RESEARCH ARTICLE

 

Food tree species consumed during periods of food shortage in Burkina Faso and their threats

 

Barbara Vinceti

Bioversity International, 00057 Maccarese, Rome, Italy.

Céline Termote

Bioversity International, Nairobi, Kenya.

Natacha Thiombiano

University of Ouagadougou, Laboratory of Plant Biology and Ecology. Ouagadougou, Burkina Faso.

Dolores Agúndez

INIA, Forest Research Centre (CIFOR), Ctra de La Coruña km. 7.5, 28040 Madrid, Spain.

iuFOR, Sustainable Forest Management Research Institute, University of Valladolid, Spain.

Niéyidouba Lamien

West and Central African Council for Agricultural Research and Development (CORAF), BP 48, Dakar RP, Sénégal.

 

Abstract

Aim of study: Edible products from tree species were identified in Burkina Faso and their contribution to the diet in the lean season was assessed. The main threats affecting most consumed food tree species were also documented.

Area of study: Six villages across two phytogeographic regions of Burkina Faso.

Material and methods: Focus group discussions and semi-structured interviews, including a 7-day dietary intake recall targeting women; semi-structured interviews targeting key male informants.

Main results: The number of edible tree products consumed was found to vary according to phytogeographic region and ethnic group. A few tree species played a disproportionally greater role in the diet and were characterized by very high frequency of consumption by the majority of households in both phytogeographic regions and across ethnicities: Adansonia digitata, Parkia biglobosa and Vitellaria paradoxa. These species are not critically endangered at country level but they are perceived as scarcely available at local level. Considering that the main threats on priority tree species (fires, drought, pest and diseases) vary across regions, to maintain sustainable sources of nutrients in the landscape, mitigation measures should be diversified and adapted to local pressures.

Research highlights: Priorities for conservation are emerging clearly, but research efforts should also target underutilized tree species for their potential to diversify nutrient-poor diets.

Additional Keywords: edible tree products; livelihood; non-timber forest products; forest conservation.

Abbreviations used: HFIAS (Household Food Insecurity Access Scale); HH (Household); HHS (Household Hunger Score).

Authors' contributions: Conceived and designed the experiments: BV, DA, NL. Performed the experiments: NT, DA. Analyzed the data: BV, CT. Wrote the paper: BV, CT. All authors read and approved the final manuscript.

Citation: Vinceti, B.; Termote, C.; Thiombiano, N.; Agúndez, D.; Lamien, N. (2018). Food tree species consumed during periods of food shortage in Burkina Faso and their threats. Forest Systems, Volume 27, Issue 2, e006. https://doi.org/10.5424/fs/2018272-12157

Received: 14 Aug 2017. Accepted: 06 Jul 2018.

Copyright © 2018 INIA. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC-by 4.0) License.

Funding: Collaboration between Bioversity International, the Forest Research Center (CIFOR) of INIA-Spain, and several national partners from African countries, under the umbrella of SAFORGEN, the sub-Saharan African Forest Genetic Resources Programme.

Competing interests: The authors have declared that no competing interests exist.

Correspondence should be addressed to Barbara Vinceti: b.vinceti@cgiar.org


 

CONTENTS

Abstract

Introduction

Material and methods

Results

Discussion

Conclusions

Acknowledgments

References

IntroductionTop

Forests play a role in many food systems, through direct and indirect provisioning for human nutrition and through ecosystem services. Globally, 800 million people remain hungry, while 2 billion are suffering from hidden hunger (micronutrient deficiencies). Consumption of wild foods from forest landscapes has a large potential to contribute to mitigating nutritional deficiencies (Powell et al., 2015). In most cases, these are due to a lack of diversity in the diet (Lachat et al., 2017) and a poor supply of micronutrients (Black et al., 2013). An increasing number of studies has documented the contribution of wild forest foods to the diet and suggested a link between forest cover and dietary quality (Johnson et al., 2013; Ickowitz et al., 2014). Assessments of actual quantities of forest foods consumed have been carried out (Termote et al., 2012; Powell et al., 2013; Rowland et al., 2016) and it has been found that their contribution to the diet varies considerably. Semi-disturbed forested environments with anthropic influence and mixed land use types (e.g., swidden agriculture, agroforestry, natural forest, tree crop plantations) seem to be associated with higher frequency of consumption of food groups rich in micronutrients (Ickowitz et al., 2016).

Research on consumption of wild foods in dry forest areas, and on their nutritional importance, are very few (Rowland et al., 2015) despite the large extension of dry forests and their relatively large supply of edible products compared to alternative land uses in the same regions (Wunder, 2001).

Seasonality is a key element of food availability, especially in the Sahelian countries, and the contribution of food tree species to the diet is particularly important during periods of food scarcity or extreme drought (Faye et al., 2010; Atato et al., 2011; Agúndez et al., 2016).

In West Africa, food tree species are valued by lo­cal people. Preferred trees are usually multifunctional (Gijsbers et al., 1994; Faye et al., 2010) and sup­ply edible products (Kris­­tensen & Lykke, 2003; Kristensen & Balslev, 2003). When the land is cleared for agriculture, favoured trees are retained and their natural regeneration in farmed fields is protec­ted (Ræbild et al., 2011). Indigenous communities appear to have favoured edible-fruit-yielding species normally found in the wetter Sudanian and Guinean phytogeographic zones (Maranz, 2009). Their density tend to be generally higher in farmed versus non-farmed areas (Maranz & Wiesman, 2003).

Based on increasing evidence, dry forests in tropical areas are vulnerable to several threats. Tree species richness and density declined in the West African Sahel in the second half of the 20th century (Gonzalez, 2001). About 97% of the remaining area of tropical dry forest is at risk from one or more of threats, with the largest effects attributable to habitat fragmentation and fire (Miles et al., 2006).

In West Africa, dry forest cover coincides with areas of high population density. Southern Burkina Faso has experienced rapid population growth, mostly determined by immigration of farmers. Cropland has expanded at an annualized rate of 0.46% at the expense of forest cover, which decreased by 0.57% per year. In the same areas, migrant population has increased from 3% in 1976 to 57% in 2007 (Paré et al., 2008; Ouedraogo et al., 2009, 2010). In some regions, this has determined a considerable exploitation of non-timber forest products (NTFPs) and an associated decline in the density of some tree species (Boffa, 1999; Kristensen & Balslev, 2003; Lykke et al., 2004; Paré et al., 2010), with potential consequences on various ecosystem services, including nutrition security (Jones et al., 2017).

