12 research outputs found
Chapitre 2 - Agriculture pluviale et petite irrigation : plateaux dâAfrique orientale et australe
Trois sites reprĂ©sentatifs de trois rĂ©gions dâagriculture essentiellement pluviale, mais oĂč la petite irrigation sâavĂšre aussi essentielle, ont Ă©tĂ© Ă©tudiĂ©s dans le cadre de cet ouvrage. Deux dâentre eux sont situĂ©s en Zambie : le site de Katongo Kapala dans le district de Mpika (1 500 m dâaltitude) et celui de Miloso dans le district de Mkushi (1 400 m) . Le troisiĂšme site est localisĂ© non loin dâIringa, sur les hauts plateaux du Sud..
SystĂšmes agraires et changement climatique au Sud
Ă partir de lâĂ©tude dĂ©taillĂ©e et de la comparaison dâune douzaine de situations locales contrastĂ©es en Afrique sub-saharienne et en Asie du Sud-Est, les auteurs mettent en Ă©vidence les processus et les trajectoires qui expliquent la forte exposition aux alĂ©as des diffĂ©rents groupes dâagriculteurs, ainsi que leur inĂ©gale capacitĂ© dâadaptation. Ils expliquent les ressorts de cette vulnĂ©rabilitĂ© et illustrent le poids des choix passĂ©s et actuels en matiĂšre de politiques agricole, environnementale et commerciale. Enfin, ils prĂ©sentent les modalitĂ©s dâajustement et les transformations passĂ©es et en cours des pratiques paysannes allant dans le sens dâune rĂ©duction de lâexposition Ă lâalĂ©a, dâune attĂ©nuation de la vulnĂ©rabilitĂ©, et dâune meilleure adaptation aux changements globaux : dĂ©rĂšglement climatique bien sĂ»r, mais aussi accroissement dĂ©mographique, compĂ©tition accrue pour lâaccĂšs aux ressources, Ă©volution des prix relatifs et fluctuations des marchĂ©s, dĂ©rĂ©gulation et baisse des soutiens publics, etc. Ils esquissent en conclusion les chemins possibles en matiĂšre dâadaptation et des propositions de mesures politiques pour accompagner les producteurs.Pour des raisons de diffĂ©rences de fabrication, les figures et photos en couleurs de la prĂ©sente version sont dissĂ©minĂ©es au sein des diffĂ©rents chapitres, mais sont rĂ©unies Ă la fin du chapitre 4 de la version PDF
The BDNFVal66Met SNP modulates the association between beta-amyloid and hippocampal disconnection in Alzheimerâs disease
In Alzheimerâs disease (AD), a single-nucleotide polymorphism in the gene encoding brain-derived neurotrophic factor (BDNFVal66Met) is associated with worse impact of primary AD pathology (beta-amyloid, AÎČ) on neurodegeneration and cognitive decline, rendering BDNFVal66Met an important modulating factor of cognitive impairment in AD. However, the effect of BDNFVal66Met on functional networks that may underlie cognitive impairment in AD is poorly understood. Using a cross-validation approach, we first explored in subjects with autosomal dominant AD (ADAD) from the Dominantly Inherited Alzheimer Network (DIAN) the effect of BDNFVal66Met on resting-state fMRI assessed functional networks. In seed-based connectivity analysis of six major large-scale networks, we found a stronger decrease of hippocampus (seed) to medial-frontal connectivity in the BDNFVal66Met carriers compared to BDNFVal homozogytes. BDNFVal66Met was not associated with connectivity in any other networks. Next, we tested whether the finding of more pronounced decrease in hippocampal-medial-frontal connectivity in BDNFVal66Met could be also found in elderly subjects with sporadically occurring AÎČ, including a group with subjective cognitive decline (N = 149, FACEHBI study) and a group ranging from preclinical to AD dementia (N = 114, DELCODE study). In both of these independently recruited groups, BDNFVal66Met was associated with a stronger effect of more abnormal AÎČ-levels (assessed by biofluid-assay or amyloid-PET) on hippocampal-medial-frontal connectivity decreases, controlled for hippocampus volume and other confounds. Lower hippocampal-medial-frontal connectivity was associated with lower global cognitive performance in the DIAN and DELCODE studies. Together these results suggest that BDNFVal66Met is selectively associated with a higher vulnerability of hippocampus-frontal connectivity to primary AD pathology, resulting in greater AD-related cognitive impairment
Multiancestry analysis of the HLA locus in Alzheimerâs and Parkinsonâs diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes
Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinsonâs disease (PD) and Alzheimerâs disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased AÎČ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues
