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Explorer l&8217;impact environnemental des transformations agraires en Asie du Sud-Est grâce à l&8217;évaluation participative des services écosystémiques
No full textDifferent intervention mechanisms are proposed to transform agricultural landscapes so that they fulfill multiple functions, compatible with sustainable development goals. In the case of climate change mitigation and adaptation, support policies and direct payments to affected populations are promoted as part of REDD+ initiatives. These interventions attempt to balance the provision of multiple ecosystem services with the maintenance or improvement of local livelihoods. In this paper, we explore the role that participatory evaluation can play in the implementation of payments for ecosystem services in rural communities in Indonesia, Laos, Vietnam and China. Engaged in a process of rapid integration into the market economy, these communities have been transforming their traditional Slash-and-burn systems in recent years and followed different paths of agricultural intensification. The positive or negative assessment of these developments is necessarily subject to value judgements in the choices made between different options. Ecosystem services allow for the comparison of landscape trajectories. Village communities explored scenarios for the evolution of their local agriculture, negotiated trade-offs between ecosystem services and identified potential "winners" and "losers". These simulations showed the importance of the timing of REDD+ programs in relation to ongoing agrarian transformations. They point to the risk of moving away from the initial ambitions related to the carbon ecosystem service to become an additional instrument for sustainable development
Coastal upwelling limitation by onshore geostrophic flow in the Gulf of Guinea around the Niger River plume
No full textWind-driven coastal upwelling can be compensated by onshore geostrophic flow, and river plumes are associated with such flow. We investigate possible limitation of the northeast Gulf of Guinea upwelling by the Niger River plume, using regional ocean model simulations with or without river and dynamical upwelling indices. Here, the upwelling is weakened by 50% due to an onshore geostrophic flow equally controlled by alongshore thermosteric and halosteric sea-level changes. The river contributes to only 20% of this flow, as its plume is shallow while upwelling affects coastal temperature and salinity over a larger depth. Moreover, the river-induced mixed-layer thinning compensates the current increase, with no net effect on upwelling. The geostrophic compensation is due to an abrupt change in coastline orientation that creates the upwelling cross-shore front. The river nonetheless warms the upwelling tongue by 1 degrees C, probably due to induced changes in horizontal advection and/or stratification
A systematic revision of the five-spotted Hemichromis complex (Cichliformes : Cichlidae) from West Africa and Lower Guinea, with the description of a new species from Cameroon
No full textThe group of large five-spotted Hemichromis species from West Africa and Lower Guinea was revised using an integrative approach combining morphometry (measurements, meristics and colour patterns) and genetics (cytochrome b gene). Specimens from 100 populations were sorted into three main groups on the basis of morphological criteria. Samples from Lake Bosumtwi clustered together with others from West Africa in a large well-supported clade (bootstrap values and posterior probabilities: 98/96/100), both in morphometric and genetic analyses, raising again the hypothesis of synonymy of H. frempongi with H. fasciatus. Samples from southern Lower Guinea, including the type locality (Gabon) of H. elongatus, constituted a second weakly resolved cluster (64/38/51), resulting from a potential admixture of populations of diverse origins which share common morphological traits. Populations from northern Lower Guinea (Atlantic coastal basins) and the upper Chad basin in Cameroon formed a third strongly supported clade (99/100/100), which corresponds to a new species, Hemichromis camerounensis sp. nov., herein described
La politique de mise en valeur des terres arides en Algérie : une lecture en termes d'equite
