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Par la qualité de leur bois et leurs nombreux usages traditionnels, les espèces du genre Entandrophragma font l’objet d’une intense exploitation, susceptible de compromettre leur pérennité en l’absence de gestion durable. La présente étude dresse un état de la situation de cinq espèces commerciales principales de ce genre : Entandrophragma angolense, E. congoense (souvent assimilée par erreur à E. angolense), E. candollei, E. cylindricum et E. utile. Elle propose des pistes de recherche pour améliorer les stratégies de gestion durable au sein de ce genre. L’étude est principalement basée sur les données scientifiques (publications), économiques (statistiques de production et d’exportation) et juridiques (lois et réglementations), mais aussi sur les plans d’aménagement et les rapports d’inventaire. Les connaissances sur leur gestion sont encore fragmentaires alors qu’elles sont considérées comme vulnérables dans la liste rouge de l’UICN. La forte exploitation industrielle ou artisanale de ces espèces ne s’effectue pas toujours dans le respect d’un plan d’aménagement validé, ni de la durée minimum des rotations qui permettraient l’un et l’autre un taux de reconstitution pérennisant cette ressource. Leur gestion durable exige notamment le développement et le respect de mesures d’aménagement pour rendre leur exploitation renouvelable à long terme. Cette exploitation doit s’appuyer sur une gestion adéquate des peuplements naturels et sur le reboisement ainsi que sur des mesures de conservation. Les recherches à développer doivent intéresser leur vitesse de croissance face aux évolutions climatiques, l’évaluation de leurs stocks (production, biomasse, carbone), l’actualisation de leur distribution spatiale, l’amélioration de leur régénération naturelle, les processus de leur reproduction, leurs propriétés anatomiques et technologiques, autant de pistes pertinentes pour garantir la pérennité des espèces exploitables du genre Entandrophragma. 

Reducing emissions from deforestation and forest degradation (REDD+) is primarily a market-based mechanism for achieving the effective reduction of carbon emissions from forests. Increasingly, however, concerns are being raised about the implications of REDD+ for equity, including the importance of equity for achieving effective carbon emission reductions from forests. Equity is a multifaceted concept that is understood differently by different actors and at different scales, and public discourse helps determine which equity concerns reach the national policy agenda. Results from a comparative media analysis of REDD+ public discourse in four countries show that policy makers focus more on international than national equity concerns, and that they neglect both the need for increased participation in decision making and recognition of local and indigenous rights. To move from addressing the symptoms to addressing the causes of inequality in REDD+, policy actors need to address issues related to contextual equity, that is, the social and political root causes of inequality.

Life Cycle Assessment (LCA) provides a rigorous framework to assess a product against a range of environmental impact categories from the ‘cradle to the grave’. LCA sets out a clear method for analysis, including goal and scope definition, Life Cycle Inventory (LCI) development, Life Cycle Impact Assessment (LCIA) and interpretation. This article provides an overview of each of these LCA phases, with a specific focus on food and agriculture. We provide a summary of LCAs applied to food and agriculture, as well as insights into LCA’s function in providing a more food secure future.

The impact of agricultural practices on CO2 emissions from soils needs to be understood and quantified to enhance ecosystem functions, especially the ability of soils to sequester atmospheric carbon (C), while enhancing food and biomass production. The objective of this study was to assess CO2 emissions in the soil surface following tillage abandonment and to investigate some of the underlying soil physical, chemical and biological controls. Maize (Zea mays) was planted under conventional tillage (T) and no-tillage (NT), both without crop residues under smallholder farming conditions in Potshini, South Africa. Intact top-soil (0–0.05 m) core samples (N = 54) from three 5 × 15 m2 plots per treatment were collected two years after conversion of T to NT to evaluate the short-term CO2 emissions. Depending on the treatment, cores were left intact, compacted by 5 and 10 or had surface crusts removed. They were incubated for 20 days with measurements of CO2 fluxes twice a day during the first three days and once a day thereafter. Soil organic C (SOC) content, soil bulk density (ρb), aggregate stability, soil organic matter quality, and microbial biomass and its activity were evaluated at the onset of the incubation. CO2 emissions were 22% lower under NT compared with T with CO2 emissions of 0.9 ± 0.10 vs 1.1 ± 0.10 mg C–CO2 gC−1 day−1 under NT and T, respectively, suggesting greater SOC protection under NT. However, there were greater total CO2 emissions per unit of surface by 9% under NT compared to T (1.15 ± 0.03 vs 1.05 ± 0.04 g C–CO2 m−2 day−1). SOC protection significantly increased with the increase in soil bulk density (r = 0.89) and aggregate stability (from 1.7 ± 0.25 mm to 2.3 ± 0.31, r = 0.50), and to the decrease in microbial biomass and its activity (r = −0.59 and −0.57, respectively). In contrast, the greater NT CO2 emissions per m2 were explained by top-soil enrichment in SOC by 48% (from 12.4 ± 0.2 to 19.1 ± 0.4 g kg−1, r = 0.59). These results on the soil controls of tillage impact on CO2 emissions are expected to inform on the required shifts in agricultural practices for enhancing C sequestration in soils. In the context of the study, any mechanism favoring aggregate stability and promoting SOC allocation deep in the soil profile rather than in the top-soil would greatly diminish soil CO2 outputs and thus stimulate C sequestration.

AbstractGeoengineering has been proposed to stabilize global temperature, but its impacts on crop production and stability are not fully understood. A few case studies suggest that certain crops are likely to benefit from solar dimming geoengineering, yet we show that geoengineering is projected to have detrimental effects for groundnut. Using an ensemble of crop‐climate model simulations, we illustrate that groundnut yields in India undergo a statistically significant decrease of up to 20% as a result of solar dimming geoengineering relative to RCP4.5. It is somewhat reassuring, however, to find that after a sustained period of 50 years of geoengineering crop yields return to the nongeoengineered values within a few years once the intervention is ceased.

Abstract Due to the rise in anthropogenic greenhouse gas concentrations, the earth's climate is expected to change, with precipitation being reduced in some areas resulting in growth-limiting drought and, as a consequence, reduced plant productivity. We investigated the physiological and growth responses of cassava (Manihot esculenta Crantz) to approximate present-day ambient (390 μL L−1) and elevated (750 μL L−1) atmospheric CO2 concentrations under well-watered and water deficit conditions, aiming at understanding how cassava would face those problems. Water deficits led to reductions in the Leaf Elongation Rate of plants grown at ambient as well as CO2-enriched concentrations. However, plants grown at 750 μL L−1 of CO2 maintained leaf growth two days longer than plants grown at 390 μL L−1. Three Days After Withholding Water (DAWW), photosynthesis and stomatal conductance were reduced in plants grown under ambient CO2, while in plants under an elevated CO2 concentration, these physiological functions remained similar to that of control plants grown under good water availability. Five DAWW plants grown with 750 μL L−1 continued to have enhanced gas exchange compared with plants grown under 390 μL L−1. Under drought stress, the instantaneous transpiration efficiency was always greatest for plants grown under elevated CO2. The positive response of elevated CO2 levels on total dry mass was 61% in the water-stressed plants and only 20% for the plants grown under good water availability. Stomatal limitation was an important factor reducing CO2 assimilation in cassava growing under drought conditions.