Measuring the employment content of agriculture in sub-Saharan Africa : comparison of agroecological and conventional models
Un accroissement dĂ©mographique considĂ©rable est Ă lâĆuvre en Afrique subsaharienne (ASS) et exerce une pression croissante sur les marchĂ©s du travail. Le dernier rapport des Nations Unies portant sur les prospectives dĂ©mographiques fait Ă©tat dâune augmentation dâun milliard dâĂȘtres humains pour le continent dâici Ă 2050, reprĂ©sentant 52% de lâaccroissement de la population mondiale (UNDESA 2019). Or, les progrĂšs Ă©conomiques rĂ©cents de la rĂ©gion reposeraient dans certains cas sur des processus rĂ©versibles tels que lâurbanisation sans industrialisation (Rodrik 2018) et un basculement de la main-dâĆuvre hors de lâagriculture vers des activitĂ©s de services informelles Ă faible productivitĂ© (Yeboah et Jayne 2018 ; Jayne, Chamberlin, et Benfica 2018). Ces tendances ne laissent pas prĂ©sager lâĂ©mergence dâun secteur secondaire Ă mĂȘme dâabsorber les nouvelles gĂ©nĂ©rations de travailleurs (Rodrik 2016). Lâimportance de lâagriculture comme premier employeur d'ASS ainsi que le fait quâune part consĂ©quente de cet accroissement dĂ©mographique devrait avoir lieu dans les zones rurales (UNDESA 2018) appellent Ă considĂ©rer le rĂŽle du secteur agricole pour faire face au dĂ©fi de lâemploi Ă moyen-terme. LâagroĂ©cologie constitue une alternative au modĂšle conventionnel du dĂ©veloppement agricole par lâaugmentation de la productivitĂ© en intĂ©grant les services Ă©cosystĂ©miques dans le processus de production. LâhypothĂšse originale de cette thĂšse est que les modes de production agroĂ©cologiques pourraient contribuer Ă fournir des activitĂ©s rĂ©munĂ©ratrices en ASS, par lâaccroissement en travail quâils induisent. Afin dâĂ©valuer un potentiel en crĂ©ation dâemploi par lâadoption de lâagroĂ©cologie dans lâagriculture familiale, des donnĂ©es primaires ont Ă©tĂ© collectĂ©es dans la zone des Niayes au SĂ©nĂ©gal auprĂšs de 180 mĂ©nages ruraux, dont 50 engagĂ©s dans lâagriculture biologique. Le premier article de la thĂšse propose une mĂ©thode pour Ă©valuer des niveaux dâagroĂ©cologie entre les exploitations agricoles et compare ceux-ci du point de vue du travail et de la main-dâĆuvre. Des scores agroĂ©cologiques sont construits Ă partir des pratiques mises en Ćuvre sur les exploitations. Ainsi, les exploitations sont groupĂ©es en classes avec diffĂ©rents niveaux dâagroĂ©cologie ce qui met en Ă©vidence un gradient agroĂ©cologique de systĂšmes agricoles. Des variables relatives aux volumes de travail, au nombre et aux types dâactifs impliquĂ©s dans lâactivitĂ© agricole sont ensuite comparĂ©es entre ces systĂšmes sans identifier de diffĂ©rence significative entre ces catĂ©gories.Dans le second article, un cadre dâanalyse dâĂ©conomie institutionnelle est proposĂ© pour comprendre le processus de mobilisation de la main-dâĆuvre dans lâagriculture familiale qui pourrait ĂȘtre affectĂ© par lâadoption de lâagroĂ©cologie. Il est appliquĂ© au contexte des Niayes et permet de comprendre les mĂ©canismes dâallocation du travail observĂ©s sur la zone. Ensuite, une analyse Ă©conomĂ©trique est conduite pour isoler un effet spĂ©cifique des pratiques agroĂ©cologiques sur lâemploi. Nos rĂ©sultats ne mettent pas en Ă©vidence de crĂ©ation dâemploi liĂ©e Ă lâadoption de ces pratiques dans lâagriculture familiale des Niayes mais suggĂšrent le caractĂšre multifactoriel dâun tel processus.Enfin, le troisiĂšme article vise Ă caractĂ©riser les configurations socio-Ă©conomiques des mĂ©nages ruraux dans lesquelles des formes de production agroĂ©cologique, dĂ©finies par nos systĂšmes agricoles, sont mises en Ćuvre dans les Niayes. Pour ce faire, une classification hiĂ©rarchique Ă composante principale est mobilisĂ©e. Ces configurations sont ensuite comparĂ©es aux modĂšles agricoles et typologies incluant lâagroĂ©cologie de la littĂ©rature permettant dâobserver un certain dĂ©calage avec la rĂ©alitĂ© des zones rurales dâASS. Ces rĂ©sultats illustrent la diversitĂ© des modĂšles agricoles sur le terrain Ă lâinverse des reprĂ©sentations simplifiĂ©es souvent mobilisĂ©es dans les discussions sur le dĂ©veloppement agricole.Sub-Saharan Africa (SSA) is experiencing massive population growth, which is exerting increasing pressure on labor markets. The latest United Nations demographic outlook report shows an increase of one billion human beings on the continent by 2050, accounting for 52% of the world's population growth (UNDESA 2019). However, some of the recent economic progress