species would remain significantly unaffected compared to avoiding deforestation only (Fig. 4). While complete avoidance of current adult mortality will ensure existence of 97.8% of the current population at the end of 30 years, complete avoidance of deforestation will only manage to ensure 11.3% of the
current population after the 30 years. This implies future management of the woodlands should focus more on how to reduce mortality as its primary goal above any other measures. The causes of the high rate of adult mortality is not clearly known but free grazing, pest and increased frequency of fire are assumed to be the proximate causes. Therefore, management should focus on controlling these causes before planning for high investment to traditional management practices such as reforestation, afforestation and the like that apparently are straight forward solutions under normal circumstance. It is interesting to note here that avoidance of deforestation, which many study reports put forward as a major problem of the woodlands, particularly for Metema seems to have less impact than overall adult mortality. 4. Discussion
Fig. 4. Test of model predictions sensitivity to various mortality and deforestation assumptions to identify the most important factor for priority setting in future intervention.
The model outputs from this study prompt the rapid downward spiral of Boswellia resources and the likely scarce supply of frankincense product from Ethiopia to the world market in the near future. It is obvious that the outcomes of the model simulation are expression of the relationships between factor included in the modelling as well as the data input used. Some of these data were empirical generated through field studies but others were subjective as obtained through analysis of the perception of stakeholders. Therefore, the usefulness of the predicted trends depends to a large extent on the realism of the perceptions and assumptions of the
M. Lemenih et al. / Journal of Arid Environments 105 (2014) 33e40
stakeholders involved in this particular study. It is obvious in this study that the degradation wing of the model is based on empirical studies, while the restoration wind is what has been assumed possible by stakeholders engaged in the participatory scenario development process. The model output is clearly showing that despite the likely management intervention proposed by the stakeholders, the model predicted a continuous degradation of Boswellia and its frankincense including under the best case scenario (HS). This clearly indicates that the expected management inputs for the resource is far lower than the on-going degradation force, which is likely to lead to a continuous rapid decline of both the stem density and frankincense yield in the future. This will affect both the livelihoods of millions of communities that depend on dry forests and their products, citizens that involve along the value chain of frankincense as well as the national economy that has been generating millions of dollars each year. It is also likely to affect several global industries particularly those in the perfumery and pharmaceutical sectors. Furthermore, despite huge differences in socio-economic environment between the two case study districts, the modelled trends in frankincense resource happen to be similar. This may reflect that any level of human interference, whether big or small, is likely to cause significant threat on the Boswellia resource and the ensuing frankincense production. Several previous studies have also reflected the same gloomy situations (Eshete et al., 2012a, 2011; Lemenih et al., 2012c; Tolera et al., 2013). The major threat, as can be shown in the sensitivity analysis is the extra high adult mortality of Boswellia trees. This has been reported in a similar study as well (Groenendijk et al., 2012). The second most serious problem is the complete absence of recruitment through natural regeneration from the two districts. These two problems are in fact driven by several direct and underlying factors of degradation (Lemenih et al., 2012c). The most direct is increasing fire frequency and livestock grazing (Eshete, 2011; Lemenih et al., 2007). The underlying drivers are probably population growth (Lemenih et al., 2007; Dejene et al., 2013; Lemenih et al., 2012a,c). Human and livestock population are increasing in these woodlands. These have in turn instigated new forms of woodlandepeople relationships in which fire incidences, livestock grazing and intensification of incense tapping are observed. There is heavy unregulated and unmanaged livestock grazing and wood product harvest in most Boswellia woodlands. The high level of negative anthropogenic interferences in frankincense woodlands are severely threatening not only the rapid decline but also the likelihood of disappearance of the resource in just half a century from now if conditions of management will not change. This is alarming for a country with a long history of frankincense production and trade as well as cultural attachment. Efforts so far both at local grassroots and country levels for improved management of the species and conservation of frankincense woodlands are limited or better called non-existent. Domestication processes and efforts are very low (Lemenih et al., 2012b). Most alarming is the fact that plausible future management intervention alternatives as perceived by the local stakeholders do not seem to reverse the downward trend of frankincense resources. This might call for rather concerted and large scale efforts from all concerned at much higher decision making level than just local stakeholders. Moreover, some trials with planting reports low survival rate of seedlings. So far limited success has been reported only from vegetative reproduction (Haile et al., 2011; Negussie et al., 2009). Yet, no relation between survival rates both for adult and young seedlings and soil and other biotic conditions common to the environment of the woodlands can be established (Eshete, 2011). Therefore, factors that constrain stability of Boswellia population are those beyond the natural environment of soil and associated
39
biotic effects. Furthermore, seeds of the species show no problem of germination (Eshete et al., 2012b), and annual seedling emergence in the woodlands are also more than sufficient to ensure stable population (Eshete, 2011). However, no seedlings survive and grow into adult tree in the studied districts (Groenendijk et al., 2012; Tolera et al., 2013). A recent comparative study of regional differences in population structure of Boswellia species is prompting the problem to the degree of human disturbance of the natural environment of the species (Lemenih et al., 2012c). The anthropogenic factors assumed to drive the problem are increased livestock grazing pressure and fire incidences. Over the last four to five decades human and livestock population have rapidly increased in the Boswellia woodlands, and so do fire incidences, livestockewoodland interactions and human harvest of forest products, not only in Ethiopia (Lemenih et al., 2007, 2012a,b; Eshete, 2011) but also in Eritrea (Ogbazghi et al., 2006) and Sudan (Adam and El, 2008). Local people also associate the problem observed in the woodlands to these causative factors (e.g. Eshete et al., 2011; Lemenih et al., 2007, 2012c). Whether the problem is caused by the aforementioned anthropogenic factors or more by global phenomena such as environmental changes like climate change is hard to specify. The correlation between local anthropogenic factors and problems of frankincense resource is simply based on the fact that as human and livestock population grow in the frankincense woodlands, their vitality tended to degrade. To confirm such hypothetical and casual relationships, more rigorous and well designed researches need to be conducted. Therefore, besides policy measures to manage humanewoodland interactions, researches need to be strengthened on the interactive effects of soil conditions, climate, disturbances by grazing, fire, forest product harvest including frankincense production through tapping. For the short term, strategic intervention is needed through conservation area delineation of large tracts of land in which human-livestock contacts will be minimized as much as possible. It is worth mentioning that the model simulated results are not forecasts but are reflection of what are likely to happen given the assumptions and conditions considered in the alternative futures, which may or may not in real world situation. This means that policy makers and woodland managers should consider the outcomes as a signal or sign post to future management planning and policy reframing tool. However, the fact that all the scenarios suggest a decline trend implies that on-going management efforts and those possibly taken in the future are unlikely to effectively address the challenge facing frankincense resources in the two dry land areas of Ethiopia. This should stimulate questions such as why this happens, what then next and the like, and based on answers for such questions revisit the on-going management practices and existing national or local development strategies for the resource. It is also interesting to indicate that the participatory approach to scenario development is an effective platform for generating data and assumptions to be used in simulation modeling, and to see the implications to come, assisting policy makers and practitioners to think of better strategies in the future. 5. Conclusion This study reveals that B. papyrifera and its frankincense products in Ethiopia are under severe threat. Most worrying is the fact that the interventions perceived as practicable by local stakeholders fall short to stabilize the situation. The conditions in the SS prompted that much more efforts than those conditions suggested by the stakeholders are needed to stabilize the stem population and sustain frankincense yield at current level, and whether these interventions suggested by SS are likely to be implemented or not is yet to be seen. Whatever the case, the situation tends to call upon
