Does social organisation shape crop diversity? A case study among Tharaka farmers in Kenya

Identifying the factors that influence crop diversity patterns in-situ is a major challenge for its conservation. Despite the role of farmers in the construction and management of crop diversity, social factors have been widely neglected in this approach. Can different social groups living in the same environment have different folktaxonomy underlying crop diversity ? In the Tharaka community on the Eastern side of Mount Kenya, farmers living in the same neighboring group (ntora) usually cooperate for agricultural tasks. In contrast, cooperation between groups is uncommon and reflects the scarcity of their social relations which limits potentially the exchange of knowledge. Sorghum (Sorghum bicolor (L.) Moench) folktaxonomies of 95 tharaka farmers belonging to 11 ntora were compared to describe knowledge exchange patterns through social network. Inter-class multivariate analysis was applied to compare crop species and sorghum landraces inventory between ntora. The comparison or crop species inventory between ntora reveals differences. Free lists of sorghum landraces cultivated by tharaka farmers were recorded, enabling us to compare the sorghum folktaxonomy between ntora. The names used by farmers to identify sorghum landraces were significantly different between ntora and reflected differences of folktaxonomy. The influence of social network on crop diversity patterns in- situ is hence discussed. (Résumé d'auteur

Farmers' social identity and crop genetic diversity. The G x E x S model

A better knowledge of factors organizing crop genetic diversity in situ increases the efficiency of diversity analyses and conservation strategies, and requires collaboration between social and biological disciplines. Four areas of anthropology may contribute to understand the impact of social factors on crop diversity: ethnobotany, cultural, cognitive and social anthropology. So far, most collaborative studies have been based on ethnobotanical methods, focusing on farmers' individual motivations and actions, but overlooking the effects of farmer's social organization per se. We analyze how social anthropology, analyzing intermarriage, residence and seed inheritance, can contribute to studies of crop genetic diversity in situ, by considering crop varieties as social objects and by designing socially based sampling strategies. Because seed exchange is built upon trust, seed systems are embedded in a pre-existing social structure and centripetally oriented as a function of farmers' social identity. The strong analogy between farmers' cultural differentiation and crop genetic differentiation; both submitted to the same vertical transmission processes, allows proposing a common methodological framework for social anthropology and crop population genetics, where the classical interaction between genetic and environmental factors, G x E, is replaced by a three-way interaction G x E x S, with "S" designating the social differentiation factors. (Résumé d'auteur

The social diffusion pathways of sorghum varieties and associated knowledge in the Mount Kenya region

Small-scale farming systems present a major interest for the conservation of crop diversity in situ. In these systems, farmers act on crop diversity through their management practices, mainly seed selection and exchange. Understanding the diffusion pathways of crop seeds and associated indigenous traditional knowledge (ITK) within and among farmers' communities would hence be usefull for designing conservation strategies for agrobiodiversity. In smallholders' communities, the relationship among farmers are largely determined by social rules and customs, partly inherited from the pre-colonial period. It is notably the case in the Mount Kenya region, which still shelters an impressive cultural diversity with more than nine ethnolinguistic groups coexisiting on its Eastern slope. This study focused on three of these ethnolinguistic groups: the Chuka and Tharaka groups, which had a long standing alliance but have no alliance with a third group, the Mbeere, despite their spatial adjacency. Does this social organization determine the diffusion pathways of the sorghum varieties and that of the ITK associated? This study attempts to adress this question. The sorghum seed exchange network was characterized using Social Network Analysis. The dependance of seed exchanges regarding the social organization of farmers was tested based on the interviews of 218 farmers in the three ethnolinguistic groups. We also measured the consistency of 96 farmers belonging to the three ethnic groups in naming sorghum varieties, in order to test whether both the material (seed) and the cultural (sorghum variety names) diffusion pathways corresponded. This study showed that the social organization of farmers in the Mount Kenya region still shapes today not only the seed exchange network, but also the ITK diffusion pathways. This study hence illustrates the relevance of considering the social organization of farmers' communities for the conservation of agrobiodiversity in situ. (Résumé d'auteur

Climate variability as experienced by farmers. [K-2224-04]