The views of local people are central in providing information on general trends in vegetation dynamics and particularly on changes in occurrence of rare species (Lykke, 1998). Preferences of local people are also crucial in the definition of locally acceptable management solutions.

A first objective of this study was to identify tree species that provide edible products to rural communities during the lean season across two ecoregions of Burkina Faso. A second objective was to understand what household (HH) characteristics (e.g., ethnicity, origin, ecoregion, level of education) had most influence in determining the observed patterns of consumption of edible tree products. Finally, based on the perception of local key informants, the main threats affecting the most consumed food tree species were documented, with the objective to assess 1) how threats varied across the ecoregions and villages investigated and 2) whether species-specific threats could be identified. The ultimate objective was to single out priority food tree species, relate these to their main threats and determine if implementation of conservation and mitigation measures would require adaptation to highly diversified contexts.

Material and methodsTop

Study sites

The study included two regions, the Sahelian and Sudanian phytogeographic zones of Burkina Fa­so. ­The Sahelian region has an annual rainfall between 400 and 700 mm, the Sudanian between 700 and 1000 mm. The rainy season lasts 3 to 5 months and the dry season 9 to 7 months, for the Sahelian and Sudanian region respectively (Fontes & Guinko, 1995). The boundary between the two zones is defined by the 750 mm isohyet. The study sites were selected from the most recent national census database (INSD, 2010), based on the total number of inhabitants. A total of 3 villages were sampled in both the Sudanian (Barcé, Péni and Sara) and Sahelian phytogeographic zone (Barsalgho, Bourgou, and Pobé-Mengao) (Fig. 1). The study was conducted during the lean season (June-July 2011). In the Sahelian zone, the lean season extends from April to September, when harvest is good, and from February to September, when harvest is bad. In the Sudanian zone, the lean season lasts from May to September.

Figure 1. Location of the six selected study sites in Burkina Faso. The boundaries of the phytogeographic zones are adapted from White (1983) and Guinko (1984).

The most typical configuration of the vegetation is represented by a savanna characterized by a decreasing tree density along the main bioclimatic gradient, from South to North (Guinko, 1984). Land that is converted to agriculture usually presents scattered trees. Other common land uses are fallow of different ages, forest reserves and plantations of exotic trees (e.g., cashew nut) (Augusseau et al., 2006). The spatial configuration of multipurpose trees, whose diversity in the landscape can be considerable [> 50 tree species recorded at village level by Boffa (1995)], is intimately linked to human influences (Lovett & Haq, 2000).

Methodology

Eighteen focus group discussion were organized across all villages (2 in both Barcé and Barsalgho, 3 in both Bourgou and Pobé-Mengao and 4 in both Péni and Sara) with 10 women of different age and ethnicity (see Table 1). The purpose of the discussion was to produce a list of the dishes most commonly prepared during the lean period and to identify a complete list of tree species commonly consumed during the lean season.

Table 1. Ethnic composition of the six selected study sites (Burkina Faso).

Subsequently, in each village, a total of 50 HHs were randomly selected for semi-structured interviews based on the most recent population census database (INSD, 2010). A total of 300 female informants were interviewed individually in their local language. In Burkina Faso, women take care of the cooking and have a central role in ensuring food security and nutrition (Savy et al., 2005; Martin-Prével et al., 2012), therefore the informants identified were all female. The first part of the questionnaire dealt with demographic and socio-economic characteristics of the HH (number of HH members, number of children, ethnicity, migration status, education level of the wife of the HH’s head, her income activities and an evaluation of the last harvest). Then, a standard set of nine key questions were posed to assess the degree of food insecurity based on HH’s experience of the problem, based on the Household Food Insecurity Access Scale (HFIAS, Coates et al., 2007). The last three questions of the HFIAS, were used to calculate the Household Hunger Score (HHS, Ballard et al., 2011).

The second part of the questionnaire consisted of a 7-day qualitative HH food intake recall, limited to the foods prepared at home and/or consumed at home. Respondents first answered spontaneously, describing HH food consumption over the past week, they were then prompted to be sure that no meal or snack had been forgotten. Next, a detailed list of all the ingredients of the dishes, snacks, or other foods mentioned was collected. Finally, the recall information was cross-checked with the list of dishes and ingredients collected during the focus group discussions to verify if nothing was omitted in the recall.

Total number of tree species and total number of tree products consumed per HH over a 7-day period in the lean season were calculated. Bivariate statistical analyses were performed to explore relationships between the dependent variables (i.e., total number of tree products used per HH and total number of tree species consumed per HH during the lean season) and the independent variables collected in the HH survey (i.e., socio-economic characteristics of the HH, HFIAS and HHS). The dependent variable being a count (number of species consumed) over a period of time (7 days), Poisson regressions were used. Subsequently, the independent variables with p-values 0.10 or lower in the bivariate analyses were entered together in a multivariate Poisson regression model run once for tree products and once for tree species consumed as dependent variables. Significance levels were set at p<0.05.

A rapid market survey was conducted to observe what edible products derived from food tree species were available at the time the study was conducted. In addition, a total of 35 male key informants were interviewed individually in their local language about their perception of the most significant threats to a set of food tree species, whose list had been predetermined for each village, through focus group discussions and HH surveys. The assumption was that male farmers more frequently travel further away from the village, thus their observations and perception of changes in tree species density would relate to a wider area around the village. Local perception of threats affecting the most important food tree species was considered a reliable proxy for actual threats as assessed in similar studies in relation to climate change (West et al., 2008).

Key informants were requested to attribute a score from 0 to 3 to a list of pre-defined threats (0 = not a threat, 1 = not important, 2 = important and 3 = very important threat). The 12 pre-defined threats, based on a screening of the literature, were the following: land clearance, fire, grazing, wood exploitation, consumption of fruits and flowers, harvest of leaves, exploitation of bark, charcoal production, pests and diseases, drought, aging, loss of soil fertility (Ræbild et al., 2011). Key informants also had the possibility to add threats not yet listed.

