Gaëtan Lefebvre's research while affiliated with Tour du Valat, Research Institute for the Conservation of Mediterranean Wetlands and other places

Publications (46)

Article
Full-text available
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 tax...
Poster
Full-text available
Our study tested the hypothesis that pesticide use influences the effect of different components of landscape complexity on different taxonomic groups. We assessed the abundance and diversity of 7 taxa in 118 crop fields in 32 rice paddy landscapes of 1*1 km in the Camargue. For each landscape, we measured the length of different field margins, the...
Article
Full-text available
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 ti...
Article
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...
Article
Full-text available
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. Rec...
Article
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...
Article
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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...
Article
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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...
Preprint
Full-text available
We tested the use of mosquito traps as an alternative to insecticide spraying 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...
Article
Full-text available
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 grasslan...
Article
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 o...
Article
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-contr...
Article
Reflectance data from multiseasonal SPOT-5 imagery was combined with monthly measures of water levels collected in the Rhône river delta (Camargue) in 2005 and 2006. Classification tree and regression models using monthly values of 17 multispectral indices and 4 bands, as well as their seasonal variations, were used for predicting the presence and...
Article
Data collected in a 40-ha reedbed of southern France were used to compare the efficiency and limitation of mist-net and point-count techniques in estimating the composition and structure of a bird assemblage dominated by the Bearded Tit (Panurus biarmicus), the Moustached Warbler (Acrocephalus melanopogon), and the Reed Warbler (Acrocephalus scirpa...
Article
Full-text available
The winter ecology of the Northern Waterthrush (Seiurus noveboracensis), the Prothonotary Warbler (Protonotaria citrea), and the American Redstart (Setophaga ruticilla) was studied in tropical mangroves of northeastern Venezuela. The birds' spatial and social behaviours were assessed through intensive mist-netting and observation sessions over two...
Article
1. The expanding use of selective pest-control agents provides a unique opportunity to study food web interactions in the field while addressing major environmental issues. Bacillus thuringiensis israelensis (Bti) is the most commonly used microbial agent to control mosquitoes worldwide. 2. Using breeding house martins Delichon urbicum as a model s...
Article
Ecologists and conservationists need accurate and replicable tools for monitoring wetland conditions in order to develop and implement adaptive management strategies efficiently. The Rhone Delta (Camargue) in southern France encloses 9200 ha of fragmented reed marshes actively managed for reed harvesting, waterfowl hunting or cattle grazing, and ho...
Article
Full-text available
Se realizaron capturas con grabaciones de cantos en cinco localidades de La Camarga (Francia) en abril y mayo de 2009 para documentar el uso de una ruta mediterránea por el carricerín cejudo durante la migración prenupcial. Seis individuos fueron capturados u observados en tres localidades correspondientes a dos tipos de hábitat: carrizales pastore...
Article
Multiseason reflectance data from radiometrically and geometrically corrected multispectral SPOT-5 images of 10-m resolution were combined with thorough field campaigns and land cover digitizing using a binary classification tree algorithm to estimate the area of marshes covered with common reeds (Phragmites australis) and submerged macrophytes (Po...
Conference Paper
Les marais de Larache abritent une importante fraction de la population nicheuse de la foulque caronculé Fulica cristata au Maroc, espèce menacée inscrite sur la liste rouge de l’UICN. Une méthode de dénombrement, basée sur la phénologie journalière et saisonnière du chant, a été mise au point afin d’obtenir des indices d’abondance qui ont été par...
Article
Full-text available
We compared the efficiency and robustness of two radiomet-ric correction techniques applied to six SPOT-5 scenes used for assessing environmental changes of Camargue wetlands: the 6S atmospheric model and 86 pseudo-invariant features (PIFs) found in deep water, pine trees, roofs and sand. The few PIFs were selected subjectively following the low nu...
Article
The vulnerable Eurasian bittern Botaurus stellaris has recently benefited from conservation actions in several European countries. The Camargue in Mediterranean France holds 8000ha of reed marshes and 50% of the French bittern population estimated at 300–350 booming males. Although reed cutting in Europe is a current practice, we provide the first...
Article
Temporal variation in bird abundance was studied during a complete annual cycle in a thorn scrub, a thorn woodland and a deciduous forest in northeastern Venezuela. Abundance of site-attached and transient birds from different feeding guilds was determined by mist-netting at 2-week intervals. Diets were investigated by regurgitated samples. The ove...
Article
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Les roselières constituent des systèmes écologiques et sociaux complexes. Dans le contexte de leur régression, un jeu de rôles assisté par ordinateur appelé ButorStar a été développé. Cet outil met l’accent sur l’ apprentissage du dialogue social et la compréhension des processus socio-écologiques. La structure du jeu de rôles et le modèle multi-ag...
Article
Few data exist on the relationships between food levels and breeding density of the Eurasian bittern Botaurus stellaris, a vulnerable species of high-priority concern in Europe. Concurrent data were obtained on male bittern density and relative food abundance over a 3-year period in two wetlands totalling 2500 ha of Mediterranean reed marsh enclosi...