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urgent supports from a wider community than just the local stakeholders and indeed engagement of local, national and international community might be necessary to sustain the production of this ancient product, frankincense, and its resource base. Acknowledgement This study was largely funded by The Netherlands Foundation for the Advancement of Scientific Research in the Tropics (NWOWOTRO) as part of the integrated research programme FRAME (frankincense, myrrh and gum arabic: sustainable use of dry woodlands resources in Ethiopia, grant number W01.65.220.00). References Abiyu, A., Bongers, F., Eshete, A., Gebrehiwot, K., Kindu, M., Lemenih, M., Moges, Y., Ogbazghi, W., Sterck, F., 2010. Incense woodlands in Ethiopia and Eritrea: regeneration problems and restorations possibilities. In: Bongers, F., Tennigkeit, T. (Eds.), Degraded Forests in Eastern Africa: Management and Restoration. Earthscan Ltd, London, UK, pp. 133e152. Adam, A.A., El, T.A.M., 2008. A comparative study of natural regeneration of B. papyrifera and other tree species in Jebel Marra Darfur, Sudan. Res. J. Agric. Biol. Sci. 4, 94e102. Alemu, B., Garedew, E., Eshetu, Z., Kassa, H., Zewdu, Y., Temesgen, Y., 2012. Land use and land cover changes and associated driving forces in northwestern lowlands of Ethiopia. In: Eshetu, Z., Kassa, H., Garedew, E., Lemenih, M., Tadesse, W. (Eds.), Proceedings Joint CIFOR-EIAR National Workshop to Review Research Findings on Dry Forests and Synthesize Lessons for Policy and Practice, 31 December 2012, Addis Ababa, Ethiopia, pp. 88e115. Bard, A.K., Coltorti, M., DiBlasi, C.M., Dramis, F., Fattovich, F., 2000. The environmental history of Tigray (Northern Ethiopia) in the middle and late Holocene: a preliminary outline. Afr. Archaeol. Rev. 17, 65e86. http://dx.doi.org/10.1023/A: 1006630609041. Bongers, F., Tennigkeit, R. (Eds.), 2010. Degraded Forests in Eastern Africa: Management and Restoration. Earthscan Publications, London. Butzer, K.W., 1981. Rise and fall of Axum, Ethiopia: a geo-archaeological interpretation. Am. Antiq. 46, 471e495. Chidumayo, E.N., Gumbo, D.J., 2010. The Dry Forests and Woodlands of Africa: Managing for Products and Services. CIFOR, Bogota, Indonesia. Chikamai, B., 2002. Review and Synthesis on the State of Knowledge of Boswellia Species and Commercialization of Frankincense in the Drylands of Eastern Africa (Nairobi, Kenya). Chikamai, B., Casade, E., 2005. Production and Marketing of Gum Resins: Frankincense, Myrrh and Opoponax. FAO/NGARA, Nairobi, Kenya. Chikamai, B., Tchatat, M., Tieguhong, J., Ndoye, O., 2009. Forest management for non-wood forest products and services in sub-Saharan Africa. Discov. Innov. 21. Online: http://www.ajol.info/index.php/dai/article/view/48213. Costanza, R., Voinov, A., 2001. Modelling ecological and economic systems with STELLA: part III. Ecol. Model. 143, 1e7. Costanza, R., Duplisea, D., Kautsky, U., 1998. Introduction to special issue: ecological modelling on modelling ecological and economic systems with STELLA. Ecol. Model. 110, 1e4. Dejene, T., Lemenih, M., Bongers, B., 2013. Manage or convert Boswellia woodlands? Can frankincense production payoff? J. Arid Environ. 89, 77e83. Doerr, H.M., 1996. STELLA ten years later: a review of the literature. Int. J. Comput. Math. Learn. 1, 201e224. Eshete, A., Sterck, F.J., Bongers, F., 2011. Diversity and production of Ethiopian dry woodlands explained by climate e and soil e stress gradients. For. Ecol. Manag. 261, 1499e1509. Eshete, A., 2011. The Frankincense Tree of Ethiopia: Ecology, Productivity and Population Dynamics (PhD thesis). Wageningen University, Wageningen, Netherlands. Eshete, A., Sterck, F.J., Bongers, F., 2012a. Frankincense production is determined by tree size and tapping frequency and intensity. For. Ecol. Manag. 274, 136e142. Eshete, A., Teketay, D., Lemenih, M., Bongers, F., 2012b. Effects of resin tapping and tree size on the purity, germination and storage behaviour of Boswellia papyrifera (Del.) Hochst. seeds from Metema District, Northwestern Ethiopia. For. Ecol. Manag. 269, 31e36. FAO, 1995. Flavors and Fragrance of Plant Origin. Non-wood Forest Products. FAO, Rome, Italy.
Garedew, E., Sandewall, M., Soderberg, U., 2012. A dynamic simulation model of land-use, population, and rural livelihoods in the Central Rift Valley of Ethiopia. Environ. Manag. 49, 151e162. http://dx.doi.org/10.1007/s00267-011-9783-4. Groenendijk, P., Eshete, A., Sterck, F.J., Zuidema, P.A., Bongers, F., 2012. Limitations to sustainable frankincense production: blocked regeneration, high adult mortality and declining populations. J. Appl. Ecol. 49, 164e173. Hannon, B., Ruth, M., 1994. Dynamic Modelling. Springer-Verlag, New York. Haile, G., Gebrehiwot, K., Lemenih, M., Bongers, F., 2011. Time of collection and cutting sizes affect vegetative propagation of Boswellia papyrifera (Del.) Hochst through leafless branch cuttings. J. Arid Environ. 75, 873e877. Lemenih, M., 2005. Production and marketing of gums and gum resins in Ethiopia. In: Chikamai, B., Casade, E. (Eds.), Production and Marketing of Gum Resins: Frankincense, Myrrh and Opoponax. FAO/NGARA, Nairobi, Kenya, pp. 55e70. Lemenih, M., Feleke, S., Tadesse, W., 2007. Constraints to smallholders production of frankincense in Metema district, North-western Ethiopia. J. Arid Environ. 71, 393e403. Lemenih, M., Kassa, H., 2011. Gums and Resins of Ethiopia, Info-brief. CIFOR, Bogor Indonesia. Lemenih, M., Kassa, H., Tesfahun, G., Getnet, D., Worku, T., 2012a. Resettlement and woodland management problems and options: a case study from a resettlement district in northwestern Ethiopia. Land Degrad. Dev.. http://dx.doi.org/ 10.1002/ldr.2136. On-line. Lemenih, M., Wiersum, F., Woldeamanuel, T., Bongers, F., 2012b. Diversity and dynamics of management of gum and resin producing woodlands in Ethiopia: a trade-off between degradation and domestication. Land Degrad. Dev.. http:// dx.doi.org/10.1002/ldr.1153. Available online. Lemenih, M., Woldeamanuel, T., Yilma, Z., Kassa, H., 2012c. Understanding factors behind recruitment bottleneck for Boswellia papyrifera: a comparative study of two regions with contrasting population structure. In: Eshetu, Z., Kassa, H., Garedew, E., Lemenih, M., Tadesse, W. (Eds.), Proceedings Joint CIFOR-EIAR National Workshop to Review Research Findings on Dry Forests and Synthesize Lessons for Policy and Practice, 31 December 2012, Addis Ababa, Ethiopia, pp. 71e79. Mayaux, P., Holmgren, P., Achard, F., Eva, H., Stibig, H.-J., Branthomme, A., 2005. Tropical forest cover change in the 1990s and options for future monitoring. Philos. Trans. R. Soc. Lond. Ser. B Biol. Sci. 360 (1454), 373e384. Mekonnen, M.B., 2004. The Past in the Present: the Dynamics of Identity and Otherness Among the Gumuz of Ethiopia (PhD dissertation). Norwegian University of Science and Technology, Trondheim. Mengistu, T., 2011. Physiological Ecology of the Frankincense Tree (PhD thesis). Wageningen University, Wageningen, Netherlands. Murphy, P.G., Lugo, A.E., 1986. Ecology of tropical dry forest. Annu. Rev. Ecol. Syst. 17, 67e88. Negussie, A., Aerts, R., Gebrehiwot, K., Prinsen, E., Muys, B., 2009. Euphorbia abyssinica latex promotes rooting of Boswellia cuttings. New. For. 37, 35e42. Ogbazghi, W., 2005. Production and marketing of gums and resins in Eritrea. In: Chikamai, B., Casade, E. (Eds.), Production and Marketing of Gum Resins: Frankincense, Myrrh and Opoponax. FAO/NGARA, Nairobi, Kenya, pp. 55e70. Ogbazghi, W., Rijkers, T., Wessel, M., Bongers, F., 2006. The distribution of the francincense tree Boswellia papyrifera in Eritrea: the role of environment and land use. J. Biogeogr. 