Global Ecology and Conservation 4 (2015) 14–25

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Global Ecology and Conservation

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Original research article Distribution, biomass and local importance of in south-western Madagascar

Tahiry Ranaivoson a, Katja Brinkmann b,∗, Bakolimalala Rakouth a, Andreas Buerkert b a Department of Plant Biology and Ecology, University of Antananarivo, SBP 566, Antananarivo 101, Madagascar b Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics, University of Kassel, Steinstrasse 19, 37213 Witzenhausen, Germany article info a b s t r a c t

Article history: The multipurpose tamarind (Tamarindus indica L.) is important for people’s livelihood Received 11 May 2015 and considered as sacred in the Mahafaly region of south-western Madagascar. However, Accepted 11 May 2015 the ongoing overexploitation of this species has caused a decline of tamarind trees. In this Available online 16 May 2015 study, the species distribution, changes in tamarind biomass and the role of traditional taboos for the conservation of this species were determined to identify opportunities Keywords: and constraints for its conservation and appropriate land management planning. Semi- Allometric equation structured interviews (N = 63) were conducted in 10 villages in the study region to obtain Fady Local taboos information regarding the utilization of tamarind trees. During field surveys, the diameter Tamarindus indica at breast height (DBH), height, wood volume and wood biomass were measured for already Wood biomass felled trees (N = 25). Additionally, 318 trees were inventoried by measuring their DBH, Mahafaly region height and GPS location. Using high resolution satellite images from 2004/2005 and 2012 the crown areas of all tamarind trees in six village areas were identified. Allometric equations were established to predict their wood biomass from DBH, crown surface and wood volume. Tamarind trees are mainly used as supplementary food, as well as for traditional ceremonies, charcoal production and medicinal purposes. Altogether, 0.06–0.35 trees ha−1 were observed. A regression analysis yielded high coefficients of determination for the relationships between DBH and wood biomass (r2 = 0.98), DBH and crown area (r2 = 0.72), and crown area and wood biomass (r2 = 0.71). From 2004/2005 to 2012, wood biomass losses of 12%–90% were caused by charcoal production and slash and burn agriculture. The traditionally sacred status of the tree has become insufficient to secure its conservation in the Mahafaly region. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

Wild trees, such as tamarind, provide a range of ecological and economic services and may play an important role in the livelihoods of rural communities acting as a source of food during lean periods or as an alternative source of income (Jama et al., 2008; Fandohan et al., 2010a; Dawson et al., 2014). The tamarind (Tamarindus indica L.) is indigenous to Africa and typical of wooded savanna ecosystems (Diallo et al., 2008; El-Siddig et al., 2006), but nowadays it is distributed in more