A deeper analysis of threat patterns was conducted for the most important tree species (i.e., consumed by > 5% of the HHs). Average threat scores were presented as 1) individual species threat profiles, considering all villages together and 2) village threat profiles, considering all species together. Subsequently, the average threat scores were summed i) for each species (across all villages and including all types of threats); ii) for each village (across species and including all types of threats) and iii) for each type of threat (across all villages and including all species).

ResultsTop

Survey household characteristics

The majority of participants in both phytogeographic zones belonged to the Mossi ethnic group (49%) followed by Tiego and Bwaba in the Sudanian villages (both about 15%) and Gourmanthché and Fulsé in the Sahelian villages (30 and 18% respectively) (Table 2). In the Sudanian villages, 68 % of HHs had an immigration background and 27% stated to have migrated to the village less than 20 years before. These figures were 47% and 35% for the Sahelian villages and differences were statistically significant. A significantly higher percentage of participants was illiterate in the Sudanian zone (67%) than in the Sahelian zone (33%). Almost all women involved in the study had agriculture as their main income activity (97%). The last harvest was estimated as rather bad in the Sudanian zone (46%) and as good in the Sahelian zone (62%). The average number of HH members was 11 in both zones, with on average 4.5 children. The HH food insecurity scores were quite similar for the two zones, though the HH hunger score was significantly higher in the Sudanian (0.43) compared to the Sahelian (0.09) zone.

Table 2. Demographic data of the study sites. Values between parentheses are percentages calculated within a category (e.g. ethnicity) within the same ecoregion (e.g. Sudanian).

Commonly consumed ingredients from tree species during the lean period

The qualitative assessment of the diet showed that, during the lean period, this was mainly based on cereals (100% of the HHs interviewed had consumed cereals over the past week) and leafy vegetables (100% of HHs had consumed leafy vegetables over the past week), complemented by fruits (89% of HHs consumed at least 1 fruit over the past week) and accompanied by products of animal origin (eggs in 38% of HHs, milk in 62%, meat in 61% and fish in 91%).

Fruits consumed in the lean season by the majority of HHs were collected from the following tree species: Lannea microcarpa (76%), Vitellaria paradoxa (68%), Parkia biglobosa (48%). Mangifera indica was also largely reported by 68% of the HHs, although this is not a savanna tree species, but it is commonly planted by villagers nearby households or farmers’ fields. Fruits were usually consumed raw but sometimes were cooked and added to porridges or combined with other foods (e.g., P. biglobosa pulp was sometimes cooked and added to the couscous of maize). Vegetables and leafy vegetables were generally used in the preparation of sauces as side dishes. Adansonia digitata leaves were the most consumed leafy vegetables (96% of HHs had consumed A. digitata leaves over the past week). The seeds of P. biglobosa were transformed into a kind of mustard used as condiment in various dishes (70% of HHs consumed P. biglobosa seeds over the past week). Butter and oil were largely consumed. Approximately 40% of HHs consumed shea butter, derived from the kernels of V. paradoxa. Alternatively, other types of oil (e.g., red palm oil) were commonly used.

Food tree species consumed

The analysis of the composition of the diet during the lean season across the six study sites revealed that a total of 25 tree species contributed to it (Table 3). Across the two phytogeographic zones, only 10 species were consumed over the past week by a large part of the HHs surveyed (> 20%). All other species were consumed by a considerably lower percentage of HHs. The most widely consumed products were the leaves of A. digitata, eaten over the past week by > 96% of the HHs surveyed. The discrepancy between the few largely consumed species and all others was particularly remarkable for tree species consumed as leafy vegetables: of the 12 species reported, 10 were consumed by less than 10% of the HHs (Fig. 2b). The pattern was similar for tree species consumed for their fruits: of the 16 species reported, 13 were consumed by less than 10% of the HHs (Fig. 2a).

Table 3. A list of all 25 indigenous food tree species mentioned as edible in the HH survey and the results of a literature review about their characteristics. Sources: Guinko, 1984; Lebrun et al., 1991; Arbonnier, 2004; Nikiema, 2005; Akoègninou et al., 2006; Orwa et al., 2009; Sacande et al., 2012; Global Plants, JSTOR, http://plants.jstor. org/; Plant Resources of tropical Africa – PROTA, http://www.prota.org/

Figure 2. Percentage of HHs consuming different edible products from tree species in the Sahelian and Sudanian phytogeographic regions, during the lean season. Edible products are divided in three groups: a) fruits, b) vegetables and c) seeds and pulses.

Consumption patterns varied by ecoregion. The percen­tage of HHs consuming tree species as leafy vegetables was higher in the Sahelian region compared to the Sudanian region, but this difference was not statistically significant. The consumption of individual tree leafy vegetable species, however, could differ significantly between the two ecoregions. For example, Bombax costatum and Leptadenia hastata were consumed by a higher percentage of HHs in the Sahelian region where these two species were better represented compared to the Sudanian ecoregion (Fig. 2b). Grouping all species, the percentage of HHs consuming tree species for their fruits was remarkably higher in the Sahelian region, although some of the top ranking food tree species were consumed by a higher percentage of HHs in the Sudanian ecoregion where these species were better represented (e.g., V. paradoxa and P. biglobosa) (Fig. 2a). A higher percentage of HHs was consuming tree species for their seeds and nuts in the Sudanian ecoregion, where the top ranking species (V. paradoxa and P. biglobosa) were mainly found. V. paradoxa, in particular, is almost absent from the Sahelian ecoregion) (Fig. 2c).

Modalities of procurement varied also by ecoregion. Fruits and leaves from Vitex doniana were available in the markets in the Sudanian zone. Several other food products derived from trees were also available in the market, not only in the wild (e.g., A. digitata, B. costatum, L. microcarpa, V. paradoxa). In particular, the leaves of A. digitata could be easily transformed (dried and powdered), stored and sold later during the year, so when found in the diet, their source could be different (wild, farmers’ fields, market).