33, 524e535. Pausas, J.G., 1999. Response of plant functional types to changes in the fire regime in Mediterranean ecosystems: a simulation approach. J. Veg. Sci. 10, 717e722. Rogan, J., Chen, D., 2004. Remote sensing technology for mapping and monitoring land-cover and land-use change. Prog. Plan. 61, 301e325. Tegegne, A., Mengistie, T., Desalew, T., Teka, W., Dejen, E., 2009. Transhumance Cattle Production System in North Gondar, Amhara Region, Ethiopia: is it Sustainable? IPMS (Improving Productivity and Market Success) of Ethiopian Farmers Project. Working Paper No. 14. ILRI, International Livestock Research Institute, Nairobi, Kenya, p. 73. Tolera, M., Sass-Klaassen, U., Eshete, A., Bongers, F., Sterck, F.J., 2013. Frankincense tree recruitment failed over the past half century. For. Ecol. Manag. 304, 65e72. Tilahun, M., Olschewski, R., Kleinn, C., Gebrehiwot, K., 2007. Economic analysis of closing degraded Boswellia papyrifera dry forest from human interventions e a study from Tigray, Northern Ethiopia. For. Policy Econ. 9, 996e1005. Vollesen, K., 1989. BURSERACEAE. In: Hedberg, I., Edwards, S. (Eds.), Flora of Ethiopia, vol. 3. National Herbarium, Addis Abeba University, Addis Abeba and Uppsala University, Uppsala, pp. 442e478. WBISPP, 2004. Forest Resources of Ethiopia (Addis Ababa, Ethiopia). White, F., 1983. The Vegetation of Africa. A Descriptive Memoir to Accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa. Natural Resources Research 20. UNESCO, Paris, France. Woldeamanuel, T., 2011. Dryland Resources, Livelihoods and Governance: Diversity and Dynamics in Use and Management of Gum/Resin Trees in Ethiopia (PhD thesis). Wageningen University, Wageningen, the Netherlands.
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Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv
Modelling the future of Boswellia papyrifera population and its frankincense production M. Lemenih a, *, B. Arts b, K.F. Wiersum b, F. Bongers a a Center for Ecosystem Studies, Forest Ecology and Forest Management Group, Wageningen University and Research Center, P.O. Box 47, 6700 AA Wageningen, The Netherlands b Forest and Nature Conservation Policy Group, Wageningen University and Research Center, PO Box 47, 6700 AA Wageningen, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 September 2013 Received in revised form 5 February 2014 Accepted 14 February 2014 Available online 19 March 2014
Sustainable production of the aromatic forest product frankincense is at stake due to rapid decline in its resource base. This affects livelihoods of thousands of citizens and several global industries. A system dynamic model approach is used to predict the future population of Boswellia papyrifera trees and its frankincense yield for three decades (2010e2040) in Metema and Abergelle districts in northern Ethiopia. Data from studies on the ecology, distribution, rate of deforestation and participatory future scenario development were put together and analysed using a model platform developed with STELLA. Four alternative scenarios namely Business As Usual (BAU); Low Intervention Scenario (LS), High Intervention Scenario (HS) and Stabilization Scenario (SS) were used. The model predicts 3%, 8% and 37% of the current stem population to exist in 2040 under BAU, LS, HS scenarios, respectively in Metema. Similarly, 11%, 13% and 46% stem density is predicted under BAU, LS and HS, respectively for Abergelle. Test of model sensitivity shows adult mortality is the most serious problem facing the resource. Immediate management intervention should focus on reducing adult tree mortality followed by reducing deforestation. Medium and long term interventions need to focus on how to improve recruitment and afforestation/reforestation of the species. Ó 2014 Elsevier Ltd. All rights reserved.
Keywords: Abergelle Deforestation Metema Reforestation Participatory future scenario
1. Introduction Dry tropical forests including woodlands cover over 40% of the global tropical forest areas (Mayaux et al., 2005). In Africa alone, these forests cover 17.3 M km2, and are home for half a billion people (Chidumayo and Gumbo, 2010). About 28 African countries host such vegetation types and in some of the countries they are the only forest resources. Although less diverse than the wet tropical forests, African dry forests also host considerable biological diversity of immense local, regional and international significances (Bongers and Tennigkeit, 2010; Murphy and Lugo, 1986; White, 1983). An important feature of the dry forests in East Africa in particular is their richness in plant species of the genera Acacia, Boswellia and Commiphora (Chikamai et al., 2009; Lemenih, 2005; Vollesen, 1989). Several of the species in these genera are renowned for being the sources of commercial gums and gum resins such as gum arabic, frankincense and myrrh; important export forest products for several countries in the Horn of Africa
* Corresponding author. Tel.: þ31 251 912066839; fax: þ31 251 116612877. E-mail address: [email protected] (M. Lemenih). http://dx.doi.org/10.1016/j.jaridenv.2014.02.006 0140-1963/Ó 2014 Elsevier Ltd. All rights reserved.
including Ethiopia, Sudan, Eritrea, Somalia and Kenya (Chikamai, 2002; Chikamai and Cascade, 2005; FAO, 1995). In Ethiopia alone, dry forests and woodlands cover ca. 55 M ha (WBISPP, 2004). The vast Combretum e Terminalia broadleaved deciduous woodlands in the western and north-western lowlands of the country are the home for the frankincense tree species Boswellia papyrifera. Those in the east, southeast, along the rift valley, in the south and southwest host diverse Acacia, Boswellia and Commiphora species. Frankincense from B. papyrifera in particular has been produced and traded since antiquity (Bard et al., 2000; Butzer, 1981), and still today produce to feed domestic and international markets for fragrance (Lemenih, 2005; Ogbazghi, 2005). Despite their economic and ecological importance, dry forests and woodlands in Africa in general and those in Ethiopia in particular are rapidly declining and degrading (Bongers and Tennigkeit, 2010; Chidumayo and Gumbo, 2010; Lemenih and Kassa, 2011). With these changes, biodiversity of the forests and woodlands and their ecosystem services are severely threatened (Chidumayo and Gumbo, 2010; Eshete et al., 2011). In Ethiopia the current status of the resource shows a worrying trend (Abiyu et al., 2010; Eshete et al., 2011; Groenendijk et al., 2012; Lemenih et al., 2012a,b). Most of the Boswellia natural
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stands are characterized by a lack of recruitment (complete hindrance of recruitment) through natural regeneration, high rate of deforestation and widespread encroachment by expanding cropland and very high adult mortality; hence a declining population (Abiyu et al., 2010; Eshete et al., 2012a; Groenendijk et al., 2012; Lemenih et al., 2012a,b; Tolera et al., 2013). There is no forest management plan put in place in major producing areas, tapping is uncontrolled and enrichment planting is also absent. Promoting sustainable frankincense production requires the balance between economic and ecological uses of the woodlands and comparative analysis of the short term rural development demand from alternative land uses on the one hand and the long term ecological and economic benefits from the woodlands on the other (Dejene et al., 2013). Some studies are showing that managing the Boswellia woodlands for frankincense and other nontimber forest products can offer competitive financial return with alternative agricultural land uses (Dejene et al., 2013; Tilahun et al., 2007), yet the woodlands are considered generally as having low economic potential, one of the factors leading to their wide spread conversion and use for resettlement programs (Dejene et al., 2013; Lemenih et al., 2012a). Given all the challenges that the woodlands and the frankincense trees are facing there is serious doubt of long term prospect for a sustained supply of frankincense and other ecosystem services from the woodlands and the species. One way to explore and predict potential future threats facing Boswellia resources and the production of the fragrance frankincense is by means of modelling. Modelling future trends under sets of scenarios provide good information on how various courses of action may affect the future of a resource in question. Thus, it significantly contributes to the understanding of the potential impacts associated with various threats and enhances early decision making process to minimize consequences. Therefore, the model outputs could play an important role in facilitating the identification and planning of management strategies that could reverse the trend and promote improved management of the resource. In this study, a system dynamic simulation modeling approach is employed to compose data and assumptions generated from our own research and a number of parallel studies from an integrated project (Eshete, 2011; Mengistu, 2011; Woldeamanuel, 2011; Lemenih, unpublished; Atkilt, unpublished) to predict the future of Boswellia population and its frankincense production in the northern lowlands of Ethiopia (Sections 2.2e2.5). Modeling approach to vegetation study is a useful approach to investigate the
