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In Ceara (semi-arid Northeast Brazil), although still fragile, the sociotechnical system "agroecology" has established itself as an alternative to the dominant agribusiness. The controversies and clashes between the respective public and private actors that defend them highlight two polarized visions for the rural territory. In this work conducted in the Jaguaribe region, we questioned these controversies in the face of family farmers' practices and analyzed the determinants of farmers' practices. The methodology associated a participatory systemic and multi-actor diagnosis coupled with semi-structured interviews with farmers (40) and institutional representatives. On one hand, the two socio-technical poles were characterized (actors, visions, rules, instruments and mechanisms for strengthening, etc.). On the other hand, farmers' practices determinantes were analyzed through the framework of sustainable livelihoods and historical perspective. In the field, the two systems coexist, increasing farmers' capacity to adapt. Without getting too involved in the controversies, farmers pragmatically take advantage of the opportunities offered by both systems to implement their life strategies: instruments (public and private), narratives, rules. Innovative practices often arise from this re-appropriation. They are sometimes in contradiction with the initial purpose of the instruments of both systems (such as subsidies, credits, etc.) that were designed within a polarized vision. Access to opportunities remains strongly dependent on key actors, in often clientelistic relationships. Information and debate arenas are informal and not very inclusive. This contributes to the great heterogeneity in the capacity of farmers and communities and to social-environmental inequality. The absence of a formal local governance framework may favors adaptability and innovation at various levels (individual, family, community, ...). But at the territorial level, the lacking of natural resources management increases socio-environnemental vulnerability.

Le développement durable d'un territoire passe par la capacité des acteurs à définir, à planifier, et à financer des actions qui s'insèrent dans une vision stratégique portée par la collectivité territoriale et une institution légitimée localement. La mise en place ou le renforcement des dispositifs inclusifs de gouvernance territoriale permet d'amener les acteurs locaux à s'engager dans la gestion des ressources, la planification des investissements et le règlement des conflits. Ces dispositifs doivent s'appuyer sur un système de production et de partage de connaissances concernant le territoire et ses ressources.

To ensure agricultural land in rural territories is managed sustainably, environmental assessment need to be undertaken to support decision making. However, the development of sustainable agriculture and the sustainable use of natural resources is a major challenge for the Southern countries, which are subject to strong climatic and socio-political constraints, making it necessary to develop environmentally efficient agricultural systems that take into account the social and economic components of sustainability. Life cycle assessment (LCA) is a standardized method (ISO 14000 series) widely recognized for its completeness. It provides full multidimensional knowledge about potential environmental impacts, linked to a functional unit that characterizes a service rendered, in a global and long-term perspective. The aim of this study was to design an innovative operational framework to couple life cycle assessment approach and a participatory approach for developing countries with two objectives: First, to make it possible to perform environmental assessment even with the diversity of small farming systems and despite data scarcity, second to involve all the stakeholders and to facilitate the discussion of the results to enable further decision making for the management of a rural territory. We tested the applicability of our framework on a case study in a semi-arid region in central Tunisia where agricultural is based on scarce and overused natural resources. This framework made it possible to gather local knowledge about the systems under to be analysed, to involve all the stakeholders right from the beginning of the process and to consider all the interests and values as well as the diversity of social representations in the territory. In this way, the stakeholders were empowered by the assessment of the environmental impacts of their agricultural practices and land management in a context of decision making. As a matter of fact, social learning favourable conditions were created.