The typical approach of estimating crop response to future climate scenarios may be inappropriate in the case of smallholder multi cropping rain-fed agriculture. Indeed, a crop-by-crop simulation, based on current varieties, cannot take into account the dynamics among crops as well as within crops i.e. among varieties, in time and space. We implemented a comparative study to understand interactions between cropping system dynamics and pas climate variations, taking into account the diversity of farmers' experiences and socio-cultural organization. in Kenya, farmers who adopted maize a few years ago are still cultivating traditional sorghum and pearl millet varieties, while others abandoned them earlier in favour of maize. Farming systems were thus dynamic, with different crop assemblages over time. Thus, retrospectively, farmers' capacity to mitigate crop failure risk due to extreme rainfall events has never been constant. Has the farming system lost part of its capacity to cope with climate variability, as maize is known to be less resistant to drought than sorghum and pearl millet? While this is usually demonstrated using yield parameter, we used see losses, which is consistent with a multicrop system. Combining ecological anthropology and climatology, we confronted the results of a retrospective survey of farmers' seed loss reminiscence about the period 1961-2006 and climatic records for three altitudinal levels on the eastern slope of Mount Kenya were analysed. Over the period 3204 seed loss events were reported independently by 208 farmers, for eight main crops of their rain-fed farming systems. the causes given for these losses according to farmers' experience and knowledge were recorded yearly. We first assessed whether these causes were related to recorded rainfall values, and, second, analysed the proportion of lost seed on a yearly basis, crop by crop and on the whole farming system, using logistic regression. Drought was mentioned 73.5% of the time whereas 8.5% of the losses were attributed to heavy rainfall. Farmers recalls coincided on drought years associated with crop diversity losses: conditional Chi-square tests based on Monte Carlo simulation clearly rejected independence (p = 0.001) between climatic reasons given by farmers and recorded rainfall, for both droughts and heavy rainfall. Farmers' retrospective perception of drought corresponds to major droughts reported for Kenya. By favouring maize at the expense of sorghum and pearl millet, cropping system dynamics have promoted an increasing risk of drought-associated seed loss. t he probability to lose sorghum seed (0.056– 0.065) was significantly lower than the probability to lose maize seed (0.071–0.087). all crops were affected more by droughts than by heavy rainfall. s eed loss probability increased for a rainy season shorter than 50 days, with less than 28 rain days, and with a precipitation under 400 mm. l ogistic regression confirmed that a change in cropping systems increased the risk of seed losses due to drought over the 46-yr period. Farmers experienced climate variability differently, with greater negative impact on farmers cultivating maize. e cological and social components thus cannot be analytically isolated but have to be considered as parts of a socio-ecological system. While usual approaches consider present-day characteristics of agricultural systems to assess their adaptability to hypothetical rainfall variability (projection into the future), our study used farmer experiences to look into the past. i n our approach, past rainfall variability is already known, not hypothetical, while farmers' experiences can allow assessment of the evolution of their agricultural systems, which can be monitored over time, and related to climate variability. t he cropping system dynamics, by favouring maize at the expense of sorghum and pearl millet are partly related to agricultural policies that positively valued maize, whereas sorghum and pearl millet were devalued, being perceived as ''poor people crops''. The current dynamics of agricultural systems thus imply many dimensions, not only economical, political, and agronomical, but also cultural. (Texte intégral

Reproduire des plantes, reproduire une société. Structuration sociale de la diversité des ressources génétiques in situ : Rapport scientifique de l'ATP 06/01

Si le climat et le sol ont depuis longtemps été étudiés pour leur effet structurant sur les agro-écosystèmes, il est moins courant d'étudier l'action de facteurs anthropologiques comme l'identité sociale des agriculteurs et la différenciation de leurs systèmes d'alliance, de mariage et d'échange. Cette étude montre comment la différenciation sociale des agriculteurs constitue un facteur clé de la diversité in situ des ressources génétiques. Sur le versant Est du Mont Kenya, la différenciation linguistique des groupes sociaux soulève un problème anthropologique. Cette différenciation et le fait qu'elle se maintienne au fil des générations sont expliqués par le taux d'endogamie linguistique, c'est-à-dire par la proportion de mariages conclus entre locuteurs d'un même dialecte. Ce système d'alliance et de mariage détermine directement l'orientation des systèmes d'échanges de semences. En effet, proportionnellement au taux d'endogamie, les semences acquises auprès des alliés proviennent du même groupe linguistique. L'effet structurant de ce système d'échange centripète sur la diversité variétale et génétique des plantes cultivées est analysé. Les groupes sociaux cultivent d'autant plus les mêmes variétés qu'ils sont proches linguistiquement. Au-delà du système d'alliance et de mariage, l'identité sociale des agriculteurs est ensuite considérée comme facteur de structuration de la diversité. Une étude des marchés locaux de semence montre comment la différenciation des réseaux sociaux constatés en dehors des marchés se prolonge à l'intérieur des marchés. Les transactions ne sont pas conclues au hasard. Significativement, l'identité linguistique du vendeur et celle de l'acheteur correspondent, de sorte que la circulation des semences acquises au marché est là encore centripète, c'est-à-dire orientée vers l'intérieur des groupes sociaux. L'impact de la différenciation sociale des agriculteurs sur la différenciation génétique des plantes a été évalué à l'échelle régionale à l'aide de marqueurs moléculaires sur le mil et le sorgho. Les résultats sur le mil, allogame, soulignent l'importance des flux de pollen qui nivèlent la différenciation entre les dialectes alors qu'une différenciation morphologique et génétique se maintient au niveau local. En revanche, les populations de sorgho préférentiellement autogame sont fortement structurées. Cette étude représente une réelle avancée pluridisciplinaire combinant les sciences sociales et biologiques. Elle établit de nouvelles passerelles à travers un dispositif conceptuel et des méthodes d'analyse communs aux deux disciplines. Une approche comparative des agriculteurs et une stratégie d'échantillonnage, également comparative, des plantes apparaissent comme un point focal de l'interdisciplinarité. (Résumé d'auteur

