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Trees in dryland forests and wooded areas provide key ecosystem services such as animal feed, timber, fruits and, regulation of soil and water cycles. Equally, the presence of livestock in dryland woody areas can also play an important role in the local ecosystem; not only are they a source of income for local communities, but they also help vegetation and mobilise stored biomass. When both of these ecosystem elements are wisely combined – livestock and trees – it creates an integrated agricultural system that can boost the local ecosystem, representing a welcome agro-ecological transition in livestock farming. The ‘Grazing with Trees’ report gives a thorough assessment of the positive role that optimized extensive grazing livestock farming can play in the management and restoration of drylands’ forests and lands with trees. It assesses and provides sound evidence on the benefits of applying an integrated landscape approach and utilizing farmers and pastoralists’ knowledge to halt desertification, increase resilience, and enhance food security under the actual changing scenario. The report confirms the importance of agroforestry as a primary pathway for forest restoration in dryland areas as recommended by FAO’s State of Forests 2022, and its recommendations encourage landscape planners and decision makers to consider livestock as allies, carefully restore tree cover and accelerate action to promote healthy ecosystems.

Bush fires are increasingly becoming a threat to Guinean ecosystems and their understanding is a big challenge to scientists and environmental managers. Using the FARSITE model (Fire Area Simulator), this paper presents the prediction of the spread and characteristics of bush fires in the savannahs of North-eastern Guinea, specifically in Malea/Siguiri prefecture. Inputs, vegetation and topography dataset from satellite imagery (30 m resolution, Landsat and SRTM respectively) as well as in-situ meteorological data (wind, temperature and humidity) were used. These data obtained from the boundaries of the area of study were prepared using Geographic Information System (GIS). The burning time and the ignition points were fixed while admitting 3 scenarios: spread of fire in a plain without wind; spread on hills without wind effect and spread with wind effect. The results show that, in these savannahs, the intensity of the fire lines can reach 4133,3 KW/m under the effect of winds. Without winds, a decrease of 69% over plains and 68% over hills is noted. The amount of heat released could go up to 38000 KJ/m2 with the wind effect. While, without the wind effect a decrease of 10 and 9% over the plains and hills is observed respectively. Eventually, the speed of propagation reaches 8 m/min (0.5 km/h), but without the wind, it would decrease up to 73 and 61% over plains and hills, respectively. This study could be improved to serve as a decision support tool for the management of ecosystems North-eastern Guinea. Key words: Fire area, prediction modeling, simulator, ecosystem managers, Guinea.

Pastoralists make the most of resources distributed unevenly over space and time to provide a range of goods and services. Operating in a shock-prone environment, pastoralists deploy endogenous strategies such as mobility, diversification in agriculture or in non-agricultural activities, management of social networks, etc. However, accurate and reliable knowledge about the economics of pastoralism is yet to be understood and absorbed at the local, regional and national levels, based on reliable data. In the absence of such knowledge, governments and private firms neglect investment that would allow those systems to better connect to markets, and are unable to provide appropriate services, infrastructure and tenure security. With Argentina, Chad and Mongolia as pilot cases, this study by CIRAD, commissioned by FAO, funded by IFAD and facilitated by pastoralist associations (Fundacion Gran Chaco, Reseau Billital Maroobe, and the National Federation of Pasture User Groups), aimed to fulfil this knowledge gap through a multifunctional assessment of pastoral production systems and their economic contribution. Importantly, incorporating self-consumption of pastoralist households' productions themselves as an key component of gross revenue shows a significant increase in their contribution to national GDPs. The diversified sources of revenue and the importance of self-consumption also indicate that pastoral systems fulfil a range of functions (income, food security, flexible labor, etc.). Further, the study promotes close cooperation between pastoralist associations, research institutions and development partners. Such new partnerships allow strengthening the capacity of those pastoralist associations in collecting and managing their own data, as well as using this data in policy dialogue.

Guinea is confronted to the increasing risks of bushfires that destroy thousands of hectares of vegetation cover every year. Very little research is devoted to the variability of those fires, which makes it a serious threat to both wildlife and human habitats. The current study investigates the spatial and temporal distribution of bushfires in the period from 2003 to 2016. The method used is the geospatial technology: we first filter pixels corresponding with active light supplied by MODIS images (Moderate Resolution Imaging Spectroradiometer) and estimate their densities following the square meshing procedure. Burned areas are deducted from the estimated pixel densities by calculations. The results highlight great occurrence of fires: 4 to 48 pixels of active fire per year and per 100 km2 depending on the location; 2 to 5 million hectares per year of burned areas (20,000 to 50,000 sqkm). Almost 8 to 24% the size of the whole country. The prefectures of Beyla, Siguiri, Kouroussa, Kankan, Dinguiraye, Mali and Tougue are the most exposed areas. Every year, fire activities are observed as from October and between May and June. They are however mitigated according to the regions (or the geographical domains). Summits of bushfires activities are generally reached between December and January.

