Les articles de Gaëtan Lefebvre

A multi-sensor approach to monitor the ongoing restoration of edaphic conditions for salt marsh species facing sea level rise: An adaptive management case study in Camargue, France

Mon, 13 Nov 2023 17:02:48

de Aurélie Davranche, Céline Arzel, Pierre Pouzet, A. Rita Carrasco, Gaëtan Lefebvre, Dimitri Lague, Marc Thibault, Alice Newton, Cyril Fleurant, Mohamed Maanan, et al.
In Science of The Total Environment, 908 (January, 2024), 168289
En ligne : hal.science[...]

The Camargue or Rhône delta is a coastal wetland in southern France of which parts formerly devoted to salt production are undergoing a renaturation process. This study assessed a multisensor approach to investigate the link between sediment size distribution, habitat development mapped with Worldview 2, flooding durations estimated with time series of SENTINEL 2 images and elevation modelled with a LIDAR point cloud in former saltworks. A Random Forest classification algorithm was used to map the vegetation distributions of Sarcocornia fruticosa and Arthrocnemum macrostachyum, main representatives of the NATURA 2000 “Mediterranean and thermo-Atlantic halophilous scrubs (Sarcocornetea fruticosi)” habitat on the site. The best habitat map was obtained when considering the species separately. The random forest Out-of-bag errors were 1.43 % for S. fruticosa and 2.18 % for A. macrostachyum. Both species were generally distributed on different elevation and flooding duration zones considering mean values. Flooding duration was estimated with the Water In Wetland index (WIW) based on 15 Sentinel-2 scenes. Two models related to sediment grain size distribution were developed: one predicting the flooding duration and one predicting the halophilous scrub distribution. Maps of flooding duration, sediment grain size distribution and elevation highlighted two main zones in the study area: a western section with coarser sediments, shorter flooding durations and higher elevations under sea influence; an eastern section with finer sediments, longer hydroperiods and lower elevations under a historic river influence. This multidisciplinary approach offers perspectives for using space-based data over large scales to monitor changes in edaphic conditions of coastal areas facing natural and anthropogenic forcings. The results call for further investigations to predict the dynamic distribution of other coastal habitats following climate change impacts, such as sea level rise.

Long-term persistence and recycling of Bacillus thuringiensis israelensis spores in wetlands sprayed for mosquito control

Thu, 1 Sep 2022 16:58:24

de Brigitte Poulin, Gaëtan Lefebvre, Samuel Hilaire, Laurence Després
In Ecotoxicology and Environmental Safety, 243 (September, 2022), 10
En ligne : linkinghub.elsevier.com[...]

Bacillus thuringiensis subsp. israelensis (Bti) is the main larvicide used to control mosquitoes worldwide. Although there is accumulating evidence of Bti having environmental effects on non-target fauna, relatively few field studies have documented the fate of Bti spores in the environment. Spore density was quantified over a 6-yr period (2012–2017) in Mediterranean marshes sprayed with Vectobac 12AS (32 ITU/ha) since 2006 to reduce the nuisance caused by Aedes caspius. Bti spores were naturally found in all habitat types. Spore density expressed as colony-forming units per gram of soil (CFU g− 1) increased significantly at treated sites by a factor of 22 to 500 times relative to control sites, with mean values of 7730 CFU g− 1 in halophilous scrubs, 38,000 in reed beds, 49,000 in bulrush beds and 50 000 in rush beds. Spore density varied little in the first months after the spraying season (April-October), but increased sharply in spring, just before the annual launch of mosquito control. Considering that Bti is an insect pathogen that cannot proliferate without a suitable insect host, this unexpected recrudescence in spring could be related to the warming of water that triggers activity and development of benthic organisms such as chironomids, which may contribute to Bti proliferation by ingesting accumulated spores at the surface of sediments. While spore density tends to decrease over time, presumably during the summer period as a result of increased UV exposure, three to four years were necessary for spore density to return to normal levels after mosquito-control interruption. This study is important because it demonstrates that environmental effects of mosquito-control using Bti can far exceed the short period of Bti efficacy against lentic mosquitoes. Considering that Bti is a microbial agent, these long-term effects should be addressed at multiple levels of ecosystem organization from a one-health perspective.