Based on findings from focus groups discussions, some species appeared to be no longer available. In the Sudanian zone, the fruits of Ficus sycomorus and Ficus ingens in particular, were not consumed in the village of Barcé because these species were too difficult to find given their habitat is disappearing. In Péni, the fruits of Ximenia americana have become rare. In the Sahelian zone, the fruits of Boscia senegalensis and X. americana have become almost completely unavailable in the surroundings of Barsalgho. In this village, the fruits of X. americana were consumed by just 2% of the HHs surveyed. In the case of B. senegalensis only seeds were consumed by a very small fraction of the population surveyed in the Sahelian zone. In Bourgou, in addition to the products from the two species above, others were becoming less available, such as the leaves of Crataeva adansonii and the fruits of P. biglobosa (consumed by 16% of the HHs). In Pobé-Mengao, the fruits of F. sycomorus were no longer consumed as they were too rare.

Relationships between the consumption patterns of food tree species, and some socio-demographic variables

In the lean season, each household consumed on average 4.92 tree products during the 7-days preceding the interviews from on average 4.3 different tree species.

Bivariate Poisson regressions showed no significant relationships at p<0.05 level between the dependent variables ‘total tree products consumed’ and ‘total tree species consumed’ and the independent socioeconomic variables ‘number of HH members’, ‘number of children’, ‘residence status’, ‘women education’, ‘women activities’, ‘evaluation of last harvest’ ‘HFIAS’ and ‘HHS’ (Table 4). The only significant relationships were found between the dependent variable ‘total tree products consumed’ and the independent variables ‘ethnicity’ and ‘ecoregion’ (p = 0.041 and p=0.000, respectively).

Table 4. p-values of bivariate Poisson regressions with total tree products and total tree species as dependent variables and socio-economics as independent variables.

In the bivariate analyses, the relationship between the dependent variable ‘total tree products consumed’ and the independent variables ‘ethnicity’, ‘ecoregion’ and ‘residence status’ obtained a p-value <0.1 (see Table 4). ‘Ethnicity’, ‘ecoregion’ and ‘residence status’ were entered in the multivariate Poisson regressions with ‘total tree products consumed’ as dependent variable. The multivariate model showed that ecoregion as well as ethnicity (p=0.000 and p=0.015, respectively) had a significant relationship with ‘total tree products consumed’ ‘Residence status’ was not significant in the multivariate regression. However, ‘ethnicity’, ‘residence status’, ‘mothers’ education level’, ‘activity of the mother’ and ‘evaluation of last harvest’ as well as ‘HHS’ were all significantly different between phytogeographic zones (Table 2). The analysis was repeated for each of the zones separately. Within the Sudanian region, ‘ethnicity’ (p=0.01), ‘residence status’ (p=0.088) and ‘mother’s education level’ (p=0.08) obtained p-values <0.1 in the bivariate Poisson regressions with 'total tree products consumed' as dependent variable. Entered together in a multivariate Poisson regression, none of them was significant at p<0.05 level. Within the Sahelian region, only ‘mother’s education level’ obtained a p <0.1 (p=0.079). The bivariate Poisson regressions with ‘total tree species consumed’ as dependent variable did not show produce significant result at p <0.1, neither when both phytogeographic zones were considered together nor for each of the zones considered separately.

Main threats to food tree species based on the perception of farmers

Key informants did not indicate any additional threats beyond the 12 threats pre-identified. Results are only presented for the six tree species most consumed. In order of decreasing importance, these were: A. digitata, P. biglobosa, L. microcarpa; V. paradoxa; B. costatum, and V. doniana.

Based on the perception of local people, the most threatened species were those ranking highest in terms of consumption (% of HHs): V. paradoxa, P. biglobosa and A. digitata (Fig. 3a). The greatest threats for V. paradoxa were pests and diseases, drought and aging of tree individuals; for P. biglobosa as well as A. digitata, the main threats were drought, aging of trees, and loss of soil fertility.

Figure 3. Sum of average threat scores per species, for each of the six most consumed tree species. Average values were summed across all villages and including all types of threats (a). Sum of average threat scores per type of threat, for the six most consumed tree species (b); the red line separates threats that are more directly linked to anthropic influence (on the left), from the others. Sum of average threat scores per village, for the six most consumed tree species (c).

The sum of average threat scores per type of threat indicated that the most significant threats, based on the perception of local people, were drought and aging of tree populations, followed by a decline in soil fertility and the effect of pests and diseases (Fig. 3b).

The sum of average threat scores per village indicated some variability across study sites (Fig. 3c). Based on the perception of local people, Péni had the highest burden of threats, followed by Bourgou, while Barcé was attributed the lowest threat score among all study sites.

The analysis of threat profiles for each village showed some differences between the two ecoregions investigated. While in the Sahelian villages, the most prevalent threat was aging followed by loss of soil fertility (in 2 out 3 villages) and pests and diseases in one village, in all three Sudanian villages, fire was the highest ranking threat (Fig. 4).

Figure 4. Germination index (GI) for wheat cultivars Piko and S.awa. Grains were harvested at different days after pollination (DAP), and incubated for 7 days in water at 20ºC. Each value represents the mean of three independent replicates. Bars represent standard deviation.

DiscussionTop

The list of 25 indigenous tree species, mentioned as edible and consumed during the lean season shows that, during the lean season, edible products derived from trees are a significant supplement in the diet, mainly based on cereals. Leaves and fruits are particularly effective in diet diversification due to their rich content in micronutrients (Bvenura & Sivakumar, 2017).

The knowledge available in the literature on important food tree species in Burkina Faso is usually derived from small-scale case studies. The sampling in this research was designed to capture a representative diversity of contexts across phytogeographic regions and provinces with different ethnic composition. Nevertheless, the priority species that emerged from this study seem to be aligned with those derived from other ranking exercises carried out in Burkina Faso (Kristensen & Lykke, 2003; Lykke et al., 2004; Thiombiano et al., 2012, 2014). A total of 12 out of the 25 species identified as important in this study are considered among the top most useful plant species in Burkina Faso (Zizka et al., 2015), all characterized by multiple uses (up to eight different uses for A. digitata). Interestingly, only a few species emerge for their considerably greater importance in the diet, A. digitata in particular, and their edible products are consumed by a very large percentage of HHs. Overall, only three tree species (A. digitata, P. biglobosa and V. paradoxa) are consumed by a large majority of HHs.