∗ Corresponding author. Tel.: +49 5542 98 1280. E-mail addresses: [email protected] (T. Ranaivoson), [email protected] (K. Brinkmann), [email protected] (B. Rakouth), [email protected] (A. Buerkert). http://dx.doi.org/10.1016/j.gecco.2015.05.004 2351-9894/© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/). T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25 15 than 50 tropical countries (El-Siddig et al., 2006). In Asia (India, Thailand, Sri Lanka and Indonesia) and South America (Mex- ico, Brazil, Venezuela and Costa Rica), tamarind trees are often cultivated for commercial fruit production, whereas such commercialization is not yet developed in Africa. Here, are mainly used for home-consumption (De-Caluwé et al., 2010; Van-der-Stege et al., 2011) to provide food and traditional medicinal products and for cultural practices (Havinga et al., 2010; Norscia and Borgognini-Tarli, 2006; Van-der-Stege et al., 2011). Despite its cultural and economic importance, there is still a lack of knowledge on the reproductive ecology, population genetics, biomass production and natural distribution of tamarinds (Diallo et al., 2008; Fandohan et al., 2011b). In Madagascar, the drought-tolerant tamarind occurs in the dry and semi-arid regions of the country’s south (Schatz, 2001) and trees were often planted when a village was founded (Blanc-Pamard, 2002). In the south-western region of the country, tamarind trees are often sacred and protected by local taboos (fady or faly) due to their cultural and nutritional value (Bayala et al., 2003). Faly means ‘you shall not’ and is an important component of social–ecological systems in Madagascar. Such taboos are part of the laws inherited from the ancestors and reportedly have a strong impact on human behaviour and local resource management, including the regulations of forest access and the use of species (Lingard et al., 2003; Tengö et al., 2007; Jones et al., 2008; Rabearivony et al., 2008; von Heland and Folke, 2014). According to local traditional beliefs, the tamarind constitutes a mediator between living people and the ancestors. The spirits of the ancestors are believed to reside in tamarind trees and local people use them in traditional ceremonies in which ancestral benediction is requested (Stiles, 1998; Blanc-Pamard, 2002). The tamarind is also one of the few available local fruit trees (Faust et al., 2015), rendering it important for people’s diet, especially in south-western Madagascar, where people are recurrently confronted with food insecurity (WFP, UNICEF, 2011; Mathys and Maalouf-Manasseh, 2013). Furthermore, due to low economic development, lack of infrastructure and harsh environmental conditions, smallholder farmers rely on di- versification of income including earnings from forest products (Neudert et al., in press). Some Mahafaly households produce charcoal to obtain supplementary income (Mana et al., 2001; Randriamanarivo, 2001). Similar to Sub-Saharan Africa (Zulu and Richardson, 2013), in Madagascar charcoal constitutes a major energy source in urban areas (Mana et al., 2001; Randriamanarivo, 2001) due to its competitive price compared with petroleum or gas (Montagne et al., 2010). Charcoal production, therefore, is a strong contributor to the rampant deforestation process in the southwestern region (Casse et al., 2004; Brinkmann et al., 2014). Although officially prohibited (Montagne et al., 2010; Randriamanarivo, 2001), tamarind trees are one of the main species used for charcoal production in the Mahafaly region (SuLaMa, 2011). Studies on the distribution and utilization intensity of tamarind trees in southwestern Madagascar are scarce (Bayala et al., 2003; Ramalanjaona, 2013; Mertl-Millhollen et al., 2011), and little is known on the effects of the changing traditional belief system on tamarind use. However, such information is urgently needed for sustainable management of tamarind pop- ulations (Okello et al., 2001) in order to avoid overutilization of this multipurpose tree (El-Siddig et al., 2006; De-Caluwé et al., 2010; Havinga et al., 2010; Van-der-Stege et al., 2011). Therefore, the aims of this study were to (i) assess the im- portance of tamarind trees for the local population in the Mahafaly region, (ii) analyse the tamarind distribution and wood biomass availability and (iii) evaluate the changes of the tamarind tree distribution and biomass throughout the recent years using remote sensing data. We hypothesized that the sacred status of tamarind trees is no longer sufficient to ensure their conservation in south-western Madagascar.

2. Materials and methods

2.1. Description of the study area

The study was conducted in the Mahafaly region of south-western Madagascar, located 90 km south of Tuléar (Fig. 1). This region is one of the country’s poorest regions with an altitude varying between 0 and 400 m and a semi-arid climate char- acterized by a dry period lasting eight to nine months and very irregular rainfall with long term annual averages < 500 mm (UPDR, 2003). The region comprises different habitats from the coastal area to the plateau including the dry spiny forest thickets of the Tsimanampetsotsa National Park with a high number of endemic species (Mamokatra, 1999). Coastal shrub- lands on unconsolidated sands and saline (Besaire, 1946) dominate in the coastal zone, with an annual precipitation between 150 and 300 mm (Hanisch et al., submitted for publication). The local population near the border of the sea (Mozam- bique channel) mostly belong to the Vezo tribe, who traditionally earn their living from fishing and the collection of sea prod- ucts, whereas the livelihood strategies of the Tanalana and Mahafaly people in the inland are based on animal husbandry and crop production. The plateau area at the eastern border of the Tsimanampetsotsa National Park is characterized by limestone and siliceous red soils (Besaire, 1946) covered by dry spiny forest patches, shrublands and savannah. Annual rainfall varies between 500 and 700 mm with a mean temperature of 24 °C(Hanisch et al., submitted for publication). Due to the scarcity and irregularity of rainfall and the low chemical fertility of the weathered sandy soils, crop yields are mostly too low to cover subsistence needs of the local population mostly too low to cover subsistence needs of the local population. Recently, the presence of cattle raiders (Malaso) increased the production risk in animal husbandry (Goetter, submitted for publication) and alternative income activities have thus become even more popular to sustain people’s livelihood. 16 T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25

In the coastal area and the plateau region, charcoal production constitutes an important coping strategy to obtain sup- plementary income. Charcoal is produced from the surrounding natural indigenous tree species and sold on the markets in Tuléar, where the demand is high. In the plateau zone charcoal is transported to Tuléar via the national road RN10. In the coastal zone, an inter-ethnic network exists, whereby the Tanalana people produce charcoal while the Vezo people transport it with pirogues across the sea to the Tuléar market.