Different components of landscape complexity are necessary to preserve multiple taxonomic groups in intensively-managed rice paddy landscapes (2022)

Mon, 17 Jan 2022 10:02:41

de Pierre Mallet, Arnaud Béchet, Thomas Galewski, François Mesléard, Samuel Hilaire, Gaëtan Lefebvre, Brigitte Poulin, Clelia Sirami
2022, 8
En ligne : www.sciencedirect.com[...]

Increase in pesticide use and landscape homogenization are two key drivers of the decline in farmland biodiversity. The effects of these two drivers are often complex, interactive and vary among taxonomic groups. Our study tested the hypothesis that pesticide use influences the effect of different components of landscape complexity on different taxonomic groups. We sampled 32 rice paddy landscapes of 1 * 1 km in the Camargue (south of France), a wetland internationally recognized as an exceptional biodiversity hotspot. We assessed the abundance and diversity of 7 taxa (plants, bees, butterflies, hoverflies, carabids, spiders and birds) in 3 or 4 crop fields per landscape. For each landscape, we measured the length of different field margins (ditch, grass strip, hedgerow), the proportion of semi-natural areas and crop diversity. For each field, we measured management intensity by the treatment frequency index (TFI) of pesticides. We then tested our hypothesis across 118 fields. Our results show that different components of landscape complexity influence different taxonomic groups: crop diversity and the length of ditches influence bee abundance and species richness, the proportion of semi-natural areas influence spider abundance and species richness, and the length of grass strips influences bird abundance. Moreover, we show that local pesticide use modulates these effects, with more positive effects of landscape complexity in intensively-managed fields. However, we found no interactive effect between landscape complexity and field management for plants, butterflies, hoverflies and carabids. Our study therefore suggests that different components of landscape complexity need to be maintained in order to preserve multiple taxonomic groups. Moreover, it suggests that increasing landscape complexity is particularly relevant to restore biodiversity in intensively-managed fields. Agricultural policies should therefore support the simultaneous increase in semi-natural areas, field margins length and crop diversity to conserve a wide range of taxonomic groups in intensively-managed rice paddy landscapes.

Impact of mosquito control operations on waterbirds in a Camargue nature reserve

Tue, 9 Nov 2021 09:20:12

de Brigitte Poulin, Claire Tetrel, Gaëtan Lefebvre
In Wetlands Ecology and Management, Online (October, 2021)
En ligne : rdcu.be[...]

The Domaine de la Palissade is a 700-ha nature reserve located at the mouth of the Rhône river in southern France. Since 2006, the tidal wetlands have been sprayed with Bacillus thuringiensis israelensis (Bti) and water level fluctuations minimized to reduce mosquito nuisance. Aerial spraying of VectoBac® 12AS (32 ITU/ha) is carried out 10 to 23 times a year, whenever Ochlerotatus caspius and Oc. detritus larvae develop, covering between 611 and 1937 cumulated hectares. Long-term trends (2000–2013) in monthly abundance of 50 bird species were compared with two nearby nature reserves that served as controls. A significant decrease in abundance of eight species (from 1958 to 941 monthly counts) was attributed to mosquito control operations and more specifically to: (1) aircraft disturbance caused by aerial spraying in a proportion of 36%, affecting mostly ducks; (2) stabilization of water levels in a proportion of 34%, affecting mostly grebes; and/or (3) reduced food resources caused by Bti effects in a proportion of 30%, affecting mostly waders. The European coot, affected negatively by all three factors, suffered the highest decline. Alternatively, the lower water levels and higher salinity resulting from the reduced exchanges with the Rhône River had a positive impact on five species, mostly gull and shorebirds (from 201 to 280 monthly observations). Overall, this study suggests a 23% significant decrease in waterbird abundance due to mosquito control, in spite of the collaboration between site managers and the operator of mosquito control to minimize negative effects on the non-target fauna.

Foreseen impact of climate change on temporary ponds located along a latitudinal gradient in Morocco

Mon, 27 Sep 2021 09:36:30

de Patrick Grillas, Laïla Rhazi, Gaëtan Lefebvre, Mohammed El Madihi, Brigitte Poulin
In Inland Waters, Online (Septembre, 2021), 1-16
En ligne : www.tandfonline.com[...]