The livestock sector contributes around 14.5 percent of total anthropogenic greenhouse gas (GHG) emissions. Developing mitigation strategies is a serious challenge, especially if we anticipate a rapid growth in the consumption of animal products in Low-Income (LI) and Lower Middle-Income (LMI) countries. Across the planet, livestock systems are highly diverse and the livestock sector offers many possibilities for carbon sinking that can help to reduce emissions. In particular, carbon sequestration in grasslands, rangelands and feed crop fields and manure recycling are crucial in the assessment of the carbon efficiency of livestock value chains. Supporting sustainable livestock production systems, together with sustainable animal product market chains and consumption, requires the completion of GHG inventories based on landscape carbon balances.

International audience; Sahelian pastoralists use mobility, diversification, and even pluriactivity as main adaptation strategies to the asymmetrical distribution of multifaceted resources. Complex relations vis-a-vis this risky environment hide slowing transitions from a traditional inward-looking to an outward-looking economy, which is characterised by increasing use of a remunerated workforce. The growing commodification of the economy of Sahelian pastoralists could generate new forms of uncertainty. The authors of this paper use a principal-agent model to analyse the remunerated workforce and demonstrate the mixed results of this strategy in the context of structural risk in the Sahel. The authors then highlight the conditions under which trust and reputation are developed to stabilise employment relations and better cope with and/or mitigate various shocks.

Greenhouse gas (GHG) emissions from the surface soils and surface water receiving animal excreta may be important components of the GHG balance of terrestrial ecosystems, but the associated processes are poorly documented in tropical environments, especially in tropical arid and semi-arid areas. A typical sylvo-pastoral landscape in the semi-arid zone of Senegal, West Africa, was investigated in this study. The study area (706 kmA(2) of managed pastoral land) was a circular zone with a radius of 15 km centered on a borehole used to water livestock. The landscape supports a stocking rate ranging from 0.11 to 0.39 tropical livestock units per hectare depending on the seasonal movements of the livestock. Six landscape units were investigated (land in the vicinity of the borehole, natural ponds, natural rangelands, forest plantations, settlements, and enclosed plots). Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes were measured with static chambers set up at 13 sites covering the six landscape units, and the 13 sites are assumed to be representative of the spatial heterogeneity of the emissions. A total of 216 fluxes were measured during the one-year study period (May 2014 to April 2015). At the landscape level, soils and surface water emitted an average 19.8 t C-CO2 eq/(hm(2).a) (CO2: 82%, N2O: 15%, and CH4: 3%), but detailed results revealed notable spatial heterogeneity of GHG emissions. CO2 fluxes ranged from 1148.2 (+/- 91.6) mg/(m(2).d) in rangelands to 97,980.2 (+/- 14,861.7) mg/(m(2).d) in surface water in the vicinity of the borehole. N2O fluxes ranged from 0.6 (+/- 0.1) mg/(m(2).d) in forest plantations to 22.6 (+/- 10.8) mg/(m(2).d) in the vicinity of the borehole. CH4 fluxes ranged from-3.2 (+/- 0.3) mg/(m(2).d) in forest plantations to 8788.5 (+/- 2295.9) mg/(m(2).d) from surface water in the vicinity of the borehole. This study identified GHG emission "hot spots" in the landscape. Emissions from the surface soils were significantly higher in the landscape units most frequently used by the animals, i.e., in the vicinity of the borehole and settlements; and emissions measured from surface water in the vicinity of the borehole and from natural ponds were on average about 10 times higher than soil emissions.

In the Sahelian context of shocks and structural uncertainties, transhumant breeding has proved its resilience by relying on traditional strategies such as mobility and diversification. Today, 25 percent of the investigated encampments of Ferlo have used a salaried workforce, renewing the delegation of tasks usually handled at the family scale. This article shows wage-labour as a strategy for copying with uncertainties inside the family (workforce availability) and outside (diversification of species and natural resource scarcity) to ensure continuity of herd management as the central pillar of pastoral food security.

