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Mapping the diversity of land uses following deforestation across Africa
No full textInternational audienceAfrican forest are increasingly in decline as a result of land-use conversion due to human activities. However, a consistent and detailed characterization and mapping of land-use change that results in forest loss is not available at the spatial-temporal resolution and thematic levels suitable for decision-making at the local and regional scales; so far they have only been provided on coarser scales and restricted to humid forests. Here we present the first high-resolution (5 m) and continental-scale mapping of land use following deforestation in Africa, which covers an estimated 13.85% of the global forest area, including humid and dry forests. We use reference data for 15 different land-use types from 30 countries and implement an active learning framework to train a deep learning model for predicting land-use following deforestation with an F1-score of 84 ± 0.7 for the whole of Africa. Our results show that the causes of forest loss vary by region. In general, small-scale cropland is the dominant driver of forest loss in Africa, with hotspots in Madagascar and DRC. In addition, commodity crops such as cacao, oil palm, and rubber are the dominant drivers of forest loss in the humid forests of western and central Africa, forming an “arc of commodity crops” in that region. At the same time, the hotspots for cashew are found to increasingly dominate in the dry forests of both western and south-eastern Africa, while larger hotspots for large-scale croplands were found in Nigeria and Zambia. The increased expansion of cacao, cashew, oil palm, rubber, and large-scale croplands observed in humid and dry forests of western and south-eastern Africa suggests they are vulnerable to future land-use changes by commodity crops, thus creating challenges for achieving the zero deforestation supply chains, support REDD+ initiatives, and towards sustainable development goals
Représentations sociales des plastiques dans le Sud-Ouest de Madagascar
No full textLe projet « Les plastiques marins comme vecteurs de pathogènes humains » (VectoPlastic, 2022-2026), financé par l’ANR et déployé à Madagascar, inclut un volet en sciences sociales (Tâche 4), qui a cherché à comprendre les représentations sociales associées aux plastiques sur le littoral du Sud-Ouest malgache. Pour ce faire, nous avons réalisé des entretiens semi-directifs avec 112 personnes, issues de différentes catégories d’acteur·rices qui gravitent de près ou de loin autour de la question des plastiques. Une analyse qualitative de ces entretiens nous a permis de nous distancier de l’association « plastiques = pollution » pour s’intéresser à la diversité des représentations sociales (indissociables des savoirs et des pratiques) relatives aux plastiques, tout en interrogeant les liens que les acteur·rices entrevoyaient éventuellement entre ces derniers et la santé humaine.Dans une première partie de ce rapport, nous présentons nos sites d’étude et nos méthodes de production, de traitement et d’analyse de données. Dans un second temps, nous présentons nos résultats pour chacune de nos huit catégories d’échantillonnage. Enfin, nous concluons par la présentation de certains fils d’analyse croisée, en lien avec les deux questions suivantes : quelles sont les représentations sociales associées aux plastiques ? sont-ils considérés comme une source de risques pour la santé humaine
SelNeTime : a new method inferring demography and selection from genomic time series data
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Human land occupation regulates the effect of the climate on the burned area of the Brazilian Cerrado
No full textInternational audienceHuman activities and climate change are transforming fire regimes globally. The interaction between these two drivers is poorly understood, yet critical if we aim at predicting how biomes will respond to novel fire regimes. In the Brazilian Cerrado, altered fire regimes are threatening its unique biodiversity and ecosystem functioning. Here, using geospatial data for the period 1985-2020 and a causal inference framework to design Bayesian statistical models, we demonstrate that a larger human presence in the landscape (≥40% land-use area) reduces the Cerrado’s burned area and hinders its responsiveness to climate; while climatic effects only become apparent in landscapes with little human presence, where hotter and drier conditions increase burned area. Finally, we find spatially heterogeneous burned area trends over time, with increases associated to climate change in landscapes that have remained mostly intact, and decreases caused by anthropic expansion. Both diverging trends have important implications for the conservation of the Cerrado as land-use expansion and climate change continue to unfold
Integrated crop-livestock effects on soil carbon sequestration in Benin, West Africa