Article
Full-text available
A role-playing game (RPG) supported by computer simulations, called BUTORSTAR, has been developed in the context of a LIFE-Nature European Programme (2001-2005) aiming to improve reedbed management for the conservation of a vulnerable heron, the Eurasian Bittern. The agent-based model simulates the impacts of reedbed management resulting from decis...
Article
Full-text available
Data on habitat requirements of the threatened Eurasian bittern Botaurusstellaris are largely qualitative and limited to countries holding small populations. We assessed the habitat spectrum exploited by male bitterns during the breeding season, based on the analysis of 40 booming sites and 33 non-booming sites in 2,500 ha of heterogeneous reed-bed...
Article
Winter cutting of Common Reed Phragmites australis (Poaceae) is increasing in Camargue, southern France, potentially affecting wetlands of high conservation value. We studied its impact on arthropods by comparing four cut and uncut sites with special respect to avian prey availability in the breeding season. The two most important prey groups for b...
Article
Diet of the Reed Warbler (Acrocephalus scirpaceus) was estimated by means of forced regurgitations of captured individuals during autumn migration at Kerbacha and Sidi Bou Ghaba, two wetland sites located respectively on the Mediterranean and Atlantic coasts in Morocco. Overall, 88 emetic samples were collected and 17 prey taxa were identified from...
Article
Mediterranean reedbeds are subject to different human uses, each associated with a particular water and reed management that affects the functioning of the ecosystem and the conservation of endangered species. We present here the general structure of ReedSim, a multiagent model that integrates the horizontal (spatial configurations) and vertical (s...
Article
Full-text available
We address the potential of booming in Great Bitterns as an indicator of male condition through a seasonal analysis of 5299 boom trains recorded from early Mar through mid Jul 2000 in ten reedbed sites in the Camargue, France. Boom train length peaked in May, averaging 3.6 and 4.7 booms at sites with single and multiple Great Bitterns, respectively...
Article
Full-text available
This paper addresses the sustainable management and conservation policies of large Mediterranean reedbeds. These habitats are subject to different human uses (reed harvesting, grazing, hunting, fishing and recreational activities), each associated with a particular water and reed management. Seasonal variations in water levels affect the functionin...
Article
Ecological studies and population surveys sometimes require information on the position of individuals. Because many birds are more audible than visible, we tested the potential of acoustic triangulation for locating Great Bitterns (Botaurus stellaris) within extensive reed marshes in the Camargue, France. During the breeding season, and predominan...
Article
Les roselières méditerranéennes sont l'objet de multiples usages, chacun étant associé à une gestion de l'eau et du roseau qui affecte le fonctionnement de l'écosystème et la conservation des espèces associées. Les auteurs présentent la structure générale de ReedSim, un modèle multi-agents qui intègre les relations horizontales (configurations spat...
Article
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...
Article
Reedbeds have high conservation value in Europe. In southern France, they are the major breeding habitat of five passerine species. Yet, habitat management is done primarily by water control to serve socio-economic rather than conservation interests, because we lack information on the species' ecological requirements. Determinants of passerine abun...
Article
Full-text available
Common reed is increasingly harvested from the Mediterranean region toprovide thatching material to north European countries. The impact of thesemanagement practices on the fauna is poorly known. The aim of this study was toquantify the effect of reed cutting in the Mediterranean region through acomparative analysis of water regime, vegetation stru...
Article
Full-text available
Although tropical forest birds are known to prey upon small lizards and frogs, no study has documented the attributes of vertebrate-eating birds or whether birds prey opportunistically on the different elements of the herpetofauna within tropical communities. This study is based on a 14-mo investigation on avian diet, supplemented with a 3-y census...
Article
Many reedbed passerines forage outside their nesting territory. This peculiar behaviour could allow reproductive individuals to feed in areas where resources are plentiful and/or to nest in areas where predation risks are low. These hypotheses were investigated for the Moustached Warbler Acrocephalus melanopogon and the Reed W arbler A. scirpaceus...
Article
Full-text available
Plants potentially compete for seed dispersal. Selection may favour temporally segregated fruiting phenologies to minimize this competition and also to maintain resident populations of dispersal agents. Alternatively, selection may favour temporally aggregated fruiting phenologies when the effectiveness of seed dispersal agents varies seasonally or...
Article
Full-text available
Isolated in forest patches, mangrove stands often experience different physical conditions (rainfall, tide, salinity) despite similar floristic composition and structure. These abiotic factors are known to influence mangrove phenology but their potential effect on the local invertebrate and bird fauna have not been investigated. This study contrast...
Article
Full-text available
This study reports on food selection by Nearctic migrants, especially thrushes (Catharus), wood-warblers (Oporornis, Seiurus, Wilsonia), and tyrant flycatchers (Empidonax) in a humid forest of central Panama. We attempt to determine how these migrants integrate into the resident bird community based on local food abundance and diet comparison betwe...
Article
We studied feeding guild characteristics of birds in northeastern Venezuela in three adjacent tropical habitats: thorn scrub, thorn woodland, and deciduous forest. We mist-netted and marked birds twice monthly to obtain data on site tenacity We determined diet by examining regurgitated food samples. Species were assigned to feeding guilds by a clus...