L’état actuel des paysages et des territoires sahéliens est la résultante d’interactions entre facteurs écoclimatiques, socio-économiques et politiques, à l’oeuvre depuis plus de quatre décennies. Au nord du Sénégal, l’espace géographique du Ferlo est représentatif d’une cohabitation entre des systèmes de production agrosylvopastoraux dans laquelle l’activité pastorale se maintient en compétition avec les autres, car les complémentarités anciennes entre systèmes de production agricoles et pastoraux, ou entre pasteurs et collectivite ´, tendent à se dégrader sous la pression foncière. Ces forces de pression aux intérêts quelques fois divergents ont comme indicateurs de transformation tangibles : la conversion socio-économique et environnementale ; la pluralité des modes d’accès à la terre en dehors du cadre légal ; les litiges et difficultés dans l’affectation des terres ; la fragmentation des paysages ; la restructuration agricole et pastorale des territoires. C’est aussi dans ce contexte que les politiques de décentralisation et d’aménagement du territoire ont transféré aux collectivités territoriales le pouvoir d’administrer, d’exploiter et de gérer les ressources naturelles et le foncier, afin de renforcer la gouvernance locale et de répondre aux enjeux de développement durable des systèmes de production. L’expé- rience présentée ici traite du processus de coconstruction et de mise en oeuvre d’un outil de simulation pour accompagner et instruire les prises de décision des collectivités locales chargées de l’application de la loi sur le domaine national. Les différentes étapes de cette démarche participative qui ont conduit à la conception, au test et à l’évaluation par les utilisateurs du modèle AIDA et de ses scénarios sont présentées., The present state of the landscapes and territories in the Sahel is the result of interactions between climatic, economic, social and political factors which have been taking place for more than four decades. In the north of Senegal, the Ferlo geographical space is representative of cohabitation between sylvopastoral and agricultural production systems, within which the pastoral activity is maintained under conflictual conditions as traditional complementarities between agricultural and pastoral production systems, or between pastors and communities, tend to deteriorate under land pressure. Such pressure operates for a variety of often divergent goals displaying tangible transformation indicators with social economic and environmental conversion such as illegal land access plurality, disputes and trouble in land allocation, landscape fragmentation and agricultural territory and pastoral restructuring. It is also within this framework that territory decentralisation and development policies have transferred to stakeholders the power to administer, exploit and manage natural resources and lands under their jurisdiction so as to strengthen local governance and respond to sustainable development needs of production systems. The experiment shown in this case study deals with the process of co-building and setting up tools and simulation models in order to accompany and instruct decision making by local communities responsible for applying the law 64-46 of 06 June 1964. The different steps of this participative approach leading to the “AIDA” agent model design and scenarios have been put forward, tested and evaluated by the users.

We describe an action-research project whose objective was to help stakeholders at different organisational levels achieve sustainable land management by developing mediation models and tools. We chose to test a specific approach called companion modelling in the framework of a multidisciplinary research partnership and a formal local partnership (a 'users committee') involving an array of stakeholders at different organisational levels. The study area covers 10,000 km2 of agro-pastoral land around Lake Guiers in northern Senegal. We conducted studies to update the knowledge base of the area and organised six field workshops that clearly revealed three important tool functions to support decision-making on land use at different scales, i.e. understanding maps, monitoring and evaluating land tenure, and foreseeing changes in land use. We found that a toolbox approach was the best way to implement the three functions and overcome the constraints faced by the research team and those linked to the timing of the project. Therefore, we produced five simple complementary tools aimed at various users: a farm-level optimisation model (for researchers and technical services), a database for land allocations and a discussion tool to assess the impact of land allocation decisions (for the rural council), a paper atlas (for local players) and a regional land use change simulation model (for regional and national planners). Participants were able to work with paper maps, to interpret computer-generated simulations of land use change and understand the strengths and limitations of each. Self-assessment of the research process emphasised the importance of the context and the critical role played by social capital at both the research and the field level, which, in turn, emphasised the need for major improvements in the design and implementation of a quality process for participatory modelling. It turns out that action-research may be an effective way to undertake sustainability science.

Based on primary data obtained through investigations in Ferlo (Senegalese Sahel) during a whole year, from the rainy season of 2005 to the rainy season of 2006, this article presents a thorough analysis of the market income distribution of several pastoral communities and sees it in its political perspectives. The global Gini index of this pastoral region, 52.8%, is explained particularly by between-sites inequality at 79%, although within-site inequality represents only 21%. Paradoxically, there is no bigger equality in areas well served by basic infrastructures. The efficiency of national livestock policies and area planning should be questioned. At the economic analysis level, these results show the need to maintain and secure herders’ movements and thus complete the current research with an ecological point of view.