This gap between availability and ac­tual con­sumption has been observed in other envi­ronments (Termote et al., 2012; Boedecker et al., 2014). An explanation for this has not been provided but the pattern observed could be due to the fact that highly consumed species are actively favoured and maintained in the landscape by human activities, thus they are easier to access and collect, and their edible products can also be found in the market. On the contrary, various factors may constrain consumption of less common wild species and contribute to reduce their usefulness. For example, the excessive distance to be covered to harvest less common wild species (Thomas et al., 2009; Termote et al., 2012), the significant workload needed to process them into edible products, the progressive change in dietary habits in younger generations who move away from traditional foods (Lykke et al., 2002), the declining knowledge about traditional plants, the progressive loss of habitat of some wild species (Barucha & Pretty, 2010) and the lack of information on their nutritional properties (Waswa et al., 2015), are all factors that may contribute to limit interest and consumption.

The factors that most closely explain the patterns of consumption of edible tree products in this study are phytogeographic region and ethnicity. The average number of tree products consumed was slightly higher in the Sudanian villages (5.5 tree products) compared to the Sahelian villages (4.35 tree products), however the average number of tree species used was quite similar (4.14 in the Sudanian and 4.17 species in the Sahelian zone). HH hunger score was significantly higher in the Sudanian compared to the Sahelian zone and this could be possibly due to the different quality of the last harvest, which was rated as good by villagers in the Sahelian zone and bad by those in the Sudanian zone. The average number of tree species used did not depend on any of the independent factors entered in the Poisson regressions (ecoregion, socio-economics, HFIAS, HHS), while the number of tree products used was significantly correlated with phytogeographic region as well as ethnicity. This indicates that the number and type of species/products consumed in each village depend not only on local occurrence of a species and seasonality of the parts consumed as food, but also on a mix of cultural factors that are correlated with the spatial distribution of ecoregions. This is in line with results from a study about differences in the perceptions and valuation of woody plant species in three ethnic groups (Fulani, Mossi and Samo), in the sub-Sahelian region of Burkina Faso. The latter study revealed that the most important species, identified for conservation priority, based on the informants’ perspective, were food species with a high socioeconomic value: V. paradoxa, A. digitata, Tamarindus indica, P. biglobosa, L. microcarpa and Ziziphus mauritiana (Sop et al., 2012) and preferences were similar for all ethnic groups, though plant use differed among ethnic groups, with age of respondents influencing plant knowledge in all three ethnic groups.

Some species are progressively disappearing. A review across West African countries (Burkina Faso, Mali and Niger) by Wezel & Lykke (2006) revealed that according to local perceptions 79% of the woody species mentioned were classified as having decreased or disappeared. An assessment of local perception of changes in distribution of socio-economically important tree species in the Sahelian region of Burkina Faso in three ethnic groups (Mossi, Fulani and Samo) (Sop & Oldeland, 2011) revealed a decline in occurrence of more than 80% of the 90 listed species; 40% of these were considered under threat, mainly from drought, deforestation and bushfires. Undoubtedly, the combination of future climate scenarios and land use changes is expected to have a strong negative impact on the flora of Burkina Faso (Heubes et al., 2013).

It is yet not clear what drivers of change (whether climate change, human exploitation or livestock grazing) are leading to the disappearance of tree species and a senescing of savanna in the Sahel. In this study, overall, the most prominent threats cited by the experts interviewed tend to be less directly linked to the influence of human exploitation (e.g., pests and diseases, aging of trees and loss of soil fertility). However, these threats are indirectly associated to particular practices (e.g., the lack of regeneration is most likely related to grazing pressure).

It is important to note that those species considered highly threatened are the most important in the diet. The high value of these priority species, combined with a considerable competition for their exploitation, may induce a perception of scarcity and availability lower than the demand, as illustrated by Thiombiano et al. (2013), who showed how market channels largely mitigate lack of local supply of the most demanded species.

It is interesting to note that none of the species indicated as scarce or disappearing by the villagers involved in this study is considered critically endangered in Burkina Faso at country level, according to the checklist recently developed by Schmidt et al. (2017). These species may be locally scarce or lost due to localized overexploitation. The findings from this study indicate that threats vary considerably across sites; forest clearing for agriculture is most pronounced in the South of Burkina, while livestock grazing in posing great pressure in the northern part of Burkina Faso, especially where pastora­lists have become progressively more sedentary (Lykke et al., 2004).

Regarding predominant threat types emerging from this research, the situation is indeed spatially patchy, as revealed by the diversity of threats profiles by village. In the Sudanian ecoregion, particularly in the Southern and South Western part of Burkina Faso, the main threat appears to be fire. The villages where fires is the most significant threat, Péni in particular, but also Barcé and Sara, are situated in the region neighboring the second largest city in Burkina Faso (Bobo-Dioulasso). These results seem to be validated by evidence from records on fires frequency made available by the NASA (2012). Furthermore, a spatially explicit threat analysis for food tree species in Burkina Faso (Gaisberger et al., 2017) revealed that the areas with the highest incidence of fire are in the Southern and South Western parts of Burkina Faso. The high population density in these areas is associated to large immigration, especially from drier areas in the north. This is confirmed by the ethnic composition of the three selected villages located in the Sudanian ecoregion, characterized by a high presence of immigrants (ca. 68%) significantly greater than in the Sahelian villages.

Immigrants normally occupy forested areas and clear them using fire, to make space for new cropland, thus this practice could explain the patterns observed. Forest fires are considered a significant factor contributing to deforestation in Burkina Faso, despite the large attention to this challenging issue in the existing legislation (Kalame et al., 2009). Specific management strategies are needed to contain the effects of fire on the vegetation, such as, for example, the adoption of longer intervals between fires. Droughts and aging are critical factors in the Northern part of the country, where precipitations are less and regeneration is generally more seriously compromised by grazing, due to a higher presence of pastoralists. High value species may experience particular threats across most of their range; for example regeneration of P. biglobosa is largely compromised by intensive seed harvest, so that only very few seeds germinate and survive browsing by animals (Ræbild et al., 2011). For various useful tree species, it has been observed that where regeneration is present, in all land-use types (forest, fallow, field), small trees seem unlikely able to develop into mature tree individuals due to grazing, so a demographic bottleneck is affecting most species (Ouédraogo et al., 2015).