In semi-arid areas, agriculture is based on limited and fragile "water and soil" resources that are often overexploited. To ensure the sustainability of agricultural land management in rural areas, environmental assessment must be integrated to support decision-makers and local stakeholders in their decision-making. Due to its comprehensiveness, life cycle assessment (LCA) is one of the most widely used tools for environmental impact assessment. It has global approach (all potential environmental impacts are considered) and life cycle thinking ("cradle to grave"). However, LCA is difficult to apply in rural areas of developing countries. First, LCA requires a lot of data that is difficult to collect because of the diversity of small farming systems. Second, the results of LCA are difficult for non-specialists to interpret because of the complexity of its multiple indicators. Third, the processes included in LCA often do not correspond to the values and interests of stakeholders. Our study area is located upstream of the Merguellil catchment in central Tunisia, a Mediterranean country, characterized by a semi-arid climate with high variability of precipitation and is considered an important recharge area for aquifers. The upstream Merguellil brings together major environmental challenges such as variable and limited resources, over-exploitation of water resources, poor control of access to groundwater and accelerated soil degradation. These problems are also encountered throughout the Mediterranean region. The rapid expansion of conservation measures and of intensive irrigated cropping systems have raised the question of their environmental impacts and particularly on the soil resource. In the context of managing common "water and soil" resources and taking into account the diversity of agricultural practices within a rural area, it is important to assess the impacts at the scale of a territory. Our main objective is to provide decision-makers with knowledge on the environmental impacts of water and soil conservation works (WSCW) and the most relevant cropping systems by LCA at the territory level. In this thesis, we proposed a progressive and iterative participatory approach to analyze the territory in relation to its history, its components (living territories), its functions, its agricultural productions systems and its social components (families). We provided conceptual models shared by all stakeholders, we also collected and validated all the data necessary for the environmental assessment. An innovative methodological framework was proposed to link LCA with this participatory approach and made it possible to analyse the environmental impacts of all cropping systems. Finally, the consideration of the impacts of water and soil conservation works in LCA has been the subject of a specific development. Two indicators were explored using a distributed erosion model (LandSoil): erosion resistance and mechanical filtration. These developments provide all the methods and data to inform decision-making in the context of participatory land management, and in particular to define a sustainable development strategy for water and soil conservation works.; Dans les zones semi-arides, l'agriculture est basée sur des ressources "eau et sol" limitées et fragiles souvent surexploitées. Pour garantir la durabilité de la gestion des terres agricoles dans les territoires ruraux, l'évaluations environnementale doit être intégrée pour soutenir les décideurs et les acteurs locaux dans leur prise de décision. Grâce à son exhaustivité, l'analyse du cycle de vie (ACV) est l'un des outils les plus largement utilisés pour l'évaluation des impacts sur l'environnement. Elle présente des caractéristiques d’approche globale (tous les impacts environnementaux potentiels sont considérés) et de cycle de vie (« du berceau à la tombe »). Cependant, l’ACV est difficile à appliquer dans les zones rurales des pays en développement. Premièrement, l'ACV nécessite beaucoup de données difficiles à collecter en raison de la diversité des petits systèmes agricoles. Deuxièmement, les résultats de l'ACV sont difficiles à interpréter par les non-spécialistes en raison de la complexité de ses multiples indicateurs. Troisièmement, les processus pris en compte dans l’ACV ne correspondent souvent pas aux valeurs et aux intérêts des parties prenantes. Notre zone d'étude est située à l'amont du bassin versant de Merguellil, en Tunisie centrale, un pays méditerranéen, caractérisé par un climat semi-aride avec une forte variabilité des précipitations et elle est considérée comme une importante zone de recharge des aquifères. L'amont du Merguellil réunit des enjeux environnementaux majeurs tels que des ressources variables et limitées, la sur-exploitation des ressources en eau, le faible contrôle de l'accès à l'eau et une dégradation accélérée des sols. Ces problèmes sont également rencontrés dans tout le bassin méditerranéen. Le développement d’une agriculture irriguée de plus en plus intensive et l'expansion rapide des aménagements de conservation ont posé la question de leurs impacts environnementaux et particulièrement sur la ressource sol. Dans le cadre de la gestion des ressources communes "eau et sol" et de la prise en compte de la diversité des pratiques agricoles au sein d'un territoire agricole, il est important d'évaluer les impacts à l'échelle d'un territoire. Notre objectif principal est de fournir aux décideurs des connaissances sur les impacts environnementaux des aménagements de conservation des eaux et des sols (CES) et des systèmes agricoles les plus pertinents par ACV à l’échelle du territoire. Dans cette thèse, nous avons proposé une démarche participative progressive et itérative pour analyser le territoire par rapport à son historique, ses composantes (les territoires de vie), ses fonctions, ses productions agricoles et ses composantes sociales (les familles). Nous avons fourni des modèles conceptuels partagés par tous les acteurs et avons collecté et validé toutes les données nécessaires pour l’évaluation environnementale. Un cadre méthodologique innovant a été proposé pour coupler l’ACV à cette approche participative et a permis de réaliser l’analyse des impacts environnementaux de tous les systèmes de culture. Enfin, la prise en compte des impacts des ouvrages de conservation des eaux et des sols en ACV a fait l’objet d’un développement spécifique. Deux indicateurs ont été explorés à l’aide d’un modèle d’érosion distribué (LandSoil) : la résistance à l’érosion et la filtration mécanique. Ces développements fournissent toutes les méthodes et les données pour éclairer la décision dans le cadre d’une gestion participative du territoire, et en particulier pour définir une stratégie d’aménagement durable pour les ouvrages de conservation des eaux et des sols.