2.2. Household interviews

Interviews were conducted in 10 villages as part of a larger village and household survey (Brinkmann et al., 2014; Neudert et al., in press). Village selection was based on (i) topographic conditions, (ii) intensity of charcoal production and (iii) distance to roads and markets resulting in five villages in the coastal zone and five villages in the inland plateau zone (Fig. 1). In each village semi-structured questionnaires were used to explore the importance of the tamarind and traditional usage of this species with five to nine inhabitants practising charcoal production (N = 63).

2.3. Tree inventory, volume and mass measurement

During field surveys in May–June 2012 and June–July 2013, 318 intact tamarind trees were inventoried in the study region by measuring the following parameters: diameter at breast height (DBH in cm), total height (H in m) and GPS coordinates of the location. While DBH was determined at 1.30 m above ground, the diameter of trees with enlargements or buttresses was measured at 30 cm above the main enlargement (FAO, 2004). Total tree height was measured using a Suunto (Suunto Oy, Vantaa, Finland) optical height meter. For the establishment of allometric equations the wood volume and mass were determined in tamarind trees (N = 25), which were already felled by the local population for charcoal making. For each tree the DBH and height of the stem were measured. For tree volume estimates, each stem was divided into several sections including stem parts and branches for all woody parts with a diameter ≥ 2.5 cm, which corresponds to the minimum diameter of branches used for charcoal produc- tion in this area. For each section, the volume was calculated using Smalian’s formula (Jarayaman, 1999; De-Gier, 2003) and the total tree volume (V) was obtained by adding the volume of each section. For 10 tamarind individuals, also dry mass was measured. Given likely differences in moisture content for mass measurement, tree parts were sorted in the classes small branches (diameter between 2.5 and 6.4 cm), large branches (diameter > 6.4 cm) and stem (Ketterings et al., 2001) which subsequently were weighted separately with a suspension balance to the nearest 0.25 kg. From each class, three to six samples were randomly selected for fresh weight determination with a precision balance to the nearest 0.1 g. Thereafter, these samples were dried at 105 °C for 48 h until weight constancy and reweighed. For each section the ratio of fresh to dry weight for the corresponding size class was used to calculate the dry weight. Biomass of the tree (wood and bark) was obtained by summing the dry weights of stump, stem and branch sections. This dataset was subsequently used to establish allometric equations between DBH and wood biomass.

2.4. Satellite image and spatial analysis

To complement the field inventory and gather information on the distribution of tamarind trees, remote sensing analysis was used for three villages in the coastal zone and three villages in the inland plateau. Tamarind trees can be easily identi- fied on high-resolution satellites images because they are by far the biggest evergreen trees in the study area. Using Pléiades (2012, 0.5 m resolution) and Google Earth images from different years (2012, 2004/2005; 1 m resolution), the locations of all tamarinds were mapped in the selected village areas (the village centre and its hinterland; 16–20 km2, Table 1). For each identified tamarind tree, the position and crown area (CA in m2) were subsequently digitalized. Area calculations and nearest neighbour analyses were conducted in ArcGIS 10.0 (ESRI, Redlands, CA, USA) to determine the spatial pattern of the com- pletely mapped tree data. In addition, the Euclidean distance to the nearest settlement was calculated for each tamarind loca- tion. To analyse the changes of the tamarind density (trees ha−1) with increasing distance to the village in the plateau and in the coastal area, multiple ring buffer zones were defined at distances of < 0.5 km, 0.5–1.0 km, 1.0–1.5 km, 1.5–2.0 km and > 2.0 km to the village centre. For each buffer zone we subsequently calculated the tamarind density for 2004/2005 and 2012.

2.5. Wood biomass

Regression analysis was used to examine the relationship between the tree parameters DBH, height, wood volume (V in m3) and wood biomass (B in kg) in order to establish allometric equations. We compared different statistical models com- monly used to estimate wood biomass in forestry (Picard et al., 2012). For linear regression analysis all data and residuals were tested for normal distribution and subsequently logarithmically transformed (Ln = natural logarithm) to fulfil the assumption of normal distributed data and avoid the problem of heteroscedasticity (Parresol, 1999). Equations with V, DBH and H as predictors and wood biomass as an independent variable were established using simple linear regression and multiple linear regressions. T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25 17

Fig. 1. Location of the study area in the Mahafaly region of south-western Madagascar.

Table 1 Description of the high-resolution satellite image used for tamarind mapping in the Mahafaly region of south-western Madagascar.