long term consequences of different scenarios of changes on vegetation (Pausas, 1999), thereby assisting the designing of effective management strategies (Garedew et al., 2012). System dynamics modeling in particular differs from other modeling system in its use of feedback loops, and stocks and flows (Costanza and Voinov, 2001) to provide a basis for better understanding of socioeconomic and environmental interactions (Garedew et al., 2012). It is a concept that considers dynamic interactions between various elements of the studied system to understand their behavior over time, build models, identify how information feedback governs the behavior of the system and develop strategies for better management of the system (Doerr, 1996). Since it involves various alternative scenarios, most of which are developed through stakeholder participation or expert assumptions, simulation models are not a forecasting instrument but a planning and analysis tool. The model structure developed for this study included submodels representing components of forest ecosystem dynamics: recruitment (separating between planting and natural regeneration), mortality (death and deforestation separately) as well as frankincense production. Four main scenarios were constructed together with local stakeholders using a participatory stakeholder scenario development process. The objective was to employ scenario modelling technique to simulate and examine the future population of B. papyrifera and the production of frankincense under various plausible assumptions and conditions likely to prevail in affecting management and conservation of the frankincense woodlands in Ethiopia. 2. Material and methods 2.1. Study sites The study was conducted in two woodland areas dominated by B. papyrifera trees: Abergelle in the north and Metema in the northwest. Both woodlands are known for having a high frankincense production and a long history of marketing of the product. However, there are several differences between the two sites in biophysical, socio-economic and livelihood conditions (Table 1). Abergelle is both one of the oldest and the main gum/resin production areas in Ethiopia. The production of this resource forms an important means for cash earning by local communities. This cash earning supplements the mainly subsistence-oriented mixed farming practices (Lemenih et al., 2012a). Metema was traditionally
Table 1 Major biophysical and socio-economic land-use conditions in the two study districts Metema and Abergelle, northern Ethiopia. Site attribute
Abergelle
Metema
Location Area and population Climate conditions
13 110 and 13 150 N and 37 430 and 38 070 3000 km2 with the population of 113,526 inhabitants; Semi-arid; rainfall is uni-modal and very erratic with mean annual rainfall of ca. 800 mm. Mean Annual Temperature of 22 C; Range between 1400 and 1650 m a.s.l. Homogenous, Tigre ethnic group
12 390 and 12 450 N, and 36 170 and 36 480 E 3995 km2 with population of 83,193 inhabitants; Semi-arid to sub-humid; rainfall is uni-modal with Mean Annual Rainfall of ca. 965 mm; Mean Temperature 28 C;
Altitude Ethnic composition
Main livelihoods
Original natural vegetation
History of gum-resin production
Mixed subsistence farming. Prevalent food insecurity stimulates alternative income earning Combretum-Terminalia woodlands and wooded grasslands. B. papyrifera and some Acacia spp. predominate; Woodlands cover only small portion of the district Probably the oldest commercial production region in Ethiopia (since 1940s). Systematic resin production through tapping mainly in concession areas allotted to commercial firms
Range between 549 and 600 m a.s.l. Heterogeneous, with Amhara (80%), Tigre (10%), Oromo (5%) and Gumuz (2%). Increasing importance of immigrants Traditional hunting-gathering being replaced by mixed subsistence farming. Quick expansion of commercial farming of oilseed and cotton. Combretum-Terminalia woodlands and wooded grassland. More diverse and higher in stature than in Abergelle. B. papyrifera is the main species. Woodland cover large part of the district Systematic commercial production started recently (1980’s), and has gradually intensified
M. Lemenih et al. / Journal of Arid Environments 105 (2014) 33e40
sparsely inhabited by people that practice shifting cultivation supplemented by hunting and gathering (Mekonnen, 2004). However, in recent decades, high population migration from highland to lowland is intensifying the mixed crop-livestock production system that is negatively affecting the woodlands (Lemenih et al., 2012a, 2007). Migration to Metema from the highlands has intensified since the latee1960s/earlye1970s, and it has changed significantly the demographic and ethnic composition of the district (Lemenih et al., 2007). The range use of the woodlands in Metema is also increasing. The woodlands are extensively used as rangelands by resettled local people for grazing and by seasonally migrating cattle herders from the surrounding highlands (transhumance). According to a study by Tegegne et al. (2009), 60.3 per cent of the total cattle population in three nearby highland districts (Chilga, Dembia and Gondar Zuria) trekked to Metema for 6e8 months each year while the highlands were used for cultivating food crops. Unlike in Abergelle, the climate and the soil conditions in Metema are also suitable for the intensive cultivation of various crops, such as cotton, sesame, sorghum, finger millet, maize and tef, and the area has recently been opened up for the cultivation of most of these cash crops. 2.2. Approaches and methods of data collection The study employed a system dynamics modeling technique, which is based on building a stock- and-flow model using STELLA (version 8), a software package specifically designed for dynamic systems modelling. STELLA is one of the most versatile graphical programming language used widely by ecological, economic and biological system modelers (e.g. Costanza and Voinov, 2001; Costanza et al., 1998; Hannon and Ruth, 1994). The purpose of the model in this study was to predict the population of B. papyrifera and its frankincense production over the next 30 years (i.e. by 2040) under four alternative future scenarios that take into consideration the main drivers affecting the species on one hand and possible management interventions to improve or reverse the drivers threatening the species on the other, the latter as perceived by local stakeholders that participated in the future scenario development process. The four scenarios considered in the model process were developed through a participatory process by engaging stakeholders at each locality (see Section 2.5). The structure of the model is shown in Fig. 1. The main components of the model are: i) recruitment into the standing population of B. papyrifera mainly from two means namely from natural regeneration and artificial
Fig. 1. Model components for the quantitative projection of B. papyrifera population and its gum-resin production in northern Ethiopia.
35
Table 2 Major threats to B. papyrifera and frankincense yield in the two study districts considered for model development. Current threats and management practices
Region Metema
Abergelle
Competing land use pressure (deforestation and conversion) Current reforestation and afforestation Protection of the standing stock Production intensity Adult mortality Recruitment Fire and grazing intensity
Very high
Low
Non-existent
Non-existent
Very poor High and no control Exceptionally high Non-existent High
Moderate High and no control Exceptionally high Non-existent Low
Sources: Eshete, unpublished.
2011;
Mengistu,
2011;
Woldeamanual,
2012;
Lemenih,
planting, and ii) mortality, which refers to loss of B. papyrifera from the standing population as a result of annual deforestation (ha/yr, which is also translated into Boswellia stem removal per ha and year based on its average stem density in the forest) and natural adult death (stem/ha/yr). The third component of the model is frankincense yield per year, which predicts change in total yield as a result of change in standing population of Boswellia, given a standard mean yield production per tree per year. The fourth component, which represents the stock at the centre of the model, is the current stem density of Boswellia. Recruitment adds to this stock, while mortality reduces from this stock. So the stock is the beginning of the dynamics either increased when recruitment is higher than mortality or declines when mortality is higher than recruitment. These model components were selected based on threats identified for the woodlands from parallel studies within the same project coupled with participatory problem analysis (Eshete, 2011; Mengistu, 2011; Woldeamanuel, 2011; Lemenih et al., unpublished) (Table 2). Moreover, some of the quantitative data inputs and assumptions used in the model were generated from these parallel studies. The procedures employed by the parallel studies to generate the quantitative data are described in Sections 2.3e2.5.