ConclusionsTop

This study highlights the important role of edible products harvested from trees in diversifying diets of rural communities in Burkina Faso during the lean season. The number of edible products consumed varies according to phytogeographic region and ethnic composition of the community living in a particular site. This study shows that overall a few tree species play a disproportionally greater role in the diet and are characterized by a very high frequency of consumption by the majority of households in both phytogeographic regions and across ethnicities: Adansonia digitata, Parkia biglobosa and Vitellaria paradoxa. Although these species are not listed as critically endangered or vulnerable at country level, this study reveals that they are perceived as threatened and could become scarcely available locally due to the great competition for their consumption but also due to a variable combination of threats. Some tree populations with critical traits adapted to specific environmental conditions may be lost and limit future adaptive capacity of the species. Our findings indicate that effective conservation efforts are highly needed for these priority species. However, considering how nutrient poor is the diet of the communities investigated, it would be important to explore the nutrition potential of largely underutilized tree species. Fire seems to be a critical driver of change in the savannas of the Sudanian phytogeographic zone, while drought is affecting indigenous tree species in the Sahelian zone. Our results suggest that threats vary across regions and mitigation measures need to be highly diversified and adapted to local pressures.

AcknowledgmentsTop

Estelle Bader (external consultant, nutritionist) provided great support in cleaning and reorganizing the dataset and carried out preliminary statistical analyses.


ReferencesTop

Agúndez D, Douma S, Madrigal J, Gómez-Ramos A, Vinceti B, Alía R, Mahamane A, 2016. Conservation of food tree species in Niger: towards a participatory approach in rural communities. Forest Syst 25 (3): 79-87. https://doi.org/10.5424/fs/2016253-09558

Akoègninou A, van der Burg WJ, van der Maesen LJG, 2006. Flore analytique du Bénin. Backhuys Publishers, Leiden, The Netherlands. 1034 pp.

Arbonnier M, 2004. Trees, shrubs and lianas of West African dry zones. CIRAD, MNHN, Paris. 573 pp.

Atato A, Wala K, Batawila K, Lamien N, Akpagana K, 2011. Edible wild fruit highly consumed during food shortage period in Togo: State of knowledge and conservation status. J Life Sci 5: 1046-1057.

Augusseau X, Nikiéma P, Torquebiau E, 2006. Tree biodiversity, land dynamics and farmers' strategies on the agricultural frontier of Southwestern Burkina Faso. Biodivers Conserv 15: 613-630. https://doi.org/10.1007/s10531-005-2090-8

Ballard T, Coates J, Swindale A, Deitchler M, 2011. Household hunger scale: Indicator definition and measurement guide. Washington, DC, USA: Food and Nutrition Technical Assistance II Project, FHI 360. 16 pp.

Barucha Z, Pretty J, 2010. The roles of wild foods in agricultural systems. Philos Trans R Soc Lond B 365: 2913-2926. https://doi.org/10.1098/rstb.2010.0123

Black RE, Victora CG, Walker SP, Bhutta ZA, Christian P, de Onis M, Ezzati M, Grantham-McGregor S, Katz J, Martorell R et al., 2013. Maternal and child undernutrition and overweight in low-income and middle-income countries. Lancet 382 (9890): 427-451. https://doi.org/10.1016/S0140-6736(13)60937-X

Boedecker J, Termote C, Assogbadjo AE, Van Damme P, Lachat C, 2014. Dietary contribution of wild edible plants to women's diets in the buffer zone around the Lama forest, Benin - An underutilized potential. Food Secur 6 (6): 833-849. https://doi.org/10.1007/s12571-014-0396-7

Boffa JM, 1995. Productivity and management of agroforestry and parklands in the Sudan zone of Burkina Faso. Doctoral Thesis, Purdue University, West Lafayette, IN, USA.

Boffa JM, 1999. Agroforestry parklands in Sub-Saharan Africa. FAO Conservation Guide 34. FAO, Rome. 230 pp.

Bvenura C, Sivakumar D, 2017. The role of wild fruits and vegetables in delivering a balanced and healthy diet. Food Res Int 99 (1): 15-30. https://doi.org/10.1016/j.foodres.2017.06.046

Coates J, Swindale A, Bilinsky P, 2007. Household food insecurity access scale (HFIAS) for measurement of food acces: Indicator guide. Version 3. FHI 360/FANTA, Washington DC, USA. 29 pp.

Faye MD, Weber JC, Abasse TA, Boureima M, Larwanou M, Bationo AB, Diallo BO, Sigué H, Dakouo JM, Samaké O et al., 2010. Farmers' preferences for tree functions and species in the West African Sahel. For Trees Livelihoods 20: 113-136.

Fontes J, Guinko S, 1995. Carte de végétation et de l'occupation d'un sol du Burkina Faso. Notice explicative. Ministère de la coopération française, Projet campus (8813101), Université Paul Sabatier, Toulouse, France.

Gaisberger H, Kindt R, Loo J, Schmidt M, Bognounou F, Sylvestre Da S, Diallo OB, Ganaba S, Gnoumou A, Lompo D, et al., 2017. Spatially explicit multi-threat assessment of food tree species in Burkina Faso: An approach at population level. PLoS ONE 12 (9): e0184457. https://doi.org/10.1371/journal.pone.0184457

Gijsbers HJM, Kessler JJ, Knevel MK, 1994. Dynamics and natural regeneration of woody species in farmed parkland in the Sahel region (Province of Passore) Burkina Faso. Forest Ecol Manag 64: 1-12. https://doi.org/10.1016/0378-1127(94)90122-8

Gonzalez P, 2001. Desertification and a shift of forest species in the West African Sahel. Clim Res 17: 217-228. https://doi.org/10.3354/cr017217

Guinko S, 1984. Végétation de la Haute-Volta. Doctoral Thesis, Université de Bordeaux, Bordeaux, France.