Wetlands have been declining worldwide, with an estimated 64–71% loss over the last century. Climate change is increasing pressure on wetlands, aﬀecting their hydrology, and Mediterranean temporary ponds could be particularly vulnerable to these changes. We studied the expected changes in hydrology and plant community according to climatic change scenarios in 18 temporary ponds distributed in 6 areas along a latitudinal and climatic gradient in Morocco (750 km; 4° latitudinal gradient). Richness of pond species was signiﬁcantly correlated with water level and pond hydroperiod and showed a strong decline from north to south along with increased water stress. Using the Mar-O-Sel software (mar-o-sel.net), we simulated the future evolution of water balance and wetland hydroperiod (duration and frequency of ﬂooding) in these ponds for mid- and late-21st century. Climate projections were estimated based on 2 Representative Concentration Pathway (RCP) scenarios assuming a stabilization (RCP4.5) or increase (RCP8.5) in greenhouse gas emissions. The mean water deﬁcit of the ponds currently ranges between −1380 and −1812 mm/yr and would increase by 16–67% in 2100 under the RCP8.5 scenarios. Pond richness is expected to decrease by 8–15 species in 2100, depending on area, as a result of shorter projected hydroperiods. Severity of change was not related to location of the ponds along the latitudinal (aridity) gradient, but rather to the interaction between the size of their catchment area and the thickness of the permeable soil layer.

Predicting the vulnerability of seasonally-flooded wetlands to climate change across the Mediterranean Basin

Fri, 30 Aug 2019 17:01:54

de Gaëtan Lefebvre, Lauren Redmond, Christophe Germain, Elisa Palazzi, Silvia Terzago, Loic Willm, Brigitte Poulin
In Science of The Total Environment, 692 (November, 2019), 546-555
En ligne : www.sciencedirect.com[...]

Wetlands have been declining worldwide over the last century with climate change becoming an additional pressure, especially in regions already characterized by water deficit. This paper investigates how climate change will affect the values and functions of Mediterranean seasonally-flooded wetlands with emergent vegetation. We simulated the future evolution of water balance, wetland condition and water volumes necessary to maintain these ecosystems at mid- and late- 21st century, in 229 localities around the Mediterranean basin. We considered future projections of the relevant climatic variables under two Representative Concentration Pathway scenarios assuming a stabilization (RCP4.5) or increase (RCP 8.5) of greenhouse gases emissions. We found similar increases of water deficits at most localities around 2050 under both RCP scenarios. By 2100, however, water deficits under RCP 8.5 are expected to be more severe and will impact all localities. Simulations performed under current conditions show that 97% of localities could have wetland habitats in good state. By 2050, however, this proportion would decrease to 81% and 68% under the RCP 4.5 and RCP 8.5 scenarios, respectively, decreasing further to 52% and 27% by 2100. Our results suggest that wetlands can persist with up to a 400 mm decrease in annual precipitation. Such resilience to climate change is attributed to the semi-permanent character of wetlands (lower evaporation on dry ground) and their capacity to act as reservoir (higher precipitation expected in some countries during winter). Countries at highest risk of wetland degradation and loss are Algeria, Morocco, Portugal and Spain. Degradation of wetlands with emergent vegetation will negatively affect their biodiversity and the services they provide by eliminating animal refuges and primary resources for industry and tourism. A sound strategy to preserve these wetlands would consist of proactive management to reduce non-climate.
stressors. / Grâce à un partenariat avec l’institut des Sciences Atmosphériques et du Climat du Conseil National de la Recherche à Turin dans le cadre du projet H2020 Ecopotential, les projections météo pour les période 2050 et 2100 ont été estimées pour 229 localités autour de la Méditerranée et intégrées à mar-o-sel.net selon deux scénarios, l’un prévoyant une stabilisation des émissions de gaz à effet de serre (RCP4.5) et l’autre la poursuite de leur croissance actuelle (RCP8.5).
Des simulations ont permis de paramétrer des zones humides virtuelles pour chaque localité selon les conditions climatiques actuelles, puis en fonction des conditions climatiques de 2050 et 2100 selon les deux scénarios. Des valeurs seuils en termes de durée d’inondation et de sécheresse nécessaire au bon état des zones humides ont été définies pour que l’impact des changements climatiques puisse être visualiser en termes de dégradation ou transition d’écosystèmes.
Malgré un déficit hydrique accru sur l’ensemble de la Méditerranée en 2100 (de -239 mm ou -472 mm en moyenne selon les scénarios), certaines ZH pourront se maintenir en bon état grâce à leur caractère semi-permanent (évaporation moindre lorsque le sol est sec) et leur capacité de réservoir (précipitations accrues en hiver dans certains pays). Néanmoins, c’est seulement 68% (2050) et 27% (2100) des zones humides qui se maintiendront en bon état si les émissions de gaz à effet de serre poursuivent leur croissance actuelle. Le volume annuel moyen d’eau nécessaire pour préserver la biodiversité et les services rendus par ces écosystèmes variera d’un million (sites légèrement dégradés) à plus de 3,5 millions (sites en voie d’assèchement permanent) de litres d’eau par année et hectare. Les pays les plus à risque quant à la dégradation ou perte de zones humides sont l’Algérie, le Maroc, le Portugal et l’Espagne.