International audience; The future of pastoral systems and their interactions with territories are the subject of considerable debate in the scientific literature and are still insufficiently documented. Assessing the sustainability of pastoral systems and their interactions with the sustainability of territories is thus a complex task. We proposed in this study a method to assess the sustainability of pastoral systems within their territories. After reviewing the literature, we conducted interviews with pastoralism experts in France and in Africa on the subject of sustainability in general and pastoral systems in particular. We designed our grid according to the principles-criteria-indicators approach and included 10 principles grouped into three major fields: ‘Availability of resources in the territory’, ‘Properties of the system’, and ‘Extended sustainability’. Understanding the strategies used in pastoral systems enabled us to propose a set of specific criteria per principle. Finally, we compared our grid with other methods used to assess sustainability.; El futuro de los sistemas pastoriles y sus interacciones con territorios son el foco de un debate considerable en la literatura científica y se encuentran aún insuficientemente documentados. Asesorar la sustentabilidad de los sistemas pastoriles y sus interacciones con la sustentabilidad de los territorios es por lo tanto una tarea compleja. Proponemos en este estudio un método para asesorar la sustentabilidad de los sistemas pastoriles dentro de sus territorios. Después de revisar la literatura, condujimos entrevistas con expertos en pastoreo en Francia y África sobre el tema de la sustentabilidad en general y en sistemas pastoriles en particular. Diseñamos nuestra cuadrícula según un enfoque en los principios-criterios-indicadores e incluimos 10 principios agrupados en tres campos mayores: la disponibilidad de los recursos en el territorio, las propiedades del sistema y la sustentabilidad duradera. Comprender las estrategias utilizadas en los sistemas pastoriles nos permitió proponer un set de criterios específicos por principio. Finalmente comparamos nuestra cuadrícula con otros métodos utilizados para asesorar la sustentabilidad.; L’avenir des systèmes pastoraux et leurs interactions avec les territoires sont au coeur de débats majeurs dans la littérature scientifique et sont encore insuffisamment documentés. Evaluer la durabilité de ces systèmes pastoraux et leurs interactions avec la durabilité des territoires est donc une tâche complexe. Nous proposons dans cette étude une méthode pour évaluer la durabilité des systèmes pastoraux dans leurs territoires. Suite à un travail de synthèse bibliographique, nous avons conduit des entretiens auprès d’experts du pastoralisme en France et en Afrique sur le sujet de la durabilité de manière générale et de celle des systèmes pastoraux en particulier. Nous avons conçu une grille sur la base de l’approche principes-critères-indicateurs, en incluant 10 principes autour de trois thèmes majeurs que sont la disponibilité des ressources dans le territoire, les propriétés des systèmes, et la durabilité étendue. La compréhension des stratégies utilisées dans le cadre de l’activité pastorale nous a permis de proposer un jeu de critères spécifiques par principe. Enfin, nous discutons de cette nouvelle méthode au regard d’autres méthodes utilisées pour évaluer la durabilité.

In sub-Saharan Africa, trypanosomosis continue to be a major threat to animal health. They are transmitted by tsetse flies, and the risk of transmission depends on the spatial relations between the different elements of the pathogenic system (host-vector-parasite). Health/Environment relations were studied in an agro-pastoral area of Burkina Faso by collecting georeferenced information on parasitic, agro-ecological and socio-economic systems ; these data were examined with a Geographic Information System (GIS). An original cartographic method was applied to tsetse and cattle densities, using remote sensing and field data. High spatial resolution remote sensing tools and original modelling methods were used to detect the valley landscapes most favourable to tsetse flies and to describe land use by herds. The impact of trypanosomes appeared to depend largely on animal movements, watering practices and the degree of contact with riparian tsetse flies. Linkage of this spatial information allowed to identify "high-risk meeting points" and to target the vector control., Les trypanosomoses animales, transmises par les glossines (mouches tsé-tsé), constituent un enjeu de santé majeur en Afrique sub-saharienne. Les composantes spatiales des acteurs du système pathogène (hôte-vecteur-parasite) constituent le socle sur lequel repose le risque de transmission de la maladie. Une démarche originale de cartographie des densités de glossines et de bovins appliquée à une zone agro-pastorale du sud du Burkina Faso est mise en place, à partir de données de télédétection et à l'aide d'un système d'information géographique (SIC). Les biotopes des glossines sont replacés dans leur environnement au sein de «paysages» repérés sur l'image satellite. Les déplacements des troupeaux sont modélisés pour obtenir une carte de fréquentation de l'espace. Le croisement de ces informations aboutit à une modélisation de «paysages épidémiologique- ment dangereux», localisés et identifiés dans une perspective de lutte ciblée contre le vecteur et la maladie., Michel V., de La Rocque S., Michel J.-F., De Wispelaere G., Touré I., Augusseau X., Cuisance D. Modélisation de «paysage épidémiologiquement dangereux» par télédétection et SIG. In: L'information géographique, volume 65, n°1, 2001. pp. 73-80.