in the region is believed to be based on reversible processes such as urbanization without industrialization (Rodrik 2018) and a shift in the workforce from agriculture to informal low productivity service activities (Yeboah and Jayne 2018; Jayne, Chamberlin, and Benfica 2018). These trends do not suggest the emergence of a secondary sector capable of absorbing new generations of workers (Rodrik 2016).The importance of agriculture as the main employer of SSA as well as the fact that a significant part of this population growth is expected to take place in rural areas (UNDESA 2018) call for considering the role of the agricultural sector in facing the employment challenge. Agroecology is an alternative to the conventional model of agricultural development by an increase in productivity. This form of agriculture integrates ecosystem services into the production process. It has become increasingly important in discussions about which development models to adopt in SSA. Initially limited to agricultural practices based on ecosystem processes at the farm plot scale, the concept evolved to support transformations at the scale of the entire farm and up to the food system (Wezel et al 2020).The original hypothesis of this thesis is that agroecological production methods could contribute to providing income-generating activities in SSA, through the labor increase they induce. In order to assess a potential for job creation with the adoption of agroecology in family farming, primary data was collected in the Niayes area in Senegal from 180 rural households, including 50 engaged in the organic farming.The first article of the thesis proposes a method to assess agroecology levels between farms and compares these from a labor perspective. Agroecological scores are constructed from the practices implemented on the farms. Thus, farms are grouped into classes with different levels of agroecology, which highlights an agroecological gradient in agricultural systems. Variables related to the volume of work, the number and types of workers involved in agricultural activity are then compared between these systems without identifying any significant difference between these categories.In the second article, an institutional economics analysis framework is proposed to understand the process of labor mobilization in family farming that could be affected by the adoption of agroecology. It is applied to the context of the Niayes and helps to understand the labor allocation mechanisms observed in the area. Then, an econometric analysis is conducted to isolate a specific effect of agroecological practices on employment on farms. Our results do not highlight job creation linked to the adoption of these practices in family farming in Niayes but suggest the multifactorial nature of such a process.Finally, the third article aims to characterize the socio-economic configurations of rural households in which forms of agroecological production, defined by our agricultural systems, are implemented in the Niayes. To do this, a hierarchical classification on principal components (HCPC) is mobilized. These configurations are then compared to the agricultural models and typologies including agroecology in the literature, making it possible to observe a certain gap with the reality of rural areas of SSA. These results illustrate the diversity of agricultural models in the field, unlike the simplified representations often used in discussions on agricultural development
What contribution of agroecology to job creation in sub-Saharan Africa? The case of horticulture in the Niayes, Senegal
International audienceIn the context of Sub-Saharan Africa's demographic boom, the issue of youth employment has become a major concern. Many debates are ongoing regarding agriculture's role in the structural transformation process and providing jobs. In this regard, we explore the opportunity of an agroecological intensification of family farming. We analyze data from agricultural households in the Niayes area of Senegal collected in 2019 and use a clustering method to group farms and rank them according to agroecological practices. Diversity and livestock integration are the most differentiating factors across the identified farming systems. Considering labor allocation complexity within family farms, we compare employment indicators between farming systems to look for agroecology's effect on agricultural work. We observe diversity in the intensity of labor requirements across the different systems but no overall increase for the most agroecological. However, women working hours appear significantly increased for two groups suggesting a substitution with wage workers for the most agroecological systems