Automatic Inundation Mapping Using Sentinel-2 Data Applicable to Both Camargue and Doñana Biosphere Reserves

Thu, 8 Oct 2020 11:52:17

de Georgios A. Kordelas, Ioannis Manakos, Gaëtan Lefebvre, Brigitte Poulin
In Remote Sensing, 11(19) (Septembre, 2019), 2251
En ligne : www.mdpi.com[...]

Flooding periodicity is crucial for biomass production and ecosystem functions in wetland areas. Local monitoring networks may be enriched by spaceborne derived products with a temporal resolution of a few days. Unsupervised computer vision techniques are preferred, since human interference and the use of training data may be kept to a minimum. Recently, a novel automatic local thresholding unsupervised methodology for separating inundated areas from non-inundated ones led to successful results for the Doñana Biosphere Reserve. This study examines the applicability of this approach to Camarque Biosphere Reserve, and proposes alternatives to the original approach to enhance accuracy and applicability for both Camargue and Doñana wetlands in a scientific quest for methods that may serve accurately biomes at both protected areas. In particular, it examines alternative inputs for automatically estimating thresholds while applying various algorithms for estimating the splitting thresholds. Reference maps for Camargue are provided by local authorities, and generated using Sentinel-2 Band 8A (NIR) and Band 12 (SWIR-2). The alternative approaches examined led to high inundation mapping accuracy. In particular, for the Camargue study area and 39 different dates, the alternative approach with the highest overall Kappa coefficient is 0.84, while, for the Doñana Biosphere Reserve and Doñana marshland (a subset of Doñana Reserve) and 7 different dates, is 0.85 and 0.94, respectively. Moreover, there are alternative approaches with high overall Kappa for all areas, i.e., at 0.79 for Camargue, over 0.91 for Doñana marshland, and over 0.82 for Doñana Reserve. Additionally, this study identifies the alternative approaches that perform better when the study area is extensively covered by temporary flooded and emergent vegetation areas (i.e., Camargue Reserve and Doñana marshland) or when it contains a large percentage of dry areas (i.e., Doñana Reserve). The development of credible automatic thresholding techniques that can be applied to different wetlands could lead to a higher degree of automation for map production, while enhancing service utilization by non-trained personnel.

Introducing WIW for Detecting the Presence of Water in Wetlands with Landsat and Sentinel Satellites

Tue, 24 Sep 2019 11:36:54

de Gaëtan Lefebvre, Aurélie Davranche, Loic Willm, Julie Campagna, Lauren Redmond, Clément Merle, Anis Guelmami, Brigitte Poulin
In Remote Sensing, 11(19) (Septembre, 2019), 18
En ligne : www.mdpi.com[...]

Many wetlands are characterized by a vegetation cover of variable height and density over time. Tracking spatio-temporal changes in inundation patterns of these wetlands remains a challenge for remote sensing. Water In Wetlands (WIW) was predicted using a dichotomous partitioning of reflectance values encoded based on ground-truth (n = 4038) and optical-space derived (n = 7016) data covering all land cover types (n = 17) found in the Rhône delta, southern France. The models were developed with spectral data from Sentinel 2, Landsat 7, and Landsat 8 sensors, hence providing a monitoring tool that covers a 35-year period (same sensor for Landsat 5 and 7). A single model combining the near infrared (NIR ≤ 0.1558 to 0.1804, depending on sensors) and short-wave infrared (SWIR2 ≤ 0.0871 to 0.1131) wavelengths was identified by three independent analyses, each one using a different satellite. Overall accuracy of water maps ranged from 89% to 94% for the training samples and from 90% to 94% for the validation samples, encompassing standard water indices that systematically underestimate flooding duration under vegetation cover. Sentinel 2 provided the highest performance with a kappa coefficient of 0.82 for both samples. Such tool will be most useful for monitoring the water dynamics of seasonal wetlands, which are particularly sensitive to climate change while providing multiple services to humankind. Considering the high temporal resolution of Sentinel 2 (every 5 days), cumulative water maps built with the WIW logical rule could further be used for mapping a wide range of wetlands which are either periodically or permanently flooded.