No full textLes politiques foncieres redistributives suscitent souvent des debats controverses quant a leur equite. La politique de mise en valeur agricole, en cours en Algerie depuis 1983, a donne un nouveau souffle a l'agriculture algerienne et a considerablement elargi les perspectives de developpement pour des milliers d'acteurs dans les zones arides du pays. En deverrouillant simultanement l'acces a la terre et a l'eau souterraine publiques, l'Etat joue un role d'allocation, ou dans certains cas de reallocation, des ressources productives. Un reel engouement pour le foncier est observe dans beaucoup de ces zones; l'acces au foncier public est aujourd'hui l'objet d'enjeux economiques importants. Une etude aupres de differents acteurs impliques dans cette politique (agriculteurs beneficiaires et non beneficiaires de terre, cadres du ministere de l'Agriculture, cadres des structures deconcentrees des administrations publiques concernees, elus locaux), ciblee sur la > mise en valeur, montre comment la question de l'equite de l'allocation des terres publiques dans le cadre de la politique de mise en valeur, est diversement appreciee. Les acteurs locaux, notamment les ayants droit historiques sur les terres objet de mise en valeur, sont les plus sensibles a la question de l'equite, qu'ils apprecient a l'aune de la preservation ou de la perte de leurs droits herites sur la terre. Les cadres du ministere de l'Agriculture mettent davantage en exergue la question de la reussite de la mise en valeur et considerent qu'il est plus juste d'attribuer la terre a ceux qui peuvent effectivement la mettre en valeur. Redistributive land policies often generate controversial debates about their fairness. The land development policy, ongoing in Algeria since 1983, has given a new push to Algerian agriculture and has considerably widened the development prospects for thousands of actors in the arid zones of the country. By simultaneously unlocking access to public land and groundwater, the State plays a role in allocating, or in some cases reallocating, productive resources. A real land rush is observed in many of these areas, and access to public land is today the subject of important economic stakes. A study of the different types of actors involved in this policy (beneficiaries and non-beneficiaries of land, executives from the Ministry of Agriculture, executives from the deconcentrated structures of the public administrations concerned, local elected representatives), focusing on small-scale land development schemes, shows how, in this context, the fairness of such allocation of public land is perceived. Local actors, particularly those with historical rights to the land being developed, are most sensitive to the issue of equity, which they value in terms of preservation or loss of their inherited land rights. Executives from the Ministry of Agriculture put more emphasis on the success of land development programs and consider it fairer to allocate land to those who can actually develop it
Quantifying the shelter capacity of coral reefs using photogrammetric 3D modeling : from colonies to reefscapes
No full textStructural complexity plays a key role in the functioning of coral reef ecosystems. Reef-building corals are major contributors to this complexity, providing shelter and food for numerous invertebrates and fish species. Both structural complexity and shelter capacity of reefscapes are determined by several components such as spurs and grooves, slope, caves and holes, vegetation and coral colonies. Quantifying the shelter capacity from coral colonies to reefscapes is a fundamental step to estimating ecosystem potential to support biodiversity. Here, we applied underwater photogrammetry to quantify shelter volumes provided by individual coral colonies. Overall, 120 3D models of coral colonies from branching, massive, columnar and tabular growth forms were studied. Three reefscapes were also 3D modeled. The study encompasses three Indo-Pacific Islands: Reunion, Europa and New Caledonia. At the colony level, measurements of diameter, planar area, surface and shelter volume were computed. At the reefscape, the diameter and planar area of each colony were extracted from orthomosaics and then used to estimate shelter capacity. Linear models had high accuracy for predicting shelter volume (a 3D metric) from 2D metrics: the diameter= 83.1%, R-2 = 0.95; the planar area= 87.5%, R-2 = 0.95 and the colony surface= 87.3%, R-2 = 0.96. The surface complexity and the shelter volume of the colonies allowed inferring the size of shelters provided by coral growth forms. Quantitative descriptors (i.e. relative percentage of shelter by growth form, the abundance of coral colonies, "Shannon-Shelter Index") revealed reefscape-scale shelter differences. Our major finding is that planar area and diameter of coral colonies are satisfactory proxies for estimating shelter volume. These new proxies allow 2D metrics to quantify 3D shelter provision, which can support scientists and managers in conservation actions since such metrics are widely used in monitoring programs. Future investigations on the relationships between shelter provision and reef biodiversity will improve the understanding of these complex ecosystems
Eastern Atlantic deep-water circulation and carbon storage inferred from neodymium and carbon isotopic compositions over the past 1.1 million years
