Local perception of vegetation J.G.-University Mainz
Goethe-University Frankfurt
Senckenberg Research Institute
K. Hahn-Hadjali1, K. Langewiesche 2, 1 Ecology
and Geobotany, Botanical Institut, J.W.Goethe-Universität Frankfurt/M., Germany,
[email protected] 2Institut for Ethnology and Afrikastudies, J. G.-University of Mainz, Germany,
[email protected]
Introduction
Study area
While changes of vegetation cover in West African Savannas are well documented, detailed knowledge about changing species composition remains scarce. In this regard the perception of local people is of special importance as there is a lack of data on former vegetation composition. However, it is difficult to evaluate the reliability of this information, as the perception is influenced by different factors. Our study focused on the identification and evaluation of changes in species composition, especially the decrease of species. Also the importance of the use-value of these species and their distribution patterns were analyzed for a better understanding of the perceived changes. Therefore ethnobotanical results were cross-linked to plant distribution data.
Sahelian Zone
Burkina Faso Ouagadougou Fada N‘Gourma
N-Sudanian Zone
Study area
S-Sudanian Zone
Methods
Plant distribution and abundance • phytosociological relevés were carried out in all vegetation types of the study area
Ethnobotanical data • Selection of 10 villages in the study area of Fada N’Gourma • Semi-structured interviews with groups (10-12 pers.) and single persons about the utilisation of species, their distribution and decrease • Standardized questionnaires • Fieldwalks for identification of plants
Results Local perception of decreasing species Throughout the 65 interviews in the 10 villages a total of 59 woody species and 22 herb and grass species were mentionned by the local people as decreasing. This is about 15% of the species recorded from the study area. The given time spans for the decrease vary strongly: for the woody species time spans from several years up to more than 30 years were mentionnend, whereas herbaceous species seem to have declined more recently within the last decade. This corresponds quite well with an increase of pasture pressure in the last decade, which effects mainly the herbaceous species.
Decreasing woody species Adansonia digitata Vitellaria paradoxa Parkia biglobosa Tamarindus indica Lannea microcarpa Anogeissus leiocarpus Gardenia erubescens
Decreasing grass species
Khaya senegalensis Acacia albida
Andropogon chinensis
Bombax costatum
Cymbopogon giganteus
Combretum nigricans
Andropogon gayanus Pterocarpus erinaceus
Sporobolus pyramidalis
Lannea acida
Ctenium newtonii
Detarium microcarpum
Vetiveria nigritana
Capparis corymbosa
Cymbopogon schoenanthus
Mitragyna inermis
Andropogon pseudapricus Heteropogon contortus
Combretum glutinosum
Diheteropogon amplectens
Securidaca longependunculata
0
10
20
30
40
50
60
70
no. of quotations in %
Many perennial grass species, like Cymbopogon giganteus , A. ascinodis and Andropogon gayanus occur only in protected places
Due to ist scarcity in the wild, villagers started to plant Andropogon gayanus (in mixed culture with sesame and peanuts).
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5
10
15
20
25
30
35
40
45
no. of quotations in %
Vitellaria paradoxa (Shea butter tree) although still abundant is also perceived as decreasing
Afzelia africana chopped for fodder
50
dynamics by peasants in SE-Burkina Faso
W e s t A f r i c a W11
M. Schmidt³ ³Reserach Institute Senckenberg, Paleobotany/Botany, Franfkurt/M., Germany,
[email protected]
Utilization purposes of decreasing woody species
Adansonia digitata Vitellaria paradoxa Parkia biglobosa Tamarindus indica Lannea microcarpa Anogeissus leiocarpus Gardenia erubescens Khaya senegalensis Combretum nigricans Pterocarpus erinaceus Bombax costatum Acacia albida Lannea acida Detarium microcarpum Capparis corymbosa Mitragyna inermis Combretum glutinosum Securidaca longependunculata Ximenia americana Pseudocedrela kotschyi Maerua angolensis Afzelia africana Annona senegalensis Acacia dudgeoni Balanites aegyptiaca Acacia gourmaensis Combretum micranthum Borassus aethiopum
alimentation construction/ furniture x x x x x x x x x x x x x x x
firewood
fodder
medicine
x x
x x x x x
x x x x x x x x x x x x x x x x x x x
x x x x
x x x
x x x
x x
x x
All of the mentionned species are used in several ways as fodder, for alimentation and medicine or as raw material for making mats for roofs and fences. So, we can presume, that species highly valued are also well observed in their population dynamics, whereas plants without use might hardly be noticed at all. But this is also an indication that the decrease might be caused partly by the utilization itself.
x x x x x x
x x x x x
x
x
x x x x x x
Anogeissur leiocarpus is one of the favorite species for construction and firewood
Combretum nigricans has a high usevalue for at least three use-purposes
Frequency of decreasing woody species Frequency of the most mentionnend decreasing woody species decreasing woody species (local perception)
It shows that not only species with a high frequency are mentionend by the people. Also species occurring in less than 3% of the relevés of the study area (e.g. Adansonia digitata, Acacia albida) are well perceived in their dynamics. In all 24 woody species which can be considered as occasional or rare in the study area were mentionned. This indicates that species abundance plays a minor role for the perception of the species changes.
frequency in relevés (330 relevés)
Adansonia digitata Vitellaria paradoxa Parkia biglobosa Tamarindus indica Lannea microcarpa Gardenia erubescens Anogeissus leiocarpus Khaya senegalensis Acacia albida Bombax costatum
Adansonia digitata, the Baobob, is well perceived in his dynamics In spite of his very low frequency in the study area.
Pterocarpus erinaceus Combretum nigricans Detarium microcarpum Lannea acida Capparis corymbosa Mitragyna inermis 0%
10%
20%
30%
40%
50%
60%
Conclusion The comparison of the species perceived as decreasing with their use-value reveals that people perceive and mention decreasing species mainly according to their use-value and socio-economic interests. Among the most frequently quoted species were many multipurpose trees which are highly appreciated due to the value of their fruit and for firewood and construction. A decline partly due to the intensive use can also be presumed for these species.
Species frequencies seems to be of less importance for the perception of the changes as there were also many species quoted, which occur in the study area with a low frequency and abundance. Under consideration of these results local environmental perceptions can provide good indications on species composition dynamics and permit to identify decreasing species. Furthermore, the information serves to compile priority lists with regard to local people’s needs and interests and for conservation aspects.