Increasing crop heterogeneity enhances multitrophic diversity across agricultural regions

Fri, 30 Aug 2019 17:01:17

de Clelia Sirami, Nicolas Gross, Aliette Bosem Baillod, Colette Bertrand, Romain Carrié, Annika Hass, Laura Henckel, Paul Miguet, Carole Vuillot, Audrey Alignier, et al.
In Proceedings of the National Academy of Sciences, 116(33) (2019-08-13), 16442-16447
En ligne : www.pnas.org[...]

Agricultural landscape homogenization has detrimental effects on biodiversity and key ecosystem services. Increasing agricultural landscape heterogeneity by increasing seminatural cover can help to mitigate biodiversity loss. However, the amount of seminatural cover is generally low and difficult to increase in many intensively managed agricultural landscapes. We hypothesized that increasing the heterogeneity of the crop mosaic itself (hereafter “crop heterogeneity”) can also have positive effects on biodiversity. In 8 contrasting regions of Europe and North America, we selected 435 landscapes along independent gradients of crop diversity and mean field size. Within each landscape, we selected 3 sampling sites in 1, 2, or 3 crop types. We sampled 7 taxa (plants, bees, butterflies, hoverflies, carabids, spiders, and birds) and calculated a synthetic index of multitrophic diversity at the landscape level. Increasing crop heterogeneity was more beneficial for multitrophic diversity than increasing seminatural cover. For instance, the effect of decreasing mean field size from 5 to 2.8 ha was as strong as the effect of increasing seminatural cover from 0.5 to 11%. Decreasing mean field size benefited multitrophic diversity even in the absence of seminatural vegetation between fields. Increasing the number of crop types sampled had a positive effect on landscape-level multitrophic diversity. However, the effect of increasing crop diversity in the landscape surrounding fields sampled depended on the amount of seminatural cover. Our study provides large-scale, multitrophic, cross-regional evidence that increasing crop heterogeneity can be an effective way to increase biodiversity in agricultural landscapes without taking land out of agricultural production. / Cet article est issu du projet Farmland (2011-2015) financé par Biodiversa et réalisé sur 7 sites Européens dont la Camargue. Cette étude s’appuie sur deux saisons intensives de terrain pour échantillonner les plantes, insectes et oiseaux sur les parcelles agricoles. Ces données, combinées à une numérisation précise du paysage sur SIG, ont permis de démontrer qu’il était possible d’augmenter la biodiversité et les services qu’elle rend aux agriculteurs (pollinisation, contrôle des ravageurs) en diversifiant le nombre de cultures et en réduisant la taille des parcelles, sans nécessairement diminuer la surface agricole utile.

Perturbation and delayed recovery of the reed invertebrate assemblage in Camargue marshes sprayed with Bacillus thuringiensis israelensis

Thu, 16 Aug 2018 15:25:20

de Brigitte Poulin, Gaëtan Lefebvre
In Insect Science, 25(4) (2018/08/01), 542-548
En ligne : onlinelibrary.wiley.com[...]

Bacillus thuringiensis var. israelensis (Bti) is the most commonly used larvicide to control mosquitoes worldwide. Considered as nontoxic to most organisms, Bti can nevertheless cause trophic perturbations to natural communities by reducing the abundance of Chironomidae, which are a key element of wetland food webs. Since August 2006, up to 8400 of the 33 000 ha of mosquito larval biotopes in the Camargue (Rhône delta, in southern France), are monitored by a public agency and Bti‐sprayed (aqueous solution of VectoBac 12AS at 2.5 L/ha) whenever mosquito larvae (Ochlerotatus caspius and Oc. detritus) appeared in water bodies. This resulted in 30–50 aerial treatments/year, in addition to ground spraying of unknown frequency. The sprayed habitats include Phragmites australis reedbeds, which support a specific avifauna of conservation concern. We compared the abundance of invertebrate prey available to passerine birds at treated and control sites relative to the predicted values based on hydrology over a 9‐year period. Food available to reed passerines was significantly reduced at treated areas, translating into a 34% decrease in breeding birds based on predictive modeling. The most affected arthropods were Diptera, Aranaea, Coleoptera, and Hymenoptera. No cumulative effects were observed over time, but the recovery of the invertebrate assemblage after the cessation of mosquito control was delayed due to Bti spore persistence and proliferation in the sediments. While hydrology remains a prime factor influencing primary and secondary productivity of the Camargue reed marshes, Bti spraying had significant negative effects on animal communities at several trophic levels.