2.3. Model input: stand density, recruitment, mortality and yield estimate In Metema, 12 plots of 1.6e2.0 ha each were established. In these plots complete census of population took place in 2007, 2008 and 2009 with the first census result of a total of 4370 trees with >1 cm DBH and 2228 smaller individuals (seedlings and saplings) (Eshete et al., 2012a, 2011; Groenendijk et al., 2012). Identity of all species within the plot were recorded and the stem density of B. papyrifera per ha also determined. In the subsequent years (2008 and 2009) survival was assessed for all individuals. A similar study was carried out in Abergelle on six plots of 1.2e2.0 ha in size. What is found for both woodlands is the high rate of adult mortality and complete absence of recruitment in the current populations (Eshete, 2011; Groenendijk et al., 2012). Adult Boswellia tree mortality is huge taking place at the annual rate of 7% in both woodlands (Eshete, 2011). These two factors, mortality and lack of recruitment, are critical degradative factors threatening the future of Boswellia tree population and frankincense production (Table 2). Causes for the high rate of adult mortality are not known for sure but insect attack and windfall are assumed to be the direct causes. Increased fire frequency, and human and livestock population pressure are also blamed for this (Eshete, 2011; Lemenih et al., 2007).
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Furthermore, at both sites tapping experiment to assess frankincense production per tree and year was also conducted. In both places 25 trees of different diameter categories were marked and tapped during 2008 and 2009 tapping seasons (Eshete et al., 2012a). Incense tears produced during each cycle of collection were gathered, weighted and annual yield was obtained to provide estimate of average production per tree/yr. 2.4. Model input: deforestation rates in the studied districts Rate of deforestation of the woodlands, hence loss of B. papyrifera population was assessed using multi-temporal satellite images from 1985 and 2010. Both Landsat and SPOT satellite images were used for the assessment. Supervised classification using ERDAS Imagine 9.1 software was conducted to identify major land cover/land use in the districts and detect changes. First scenes covering the area are identified and important bands are collected. Then, triple images of bands 4, 3, 2 in Landsat and 3, 2, 1 in SPOT are stacked to one image as layers. After identifying images that cover the entire Metema and Abergelle districts, their mosaic was created and clipped to the district boundaries. Pseudocolor combination (bands 4, 3, and 2 as Red, Green, and Blue layers in Landsat and 3-21 in SPOT images), which is good in vegetation identification, was employed for the land use/land cover classification. The images where corrected geometrically, colour enhanced and classified. To assist the supervised image classification, training areas that represent separate land use/cover types existing in the district were entered as signatures to the software. Combinations of prior field knowledge, field observations, ancillary data from Google Earth and unsupervised image classifications were used in defining the training area (Alemu et al., 2012). Finally the supervised image classification was run for each site in an iterative approach until land use/cover classification of acceptable accuracy level was obtained for the two periods (Rogan and Chen, 2004). Change detection and rate of changes of different land use/land cover were assessed, and areas converted from one cover or use to the other was computed. ERDAS Imagine version 9.1was used for image classification, while ArcGIS version 9.3 was used for mapping and area estimation. For Metema district in 2010 land use/land cover map showed 42.2% cropland, 46.5% woodland and shrubland, 7% grassland and 9.7% bare land. In 1985, however, cropland cover was 24.1%, woodland and shrubland was 58.6%, grassland was 10.3% and bare land was 7% (Table 3). It is clear from these figures that cropland has increased significantly while woodlands and shrublands decreased. Based on this, the average deforestation rate in Metema for the past four decades is estimated at 1796.42 ha/yr. On the contrary in Abergelle there has been no detectable deforestation since the 1970s. Absence of detectable woodlands deforestation in Abergelle is attributed to stringent local institutions that control forest clearance and conversion to other forms of use or cover. This is
verified during the interviews and participatory stakeholder workshop. 2.5. Scenario construction: stakeholder engagement and future scenario definition The alternative future scenarios used in the study were developed by engaging stakeholders that comprise local communities, Development Agents and experts of Office of Agriculture at district level. Two levels of engagement were conducted. First interviews (household survey, key informant and focus group discussions) were conducted to collect major drivers of Boswellia woodland change and the perception of the interviewees on how the woodland will develop over the 30 years to come. This was followed by local level workshops one per site to present the findings from the interview and to develop the alternative scenarios together. In Metema five key informants and 4 group discussions were held, while in Abergelle 20 household heads were interviewed. In Metema 34 individuals participated in the workshop, while in Abergelle 36 participants involved. The workshops were facilitated by the researchers assisted by local experts. The workshops had two major sessions: a morning session was dedicated to presentation of the key findings from the questionnaire survey and discussion on it. An afternoon session was dedicated to jointly define the alternative scenarios. For both sites four alterative future scenarios were developed. The first was Business As Usual (BAU, here after), which refers to no management intervention to reverse the current trend of woodland degradation. The second scenario was called Low Intervention Scenario (LS, here after), which refers to the least management intervention that are probable to have. The third was called High Intervention Scenario (HS, hereafter), which referred to the best possible management intervention likely to be exercised to manage the woodlands. The last and fourth scenario was called stabilizing scenario (SS, hereafter), was added by the researchers to indicate the maximum conditions that are expected to maintain the current Boswellia population, which is supposed to indicate the utmost efforts needed to stabilize the population at its current state compared to what the stakeholders indicated as likely possible both in LS and HS. Since the two sites vary in terms of institutional and local efforts to stop degradation and restore the woodlands (Table 2), the definitions of data inputs for the various components of the model also varied. In Metema participants of the scenario workshop expected the probable reduction in deforestation of the woodlands by 30% and 70% under the LS and HS, respectively (Table 4). On the other hand, afforestation/reforestation rate was estimated to be equal to 50 ha/yr and 100 ha/yr for the LS and HS respectively. In addition in the case of HS, enrichment planting was expected to replace 2.1% of the 7% adult mortality, which was equal to 4 stem/ha/yr (Table 4). The SS assumes replacement of the deforestation rate through
Table 3 Land use/land cover change in Metema district between 1985 and 2010. Land cover/land use type
Cover extent (in ha and %) 1985
1995
Cropland/settlement Woodlands Shrub lands Grassland Water body Bare land
91,889.7 108,333.5 114,570.9 39,300.9 444.5 26,137.7
Total
380,677.3 (100)
Source: Alemu et al., 2012.