Zone Villages Sample area (km2) Satellites images Type Date of acquisition

Google Earth January 2012 Antanatsoa 16 Google Earth June 2005 Astrium, Pléiades March 2012 Plateau Andremba 17 Google Earth September 2004 Astrium, Pléiades March 2012 Miarintsoa 17 Google Earth September 2004 Astrium, Pléiades March 2012 Efoetsy 20 Google Earth June 2004 Astrium, Pléiades March 2012 Coastal Marofijery 20 Google Earth June 2004 Astrium, Pléiades March 2012 Ankilibory 19 Google Earth June 2004

For the basic regression model we used the 10 biomass samples to establish the equation for wood biomass calculation using the volume parameter as a predictor. Based on this equation, we calculated the dry mass for the 25 volume samples and established an allometric equation for wood biomass using DBH as predictor. Subsequently, a multiple regression model was used with the total height as an additional predictor, which was available for 14 tamarind trees (the other 11 tamarind trees were already felled and cut into pieces before measurement occurred). Furthermore, the correlation between DBH and crown area was analysed using the DBH values of the inventoried tamarind trees with known GPS location and their corresponding crown areas calculated from the satellite image anal- ysis. Extreme outliers were identified using the Cook’s distance (Cook, 1977) and removed from the dataset. The resulting high correlation between DBH and CA and between the different tree parameters (volume, DBH and wood biomass) allowed for the establishment of another allometric equation using the crown parameter as a predictor for wood biomass. The total tamarind wood biomass in the study region was finally calculated with this equation using the digitalized CA of all tamarind trees. 18 T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25

Table 2 Utilization of the tamarind tree in the Mahafaly region of south-western Madagascar (all data are in %).

Utilization Parts of the plant Frequency in use Coastal (N = 32) Plateau (N = 31) Total (N = 63)

Alimentation Food 91 97 94 Juice production FruitsOccasional, seasonal (lean 3 16 10 Rum production Fruitsperiods) 9 10 10 Fodder for ruminants 16 10 13 Cultural importance—sacred tree Benediction of ancestors Whole tree Frequent 72 84 78 Commerce Charcoal production Wood 63 29 46 Occasional, seasonal Sale Fruits – 13 6 Medicine Anti-hurt, anti-fatigue, Bark, leaves, Frequent 53 3 29 stomach disorders, eye fruits disease Other utilizations Shade provision Whole tree 19 10 14 Very frequent, daily Village meeting place Whole tree 3 – 2

Model validation and selection were based on the Furnival Index (Furnival, 1961; Jarayaman, 1999; Eq. (1)) which has been widely used to compare different models (Addo-Fordjour and Rahmad, 2013). The model having the lowest Furnival Index best describes the relationship and was used for the estimation of tamarind biomass. The Furnival Index (FI) is calculated as follows:

 1  FI = RMSE ∗ (1) Geomean f ′(Y ) where RMSE is the mean square error of the fitted equation, f ′(Y ) is the first derivative of the dependent variable with respect to biomass, and Geomean denotes the geometric mean. The logarithm transformation of the data entails a bias in final biomass estimation (Parresol, 1999). This transformation underestimates the real value of the biomass which was corrected using a correction factor (Chave et al., 2005; Mwakalukwa et al., 2014) formula as follows:

 RSE2  CF = exp (2) 2 where RSE is the residual standard error of the model.

3. Results

3.1. Importance of the tamarind

The survey data show the wide use of tamarind tree components (fruit, whole tree, wood, leaves) by the local population in the Mahafaly region. Altogether, 13 types of utilization were identified, which were regrouped in five principal use categories (Table 2).

3.2. Tamarind density and distribution

The overall tamarind density in the study region varied from 0.06 trees ha−1 to 0.47 trees ha−1 with significant density differences between zones (P < 0.001; Table 3). A t-test revealed significant differences between the tamarind density in the plateau zone and the coastal zone (p < 0.001). However, based on a paired t-test no significant differences were found in tamarind densities between the two different observation periods (P = 0.24), because the variation of tamarind losses between villages was high. However, there was a clear decrease in tamarind density with a loss of tamarind trees in both zones (Table 3). Consequently, the observed nearest neighbour distance increased by 10–20 m from 2004/2005 to 2012. The tree density differed significantly between habitats (Fig. 2 (a), (b)). Tree density was highest in savannahs (0.4–0.6 tree per ha−1) and shrublands (0.2–0.5 trees per ha−1) on the plateau and for cropland areas in the coastal zone (0.15–0.17 trees per ha−1). In both zones the tamarind density in the cropland areas barely changed between years. A recent study by Brinkmann et al.(2014) showed major land cover changes in the study region from 2006 to 2012, reflected in an increase in savannahs and cropland and a concomitant decrease in forests and shrubland. These changes T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25 19

Fig. 2. Distribution of tamarind trees (trees ha−1) in each land cover class (LCC) on the plateau (a) and in the coastal zone (b) of south-western Madagascar. Land cover data are simplified after Brinkmann et al.(2014).