Mosquito Traps: An Innovative, Environmentally Friendly Technique to Control Mosquitoes

Tue, 21 Mar 2017 16:40:42

de Brigitte Poulin, Gaëtan Lefebvre, Camille Muranyi-Kovacs, Samuel Hilaire
In International Journal of Environmental Research and Public Health, 14(3) (2017-03-18), 313
En ligne : www.mdpi.com[...]

We tested the use of mosquito traps as an alternative to spraying insecticide in Camargue (France) following the significant impacts observed on the non-target fauna through Bti persistence and trophic perturbations. In a village of 600 inhabitants, 16 Techno Bam traps emitting CO2 and using octenol lures were set from April to November 2016. Trap performance was estimated at 70% overall based on mosquitoes landing on human bait in areas with and without traps. The reduction of Ochlerotatus caspius and Oc. detritus, the two species targeted by Bti spraying, was, respectively, 74% and 98%. Traps were less efficient against Anopheles hyrcanus (46%), which was more attracted by lactic acid than octenol lures based on previous tests. Nearly 300,000 mosquitoes from nine species were captured, with large variations among traps, emphasizing that trap performance is also influenced by surrounding factors. Environmental impact, based on the proportion of non-target insects captured, was mostly limited to small chironomids attracted by street lights. The breeding success of a house martin colony was not significantly affected by trap use, in contrast to Bti spraying. Our experiment confirms that the deployment of mosquito traps can offer a cost-effective alternative to Bti spraying for protecting local populations from mosquito nuisance in sensitive natural areas.

High Stocking Density Controls Phillyrea Angustifolia in Mediterranean Grasslands

Wed, 3 May 2017 10:21:02

de François Mesléard, Nicole Yavercovski, Gaëtan Lefebvre, Loic Willm, Anne Bonis
In Environmental Management, 59(3) (March, 2017), 455-463
En ligne : link.springer.com[...]

Extensive grazing applied in the form of low instantaneous pressure over a long period is a widespread management practice in protected areas. However this kind of stocking method does not always achieve the expected results, in particular because it fails to limit colonization by woody plants.This is the case in the relict xero-halophytic grasslands of the northern Mediterranean coastal region, subjected to widespread colonization by the shrub Phillyrea angustifolia despite the presence of extensive grazing. In this study, we investigated, for an equal annual stocking rate, the respective impact of high stocking density applied over a short period (mob grazing) and low stocking density applied over a long period on both P. angustifolia and herbaceous cover, using an in situ experimental design run for 7 years. Only mob grazing was effective both in controlling the establishment and increasing the mortality of P. angustifolia individuals. We did not find any difference after the 7 years of experimentation between the two stocking methods with regard to the herbaceous community parameters tested: species richness, diversity, evenness, contribution of annual characteristic species. By contrast, the exclusion of domestic grazing led to a strong reduction of these values.The use of mob grazing may be well suited for meeting conservation goals such as maintaining open habitats in these grasslands.

Perturbation and delayed recovery of the reed invertebrate assemblage in Camargue marshes sprayed with Bacillus thuringiensis israelensis

Tue, 8 Nov 2016 15:58:40

de Brigitte Poulin, Gaëtan Lefebvre
In Insect Science (December 2016)
En ligne : onlinelibrary.wiley.com[...]

Bacillus thuringiensis var. israelensis (Bti) is the most commonly used larvicide to control mosquitoes worldwide. Considered as non-toxic to most organisms, Bti can nevertheless cause trophic perturbations to natural communities by reducing the abundance of Chironomidae, which are a key element of wetland food webs. Since August 2006, up to 8400 of the 33 000 ha of mosquito larval biotopes in the Camargue (Rhône delta, in southern France), are monitored by a public agency and Bti-sprayed (aqueous solution of VectoBac 12AS at 2.5 L/ha) whenever mosquito larvae (Ochlerotatus caspius and Oc. detritus) appeared in water bodies. This resulted in 30–50 aerial treatments/year, in addition to ground spraying of unknown frequency. The sprayed habitats include Phragmites australis reedbeds, which support a specific avifauna of conservation concern. We compared the abundance of invertebrate prey available to passerine birds at treated and control sites relative to the predicted values based on hydrology over a nine year period. Food available to reed passerines was significantly reduced at treated areas, translating into a 34% decrease in breeding birds based on predictive modelling. The most affected arthropods were Diptera, Aranaea, Coleoptera and Hymenoptera. No cumulative effects were observed over time, but the recovery of the invertebrate assemblage after the cessation of mosquito control was delayed due to Bti spore persistence and proliferation in the sediments. While hydrology remains a prime factor influencing primary and secondary productivity of the Camargue reed marshes, Bti spraying had significant negative effects on animal communities at several trophic levels.