Agriculture pluviale et petite irrigation: plateaux dâAfrique orientale et australe
International audienc
Une agriculture familiale de plus en plus dĂ©pendante du salariat ? Les travailleurs saisonniers dans lâagriculture familiale sĂ©nĂ©galaise (rĂ©gions des Niayes et du Delta)
International audienceSenegal is experiencing an increasing demand for seasonal labour in the agricultural sector. In the context of family farming, this phenomenon results from a socio-economic differentiation induced by decades of State support for specific agricultural production models. This article analyses seasonal work from the perspective of seasonal workers, often socially and politically invisibilised. It aims to understand how this activity shapes their biographical trajectory and contributes to their livelihoods and those of their families. Based on data collected in 2018 and 2019 on seasonal workers in the Senegal River Delta and Niayes regions, we show that the precarious working conditions of this seasonal labour force, which is exclusively male in the areas studied, constraints livelihoods and accumulation as well as the collective action capacities of these workers.Le SĂ©nĂ©gal connaĂźt une demande croissante en travail saisonnier dans le secteur agricole. Dans le cadre de lâagriculture familiale, ce phĂ©nomĂšne rĂ©sulte dâune diffĂ©renciation socioĂ©conomique au sein de lâagriculture familiale induite par des dĂ©cennies de soutien de lâĂtat Ă des modĂšles productifs agricoles particuliers. Cet article analyse le travail saisonnier Ă partir de lâexpĂ©rience des salariĂ©s agricoles, socialement et politiquement invisibilisĂ©s, pour comprendre dans quelle mesure cette activitĂ© façonne leur trajectoire biographique, contribue Ă leurs moyens dâexistence et Ă ceux de leur famille. Ă partir dâun matĂ©riau collectĂ© en 2018 et 2019 dans les rĂ©gions du delta du fleuve SĂ©nĂ©gal et des Niayes, nous montrons que les conditions de travail prĂ©caires de cette main-dâĆuvre saisonniĂšre, exclusivement masculine dans les zones Ă©tudiĂ©es, limitent les moyens dâexistence et les possibilitĂ©s dâaccumulation ainsi que les capacitĂ©s dâaction collective de ces travailleurs
The BDNFVal66Met SNP modulates the association between beta-amyloid and hippocampal disconnection in Alzheimer's disease
In Alzheimer's disease (AD), a single-nucleotide polymorphism in the gene encoding brain-derived neurotrophic factor (BDNFVal66Met) is associated with worse impact of primary AD pathology (beta-amyloid, A beta) on neurodegeneration and cognitive decline, rendering BDNFVal66Met an important modulating factor of cognitive impairment in AD. However, the effect of BDNFVal66Met on functional networks that may underlie cognitive impairment in AD is poorly understood. Using a cross-validation approach, we first explored in subjects with autosomal dominant AD (ADAD) from the Dominantly Inherited Alzheimer Network (DIAN) the effect of BDNFVal66Met on resting-state fMRI assessed functional networks. In seed-based connectivity analysis of six major large-scale networks, we found a stronger decrease of hippocampus (seed) to medial-frontal connectivity in the BDNFVal66Met carriers compared to BDNFVal homozogytes. BDNFVal66Met was not associated with connectivity in any other networks. Next, we tested whether the finding of more pronounced decrease in hippocampal-medial-frontal connectivity in BDNFVal66Met could be also found in elderly subjects with sporadically occurring A beta, including a group with subjective cognitive decline (N = 149, FACEHBI study) and a group ranging from preclinical to AD dementia (N = 114, DELCODE study). In both of these independently recruited groups, BDNFVal66Met was associated with a stronger effect of more abnormal A beta-levels (assessed by biofluid-assay or amyloid-PET) on hippocampal-medial-frontal connectivity decreases, controlled for hippocampus volume and other confounds. Lower hippocampal-medial-frontal connectivity was associated with lower global cognitive performance in the DIAN and DELCODE studies. Together these results suggest that BDNFVal66Met is selectively associated with a higher vulnerability of hippocampus-frontal connectivity to primary AD pathology, resulting in greater AD-related cognitive impairment