No full textThe Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, kyr) is marked by the shift from 41-kyr to 100-kyr interglacial-glacial cyclicity without substantial change in the astronomical forcing. This change in climate response relied on internal feedback processes including interaction between ice sheet/sea ice, ocean circulation and the carbon cycle. It was suggested that a major perturbation of global oceanic carbon chemistry occurred at around 900 ka (Marine Isotope Stage, MIS, 24-22) although the mechanism responsible for the change is still to be elucidated. To investigate the link between the Atlantic Meridional Overturning Circulation (AMOC) and oceanic carbon storage for the past 1100 kyr, we combined neodymium isotopic composition (Nd-143/Nd-144 or epsilon(Nd)) recorded in foraminiferal authigenic fractions with epibenthic foraminiferal delta C-13 and delta O-13 from two cores in the North- and South-east Atlantic Ocean. Glacial/interglacial eNd amplitude is smaller before the 900-ka event than after the event. The 900-ka event is marked by increase in seawater epsilon(Nd) at both sites. These observations are consistent with previous studies, suggesting basin-wide epsilon(Nd) changes. Combined with existing data, these new results reveal a persistent meridional gradient of seawater epsilon(Nd) in the Atlantic Ocean over the past 1100 kyr. By comparing the reconstructions with numerical modelling results, we propose that weaker AMOC and changes in Nd sources to the North Atlantic were the main reasons for the observed eNd shift at the 900-ka event in relation to the evolution of the Northern hemisphere cryosphere. The influence of enhanced Southern Ocean overturning circulation on eNd values was estimated to be minor. Seawater epsilon(Nd) and benthic delta C-13 relationship for the whole study period indicates the presence of carbon-rich glacial deep water (>3000 m) in the North and the South Atlantic, in particular at MIS 22 and 24. This suggests that, in addition to weaker AMOC, reduction of deep-water ventilation and/or air-sea exchange in the Southern Ocean could have been responsible for the observed low benthic delta C-13 values. Together with increased biological productivity due to iron fertilization in the Southern Ocean, the physical process significantly contributed to the deep Atlantic carbon storage during the 900-ka event and the subsequent glacial periods
Dire wolves were the last of an ancient New World canid lineage
No full textDire wolves are considered to be one of the most common and widespread large carnivores in Pleistocene America(1), yet relatively little is known about their evolution or extinction. Here, to reconstruct the evolutionary history of dire wolves, we sequenced five genomes from sub-fossil remains dating from 13,000 to more than 50,000 years ago. Our results indicate that although they were similar morphologically to the extant grey wolf, dire wolves were a highly divergent lineage that split from living canids around 5.7 million years ago. In contrast to numerous examples of hybridization across Canidae(2,3), there is no evidence for gene flow between dire wolves and either North American grey wolves or coyotes. This suggests that dire wolves evolved in isolation from the Pleistocene ancestors of these species. Our results also support an early New World origin of dire wolves, while the ancestors of grey wolves, coyotes and dholes evolved in Eurasia and colonized North America only relatively recently. Dire wolves split from living canids around 5.7 million years ago and originated in the New World isolated from the ancestors of grey wolves and coyotes, which evolved in Eurasia and colonized North America only relatively recently
How the fishing effort control and environmental changes affect the sustainability of a tropical shrimp small scale fishery
No full textGlobal shrimp catches are reported primarily in association with large industrial trawling, but they also occur through small-scale fishing, which plays a substantial role in traditional communities. We developed an Ecopath model in north-eastern Brazil, and applied a temporally dynamic model (Ecosim) to evaluate the potential effects of different fishing effort control policies and environmental changes on marine resources and ecosystem between 2015 to 2030 with a case study for small-scale shrimp fishing, novelty for tropical region. These scenarios included different management options related to fishing controls (changing effort and closed season) and environmental changes (primary production changes). Our findings indicate that it is possible to maintain the same level of landings with a controlled reduction of bottom trawlers activities, for example, close to 10 %, without compromising the ecosystem