In semi-arid areas, agriculture is based on limited and fragile "water and soil" resources that are often overexploited. To ensure the sustainability of agricultural land management in rural areas, environmental assessment must be integrated to support decision-makers and local stakeholders in their decision-making. Due to its comprehensiveness, life cycle assessment (LCA) is one of the most widely used tools for environmental impact assessment. It has global approach (all potential environmental impacts are considered) and life cycle thinking ("cradle to grave"). However, LCA is difficult to apply in rural areas of developing countries. First, LCA requires a lot of data that is difficult to collect because of the diversity of small farming systems. Second, the results of LCA are difficult for non-specialists to interpret because of the complexity of its multiple indicators. Third, the processes included in LCA often do not correspond to the values and interests of stakeholders. Our study area is located upstream of the Merguellil catchment in central Tunisia, a Mediterranean country, characterized by a semi-arid climate with high variability of precipitation and is considered an important recharge area for aquifers. The upstream Merguellil brings together major environmental challenges such as variable and limited resources, over-exploitation of water resources, poor control of access to groundwater and accelerated soil degradation. These problems are also encountered throughout the Mediterranean region. The rapid expansion of conservation measures and of intensive irrigated cropping systems have raised the question of their environmental impacts and particularly on the soil resource. In the context of managing common "water and soil" resources and taking into account the diversity of agricultural practices within a rural area, it is important to assess the impacts at the scale of a territory. Our main objective is to provide decision-makers with knowledge on the environmental impacts of water and soil conservation works (WSCW) and the most relevant cropping systems by LCA at the territory level. In this thesis, we proposed a progressive and iterative participatory approach to analyze the territory in relation to its history, its components (living territories), its functions, its agricultural productions systems and its social components (families). We provided conceptual models shared by all stakeholders, we also collected and validated all the data necessary for the environmental assessment. An innovative methodological framework was proposed to link LCA with this participatory approach and made it possible to analyse the environmental impacts of all cropping systems. Finally, the consideration of the impacts of water and soil conservation works in LCA has been the subject of a specific development. Two indicators were explored using a distributed erosion model (LandSoil): erosion resistance and mechanical filtration. These developments provide all the methods and data to inform decision-making in the context of participatory land management, and in particular to define a sustainable development strategy for water and soil conservation works.; Dans les zones semi-arides, l'agriculture est basée sur des ressources "eau et sol" limitées et fragiles souvent surexploitées. Pour garantir la durabilité de la gestion des terres agricoles dans les territoires ruraux, l'évaluations environnementale doit être intégrée pour soutenir les décideurs et les acteurs locaux dans leur prise de décision. Grâce à son exhaustivité, l'analyse du cycle de vie (ACV) est l'un des outils les plus largement utilisés pour l'évaluation des impacts sur l'environnement. Elle présente des caractéristiques d’approche globale (tous les impacts environnementaux potentiels sont considérés) et de cycle de vie (« du berceau à la tombe »). Cependant, l’ACV est difficile à appliquer dans les zones rurales des pays en développement. Premièrement, l'ACV nécessite beaucoup de données difficiles à collecter en raison de la diversité des petits systèmes agricoles. Deuxièmement, les résultats de l'ACV sont difficiles à interpréter par les non-spécialistes en raison de la complexité de ses multiples indicateurs. Troisièmement, les processus pris en compte dans l’ACV ne correspondent souvent pas aux valeurs et aux intérêts des parties prenantes. Notre zone d'étude est située à l'amont du bassin versant de Merguellil, en Tunisie centrale, un pays méditerranéen, caractérisé par un climat semi-aride avec une forte variabilité des précipitations et elle est considérée comme une importante zone de recharge des aquifères. L'amont du Merguellil réunit des enjeux environnementaux majeurs tels que des ressources variables et limitées, la sur-exploitation des ressources en eau, le faible contrôle de l'accès à l'eau et une dégradation accélérée des sols. Ces problèmes sont également rencontrés dans tout le bassin méditerranéen. Le développement d’une agriculture irriguée de plus en plus intensive et l'expansion rapide des aménagements de conservation ont posé la question de leurs impacts environnementaux et particulièrement sur la ressource sol. Dans le cadre de la gestion des ressources communes "eau et sol" et de la prise en compte de la diversité des pratiques agricoles au sein d'un territoire agricole, il est important d'évaluer les impacts à l'échelle d'un territoire. Notre objectif principal est de fournir aux décideurs des connaissances sur les impacts environnementaux des aménagements de conservation des eaux et des sols (CES) et des systèmes agricoles les plus pertinents par ACV à l’échelle du territoire. Dans cette thèse, nous avons proposé une démarche participative progressive et itérative pour analyser le territoire par rapport à son historique, ses composantes (les territoires de vie), ses fonctions, ses productions agricoles et ses composantes sociales (les familles). Nous avons fourni des modèles conceptuels partagés par tous les acteurs et avons collecté et validé toutes les données nécessaires pour l’évaluation environnementale. Un cadre méthodologique innovant a été proposé pour coupler l’ACV à cette approche participative et a permis de réaliser l’analyse des impacts environnementaux de tous les systèmes de culture. Enfin, la prise en compte des impacts des ouvrages de conservation des eaux et des sols en ACV a fait l’objet d’un développement spécifique. Deux indicateurs ont été explorés à l’aide d’un modèle d’érosion distribué (LandSoil) : la résistance à l’érosion et la filtration mécanique. Ces développements fournissent toutes les méthodes et les données pour éclairer la décision dans le cadre d’une gestion participative du territoire, et en particulier pour définir une stratégie d’aménagement durable pour les ouvrages de conservation des eaux et des sols.