Changes in the concept of genotype x environment interactions to fit agriculture evolution : Multidisciplinary points of view

The homogenization of environments (E) encouraged by modern society and by the productivist model of agriculture has resulted in the homogeneity of genotypes (G) thereby reducing GxE interaction to a parasitic source of inaccuracy (a residual). As this model is called into question and new societal values are affirmed, agriculture is diversifying to fit contrasted environments and may be represented by four models defined by two axes, one socio economic (individual logics vs. collective governance), and the other agroecological (analytical vs. systemic approaches). Models differ by (i) the objectives (from yield improvement to farmers empowerment), (ii) specific expectations concerning genotypes (from inherited genetic resources to varieties that represent genetic, ethical and social progress), (iii) a specific representation of the environment (from E, a simple interaction between the agroecological environment (M) and cultivation system (C ), to E including a range of socioeconomic components (Actors competences (A), Outlets (O), Legislation (L), , Society (S) ) and (iv) particular relations between G and E (from GxE to GxMxCxA under evolving constraints represented by LxOxS). Taking these diverse objectives into account has changed the way plant improvement is envisaged. Thus depending on the model concerned, the order, interest and status of the five classic stages of plant improvement (setting objectives, creating variability, selecting, evaluating and disseminating) may be called into question. Between the existing analytical model and a holistic model that remains to be developed, lies the challenge of ensuring the sustainability, efficiency and acceptability of plant breeding and resulting innovations. From a simple "noticing" that we attempt to reduce the GxE interaction has become an " objective " that we try to predict and valorize. Structuring the different components of E, G and GxE, enables us to extend the basic concept of representativeness both of the cultivation conditions and of the socioeconomic "positions" of the involved actors. (Résumé d'auteur

La vie sociale des plantes cultivées. L’interaction G x E x S comme langage d’interface entre les sciences biologiques et sociales

Si le climat et le sol ont depuis longtemps été étudiés pour leur effet structurant sur les agro-écosystèmes et la diversité des plantes cultivées, il est moins courant d’étudier l’action de facteurs anthropologiques comme l’organisation et la différenciation sociale des agriculteurs. Mon parcours académique et professionnel, hybride en conciliant d’une part un Docto¬rat en ethnologie et sociologie comparative, et d’autre part l’encadrement de thèses en biologie en étroite interaction avec mes collègues généticiens de l’UMR Agap, m’a convaincu que la diversité des plantes cultivées ré¬sulte non seulement de facteurs biologiques et environnementaux, mais également de facteurs historiques et sociaux. Ce mémoire compte trois parties complémentaires. La première aborde les barrières sociales qui accompagnent l’organi¬sation de la vie en société. Les agriculteurs ne partagent pas leur savoir et n’échangent pas leurs semences ou leurs variétés aléatoirement avec les autres agriculteurs. L’absence de relation et d’échange avec certains, et des échanges privilégiés avec d’autres, sont une caractéristique de la vie en société. Les barrières sociales définissent ainsi des unités sociales au sein desquelles le savoir, les pratiques ou les variétés sont transmis ou échangés. L’interaction usuelle génétique x environnement, G x E, a été décomposée en trois termes, G x E x S, afin de rendre explicite, avec le terme S, la société comme facteur d’organisation de la diversité génétique et morphologique des plantes cultivées. La deuxième partie montre com¬ment l’orientation centripète des systèmes d’échanges — flux de gènes via les semences dirigés vers l’intérieur de groupes sociaux — contribue au Kenya et ailleurs à l’organisation de cette diversité. La troisième partie propose une approche dynamique de la diversité des plantes cultivées en s’appuyant sur la mémoire et le savoir des agriculteurs sur le versant Est du Mont Kenya. Les agriculteurs se rappellent les années où ils ont adopté ou abandonné les espèces ou variétés qu’ils cultivent. Ces biographies végétales permettent une analyse rétrospective de la diversité et de sa dynamique. L’interdépendance des facteurs biologiques, environnementaux et sociaux incite à conclure à la nécessité d’un langage d’interface entre sciences biologiques et sociales pour étudier la diversité des plantes cultivées. De portée générale, une approche comparative des agriculteurs et une stratégie d’échantillonnage, également comparative, des plantes apparaissent comme le point focal de cette interdisciplinarité. (Résumé d'auteur