Table 3 Evolution of the tamarind density and nearest neighbour distance in the studied villages on the plateau and in the coastal zone of the Mahafaly region in south-western Madagascar. Village Area CPI 2004/2005 2012 Losses (ha) (%) Trees Density Obs. NN z-score Trees Density Obs. NN z-score (trees ha−1) D. (m) (trees ha−1) D. (m)

Plateau: Antanantsoa 1621 100 766 0.47 48 0.67 −17.31 413 0.25 62 0.66 −13.41 46 Andremba 1689 3 758 0.45 50 0.68 −17.01 599 0.35 53 0.64 −16.85 21 Miarintsoa 1713 4 705 0.41 56 0.72 −14.45 569 0.33 58 0.67 −14.73 19 Total (mean, SD) –

Coastal area: Efoetsy 2066 25 210 0.10 80 0.55 −12.74 189 0.09 99 0.65 −9.28 10 Marofijery 2002 14 162 0.08 95 0.62 −9.44 123 0.06 117 0.66 −7.29 24 Ankilibory 1919 23 184 0.10 87 0.62 −9.80 147 0.08 103 0.66 −7.93 20 Total (mean, SD) – CPI: Charcoal Production Intensity (percentage of population involved in charcoal production), NN = nearest neighbour ratio, Obs.D. = observed distance.

overlaid the changes in tree densities from 2004 to 2012 with highest losses of tamarinds in savannah, shrubland and forest areas. However, in the littoral area tamarind losses across years were less pronounced (Fig. 2(b)). Tamarind density per hectare was highest in the village centre with 2 trees ha−1 in plateau villages and 0.5 trees ha−1 in coastal ones in 2004 and 2012. With increasing distance to the village, the density of tamarind trees decreased (Fig. 3), indi- cating the anthropogenic effects on the natural tree distribution. Tamarind losses from 2004 to 2012 mainly took place at dis- tances < 1 km to the village. In 2012, the tamarind density was relatively low at larger distances (> 2.0) with 0.2 trees ha−1 on the plateau and 0.03 trees ha−1 in the littoral. 20 T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25

Fig. 3. Density of tamarind trees (mean and SD of trees ha−1) in relation to the distance of the village in the plateau zone (a) and in the coastal zone (b) of the Mahafaly region in south-western Madagascar.

3.3. Allometric equations

Although climatic and conditions differ between the coastal and the plateau zone, which may restrict a generaliza- tion of allometric equations, t-tests did not show any significant differences (P > 0.05) of tree parameters. Therefore, the datasets of the two zones were used for combined regression models. A high correlation was observed between tree parameters (supplementary file Appendix A) and the equation for wood biomass, with V as predictor revealed the highest coefficient of determination (R2 = 0.99). For multiple regression models using H as an additional predictor (Table 4, model 5 and 6) the coefficient of determination was similarly high with low FI values. Equation models using CA as a predictor (model 7, 8 and 9) revealed lower coefficients of determination. Here, model 9 was the equation with the lowest FI value and was finally employed for wood biomass estimations of all tamarind trees in the study region based on the tamarind crown areas derived from the analysis of satellite images.

3.4. Biomass change

Wood biomass losses differed between villages and zones. The highest wood biomass was observed for the plateau zone for 2004 and 2005, but because of higher tamarind losses in this zone the differences between both zones decreased in 2012. Compared with the coastal zone, the tamarind biomass was only in 2012 higher for Andremba and Miarintsoa (Table 5). Losses were highest for Antanantsoa and moderate for Efoetsy, Marofijery, Ankilibory and Andremba, whereas for Miarintsoa wood biomass seemed to increase. T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25 21

Table 4 Model description for the estimation of tamarind wood biomass in the Mahafaly Plateau region of south-western Madagascar.