Article
Full-text available
We studied the territorial behavior of four insectivorous passerines residing in a tropical mangrove of northeastern Venezuela. Data were obtained through mist-netting and direct observation of color-banded individuals, regularly scheduled over two complete annual cycles. Seasonal variation in food resources (arthropods) and the birds' diet also we...

Citations

... Temporary wetlands are particularly sensitive to anthropogenic pressures (Rhazi et al. 2001, Bouahim et al. 2014) and climate change (El Madihi et al. 2017, Pinceel et al. 2018. For instance, in Morocco, climate projections reveal that the water deficit could increase by 16% to 67% in 2100 under the RCP8.5 scenario (Representative Concentration Pathway 8.5 delivers a temperature increase of about 4.3°C by 2100; Grillas et al. 2021). The flooding duration is projected to decrease substantially, and some wetlands will dry out completely (Grillas et al. 2021). ...
... It is quite common to note a dual use of participatory agent-based simulation in the field of socio-ecological science: either support to the implementation of experiential learning in classrooms to teach students who are unfamiliar with the interdependencies of ecological and social dynamics, or a direct use with the actors of the socio-ecosystems. For instance, two gaming sessions of BUTORSTAR involving stakeholders of Étang de Vendres were organized, with the aim of increasing their capacity to adopt modes of interactions favoring adaptive management of the environment [28]. This duplication of the target audience (students and local actors) was also performed with SylvoPast, NewDistrict and uva bay game. ...
... The multispectral satellite imagery allows reliable extraction of water using various water indices (McFeeters, 1996;Domenikiotis et al., 2003;Kordelas et al., 2019) and specific bands based threshold methods. However, usage of optical imagery in the presence of clouds prevents the observation of the earth's surface (Shen et al., 2019). ...
... Current policies (CAP, BGIN) are unlikely to succeed in this respect in the context of a large decrease in the farming population and an increase in farm size. While diversity in the landscape mosaic should be favored (Sirami et al., 2019) to improve local multifunctionality (Rega et al., 2019), promoting land-management practices of farms, such as maintaining extensive systems in the ecological corridors that are most important for preserving biodiversity, should consider local and regional characteristics. The location of farming practices in the landscape matters!. ...
... Second, they are considered a biodiversity hotspot, being an incredibly wide habitat with high species diversity [6,8]. However, due to their ephemeral nature and ecological features, SWEs are particularly vulnerable and threatened ecosystems, both directly and indirectly, by anthropogenicrelated activities such as the intensive exploitation of lands, eutrophication, pollution, the introduction of alien species, and climate change [4,[9][10][11][12][13]. Although, the specialist species of SWEs show remarkable growth in terms of cover in the wettest period, the sensitivity to drought may make these species particularly vulnerable to climate change in the Mediterranean region. ...
... In France, An. hyrcanus s.l. is still as abundant as in the past, and it is currently considered to be the main malaria vector species [30,33,34,[68][69][70]. In Turkey, this species has been well described only in the last few years [20,[71][72][73]. ...
... Furthermore, scientific literature reporting on mob grazing does not document levels of trampling and associated changes in soil and vegetation characteristics. Studies more commonly report on mob grazing as a means of 1) controlling undesirable shrubs ( Bailey and Brown 2011 ;Mesléard et al. 2017 ) and exotic species ( James et al. 2017 ), 2) manipulating proportions of C 3 and C 4 plants in a management unit ( Hickman et al. 2004 ), and 3) improving distribution of grazing and evenness of utilization of vegetation cover ( Barnes et al. 2008 ;Norton et al. 2013 ;Reed et al. 2019 ). Animal performance in a mob grazing system is commonly reported to be less than on less intensively managed pastures (simple rotationally and continuously stocked pastures) ( Hawkins 2017 ;Tracy and Bauer 2019 ;Augustine et al. 2020 ), likely because of extremely high grazing pressure and consumption of lower-quality forage ( Tracy and Bauer 2019 ). ...
... including dragonflies and damselflies [10], newts [11], frogs [12], and birds [13]. Therefore, reductions in mosquito density or nontarget species could affect their predators and have cascading effects on other trophic links ( Figure 2). ...
... This booming call is far-reaching and distinct, and therefore lends itself as a potential 'cue' for monitoring the species (Marchant & Higgins 1990). However, call count methods recommended for other Bittern species, such as Poulin and Lefebvre's (2003a) acoustic triangulation method, are known to have limited applicability for Australasian Bitterns (O'Donnell et al. 2013). For example, this method was found to have limited success when trialled at a large wetland in New Zealand where Bittern density was known to be high (Ogle & Cheyne 1981). ...
... 35 The hydrological dynamics in EL Hondo could be similar to other eastern Mediterranean populations (central Anatolia, Turkey) on where coexist two subpopulations of this species that, in spite of to suffer a isolament degree, they share a gene flow and between them and droughts appear to be a very important, negative factor, facing their extinction. 44,45 The results of this study are indicative that populations of this species may are suffering an acidification process in the context of global climate change, since a trend in the mean height of reservoirs decrease with years, aspect that should be take into account for further assessment. ...