Soil is a rare natural resource and it is at the center of the main issues in agronomy, environment and land use planning. At global level, erosion is one of the major soil degradation processes and it is responsible for the decrease in agronomic potential of soils and in agricultural land surfaces. Water and soil conservation works (WSCW) are built to protect soil from erosion. The financial and environmental cost the WSCW construction is very high. However, the positive impacts of WSCW are not taken into account in Life Cycle Assessment (LCA). The objectives of this study is to intergrate the impact of WSCW on soil quality in LCA. There are different types of WSCW with different functions and they act differently on erosion process. In this study we focussed on contour ridges (CR) because they are associated to crop systems. CR are generally built in upland areas to reduce runoff and erosion, to increase on-site deposition of eroded particles and to increase local water infiltration. They modify water and soil flows at catchment scale, so it is necessary to use a model able to calculate the inventory flow at the catchment and not at the plot level. In this study we present a methodology to integrate the impact of CR on topsoil erosion at the catchment level and to compute characterization factors in presence of such WSCW. The proposed method was applied in a case study in semi-arid context in central Tunisia (Merguellil watershed) which presents the issues of over-exploitation of water resources, accelerated land degradation and a high expansion of conservation works. In order to investigate the impact of WSCW on topsoil erosion, diffrent catchment scenarios (with and without CR) and land use types were tested using soil redistribution model (LandSoil model). For life cycle impact assessment, we focussed on two midpoint impact categories of LANCA soil functions : erosion resistance and mechanical infiltration. The CFs were calculated using the two models : LANCA and LandSoil models. These CFs were then compared. The results showed how contour ridges can modify topsoil erosion process, the erosion impact depend on location of landuse and contour ridges increase mechanical infiltration of soil. However, these impacts were not considered in LANCA model. In conclusion, It is necessary to integrate the positive impacts of contour ridges in life cycle assessment. It will be also neccessary to integrate the impact of the other types of WSCW in topsoil erosion impact modelling.

Semi-arid agricultural areas are fragile territories where water and soil resources must be preserved. In such zones impact evaluation is difficult due to the lack of data. We focused on the upstream Merguellil watershed, located in central Tunisia, where several water and soil conservation works were built since 1990 to control water erosion and to protect the downstream area. The rapid expansion of such conservation measures raised the issue of their impact on soil and water resources. Our main goal is the impact assessment by LCA of the most relevant farming systems in our territory, taking into account on-site and off-site contributions to local and global impacts. Our strategy is to combine LCA with a participatory approach to integrate knowledge and perceptions of local actors and to provide elements on environmental impacts for all stakeholders. The first step was a territorial systemic participatory diagnosis to characterize the dynamics of the territory, to identify the natural resources and their uses, the developments of the agricultural practices and the characterization of the existing farming systems. This diagnosis was achieved through technical field visits and interviews with farmers. The second step was a territorial LCA of representative systems, mapping the different systems to consider the characteristics of their location (access to water, soil type…). Systemic territorial participatory diagnosis allowed to define a typology of production systems and to model the territory considering the interactions between these systems. Four types of production systems were identified to proceed with territorial LCA: olive and apricot system and olive and cereals system both in rainfed and irrigated combinations. LCA results are discussed for the most important midpoint indicators. This study demonstrated two major issues of LCA use for sustainable development in semi-arid watersheds: i) LCA results communication with stakeholders to fit with their understanding of the system and ii) localized impacts on soil and water resources, taking into account Water and Soil Conservation Works.