Heubes J, Schmidt M, Stuch B, García Márquez JR, Wittig R, Zizka G, Thiombiano A, Sinsin B, Schaldach R, Hahn K, 2013. The projected impact of climate and land use change on plant diversity: An example from West Africa. J Arid Environ 96: 48-54. https://doi.org/10.1016/j.jaridenv.2013.04.008

Ickowitz A, Powell B, Salim MA, Sunderland TCH, 2014. Dietary quality and tree cover in Africa. Glob Environ Chang 24: 287-294. https://doi.org/10.1016/j.gloenvcha.2013.12.001

Ickowitz A, Rowland D, Powell B, Salim MA, Sunderland T, 2016. Forests, trees, and micronutrient-rich food consumption in Indonesia. PLoS ONE 11 (5): e0154139. https://doi.org/10.1371/journal.pone.0154139

INSD, 2010. Résultats préliminaires du recensement général de la population et de l'habitat de 2009. Institut National de la Statistique et de la Démographie, Ouagadougou, Burkina Faso.

Johnson KB, Jacob A, Brown ME, 2013. Forest cover associated with improved child health and nutrition: Evidence from the Malawi demographic and health survey and satellite data. Glob Health Sci Pract 1 (2): 237-248. https://doi.org/10.9745/GHSP-D-13-00055

Jones AD, Acharya Y, Galway LP, 2017. Deforestation and child diet diversity: a geospatial analysis of 15 sub-Saharan African countries. Lancet 389: S11. https://doi.org/10.1016/S0140-6736(17)31123-6

Kalame F, Nkem J, Idinoba M, Kanninen M, 2009. Matching national forest policies and management practices for climate change adaptation in Burkina Faso and Ghana. Mitig Adapt Strat Gl 14 (2): 135-151. https://doi.org/10.1007/s11027-008-9155-4

Kristensen M, Balslev H, 2003. Perceptions, use and availability of woody plants among the Gourounsi in Burkina Faso. Biodivers Conserv 12: 1715-1739. https://doi.org/10.1023/A:1023614816878

Kristensen M, Lykke AM, 2003. Informant-based valuation of use and conservation preferences of savanna trees in Burkina Faso. Econ Bot 57 (2): 203-217. https://doi.org/10.1663/0013-0001(2003)057[0203:IVOUAC]2.0.CO;2

Lachat C, Raneri JE, Smith KW, Kolsteren P, Van Damme P, Verzelen K, Penafiel D, Vanhove W, Kennedy G, Hunter D, et al., 2017. Dietary species richness as a measure of food biodiversity and nutritional quality of diets. PNAS 115 (1): 127-132. https://doi.org/10.1073/pnas.1709194115

Lebrun JP, Toutain B, Gaston A, Boudet G, 1991. Catalogue des plantes vasculaires du Burkina Faso. Ed. I.E.M.V.T, Maisons-Alfort, France. 341 pp.

Lovett PN, Haq N, 2000. Evidence for anthropic selection of the sheanut tree (Vitellaria paradoxa). Agroforest Syst 48: 273-288. https://doi.org/10.1023/A:1006379217851

Lykke AM, 1998. Assessment of species composition change in savanna vegetation by means of woody plants' size class distributions and local information. Biodivers Conserv 7: 1261-1275. https://doi.org/10.1023/A:1008877819286

Lykke AM, Mertz O, Ganaba S, 2002. Food consumption in rural Burkina Faso. Ecol Food Nutr 4: 119-153. https://doi.org/10.1080/03670240214492

Lykke AM, Kristensen MK, Ganaba S, 2004. Valuation of local use and dynamics of 56 woody species in the Sahel. Biodivers Conserv 13: 1961-1990. https://doi.org/10.1023/B:BIOC.0000035876.39587.1a

Maranz S, 2009. Tree mortality in the African Sahel indicates an anthropogenic ecosystem displaced by climate change. J Biogeogr 36(6): 1181-1193. https://doi.org/10.1111/j.1365-2699.2008.02081.x

Maranz S, Wiesman Z, 2003. Evidence for indigenous selection and distribution of the shea tree, Vitellaria paradoxa, and its potential significance to prevailing parkland savanna tree patterns in sub-Saharan Africa north of the equator. J Biogeogr 30: 1505-1516. https://doi.org/10.1046/j.1365-2699.2003.00892.x

Martin-Prével Y, Becquey E, Tapsoba S, Castan F, Coulibaly E, Fortin S, Zoungrana M, Lange M, Delpeuch F, Savy M, 2012. The 2008 food price crisis negatively affected household food security and dietary diversity in urban Burkina Faso. J Nutr 142: 1748-1755. https://doi.org/10.3945/jn.112.159996

Miles L, Newton AC, DeFries RS, Ravilious C, May I, Blyth S, Kapos V, Gordon JE, 2006. A global overview of the conservation status of tropical dry forests. J Biogeogr 33 (3): 491-505. https://doi.org/10.1111/j.1365-2699.2005.01424.x

NASA, 2012. Fire Information for Resource Management System (FIRMS). Earth Observing System Data and Information System (EOSDIS). http://earthdata.nasa.gov/data/near-real-time-data/firms. [10 March 2013].

Nikiema A, 2005. Agroforestry parkland species diversity: Uses and management in semi-arid West Africa (Burkina Faso). Doctoral Thesis. Wageningen University, Wageningen, The Netherlands.

Orwa C, Mutua A, Kindt R, Jamnadass R, Simons A, 2009. Agroforestree database: A tree reference and selection guide version 4.0. World Agroforestry Centre, Kenya; http://www.worldagroforestry.org/treedb/. [27 March 2017].

Ouédraogo I, Savadogo P, Tigabu M, Cole R, Odén PC, Ouadba JM, 2009. Is rural migration a threat to environmental sustainability in Southern Burkina Faso? Land Degrad Dev 20 (2): 217-230. https://doi.org/10.1002/ldr.910

Ouédraogo I, Tigabu M, Savadogo P, Compaoré H, Odén PC, Ouadba JM, 2010. Land cover change and its relation with population dynamics in Burkina Faso, West Africa. Land Degrad Dev 21 (5): 453-462. https://doi.org/10.1002/ldr.981

Ouédraogo O, Bondé L, Boussim JI, Linstädter A, 2015. Caught in a human disturbance trap: Responses of tropical savanna trees to increasing land-use pressure. Forest Ecol Manag 354: 68-76. https://doi.org/10.1016/j.foreco.2015.06.036