(24.1) (28.5) (30.1) (10.3) (0.1) (6.9)
160,699.4 63,423.1 93,076.7 26,651.25 198.99 36,627.93
Average rate of change (1985e2010 in ha/yr)
2010 (30.8) (19.4) (30.9) (10.6) (0.08) (8.3)
380,677.3 (100)
160,699.4 63,423.09 93,076.65 26,651.25 198.99 36,627.93
(42.21) (16.66) (24.45) (7.00) (0.05) (9.62)
380,677.3 (100)
þ2752.39 1796.42 859.77 505.99 9.82 þ419.61 0
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Table 4 Data inputs for the model simulation for Metema and Abergelle. Model variables
Status 2010 Average Boswellia stem density (stem/ha) Total area of woodlands in the district (ha) Initial total Boswellia population Current recruitment (No. stems/yr/ha) Frankincense yield (kg/ha/yr) Initial frankincense potential in the district in tons/yr Adult tree mortality (%) Annual deforestation rate (ha/yr)
Sites Abergelle
192 270,000 51,840,000 0 76.8 20,736 7 1796.42
281 150,000 42.150,000 0 112.4 16,860 7 0
Scenarios BAU Adult tree mortality rate (%) Annual deforestation (ha/yr) Natural recruitment (No. of stem/ha/yr) Reforestation plantation (ha/yr) Planted seedling survival rate (% of total planted) Enrichment planting (stem/ha)
Data source
Metema
7 2656.2 0 0
Field survey Secondary source Field survey Field survey Field survey Field survey Field survey Field survey
LS
HS
SS
BAU
LS
HS
SS
7 925 0 50 50 0
7 555 0 100 50 4
7 2656.2 0 444a 50 13.4
7 0 0 0 0
7 0 0 75 50 0
7 0 0 150 50 6.9
7 0 0 150 50 18.9
Field survey Field survey Field survey Based on participatory workshop Based on participatory workshop Based on participatory workshop
Reforestation practices assumed initial stocking of 1600 seedlings/ha. Enrichment planting was considered in the high case scenario to be 35% replacement of current adult death and in the stabilizing scenario is 100% replacement. a Because of 1600 stems/ha in plantation the planted area is lower than the deforested area. Enrichment planting also reduces the area needed for planting.
reforestation at 1600 stem/ha planting rate and 50% survival. The equivalent area that should be annually afforested is 444 ha. In the case of Abergelle, a reforestation rate of 75 ha/yr for the LS, and 150 ha in the HS were suggested (Table 4). In all cases it was assumed that a planted seedling needs about 10 years to produce incense and thus a 10 year time lag was considered for planted Boswellia trees to offer frankincense. Table 4 summarizes input data obtained both from the parallel studies and the participatory scenario workshops.
interventions such as reforestation and afforestation constant. Identifying which variable affect most will help to identify where management intervention should put priority and focus on. The sensitivity analysis was conducted by using a range of assumption in adult mortality such as 25% reduction in mortality, 50% reduction in mortality and 100% reduction in mortality while keeping all other factors at BAU. For deforestation zero rate i.e. no deforestation was used keeping all other factors at BAU. 3. Results
2.6. Data combination and model analysis The data and information generated from the above processes where combined together to define the alternative scenarios and fed into the model. The reference scenario, the BAU, serves to reflect what will happen to the resource if there is no intervention and current disturbances continue for three decades to come. The two other alternative scenarios, LS and HS, represent the ‘least and best’ interventions that local stakeholders perceived as practicable for interventions on these woodlands given the political and socioeconomic conditions of their respective districts. These interventions include actions to reduce deforestation, reforestation of deforested areas and replacement of adult death through enrichment planting. The data were fed into the model developed using STELLA software. The simulation time frame considered was three decades with the reference year being 2010. Some of the assumptions in the simulation include all threats and management interventions remain similar over the simulation period. This means adult mortality, deforestation rate, enrichment planting, reforestation and frankincense yield per tree per year are constant at the rate defined at the beginning of the simulation. 2.7. Sensitivity analysis The variables that drive change in B. papyrifera populations are not expected to have an equal effect. We conducted a sensitivity analysis of the model predictions to identify which of the factor(s) most strongly determine the population size of B. papyrifera. We used different ranges of mortality and deforestation rate reductions based on expert guess of the researchers, while keeping other
3.1. Predictions of Boswellia population and frankincense yield under the four scenarios The projection for B. papyrifera stem population and the subsequent volume of frankincense expected under the four scenarios for Metema showed a continuous and alarmingly decline for both (Fig. 2). After 30 years only 3% of the current stem density of B. papyrifera will be expected to remain under the BAU scenario, while 8% and 37% will be expected under LS and HS respectively (Fig. 2). The fact that expected stem density and frankincense yield are declining rapidly with widening gap under all the scenarios with respect to the SS implies that many more efforts are needed than those already considered as ‘possible interventions’ by the stakeholders to conserve the resources and sustain incense production. Whether such high efforts are likely to take place is yet to be seen. The projection for Abergelle also shows a considerable decline in stem density and frankincense yield under all the three scenarios (Fig. 3). Compared to the estimated potential current stem number of 42,150,000 Boswellia and 16,860 ton of frankincense yield in the district only 11% (4,778,439), 13.1% (5,538,419) and 33% (13,952,943) stems will be expected under BAU, LS and HS, respectively (Fig. 3). Similar trend of frankincense yield were predicted under the respective scenarios (Fig. 3). 3.2. Sensitivity of the model The sensitivity analysis shows that the population of Boswellia is very sensitive to the reduction in the rate of adult mortality. If
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Fig. 2. Simulated per cent of B. papyrifera stem (left) and frankincene yield (right) in Metema district under four alternative scenarios between 2010 and 2040 (BAU ¼ Business As Usual; LS ¼ Low intervention Scenario; HS ¼ High intervention Scenario; SS ¼ Stabilizing Scenario. It is assumed that ten years is needed for a planted Boswellia plant to start producing incense).
Fig. 3. Simulated per cent B. papyrifera stem (left) and frankincense yield (right) in Abergelle district under four alternative scenarios between 2010 and 2040 (BAU ¼ Business as usual; LS ¼ Low intervention Scenario; HS ¼ High intervention Scenario and SS ¼ Stabilizing Scenario. The jumps in the yield figure at around 10 years indicate additional new frankincense production from Boswellia trees established by planting. 10 years is considered as time lap for incense production.
mortality is completely avoided (100% reversal of adult mortality) the population of the species would remain significantly unaffected compared to avoiding deforestation only (Fig. 4). While complete avoidance of current adult mortality will ensure existence of 97.8% of the current population at the end of 30 years, complete avoidance of deforestation will only manage to ensure 11.3% of the
current population after the 30 years. This implies future management of the woodlands should focus more on how to reduce mortality as its primary goal above any other measures. The causes of the high rate of adult mortality is not clearly known but free grazing, pest and increased frequency of fire are assumed to be the proximate causes. Therefore, management should focus on controlling these causes before planning for high investment to traditional management practices such as reforestation, afforestation and the like that apparently are straight forward solutions under normal circumstance. It is interesting to note here that avoidance of deforestation, which many study reports put forward as a major problem of the woodlands, particularly for Metema seems to have less impact than overall adult mortality. 4. Discussion
Fig. 4. Test of model predictions sensitivity to various mortality and deforestation assumptions to identify the most important factor for priority setting in future intervention.