Equation N Coefficients R2 AdjR2 RMSE FI CF Symbol Value (SD)

Predictor: V a −7.193(±0.156) (1) LnY = a + bLnV 10 0.999 0.999 0.052 0.261 1.002 b 1.002(±0.013) Predictor: DBH and H a −3.774(±0.626) (2) LnY = a + bLnDBH + cLnH 14 b 2.141(±0.155) 0.989 0.987 0.159 0.834 1.015 c 1.203(±0.475) (3) LnY = a + bLnDBH2H 14 a −3.639(±0.281) 0.989 0.988 0.16 0.837 1.015 Predictor: DBH a −2.513(±0.243) (4) LnY = a + bLnDBH 25 0.982 0.981 0.19 1.105 1.020 b 2.545(±0.072) a −3.002(±1.190) (5) LnY = a + bLnDBH + c(LnDBH)2 25 b 2.850(±0.728) 0.982 0.981 0.189 1.100 1.020 c −0.046(±0.110) a 0.097(±0.452) (6) LnY = a + b(LnDBH)2 + c(LnDBH)3 25 b 0.861(±0.121) 0.982 0.981 0.188 1.092 1.019 c −0.094(±0.024) Predictor: CA a 3.448(±0.202) (7) LnY = a + bLnCA 226 0.718 0.717 0.713 5.720 1.293 b 1.080(±0.045) a 3.599(±0.410) (8) LnY = a + bLnCA + c(LnCA)2 226 b 0.992(±0.211) 0.718 0.716 0.713 5.718 1.293 c 0.011(±0.027) a 4.378(±0.241) (9) LnY = a + b(LnCA)2 + c(LnCA)3 226 b 0.336(±0.040) 0.723 0.720 0.707 5.670 1.287 c −0.031(±0.006)

Ln: natural logarithm; B: wood biomass (in kg); V: tree volume (in cm3); DBH: diameter at breast height (in cm); H: total height (in m); CA: crown area (in m2); a, b, c: regression coefficients; R2: coefficient of determination; AdjR2: adjusted coefficient of determination; RMSE: root mean square error; FI: Furnival Index and CF: correction factor and SD: standard deviation.

Table 5 Evolution of the tamarind wood biomass in the Mahafaly region of south-western Madagascar.

Zone Village Area (ha) Year Biomass (t ha−1) Biomass total (t) Changes (%)

2005 6.40 10 373.66 Antanantsoa 1621 −89.70 2012 0.66 1069.01 2004 3.71 6267.22 Plateau Andremba 1689 −12.20 2012 3.26 5502.63 2004 2.85 4889.54 Miarintsoa 1713 4.58 2012 2.98 5113.36 2004 0.71 1462.68 Efoetsy 2066 −12.42 2012 0.62 1281.01 2004 0.60 1198.40 Coastal Marofijery 2002 −19.43 2012 0.48 965.59 2004 0.68 1297.79 Ankilibory 1919 −19.69 2012 0.54 1042.25

4. Discussion

4.1. Importance of tamarind

As a multipurpose tree with nutritional, medicinal and cultural importance for rural communities tamarinds provide many ecosystem services. For cropland areas, a positive effect of tamarinds on soil organic matter and on soil biological properties has recently been demonstrated (Faust et al., 2015). Tamarind utilization for food and medicinal purposes ob- served in the Mahafaly region is similar to West Africa, but differs in its cultural importance for rituals and ceremonies (Van-der-Stege et al., 2011), and in the extent of charcoal production (Fandohan et al., 2010a). Tamarind fruits play an important role in our study area as an alimentary product, notably during the lean season like in other rural areas of the tropics and subtropics (Motlhanka et al., 2008; Iranbakhsh et al., 2009; Powell et al., 2013). In contrast to other regions where many parts of the tamarind (fruits, leaves, flowers) are used in a variety of preparation 22 T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25 techniques (De-Caluwé et al., 2010; Fandohan et al., 2010a; Van-der-Stege et al., 2011), only a few tamarind dishes and food products are known to the local Mahafaly people. Often fruits are cooked with a special soil (tany foty), transformed to juice or rum and the green leaves are used as fodder for sheep and goats. The usage of tamarind differs between the coast and the plateau, especially for juice production, charcoal production, as well as medicinal use. Juice production in the littoral is rarely practised because of the poor water quality and the high salinity content in the ground water (Rasoloariniaina et al., 2014). Charcoal production is less intensive on the plateau compared to the littoral, which is probably the result of environmental education efforts from NGOs in this region. Furthermore, the proportion of medicinal use is lower in the plateau compared to the littoral, mainly because of the availability of much more medicinal plants in the plateau, whereas inhabitants of the coastal area depend to a higher degree on tamarind products for medicinal purposes (Andriamparany et al., 2014). The introduction of more elaborate food preparation techniques such as seasoning, porridge, curries and sauces (De- Caluwé et al., 2010; Fandohan et al., 2010a) could improve tamarind valorization and in the study area. Since tamarind fruits are mainly used as an alimentation during the lean season, improved storage techniques of tamarind fruits could help to increase the food stock and reduce food security risk. Tamarind trees protected by faly are believed to be refuges of ancestor spirits (Bird, 2009) and used to request benedictions of the ancestors, with people offering rum, money or sacrificed sheep and zebus under the tree. Some villagers believe that their life will end in disaster or they will die if they cut a tamarind tree protected by faly. However, in recent days violations of faly became more common and our results indicated that people increasingly cut and use tamarind trees for charcoal production and for soil fertilization (slash and burn agriculture). The traditional taboos protecting sacred forests and trees have degraded due to changes in religion (conversion to Christianity), in-migration of people from other regions of Madagascar and economic factors such as an increasing demand for urban markets and reliance on the market economy (Jones et al., 2008; Rabearivony et al., 2008; Brinkmann et al., 2014). Similar transgressions were observed for radiated tortoise (Geochelone radiata) in southern Madagascar (Lingard et al., 2003; Castellano et al., 2013), which is considered faly but now faces a high risk of extinction because of poaching (Walker and Rafeliarisoa, 2012). The traditional sanctions, which often required to sacrifice zebus or sheep formerly used in cases of transgressions of faly by the local community (Tengö et al., 2007) are no longer imposed. Nowadays, the tamarind is one of the most often used species for charcoal production in the Mahafaly region, and often all that people need to do is pouring rum (toaka mena) under the tamarind before cutting it. Tamarinds are also used for charcoal production (Fandohan et al., 2010a; Nyadoi et al., 2009) elsewhere in Africa, however to a lesser extent. In Madagascar consumers prefer tamarind charcoal due to its high calorific value (El-Siddig et al., 2006).