Paré S, Söderberg U, Sandewall M, Ouadba JM, 2008. Land use analysis from spatial and field data capture in Southern Burkina Faso, West Africa. Agric Ecosyst Environ 127: 277-285. https://doi.org/10.1016/j.agee.2008.04.009

Paré S, Savadogo P, Tigabu M, Ouadba JM, Odén PC, 2010. Consumptive values and local perception of dry forest decline in Burkina Faso, West Africa. Environ Dev Sustain 12: 277-295. https://doi.org/10.1007/s10668-009-9194-3

Powell B, Maundu P, Kuhnlein HV, Johns T, 2013. Wild foods from farm and forest in the East Usambara Mountains, Tanzania. Ecol Food Nutr 52 (6): 451-478. https://doi.org/10.1080/03670244.2013.768122

Powell B, Thilsted SH, Ickowitz A, Termote C, Sunderland T, Herforth A, 2015. Improving diets with wild and cultivated biodiversity from across the landscape. Food Secur 7 (3): 535-554. https://doi.org/10.1007/s12571-015-0466-5

Ræbild A, Hansen UB, Kambou S, 2011. Regeneration of Vitellaria paradoxa and Parkia biglobosa in a parkland in Southern Burkina Faso. Agroforest Syst 85 (3): 443-453. https://doi.org/10.1007/s10457-011-9397-0

Rowland D, Blackie RR, Powell B, Djoudi H, Vergles E, Vinceti B, Ickowitz A, 2015. Direct contributions of dry forests to nutrition: A review. Int Forest Rev 17 (2): 45-53. https://doi.org/10.1505/146554815815834804

Rowland D, Ickowitz A, Powell B, Nasi R, Sunderland T, 2016. Forest foods and healthy diets: quantifying the contributions. Environ Conserv 44 (2): 102-114. https://doi.org/10.1017/S0376892916000151

Sacande M, Sanou L, Beentje H, 2012. Guide d'identification des arbres du Burkina Faso. Royal Botanic Gardens, Kew, UK. 288 pp.

Savy M, Martin-Prével Y, Sawadogo P, Kameli Y, Delpeuch F, 2005. Use of variety/diversity scores for diet quality measurement: relation with nutritional status of women in a rural area in Burkina Faso. Eur J Clin Nutr 59: 703-716. https://doi.org/10.1038/sj.ejcn.1602135

Schmidt M, Zizka A, Traoré S, Ataholo M, Chatelain C, Daget P, Dressler S, Hahn K, Kirchmair I, Krohmer J et al., 2017. Diversity, distribution and preliminary conservation status of the flora of Burkina Faso. Phytotaxa 304 (1): 1-215. https://doi.org/10.11646/phytotaxa.304.1.1

Sop TK, Oldeland J, 2011. Local perception of woody vegetation dynamics in the context of a "Greening Sahel": A case study from Burkina Faso. Land Degrad Dev 24 (6): 511-527. https://doi.org/10.1002/ldr.1144

Sop TK, Oldeland J, Bognounou F, Schmiedel U, Thiombiano A, 2012. Ethnobotanical knowledge and valuation of woody plants species: A comparative analysis of three ethnic groups from the sub-Sahel of Burkina Faso. Environ Dev Sustain 14 (5): 627-649. https://doi.org/10.1007/s10668-012-9345-9

Termote C, Meyi MB, Djailo BD, Huybregts L, Lachat C, Kolsteren P, Van Damme P, 2012. A biodiverse rich environment does not contribute to a better diet: A case study from DR Congo. PLoS ONE 7 (1): e30533. https://doi.org/10.1371/journal.pone.0030533

Thiombiano DNE, Lamien N, Dibong DS, Boussim IJ, Belem B, 2012. Le rôle des espèces ligneuses dans la gestion de la soudure alimentaire au Burkina Faso. Secheresse 23: 86-93.

Thiombiano DNE, Lamien N, Castro-Euler AM, Vinceti B, Agundez D, Boussim IJ, 2013. Local communities demand for food tree species and the potentialities of their landscapes in two ecological zones of Burkina Faso. Open J For 3 (3): 79-87. https://doi.org/10.4236/ojf.2013.33014

Thiombiano N, Parkouda C, Lamien N, Séré A, Castro-Euler AM, Boussim IJ, 2014. Nutritional composition of five food trees species products used in human diet during food shortage period in Burkina Faso. Afr J Biotechnol 13 (17): 1807-1812. https://doi.org/10.5897/AJB2013.13462

Thomas E, Vandebroek I, Van Damme P, Goetghebeur P, Douterlungne D, Sanca S, Arrazola S, 2009. The relation between accessibility, diversity and indigenous valuation of vegetation in the Bolivian Andes. J Arid Environ 73 (9): 854-861. https://doi.org/10.1016/j.jaridenv.2009.03.010

Waswa LM, Jordan I, Herrmann J, Krawinkel MB, Keding GB, 2015. Community-based educational intervention improved the diversity of complementary diets in western Kenya: results from a randomized controlled trial. Public Health Nutr 18 (18): 3406-3419. https://doi.org/10.1017/S1368980015000920

West CT, Roncoli C, Ouattara F, 2008. Local perceptions and regional climate trends on the Central Plateau of Burkina Faso. Land Degrad Dev 19 (3): 289-304. https://doi.org/10.1002/ldr.842

Wezel A, Lykke AM, 2006. Woody vegetation change in Sahelian West Africa: evidence from local knowledge. Environ Dev Sustain 8 (4): 553-567. https://doi.org/10.1007/s10668-006-9055-2

White F, 1983. Vegetation of Africa - A descriptive memoir to accompany the Unesco/AETFAT/UNSO vegetation map of Africa; Natural Resources Research Report XX; UNESCO, Paris. 356 pp.

Wunder S, 2001. Poverty alleviation and tropical forests: what scope for synergies? World Dev 29 (11): 1817-1833. https://doi.org/10.1016/S0305-750X(01)00070-5

Zizka A, Thiombiano A, Dressler S, Nacoulma B, Ouedraogo I, Ouédraogo O, Zizka G, Hahn K, Schmidt M, 2015. Traditional plant use in Burkina Faso (West Africa): A national-scale analysis with focus on traditional medicine. J Ethnobiol Ethnomed 11 (9): 1-10. https://doi.org/10.1186/1746-4269-11-9




 

 

 



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