The model outputs from this study prompt the rapid downward spiral of Boswellia resources and the likely scarce supply of frankincense product from Ethiopia to the world market in the near future. It is obvious that the outcomes of the model simulation are expression of the relationships between factor included in the modelling as well as the data input used. Some of these data were empirical generated through field studies but others were subjective as obtained through analysis of the perception of stakeholders. Therefore, the usefulness of the predicted trends depends to a large extent on the realism of the perceptions and assumptions of the
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stakeholders involved in this particular study. It is obvious in this study that the degradation wing of the model is based on empirical studies, while the restoration wind is what has been assumed possible by stakeholders engaged in the participatory scenario development process. The model output is clearly showing that despite the likely management intervention proposed by the stakeholders, the model predicted a continuous degradation of Boswellia and its frankincense including under the best case scenario (HS). This clearly indicates that the expected management inputs for the resource is far lower than the on-going degradation force, which is likely to lead to a continuous rapid decline of both the stem density and frankincense yield in the future. This will affect both the livelihoods of millions of communities that depend on dry forests and their products, citizens that involve along the value chain of frankincense as well as the national economy that has been generating millions of dollars each year. It is also likely to affect several global industries particularly those in the perfumery and pharmaceutical sectors. Furthermore, despite huge differences in socio-economic environment between the two case study districts, the modelled trends in frankincense resource happen to be similar. This may reflect that any level of human interference, whether big or small, is likely to cause significant threat on the Boswellia resource and the ensuing frankincense production. Several previous studies have also reflected the same gloomy situations (Eshete et al., 2012a, 2011; Lemenih et al., 2012c; Tolera et al., 2013). The major threat, as can be shown in the sensitivity analysis is the extra high adult mortality of Boswellia trees. This has been reported in a similar study as well (Groenendijk et al., 2012). The second most serious problem is the complete absence of recruitment through natural regeneration from the two districts. These two problems are in fact driven by several direct and underlying factors of degradation (Lemenih et al., 2012c). The most direct is increasing fire frequency and livestock grazing (Eshete, 2011; Lemenih et al., 2007). The underlying drivers are probably population growth (Lemenih et al., 2007; Dejene et al., 2013; Lemenih et al., 2012a,c). Human and livestock population are increasing in these woodlands. These have in turn instigated new forms of woodlandepeople relationships in which fire incidences, livestock grazing and intensification of incense tapping are observed. There is heavy unregulated and unmanaged livestock grazing and wood product harvest in most Boswellia woodlands. The high level of negative anthropogenic interferences in frankincense woodlands are severely threatening not only the rapid decline but also the likelihood of disappearance of the resource in just half a century from now if conditions of management will not change. This is alarming for a country with a long history of frankincense production and trade as well as cultural attachment. Efforts so far both at local grassroots and country levels for improved management of the species and conservation of frankincense woodlands are limited or better called non-existent. Domestication processes and efforts are very low (Lemenih et al., 2012b). Most alarming is the fact that plausible future management intervention alternatives as perceived by the local stakeholders do not seem to reverse the downward trend of frankincense resources. This might call for rather concerted and large scale efforts from all concerned at much higher decision making level than just local stakeholders. Moreover, some trials with planting reports low survival rate of seedlings. So far limited success has been reported only from vegetative reproduction (Haile et al., 2011; Negussie et al., 2009). Yet, no relation between survival rates both for adult and young seedlings and soil and other biotic conditions common to the environment of the woodlands can be established (Eshete, 2011). Therefore, factors that constrain stability of Boswellia population are those beyond the natural environment of soil and associated
39
biotic effects. Furthermore, seeds of the species show no problem of germination (Eshete et al., 2012b), and annual seedling emergence in the woodlands are also more than sufficient to ensure stable population (Eshete, 2011). However, no seedlings survive and grow into adult tree in the studied districts (Groenendijk et al., 2012; Tolera et al., 2013). A recent comparative study of regional differences in population structure of Boswellia species is prompting the problem to the degree of human disturbance of the natural environment of the species (Lemenih et al., 2012c). The anthropogenic factors assumed to drive the problem are increased livestock grazing pressure and fire incidences. Over the last four to five decades human and livestock population have rapidly increased in the Boswellia woodlands, and so do fire incidences, livestockewoodland interactions and human harvest of forest products, not only in Ethiopia (Lemenih et al., 2007, 2012a,b; Eshete, 2011) but also in Eritrea (Ogbazghi et al., 2006) and Sudan (Adam and El, 2008). Local people also associate the problem observed in the woodlands to these causative factors (e.g. Eshete et al., 2011; Lemenih et al., 2007, 2012c). Whether the problem is caused by the aforementioned anthropogenic factors or more by global phenomena such as environmental changes like climate change is hard to specify. The correlation between local anthropogenic factors and problems of frankincense resource is simply based on the fact that as human and livestock population grow in the frankincense woodlands, their vitality tended to degrade. To confirm such hypothetical and casual relationships, more rigorous and well designed researches need to be conducted. Therefore, besides policy measures to manage humanewoodland interactions, researches need to be strengthened on the interactive effects of soil conditions, climate, disturbances by grazing, fire, forest product harvest including frankincense production through tapping. For the short term, strategic intervention is needed through conservation area delineation of large tracts of land in which human-livestock contacts will be minimized as much as possible. It is worth mentioning that the model simulated results are not forecasts but are reflection of what are likely to happen given the assumptions and conditions considered in the alternative futures, which may or may not in real world situation. This means that policy makers and woodland managers should consider the outcomes as a signal or sign post to future management planning and policy reframing tool. However, the fact that all the scenarios suggest a decline trend implies that on-going management efforts and those possibly taken in the future are unlikely to effectively address the challenge facing frankincense resources in the two dry land areas of Ethiopia. This should stimulate questions such as why this happens, what then next and the like, and based on answers for such questions revisit the on-going management practices and existing national or local development strategies for the resource. It is also interesting to indicate that the participatory approach to scenario development is an effective platform for generating data and assumptions to be used in simulation modeling, and to see the implications to come, assisting policy makers and practitioners to think of better strategies in the future. 5. Conclusion This study reveals that B. papyrifera and its frankincense products in Ethiopia are under severe threat. Most worrying is the fact that the interventions perceived as practicable by local stakeholders fall short to stabilize the situation. The conditions in the SS prompted that much more efforts than those conditions suggested by the stakeholders are needed to stabilize the stem population and sustain frankincense yield at current level, and whether these interventions suggested by SS are likely to be implemented or not is yet to be seen. Whatever the case, the situation tends to call upon
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urgent supports from a wider community than just the local stakeholders and indeed engagement of local, national and international community might be necessary to sustain the production of this ancient product, frankincense, and its resource base. Acknowledgement This study was largely funded by The Netherlands Foundation for the Advancement of Scientific Research in the Tropics (NWOWOTRO) as part of the integrated research programme FRAME (frankincense, myrrh and gum arabic: sustainable use of dry woodlands resources in Ethiopia, grant number W01.65.220.00). References Abiyu, A., Bongers, F., Eshete, A., Gebrehiwot, K., Kindu, M., Lemenih, M., Moges, Y., Ogbazghi, W., Sterck, F., 2010. Incense woodlands in Ethiopia and Eritrea: regeneration problems and restorations possibilities. In: Bongers, F., Tennigkeit, T. (Eds.), Degraded Forests in Eastern Africa: Management and Restoration. Earthscan Ltd, London, UK, pp. 133e152. Adam, A.A., El, T.A.M., 2008. A comparative study of natural regeneration of B. papyrifera and other tree species in Jebel Marra Darfur, Sudan. Res. J. Agric. Biol. Sci. 4, 94e102. Alemu, B., Garedew, E., Eshetu, Z., Kassa, H., Zewdu, Y., Temesgen, Y., 2012. Land use and land cover changes and associated driving forces in northwestern lowlands of Ethiopia. In: Eshetu, Z., Kassa, H., Garedew, E., Lemenih, M., Tadesse, W. (Eds.), Proceedings Joint CIFOR-EIAR National Workshop to Review Research Findings on Dry Forests and Synthesize Lessons for Policy and Practice, 31 December 2012, Addis Ababa, Ethiopia, pp. 88e115. Bard, A.K., Coltorti, M., DiBlasi, C.M., Dramis, F., Fattovich, F., 2000. The environmental history of Tigray (Northern Ethiopia) in the middle and late Holocene: a preliminary outline. Afr. Archaeol. Rev. 17, 65e86. http://dx.doi.org/10.1023/A: 1006630609041. Bongers, F., Tennigkeit, R. (Eds.), 2010. Degraded Forests in Eastern Africa: Management and Restoration. Earthscan Publications, London. Butzer, K.W., 1981. Rise and fall of Axum, Ethiopia: a geo-archaeological interpretation. Am. Antiq. 46, 471e495. Chidumayo, E.N., Gumbo, D.J., 2010. The Dry Forests and Woodlands of Africa: Managing for Products and Services. CIFOR, Bogota, Indonesia. Chikamai, B., 2002. Review and Synthesis on the State of Knowledge of Boswellia Species and Commercialization of Frankincense in the Drylands of Eastern Africa (Nairobi, Kenya). Chikamai, B., Casade, E., 2005. Production and Marketing of Gum Resins: Frankincense, Myrrh and Opoponax. FAO/NGARA, Nairobi, Kenya. Chikamai, B., Tchatat, M., Tieguhong, J., Ndoye, O., 2009. Forest management for non-wood forest products and services in sub-Saharan Africa. Discov. Innov. 21. Online: http://www.ajol.info/index.php/dai/article/view/48213. Costanza, R., Voinov, A., 2001. Modelling ecological and economic systems with STELLA: part III. Ecol. Model. 143, 1e7. Costanza, R., Duplisea, D., Kautsky, U., 1998. Introduction to special issue: ecological modelling on modelling ecological and economic systems with STELLA. Ecol. Model. 110, 1e4. Dejene, T., Lemenih, M., Bongers, B., 2013. Manage or convert Boswellia woodlands? Can frankincense production payoff? J. Arid Environ. 89, 77e83. Doerr, H.M., 1996. STELLA ten years later: a review of the literature. Int. J. Comput. Math. Learn. 1, 201e224. Eshete, A., Sterck, F.J., Bongers, F., 2011. Diversity and production of Ethiopian dry woodlands explained by climate e and soil e stress gradients. For. Ecol. Manag. 261, 1499e1509. Eshete, A., 2011. The Frankincense Tree of Ethiopia: Ecology, Productivity and Population Dynamics (PhD thesis). Wageningen University, Wageningen, Netherlands. Eshete, A., Sterck, F.J., Bongers, F., 2012a. Frankincense production is determined by tree size and tapping frequency and intensity. For. Ecol. Manag. 274, 136e142. Eshete, A., Teketay, D., Lemenih, M., Bongers, F., 2012b. Effects of resin tapping and tree size on the purity, germination and storage behaviour of Boswellia papyrifera (Del.) Hochst. seeds from Metema District, Northwestern Ethiopia. For. Ecol. Manag. 269, 31e36. FAO, 1995. Flavors and Fragrance of Plant Origin. Non-wood Forest Products. FAO, Rome, Italy.