Le pastoralisme joue un rôle prépondérant dans l'économie des pays du Sahel et de l'Afrique de l'Ouest (AO) et participe à la sécurité alimentaire et nutritionnelle des ménages ruraux et urbains (Wane et al., 2009). La contribution du secteur élevage au PIB atteint 5 à 10% et les systèmes pastoraux fournissent plus de 50% de la production en viande et en lait (De Haan et al., 1999). Le pastoralisme s'avère économiquement viable et écologiquement adapté à la valorisation durable d'une ressource naturelle fragile et éparse dans la zone sahélienne (Toutain et al. 2012). Plus encore, le système de production mobile fournit de meilleurs rendements en termes de production annuelle de protéines animales par hectare par rapport au système de ranching ou autres systèmes intensifs à vocation commerciale. Ces systèmes d'élevage sont confrontés à de nombreux défis, liés notamment, à la marginalisation des populations pastorales dans les instances de gouvernance locale, et à la compétition croissante pour l'accès aux ressources. Dans ce contexte, les pasteurs et les politiques manquent d'informations et d'indicateurs spécifiques sur les enjeux et la viabilité de ce système de production (flux saisonniers de transhumance, vulnérabilité des ménages pastoraux, variations des prix des animaux et de denrées alimentaires¿) insuffisamment pris en compte par le cade des systèmes d'information et d'alerte précoce sur la sécurité alimentaire existants (Touré et al 2012). A cette asymétrie d'informations s'ajoute l'absence de cadre officiel de concertation entre les pasteurs, leurs organisations de producteurs faitières et les institutions techniques nationales, régionales et internationales en charge des politiques agricoles en général et de sécurité alimentaire et nutritionnelle des populations pastorales en particulier. Partant des enseignements tirés de la mise en oeuvre du système d'information sur le pastoralisme au Sahel (SIPSA) dans six pays du CILSS (Burkina, Mali, Mauritanie, Niger, Sénégal et Tchad). Cette présentation va mettre en exergue ses acquis (scientifiques, méthodologiques, pédagogiques¿ ), ses limites et ses défis (structurels, politiques..) en vue d'une amélioration des interventions publiques en période de crise.

Communication en libre accès, document est disponible en ligne : http://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDAQFjAA&url=http%3A%2F%2Fwww.au-ibar.org%2Fcomponent%2Fjdownloads%2Ffinish%2F86%2F1619&ei=9KE6U8imG8nH0QWt54HADw&usg=AFQjCNH3UAWZcijWK8vsdCwfVCjyIGNCoQ; National audience

Rift Valley fever (RVF) is an acute arboviral disease of domestic ungulates and humans in Africa and the Middle East. Since the first epidemic in 1987, Senegal has been confronted with recurrent episodes of the disease. This study aimed to model spatial distribution of ruminants in the agropastoral area of Barkedji (Senegal) where the disease is enzootic. In this Sahelian ecosystem, livestock distribution mainly depends on the availability of resources. Accordingly, remote sensing and geographic information systems (GIS) were used to seek environmental indicators of livestock density. A high-resolution Landsat image was associated with landscape field data to describe the land-cover. A series of normalized difference vegetation index values gave an estimation of the phytomass. In addition the compounds of herders in the study zone were located and sampled. Three surveys were conducted during the rainy season to record the number of herds in each compound of the sample. All these data were overlaid in the GIS. A discriminant analysis was performed to associate the observed herd density with environmental data and to develop a predictive model for the entire study zone. The final result was a 1-km resolution raster map of herd density during a normal rainy season.