structure. This scenario provided better results than 3-4 months of closing the fishing season, which led to significant losses in catches of high market-value target species (white shrimp, Penaeus schmitti and pink shrimp, Penaeus subtilis). However, intense negative effects on biomass, catch and biodiversity indicators were reported in scenarios with decreasing primary production, from 2 %, reinforcing the need to simulate and project the possible impacts caused by environmental change. However, the control of bottom trawling activity may help to reduce, even at low levels, the highly adverse effects due to primary production reduction. The impacts of climate change in a near future on organisms and ecosystems is an imminent reality, and therefore the search for measures for mitigating and even minimizing these impacts is crucial
To what extent do ageing and soil properties influence Amynthas khami cast properties ? Evidence from a small watershed in northern Vietnam
No full textUnderstanding the variables explaining earthworm cast properties remains a key challenge in soil ecology. this purpose, this study aimed to determine the relationships between the physical and chemical properties earthworm casts and those of their surrounding soil environment. Surface earthworm casts (recently emitted degraded) produced by the anecic earthworm Amynthas khami (Thai 1984) and adjacent topsoil aggregates without traces of earthworm activity were sampled in 50 different locations covering a small watershed northern Vietnam. We determined the organic carbon content, the spectral signatures of aggregates and humic index of organic matter via mid-infrared spectroscopy and analysis of pH, hydrophobicity, wet aggregate stability and bulk density of soil aggregates. While the physical properties of casts were not related to those of topsoil aggregates, correlations were measured between cast and topsoil aggregate chemical properties. The values of hydrophobicity, pH, bulk density and organic carbon were higher in casts than in topsoil aggregates, whereas the humic index values were lower in casts than in topsoil aggregates. No difference was measured between recent and degraded casts, with the exception of their spectral signatures. Interestingly, the effect of A. khami was more important in soils presenting a lower organic carbon content or higher humic index, whereas its influence on soil pH was constant (i.e., the same regardless of the pH of the topsoil). In conclusion, this study suggests a discrepancy between impact of A. khami on soil physical and chemical properties. The results also show that the spatial variability cast physical properties cannot be related with that of topsoil environment physical properties
Performance of the HYDRUS-1D model for water balance components assessment of irrigated winter wheat under different water managements in semi-arid region of Morocco
No full textThe main goal of this research was to evaluate the potential of the HYDRUS-1D numerical model for estimating the soil moisture (theta) at different depths, actual crop evapotranspiration (ETa) and its components (crop transpiration, Ta and soil evaporation, Ea) as well as the deep percolation (DP) of irrigated winter wheat under different water managements in the semi-arid region of Tensift-basin (central Morocco). The HYDRUS-1D simulations were performed at daily time step during the two growing seasons: 2002/2003 and 2015/2016. The model was firstly calibrated based on one field "denoted F1" data during the 2002/2003 cropping season by using the Levenberg-Marquardt method implemented in HYDRUS-1D model for optimizing various parameters of Van Genuchten equation that provide the minimum difference between measured and simulated soil moisture at four layers of soil (0-5, 5-10, 10-20, 20-30, 30-50 cm). Afterwards, the model validation was done based on the data from four fields of wheat: two fields "denoted F2 and F3" during the 2002/2003 and two other fields "denoted F4 and F5" during the 2015/2016 cropping season. All fields were irrigated with flooding system except the field F5 where drip irrigation was undertaken. In-situ measurements of theta was carried out using Time Domain Reflectometry (TDR) and gravimetric method ETa was measured by the Eddy Covariance system Ta and Ea were monitored using a lysimeter in F5 field. The results showed that the HYDRUS-1D model simulates the theta, ETa, Ta and Ea reasonably well. Additionally, the evaluation of the irrigation system on DP losses was investigated by comparing the simulation results over flood (F4) and drip (F5) irrigated fields. It was found that about 56% and 20% of seasonal supplied water were lost by DP in F4 and F5 sites, respectively. Such unexpected high amount of DP taking place in F5 field is due to the improper use of the drip irrigation system