Garedew, E., Sandewall, M., Soderberg, U., 2012. A dynamic simulation model of land-use, population, and rural livelihoods in the Central Rift Valley of Ethiopia. Environ. Manag. 49, 151e162. http://dx.doi.org/10.1007/s00267-011-9783-4. Groenendijk, P., Eshete, A., Sterck, F.J., Zuidema, P.A., Bongers, F., 2012. Limitations to sustainable frankincense production: blocked regeneration, high adult mortality and declining populations. J. Appl. Ecol. 49, 164e173. Hannon, B., Ruth, M., 1994. Dynamic Modelling. Springer-Verlag, New York. Haile, G., Gebrehiwot, K., Lemenih, M., Bongers, F., 2011. Time of collection and cutting sizes affect vegetative propagation of Boswellia papyrifera (Del.) Hochst through leafless branch cuttings. J. Arid Environ. 75, 873e877. Lemenih, M., 2005. Production and marketing of gums and gum resins in Ethiopia. In: Chikamai, B., Casade, E. (Eds.), Production and Marketing of Gum Resins: Frankincense, Myrrh and Opoponax. FAO/NGARA, Nairobi, Kenya, pp. 55e70. Lemenih, M., Feleke, S., Tadesse, W., 2007. Constraints to smallholders production of frankincense in Metema district, North-western Ethiopia. J. Arid Environ. 71, 393e403. Lemenih, M., Kassa, H., 2011. Gums and Resins of Ethiopia, Info-brief. CIFOR, Bogor Indonesia. Lemenih, M., Kassa, H., Tesfahun, G., Getnet, D., Worku, T., 2012a. Resettlement and woodland management problems and options: a case study from a resettlement district in northwestern Ethiopia. Land Degrad. Dev.. http://dx.doi.org/ 10.1002/ldr.2136. On-line. Lemenih, M., Wiersum, F., Woldeamanuel, T., Bongers, F., 2012b. Diversity and dynamics of management of gum and resin producing woodlands in Ethiopia: a trade-off between degradation and domestication. Land Degrad. Dev.. http:// dx.doi.org/10.1002/ldr.1153. Available online. Lemenih, M., Woldeamanuel, T., Yilma, Z., Kassa, H., 2012c. Understanding factors behind recruitment bottleneck for Boswellia papyrifera: a comparative study of two regions with contrasting population structure. In: Eshetu, Z., Kassa, H., Garedew, E., Lemenih, M., Tadesse, W. (Eds.), Proceedings Joint CIFOR-EIAR National Workshop to Review Research Findings on Dry Forests and Synthesize Lessons for Policy and Practice, 31 December 2012, Addis Ababa, Ethiopia, pp. 71e79. Mayaux, P., Holmgren, P., Achard, F., Eva, H., Stibig, H.-J., Branthomme, A., 2005. Tropical forest cover change in the 1990s and options for future monitoring. Philos. Trans. R. Soc. Lond. Ser. B Biol. Sci. 360 (1454), 373e384. Mekonnen, M.B., 2004. The Past in the Present: the Dynamics of Identity and Otherness Among the Gumuz of Ethiopia (PhD dissertation). Norwegian University of Science and Technology, Trondheim. Mengistu, T., 2011. Physiological Ecology of the Frankincense Tree (PhD thesis). Wageningen University, Wageningen, Netherlands. Murphy, P.G., Lugo, A.E., 1986. Ecology of tropical dry forest. Annu. Rev. Ecol. Syst. 17, 67e88. Negussie, A., Aerts, R., Gebrehiwot, K., Prinsen, E., Muys, B., 2009. Euphorbia abyssinica latex promotes rooting of Boswellia cuttings. New. For. 37, 35e42. Ogbazghi, W., 2005. Production and marketing of gums and resins in Eritrea. In: Chikamai, B., Casade, E. (Eds.), Production and Marketing of Gum Resins: Frankincense, Myrrh and Opoponax. FAO/NGARA, Nairobi, Kenya, pp. 55e70. Ogbazghi, W., Rijkers, T., Wessel, M., Bongers, F., 2006. The distribution of the francincense tree Boswellia papyrifera in Eritrea: the role of environment and land use. J. Biogeogr. 33, 524e535. Pausas, J.G., 1999. Response of plant functional types to changes in the fire regime in Mediterranean ecosystems: a simulation approach. J. Veg. Sci. 10, 717e722. Rogan, J., Chen, D., 2004. Remote sensing technology for mapping and monitoring land-cover and land-use change. Prog. Plan. 61, 301e325. Tegegne, A., Mengistie, T., Desalew, T., Teka, W., Dejen, E., 2009. Transhumance Cattle Production System in North Gondar, Amhara Region, Ethiopia: is it Sustainable? IPMS (Improving Productivity and Market Success) of Ethiopian Farmers Project. Working Paper No. 14. ILRI, International Livestock Research Institute, Nairobi, Kenya, p. 73. Tolera, M., Sass-Klaassen, U., Eshete, A., Bongers, F., Sterck, F.J., 2013. Frankincense tree recruitment failed over the past half century. For. Ecol. Manag. 304, 65e72. Tilahun, M., Olschewski, R., Kleinn, C., Gebrehiwot, K., 2007. Economic analysis of closing degraded Boswellia papyrifera dry forest from human interventions e a study from Tigray, Northern Ethiopia. For. Policy Econ. 9, 996e1005. Vollesen, K., 1989. BURSERACEAE. In: Hedberg, I., Edwards, S. (Eds.), Flora of Ethiopia, vol. 3. National Herbarium, Addis Abeba University, Addis Abeba and Uppsala University, Uppsala, pp. 442e478. WBISPP, 2004. Forest Resources of Ethiopia (Addis Ababa, Ethiopia). White, F., 1983. The Vegetation of Africa. A Descriptive Memoir to Accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa. Natural Resources Research 20. UNESCO, Paris, France. Woldeamanuel, T., 2011. Dryland Resources, Livelihoods and Governance: Diversity and Dynamics in Use and Management of Gum/Resin Trees in Ethiopia (PhD thesis). Wageningen University, Wageningen, the Netherlands.