Nous proposons un canevas souple et adaptable pour faciliter la conception rapide de modèles permettant d’aborder la durabilité des systèmes d’élevage extensif à l’échelle de territoires. Ce métamodèle est le fruit d’une démarche de conception à partir de systèmes multi-agents (SMA) développés sur sept sites en Amérique latine, en France et au Sénégal. Il est composé de quatre modules : Agent, Collectivité, Espace, Végétation-troupeau. Nous les illustrons par les exemples tirés des modèles élaborés sur les différents sites. Le rôle de cet outil est discuté afin d’en montrer les avantages et les limites, We propose a flexible and adaptable framework to assist the quick design of models dealing with the durability of the extensive livestock systems at the territorial scale. This metamodel results from the collaborative design starting from MAS developed on 7 sites in Latin America, France and Senegal. It is composed of four packages: Agent, Community, Space and Vegetation-Herd. We illustrate these packages with examples extracted from the various models. The role of this tool is discussed in order to show its advantages and its limits

Depuis plus d’une décennie, la globalisation des enjeux environnementaux, économiques et sociaux induit de rapides transformations du monde agricole et des territoires ruraux. Celles-ci posent en particulier la question de l’avenir des systèmes d’ élevage extensifs, face au défi du doublement attendu des productions animales d’ici 2050, tout en préservant l’environnement. Afin de mieux comprendre et accompagner ces processus de transformation, une analyse comparative des dynamiques des systèmes d’élevage et des territoires a été réalisée à partir de sept études de cas sur trois continents sur la base d’une grille de lecture commune. Les facteurs globaux (démographie, environnement, marchés) pèsent sur l’ensemble des territoires d’élevage, mais leurs impacts sont modulés de manière spécifique par des facteurs locaux : culture, histoire, enclavement, projets locaux et politiques publiques. Cependant les processus de transformation sont comparables et l’élevage extensif est souvent sous pression, notamment foncière et économique, face aux activités alternatives qui se développent sur les territoires d’élevage. Pour évaluer équitablement et de façon intégrée le rôle de l’ élevage dans le développement des territoires, il est nécessaire de mieux qualifier et de quantifier ses différentes fonctions qui sont complexes car multi- échelles sur les plans spatial et temporel., For over a decade, the globalisation of environmental, economic and social issues has induced rapid modification in agriculture and land. These changes raise the question of future extensive livestock systems in regards to the worldwide challenge to double livestock production by 2050 in ways which are safe for the environment. In order to better understand and follow modification processes, a comparative study of livestock systems and land dynamics has been carried out on seven case studies on three continents through the use of a common grid. Global factors (demography, environment, markets) are active on all livestock lands but their impacts are modulated and specific in relation to local factors (culture, history, isolation, local projects, public policies). Be that as it may, modification processes are similar and livestock production most often appears to be under pressure from alternative land-uses, especially for land-tenure and economic factors. To estimate livestock’s role in land development with equity and in an integrative way, it is necessary to improve qualitative and quantitative assessment of livestock functions which are complex due to spatial and temporal multi-scale processes.

La zone sylvopastorale du Sénégal, comme la plupart des régions sahéliennes d’Afrique, est une zone où le problème de l’eau se pose avec acuité. Les mares y sont cependant nombreuses. Du début à la fin de la saison des pluies, elles sont fréquentées par une population humaine et animale dont l’importance n’a pas baissé en dépit d’un important programme d’hydraulique basé sur l’exploitation des nappes profondes. Ces mares continuent donc à être utilisées jusqu’à la dernière goutte d’eau par différentes techniques. Mais, de plus en plus, des changements au niveau de leur capacité d’accumulation d’eau ou de la qualité de l’eau sont notés. La prévalence de la schistosomose humaine et animale est pour l’instant faible mais le mollusque, l’hôte intermédiaire, et le parasite sont présents, notamment dans la partie sud de la zone étudiée. Du fait des difficultés de plus en plus importantes notées dans la gestion des ouvrages hydrauliques (forages et puits), les pouvoirs publics ont initié un programme de remise en eau des bassins versants depuis une décennie. Le présent article est une contribution à la mise en oeuvre de ce programme dont l’aménagement des mares constitue une activité très importante en zone sylvopastorale.

L'approche suivie au Burkina Faso pour étudier l'épidémiologie des trypanosomoses bovines repose sur l'exploration des relations spatiales entre les hôtes principaux (bétail) et les glossines. A partir d'un recensement exhaustif et géoréférencé des bovins dans une zone de 1 200 kilomètres carrés, une modélisation des déplacements et des zones occupées par les animaux en fin de saison sèche, période d'interfaces maximales, a été effectuée. Basée sur deux points remarquables du parcours des animaux à cette époque, les parcs de nuit et les points d'eau, elle a permis, par manipulation simple de polygones, d'obtenir des cartes de répartition des bovins, à l'échelle de la zone d'étude.