No full textInternational audienceIn Benin, adaptation to climate change in the livestock sector has led cattle farmers to develop different livestock practices. Most research has focused on evaluating the effects of these practices on livestock productivity. However, information on the effect of these practices on carbon (C) sequestration in farmland soils is lacking. Soil C sequestration has been identified as a potential strategy to offset greenhouse gas emissions. Thus, the present study aimed at filling this gap. The calculation was one hand based on inventory data obtained from literature sources (excrement production of each cattle category, moisture content of each crop, ratio of crop residue to main product, and C content of the main product and excrement) and on the other hand on activity data (cattle herd size, manure applied, land use area, crop yield, and crop residues management) obtained from surveys carried out among 360 cattle farmers belonging to 3 cattle farming types. The results revealed that whatever the cattle farming type, annual C input from manure was higher (p˂0.05) than C input from crop residues. Annual C sequestration in farmland soil of farms integrating livestock with cereal-legume and forage crops was significantly higher (Type 2: 158.07 ± 1.79 kg C ha−1 year−1) followed by farms integrating livestock with cereal-legume crops (Type 1: 99.51 ± 0.95 kg C ha−1 year−1), which in turn had a higher value than farms practicing pastoral mobility (Type 3: 78.46 ± 0.70 kg C ha−1 year−1). These results highlight the potential for climate change mitigation through these farming practices. This is justified because the quantity of C sequestered in farmland soil of all cattle farming types was significant. Thus, for future research, it is necessary to include soil C sequestration in the calculations of farms' carbon footprint
Comment faire sortir l’insecte stérile du laboratoire ?: Agencements sociotechniques pour l’émergence d’une alternative aux pesticides : le cas de la technique de l’insecte stérile (TIS)
No full textInternational audienceThe Sterile Insect Technique (SIT) is a promising alternative to reduce the need for insecticides against mosquitoes and agricultural pests. However, its implementation in France is difficult because the existing sociotechnical system is not yet compatible with this innovation. The use of SIT would imply rethinking and building a new pest management paradigm. This article studies the different organizations between humans and non-humans that characterize the stages of development of SIT inside and outside of the laboratories, from the birth of the insects to their possible commercialization. This article shows that the implementation of SIT requires a stabilized organization between actants such as sterile insects, scientists, farmers and residents, public actors, wild insects, and firms. As there is not yet such organization, SIT is developed by scientists trying to guess the needs and expectations of future users: these anticipations highly influence the sociotechnical choices made by researchers inside and outside the laboratories.La technique de l’insecte stérile est une alternative prometteuse pour s’affranchir des pesticides en agriculture. Cependant, malgré ses promesses, elle peine à se développer car elle implique de repenser et de construire un nouveau monde sociotechnique. Cet article étudie les différents agencements entre humains et non-humains qui caractérisent chaque étape du développement de la TIS, de la naissance de l’insecte à sa potentielle commercialisation, en passant par sa stérilisation et son lâcher dans le monde réel. Nos résultats montrent que le développement de la TIS nécessite des agencements entre divers actants : insectes stériles, chercheurs, agriculteurs ou riverains, acteurs publics, insectes sauvages, industriels. Nous constatons que dans une situation où le lien entre ces actants n’est pas stabilisé, les agencements sociotechniques nécessaires sont imaginés par les chercheurs ; cette anticipation de leur part des attentes du monde non académique sur lequel ils veulent agir est très présente dans chaque choix du développement de la TIS
Development of a seed cryobank to preserve the citrus genetic resources of INRAE-Cirad germplasm: a complementary strategy to the tree field conservation
No full textInternational audienceIn genebanks, fruit trees are often maintained as grafted scions on rootstocks in field or greenhouse settings and are therefore exposed to various risks of decay. To guarantee a secure long-term conservation, cryopreservation in liquid nitrogen is currently developed for many plant species. The success of seed freezing depends on their ability to tolerate cold and desiccation. Citrus seeds are described as semiorthodox because they are partially tolerant to desiccation. Seeds of many citrus are polyembryonic and thus offer the possibility of clonal propagation by seedling. A seed cryopreservation program for polyembryonic cultivars of the INRAE-Cirad citrus collection has been initiated. We present here the protocol and the adaptations for cultivars sensitive to desiccation. The control of the water content of the seeds is ensured by incubation in atmospheres with controlled relative humidity to eliminate intracellular free water lethal to the cells during freezing. The temperature and duration of incubation during this desiccation step are factors that have a role in maintaining germination capacity. Genetics also has a strong influence on the success of cryopreservation operations. Citrus related to citron (Citrus medica) such as lemons and limes are much more tolerant of low water content than cultivars related to mandarin (C. reticulata) such as sweet and sour oranges. Seeds of Fortunella and Poncirus trifoliata and some of their hybrids are unsuitable for cryopreservation because they are too sensitive to moisture content decrease. Apex cryopreservation could be an alternative for these non-orthodox citrus trees. However, regeneration by sowing of frozen seeds is simpler than regeneration of apexes that need to be micrografted to develop a plant. Although improvements to the protocol are still needed to increase germination rates of some varieties, we estimate that we are able to cryopreserve in seed form about half of the citrus collection (~500 accessions)