Contribution of rainfall vs. water management to Mediterranean wetland hydrology: Development of an interactive simulation tool to foster adaptation to climate variability (2015)

Mon, 26 Oct 2015 10:02:23

de Gaëtan Lefebvre, Christophe Germain, Brigitte Poulin
2015

Mediterranean wetlands are increasingly managed to maintain their functions and services following modification in water allocation, embankment and climate change, calling for proactive and adaptive water management. In a first step, we used long-term monitoring of water levels in 37 adjacent embanked marshes in the Camargue as a repeated non-controlled experiment to build a hydrological model. Without information on water input/output by marsh users, we could nevertheless estimate evapotranspiration under flooding and dry conditions, and soil water coefficient. The model provided a high predictive accuracy (adjusted R-2 = 0.73-0.83) of monthly water levels when applied to an independent sample of 12 marshes. In a second step we developed an interactive decision-aid tool that allows users to visualize the impact of their management strategy (desired water level at a specific month) on subsequent water levels, and their consequence on different components of the ecosystem over a 10-yr period. (C) 2015 Elsevier Ltd. All rights reserved.

Mapping flooding regimes in Camargue wetlands using seasonal multispectral data (2013)

Mon, 26 Oct 2015 10:02:36

de A. Davranche, Brigitte Poulin, Gaëtan Lefebvre
2013

Wetland monitoring using classification trees and SPOT-5 seasonal time series (2010)

Mon, 26 Oct 2015 10:05:57

de A. Davranche, Gaëtan Lefebvre, Brigitte Poulin
2010

Ecological assessment of Phragmites australis wetlands using multi-season SPOT-5 scenes (2010)

Mon, 26 Oct 2015 10:03:34

de Brigitte Poulin, A. Davranche, Gaëtan Lefebvre
2010

Red flag for green spray: adverse trophic effects of Bti on breeding birds (2010)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, L. Paz
2010

Radiometric normalization of SPOT-5 scenes: 6S atmospheric model versus pseudo-invariant features (2009)

Mon, 26 Oct 2015 10:05:57

de A. Davranche, Gaëtan Lefebvre, Brigitte Poulin
2009

Reed harvest and summer drawdown enhance bittern habitat in the Camargue (2009)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, S. Allard, Raphael Mathevet
2009

Remote sensing based identification of environmental risk factors associated with West Nile disease in horses in Camargue, France (2007)

Mon, 26 Oct 2015 10:04:20

de A. Leblond, A. Sandoz, Gaëtan Lefebvre, H. Zeller, D.J. Bicout
2007

ButorSTar : a role-playing game for collective awareness of wise reedbed use (2007)

Mon, 26 Oct 2015 10:04:07

de Raphael Mathevet, C. Le Page, M. Etienne, Gaëtan Lefebvre, Brigitte Poulin, G. Gigot, S. Proreol, André Mauchamp
2007

The invasive red swamp crayfish as a predictor of Eurasian bittern density in the Camargue, France (2007)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, Alain Jean Crivelli
2007

Habitat selection by booming bitterns Botaurus stellaris in French Mediterranean reed-beds (2005)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, Raphael Mathevet
2005

Reed cutting affects arthropod communities, potentially reducing food for passerine birds (2005)

Mon, 26 Oct 2015 10:03:15

de M.H. Schmidt, Gaëtan Lefebvre, Brigitte Poulin, T. Tscharntke
2005

Diet of reed warblers Acrocephalus scirpaceus at two stopover sites in Morocco during autumn migration (2004)