Spatial distribution, biomass, production and phenological data were obtained for two natural populations of the cat-tail Typha dominguensis in Lagoa de Marica, a shallow sub-tropical lagoon. The area covered by T. dominguensis was estimated by satellite imagery and aerial photography. The values obtained by the two methods are concordant and close to 13 % of total wetland area. For both sites, plant growth proved to be highly influenced by water depth. Plants grew best at depths over 0.2 m depth. Productivity values (2,022 and 2,227 g m−2 y−1) are in the world-wide range for the genus. A classification of the Typha swamps in different areas according to flooding exposure is proposed.

Les auteurs rapportent les resultats d'une etude sur l'habitat, la distribution et la variation d'abondance saisonniere d'Argas persicus (Oken, 1818) au Senegal. La typologie des poulaillers en milieu traditionnel, gites des tiques, a ete realisee a cet effet et divers modeles ont ete decrits: le modele heteroclite, le modele a epineux, les modeles en vegetaux tresses et les modeles en banco. La distribution etablie a l'echelle du degre-carre a montre une presence et une abondance de cette espece d'Argas essentiellement dans la moitie septentrionale du pays, alors qu'elle a ete rare dans la partie meridionale. La variation d'abondance saisonniere a fait l'objet d'un suivi au cours de 17 mois en zone sahelienne. Le detiquage de 50 poulets et la collecte des tiques dans 30 poulaillers durant cinq minutes pour chacun de ces abris sur une base mensuelle ont indique une activite d'Argas persicus dans la basse-cour pendant toute l'annee. L'examen de 200 frottis de sang, realises a la saison seche ainsi qu'a la saison des pluies sur des poulets indigenes eleves en zone rurale, n'a pas permis d'observer des hemoparasites. Cependant, les fermes avicoles modernes implantees dans ces memes milieux connaissaient des epizooties de spirochetose aviaire. (Resume d'auteur)

Pastoralists make the most of resources distributed unevenly over space and time to provide a range of goods and services. Operating in a shock-prone environment, pastoralists deploy endogenous strategies such as mobility, diversification in agriculture or in non-agricultural activities, management of social networks, etc. However, accurate and reliable knowledge about the economics of pastoralism is yet to be understood and absorbed at the local, regional and national levels, based on reliable data. In the absence of such knowledge, governments and private firms neglect investment that would allow those systems to better connect to markets, and are unable to provide appropriate services, infrastructure and tenure security. With Argentina, Chad and Mongolia as pilot cases, this study by CIRAD, commissioned by FAO, funded by IFAD and facilitated by pastoralist associations (Fundación Gran Chaco, Réseau Billital Maroobé, and the National Federation of Pasture User Groups), aimed to fulfil this knowledge gap through a multifunctional assessment of pastoral production systems and their economic contribution. Importantly, incorporating self-consumption of pastoralist households' productions themselves as an key component of gross revenue shows a significant increase in their contribution to national GDPs. The diversified sources of revenue and the importance of self-consumption also indicate that pastoral systems fulfil a range of functions (income, food security, flexible labor, etc.). Further, the study promotes close cooperation between pastoralist associations, research institutions and development partners. Such new partnerships allow strengthening the capacity of those pastoralist associations in collecting and managing their own data, as well as using this data in policy dialogue.

Les institutions et structures en charge des questions de sécurité alimentaire au Sahel utilisent une diversité de systèmes d'information et d'alerte précoce. Toutefois les indicateurs utilisés pour caractériser la vulnérabilité des ménages pastoraux manquent d'efficacité en raison des méthodes et dispositifs élaborés plutôt pour les systèmes de cultures et ne prennent pas bien en compte la mobilité caractéristique des systèmes d'élevage pastoral au Sahel. Pourtant, le suivi de la pluviométrie et de la biomasse permet de caractériser l'évolution des ressources fourragères et hydriques et d'anticiper une situation difficile pour des populations dont l'activité économique d'élevage reste profondément tributaire des ressources naturelles. Aussi, des programmes régionaux tels que l'AMESD (African Monitoring of Environment for a Sustainable Development) piloté par l'AGRHYMET tentent de donner des indications précoces sur l'évolution de la végétation et des eaux de surfaces. A l'image des indicateurs biophysiques, cette étude propose une méthode permettant d'anticiper l'occurrence des crises alimentaires au Sahel en se basant sur les prix de marchés qui sont les principaux paramètres des termes de l'échange en milieu pastoral. Notre analyse va se fonder sur l'économétrie des séries temporelles des prix des biens constitutifs des termes de l'échange dans la zone pastorale Kidal-Gao du Mali qui, en mars 2010, a connu une grave crise alimentaire et nutritionnelle.