The essential oils in citrus taxonomy: strengths and limitations of chemotaxonomy versus genetic phylogeny
No full textInternational audienceCitrus taxonomy is confusing with several discordant classification systems. It results from the reticulate evolution of the cultivated citrus combining speciation process during allopatric evolution and further interspecific hybridizations at the origin of most citrus cultivars with interspecific mosaic genomes fixed by apomixis. This citrus evolution generated a lot of chemical and phenotypic diversity. The citrus essential oils are complex mixture of hundred aromatic compounds. The taxa specific compounds are rare and sometimes misleading in determining the taxonomic position of a citrus fruit. It is preferable to consider for classification the proportion of major compounds rather than the absence or presence of minor compounds. For example, the approximate proportions of limonene (35%), geranial (20%) and neral (15%) characterize the peel essential oil (PEO) of C. medica. The profile of myrcene (30%) and neryl acetate (25%) is specific to the leaf essential oil of P. trifoliata. Nevertheless chemotaxonomy has limitations in terms of effectiveness that can be verified by the presence of compounds in the genealogies that are absent in the parents’ essential oils. Sometimes some compounds are shared by two citrus taxa without any phylogenetic relationship between them. This is the case of β-pinene present in high proportion in C. halimii PEO as in C. maxima cultivars while the genetic markers concluded to a phylogenic relation with Fortunella species. The use of genetic markers and more specifically those that can detect the ancestral species (SNP diagnostic) is much more efficient than the comparison of secondary metabolites to resolve the taxonomic misunderstanding and the classification of unknown citrus hybrids. The main difficulty in citrus classification lies in the representativeness of a species to define the specificity of an aromatic compound or even of a diagnostic genetic marker
Improving student diet and food security in higher education using participatory and co-creation approaches: a systematic review
No full textInternational audienceBackground: Higher education students are an important target group for public health nutrition interventions. When designing tailored and contextually relevant interventions, participatory and co-creation approaches are increasingly recognized as promising but their use and effectiveness has not been assessed in this type of population. We systematically reviewed interventions aiming to improve dietary quality and/or food security in higher education settings with the aims 1) to identify and describe their participatory and co-creation approaches and 2) to compare the effectiveness of interventions using or not using participatory and co-creation approaches. Methods: Our search in PubMed, Google Scholar, Web of Science, EMBASE was performed in January 2023 and yielded 3658 unique records, out of which 42 articles (66 interventions) were included. Effectiveness of interventions was assessed at the individual level (longitudinal evaluations) or at the group level (repeated cross-sectional evaluations). A five-level classification was used to describe a continuum of engagement from students and other partners in the intervention design and implementation: no participation (level one), consultation, co-production, co-design and co-creation (levels two to five). To synthetize effectiveness, comparisons were made between studies without participation (level one) or with participation (levels two-five). Results: Ten (24%) out of 42 studies used a participatory and co-creation approach (levels two-five). Studies using a participatory and co-creation approach reported a positive finding on individual-level outcome (i.e. overall diet quality or food group intake or food security) in 5/13 (38%) intervention arms ( vs 13/31 or 42% for those without participation). Studies using a participatory and co-creation approach reported a positive finding on group-level outcomes (i.e. food choices in campus food outlets) in 4/7 (57%) ( vs 8/23 or 35% in those without participation). Conclusions: Participatory and co-creation approaches may improve the effectiveness of nutrition interventions in higher education settings but the level of evidence remains very limited. More research is warranted to identify best co-creation practices when designing, implementing and evaluating nutritional interventions in the higher education setting