Mon, 26 Oct 2015 10:03:27

de H. Rguibi Idrissi, Gaëtan Lefebvre, Brigitte Poulin
2004

Le régime alimentaire de la Rousserolle effarvatte (Acrocephalus scirpaceus) pendant la migration automnale (septembre-octobre 2000) a été étudié par analyse de régurgitats dans deux zones humides marocaines, Kerbacha en région Méditerranéenne et Sidi Bou Ghaba en région Atlantique. Dix-sept catégories de proies ont été identifiées dans 88 régurgitats totalisant 789 items, avec une prédominance de guêpes (Hyménoptères) et de coléoptères à Kerbacha, et de fourmis (ailées et non ailées) et coléoptères à Sidi Bou Ghaba. La distribution taxinomique des proies et leur diversité diffèrent significativement entre les deux sites. Les oiseaux consomment un plus petit nombre de proies de plus grande taille et de plus faible mobilité à Sidi Bou Ghaba, comparativement à Kerbacha où un grand nombre de petites proies volantes caractérisent la majorité des régurgitats. Ces différences sont vraisemblablement dues à des variations dans la disponibilité locale des proies qui peuvent expliquer en partie les stratégies migratoires différentes utilisées aux deux sites. Ainsi, le court séjour et le taux d’engraissement élevé à Kerbacha peuvent être associés à un taux d’alimentation supérieur grâce à l’abondance de quelques taxons fortement consommés. A Sidi Bou Ghaba, où la durée de stationnement est plus longue et le taux d’engraissement moindre, les rousserolles ont un régime alimentaire plus diversifié et un taux d’alimentation faible suggérant que les proies sont généralement peu abondantes à l’exception des fourmis volantes, une ressource alimentaire ponctuellement surabondante mais peu prévisible dont les rousserolles font bon usage.

Accuracy of bittern location by acoustic triangulation (2003)

Mon, 26 Oct 2015 10:04:18

de Gaëtan Lefebvre, Brigitte Poulin
2003

ReedSim: Simulating ecological and economical dynamics of Mediterranean reedbeds. In: Integrative modelling of biophysical, social and economic systems for resource management solution. POST D. (2003)

Mon, 26 Oct 2015 10:04:07

de Raphael Mathevet, André Mauchamp, R. Lifran, Brigitte Poulin, Gaëtan Lefebvre
[S.l.] : Modelling and Simulation Society of Australia and New Zealand Townsville, 2003, p1007-1012

Optimal sampling of booming Bitterns Botaurus stellaris (2003)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre
2003

The Great Bittern Botaurus stellaris is a secretive bird that lives in dense reed marshes. Population surveys of this vulnerable species are based on the characteristic vocalization (booms) of males during the breeding season. Probability of detecting a male is highly dependent upon the occurrence of booms, which is assumed to be density-dependent and highly variable over time. We studied booming frequency in relation to time of day, time of season, weather conditions, and bittern density at ten sites in the Camargue, south of France. At each site, twice monthly from 6 March through 18 July 2000, booms were recorded over two periods of 6 h, one centred on sunset, the other centred on sunrise, and both divided into 72 sampling units of 5 min each. The number of bitterns heard within a single 6-h period varied from 0 to 10. Booming frequency was highest in April and May. The proportion of males booming peaked 0-30 min after sunset (68%), and 30-60 min before sunrise (78%). Booming activity decreased significantly under cloudy and rainy conditions, but low temperatures had no effect. Optimal sampling protocols (point count duration and frequency) are suggested for various situations at dawn and dusk, during the peak and low booming periods, and for sites comprising a single or multiple bitterns. Given the daily and seasonal variation in booming frequency, only standardized protocols can provide a faithful estimate of the number of male bitterns across years.

Variation in booming among great bitterns Botaurus stellaris in the Camargue, France (2003)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre
2003

Effect of winter cutting on the passerine breeding assemblage in French Mediterranean reedbeds (2002)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre
2002

Habitat requirements of passerines and reedbed management in southern France (2002)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, André Mauchamp
2002
En ligne : crbpo.mnhn.fr[...]

Determinants of avian diversity in neotropical mangrove forests. In: Biodiversity in wetlands: assessment, function and conservation. Volume 1. GOPAL B., JUNK W.J. & DAVIS J.A. (2000)

Mon, 26 Oct 2015 10:04:18

de Gaëtan Lefebvre, Brigitte Poulin
[S.l.] : Backhuys Publishers Leiden, 2000, p161-179

Quantifying the breeding assemblage of reedbed passerines with mist-net and point-count surveys (2000)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, P. Pilard
2000

Spatial distribution of nesting and foraging sites of two Acrocephalus warblers in a Mediterranean reedbed (2000)

Mon, 26 Oct 2015 10:03:33

de Brigitte Poulin, Gaëtan Lefebvre, S. Metref
2000