Many research and development institutions advocate the integration of economic sectors to markets to benefit from them and reduce poverty. This is not so simple for Sahelian pastoralists living in uncertainty and absence of contingent markets. Sahelian pastoralists use livestock markets but these markets don't systematically influence their production and marketing decisions. Based on the case of Senegalese Sahel, we use a spatial panel model to estimate the magnitude impacts of spatial and time factors on pastoral income generation. Then, we extent discussions to show that Sahelian livestock keepers alternate homo oeconomicus and bounded behaviours vis-à-vis the markets that they know well even if markets don't know much about them-and that is one reason it can be hard for a real structural transition. The problems of pastoral marketing systems are still examined from the perspectives of infrastructure buildings while it is also necessary to reduce transaction costs and information asymmetry to boost livestock marketing.

La mise en place d'un plan d'échantillonnage dans une population mobile habitant dans une vaste zone avec une dispersion entre les maisons très importante dans un même site nécessite de réfléchir sur la meilleur e façon de tirer un échantillon représentatif. Ce papier s'est intéressé sur la population pastorale occupant le Sahel sénégalais où cohabitent pasteurs et agropasteurs pratiquant la transhumance pour s'adapter face aux changements et à la disposition de fourrage pour leurs animaux. Jusqu' à présent, il existe un déficit notoire de procédure adaptée dans ce type de population pour laquelle des statistiques fiables sont presque inexistantes. Des méthodes d'analyse de données comme l'analyse des correspondances multiples (ACM) et la classification ont été utilisées pour faire le tirage des sites au premier degré. Il s'inscrit dans une approche pluridisciplinaire pour mieux rendre compte de la complexité des systèmes de production pastoraux. Il combine des techniques d'échantillonnage mixtes (analytique et statistique).

Background Rift Valley fever (RVF) is a vector-borne viral zoonosis of increasing global importance. RVF virus (RVFV) is transmitted either through exposure to infected animals or through bites from different species of infected mosquitoes, mainly of Aedes and Culex genera. These mosquitoes are very sensitive to environmental conditions, which may determine their presence, biology, and abundance. In East Africa, RVF outbreaks are known to be closely associated with heavy rainfall events, unlike in the semi-arid regions of West Africa where the drivers of RVF emergence remain poorly understood. The assumed importance of temporary ponds and rainfall temporal distribution therefore needs to be investigated. Methodology/Principal Findings A hydrological model is combined with a mosquito population model to predict the abundance of the two main mosquito species (Aedes vexans and Culex poicilipes) involved in RVFV transmission in Senegal. The study area is an agropastoral zone located in the Ferlo Valley, characterized by a dense network of temporary water ponds which constitute mosquito breeding sites. The hydrological model uses daily rainfall as input to simulate variations of pond surface areas. The mosquito population model is mechanistic, considers both aquatic and adult stages and is driven by pond dynamics. Once validated using hydrological and entomological field data, the model was used to simulate the abundance dynamics of the two mosquito species over a 43-year period (1961–2003). We analysed the predicted dynamics of mosquito populations with regards to the years of main outbreaks. The results showed that the main RVF outbreaks occurred during years with simultaneous high abundances of both species. Conclusion/Significance Our study provides for the first time a mechanistic insight on RVFV transmission in West Africa. It highlights the complementary roles of Aedes vexans and Culex poicilipes mosquitoes in virus transmission, and recommends the identification of rainfall patterns favourable for RVFV amplification., Author Summary Rift Valley fever (RVF) is a zoonotic disease that affects domestic livestock and humans. During inter-epizootic periods, the main infection mechanism is suspected to be through bites by infected mosquitoes, mainly of Aedes and Culex genera. In East Africa, RVF outbreaks are known to be closely associated with heavy rainfall events, unlike in the semi-arid regions of West Africa where the drivers of RVF emergence remain poorly understood. This study brings mechanistic insight to explain why reported RVF outbreaks in Northern Senegal cannot be correlated directly to rainfall. This is done through the use of a rainfall-driven model of RVF vector populations that combines a hydrological model to simulate daily water variations of mosquito breeding sites, with mosquito population models capable of reproducing the major trends in population dynamics of the two main vectors of RVF virus in Senegal, Ae. vexans and Cx. poicilipes. Results show that RVF occurs during years when both species are present simultaneously in high densities. Simulations of inter-annual variations in mosquito populations successfully explained the dates of RVF outbreaks observed between 1961 and 2003.