4.2. Changes in tamarind distribution and biomass

Traditionally tamarind trees were often planted with the establishment of a settlement and its modern distribution is a re- sult of human intervention (Blanc-Pamard, 2002). In our study region inhabitants from the coast reported that the tamarind trees in their village originally came from the plateau, from where seedlings were transported during transhumance. Herders might have disseminated tamarind seeds while roaming with their zebu herds, which is confirmed by the explicit presence of tamarind trees in the middle of transhumance trails in the study region. Grazing animals may also promote tamarind dispersal. Tamarind density was highest in the village and cropland areas (Figs. 2 and3), whereas tamarind trees in forests, shrub- lands and savannah were often isolated. The variation of tamarind density between the coastal and plateau zone in the Mahafaly region may be mostly attributed to differences in the amount of annual rainfall, which is higher on the plateau and results in higher tree densities. Similar results were found in Senegal (Bourou et al., 2012) and in Benin (Fandohan et al., 2011b). Tamarinds have a minimum annual rainfall requirement of 250 mm year−1 with a particular adaptation to drought periods and grow well at 500–1500 mm (El-Siddig et al., 2006; Van-den-Bilcke et al., 2013), where regeneration and growth rates of trees are higher (Fandohan et al., 2011b; Mertl-Millhollen et al., 2011). For instance, in the more humid gallery forest of the Berenty Reserve in southern Madagascar, tree density is 17.5–18.4 trees ha−1 (Mertl-Millhollen et al., 2011) and in gallery forests of the Western National Park of Benin it amounts to 18.2 tree ha−1 (Fandohan et al., 2010b), which is 9 times higher than in our study region. Another explanation for the variation in tamarind distribution is differences in soil conditions, soil salinity, temperature and altitude between the coastal and plateau areas of the Mahafaly region. The wide geographical distribution of tamarind trees in the sub and semi-arid tropics reflects that they are well adapted to a range of sites at different elevations rang- ing from 0 to 2000 m (Gunasena and Hughes, 2000; El-Siddig et al., 2006); some authors (Gebauer et al., 2001, 2004) even indicated that the tamarind is well adapted to salinity. Similar to many regions in Africa, tamarind density decreased as a result of the intensification of local use and the overuti- lization of this species (Maranz, 2009; Fandohan et al., 2010b; Bourou et al., 2012). We observed that populations of tamarind in savannahs, shrubland and forest area were the most exploited, in contrast to those of village areas and cultivated land, where tamarind density remained stable during the observation period due to protection by village inhabitants (Figs. 2 and3). Local people avoid the logging of tamarind near villages to sustain the benefits of this tree, such as food and shade provision for both people and livestock. This was also observed in Senegal, where tamarind density was negatively corre- lated with the distance to villages (Bourou et al., 2012) and in eastern Kenya (Nyandoi, 2004). In our study, tamarind losses were highest in Antanantsoa, which is characterized by intensive charcoal production due to its location near the RN10 road simplifying charcoal marketing to Tuléar. Moreover, the high number of logged tamarind trees is often promoted by mutual T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25 23 aid, locally referred to as ‘‘rima’’ (valitanana). Rima is a kind of employment for family members, friends and neighbours, largely restricted to hard physical work. Instead of a salary, people establish an agreement of mutual assistance. This practice is also common in the highland and eastern region of Madagascar for rice cultivation (Gannon and Sandron, 2006). In contrast to the other villages, we observed a relatively stable tamarind biomass in Miarintsoa indicating that wood harvests did not exceed the tree’s reproductive capability. Moreover, the intensity of charcoal production in this village was much lower compared to other villages with only 4% of village inhabitants practicing charcoal production. The natural regeneration of the tamarind tree in our study region is lower (Ramalanjaona, 2013) compared with other arid regions (Fandohan et al., 2010b, 2011a). During field observations, many tamarind seedlings were found under ‘mother’ trees in the rainy season, but they had disappeared until the dry season, probably because of a high rate of seedling mortality as well as animal grazing and browsing (Fandohan et al., 2011a; Van-den-Bilcke et al., 2013).

4.3. Allometric equations

There are numerous allometric biomass equations for tree species in temperate tropical and subtropical forests (Siebert et al., 2004; Chave et al., 2005; Basuki et al., 2009; Mwakalukwa et al., 2014). However, such equations are still lacking for tamarind trees. Similar to other tree species in tropical countries (Basuki et al., 2009; Chave et al., 2005; Mwakalukwa et al., 2014), we found a high correlation between tree parameters (volume, DBH, CA) and wood biomass. In our study, the regression model with the predictor DBH and H yielded the most reliable equation with the lowest FI value. In order to increase the practical usefulness and avoid errors in the estimation of tree height, the regression models with one predictor (DBH or CA only) were chosen to predict tamarind biomass. The identified allometric equations allowed an accurate biomass and volume estimation obtained from diameter alone, although the number of samples was restricted, especially for large tamarind trees. The regression models using CA as a single predictor, however, were less reliable, especially for grouped tamarinds where accurate crown separation was impossible (n = 138). In addition, this method is only suitable for mature trees (DBH > 15 cm), for which the crown area is easily recognizable during visual satellite image interpretation. Thus, the total wood biomass in the study region was probably underestimated. Nevertheless, the CA-based equations combined with remote sensing techniques allowed a rapid approach to estimate the tamarind wood biomass in the study region. Satellite images with a higher resolution may improve the results, but are expensive and mostly not available for historical dates. The morphological parameters (DBH, H and CA) of tamarinds are affected by environmental and geographical factors such as rainfall, temperature, latitude and longitude, and soil conditions (Nyadoi et al., 2010), which directly affect the ac- curacy of biomass estimation. Thus, the use of site-specific equations may be recommendable for more accurate biomass estimations (Cairns et al., 2003; Basuki et al., 2009). In our study there were no differences in the morphological tamarind parameters and allometric equations among the littoral and the plateau zones. We therefore conclude, that the equations established in this study can be applied to other regions in south-western Madagascar, but may not be extrapolated to other tropical and subtropical regions.

5. Conclusions

The multi-purpose tamarinds are important for people’s livelihood and considered as sacred in the Mahafaly region of south-western Madagascar. However, the traditional belief system, which was fundamental for sacred tree conservation, appears to be gradually eroding and local people tend to establish elimination rules for taboos to log tamarinds for charcoal production and slash and burn agriculture. This resulted in a decrease of tamarind density and wood biomass and the on- going intensive charcoal production activity threatens the population of tamarind in the savannah, forest and shrublands in south-western Madagascar. To successfully conserve the tamarind germplasm in the study region, we recommend the establishment of tamarind plantations in villages as well as the general valorization of tamarinds by enhancing its contri- bution to people’s diet through the promotion of more elaborate processing and marketing of local products. For charcoal production, the use of other more abundant tree species with rapid growth, such as Acacia bellula in the coastal zone and Albizia polyphylla on the plateau, is recommended in order to reduce the pressure on tamarind populations.

Acknowledgements

We would like to thank the local population of the Mahafaly region for their cooperation and hospitality during the field survey. We acknowledge the SuLaMa project team and WWF Tulear for their support during data collection. This research was funded by the German Federal Ministry of Education and Research (BMBF, FKZ: 01LL0914C).

Appendix A. Supplementary data

Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.gecco.2015.05.004. 24 T. Ranaivoson et al. / Global Ecology and Conservation 4 (2015) 14–25

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