Les articles de Loïc Willm

Évolution des effectifs nicheurs des ardéidés coloniaux arboricoles et paludicoles en Camargue et sur la façade méditerranéenne française

Wed, 22 Oct 2025 15:17:45

de Yves Kayser, Thomas Blanchon, Antoine Arnaud, Olivier Pineau, Michel Gauthier-Clerc, Jean-Laurent Lucchesi, Gregoire Massez, Christophe Pin, Clément Pappalardo, Jérémiah Petit, et al.
In Ornithos, 172 (Juillet, août, septembre 2025), 16-33

Les suivis des populations reproductrices d’ardéidés coloniaux sont réalisés chaque année sur la bordure méditerranéenne française depuis 1968 pour les hérons paludicoles ainsi qu’en Camargue depuis 1969 pour les espèces arboricoles. Neuf espèces de hérons se reproduisent dans cette région dont sept sont concernées par ces recensements : le Bihoreau gris Nycticorax nycticorax, le Crabier chevelu Ardeola ralloides, le Héron garde-bœufs Ardea ibis, le Héron cendré Ardea cinerea, le Héron pourpré Ardea purpurea, la Grande Aigrette Ardea alba et l’Aigrette garzette Egretta garzetta.

Monitoring coastal dynamics after working with nature practices in the Rhone delta

Wed, 4 Jun 2025 15:53:40

de Morgane Jolivet, Cecile Puigserver, Olivier Boutron, Francois Sabatier, Samuel Meulé, Philippe Larroude, Loic Willm, Emilie Luna-Laurent
In Coastal Engineering Proceedings, 38 (June, 2025), 50
En ligne : icce-ojs-tamu.tdl.org[...]

The site of the “Étangs et Marais des Salins de Camargue” (EMSC) is located southern France in the Rhône Delta, facing Mediterranean sea, at the heart of the Camargue Regional Natural Park. This site, formerly dedicated to salt production, is now owned by the Coastal Conservatory and co-managed by the Camargue Regional Natural Park, Tour du Valat, and the French National Society for the Protection of Nature. A habitat restoration project was initiated in 2011 and continues as part of the development of a 2023-2032 management plan and the site's participation in the European H2020 Rest-Coast project. This restoration aims to facilitate the recolonization of the area by plant (seagrass, salt marsh) and animal species, reestablishing the natural hydrological processes of the site. An adaptive coastal management strategy is also applied on this site, with the decision to no longer maintain the historical dikes of the salt production site facing the sea, leading to their gradual collapsing. Protection against the risk of marine submersion is ensured by an landward seawall, which will be elevated, as part of the coastal strategy defined for the greater Rhône Delta. Natural hydro-morphodynamic processes are reestablishing locally, creating new connections with the sea and the formation of beach and barrier areas through overwash. This results in the emergence of a natural buffer zone that will better address the consequences of climate change or storms, such as marine submersion and salinization.

Exposure of wetlands important for nonbreeding waterbirds to sea-level rise in the Mediterranean

Fri, 17 May 2024 16:11:40

de Fabien Verniest, Thomas Galewski, Olivier Boutron, Laura Dami, Pierre Defos du Rau, Anis Guelmami, Romain Julliard, Nadège Popoff, Marie Suet, Loic Willm, et al.
In Conservation Biology, 2024 (May, 2024), e14288
En ligne : onlinelibrary.wiley.com[...]

Sea-level rise (SLR) is expected to cause major changes to coastal wetlands, which are among the world's most vulnerable ecosystems and are critical for nonbreeding waterbirds. Because strategies for adaptation to SLR, such as nature-based solutions and designation of protected areas, can locally reduce the negative effects of coastal flooding under SLR on coastal wetlands, it is crucial to prioritize adaptation efforts, especially for wetlands of international importance for biodiversity. We assessed the exposure of coastal wetlands important for nonbreeding waterbirds to projected SLR along the Mediterranean coasts of 8 countries by modeling future coastal flooding under 7 scenarios of SLR by 2100 (from 44- to 161-cm rise) with a static inundation approach. Exposure to coastal flooding under future SLR was assessed for 938 Mediterranean coastal sites (≤30 km from the coastline) where 145 species of nonbreeding birds were monitored as part of the International Waterbird Census and for which the monitoring area was delineated by a polygon (64.3% of the coastal sites monitored in the Mediterranean region). Thirty-four percent of sites were threatened by future SLR, even under the most optimistic scenarios. Protected study sites and study sites of international importance for waterbirds were, respectively, 1.5 and 2 times more exposed to SLR than the other sites under the most optimistic scenario. Accordingly, we advocate for the development of a prioritization scheme to be applied to these wetlands for the implementation of strategies for adaptation to SLR to anticipate the effects of coastal flooding. Our study provides major guidance for conservation planning under global change in several countries of the Mediterranean region.

Context in Landscape Planning: Improving Conservation Outcomes by Identifying Social Values for a Flagship Species

Wed, 30 Jun 2021 15:30:27

de Lisa Ernoul, Angela Wardell-Johnson, Raphael Mathevet, Alain Sandoz, Olivier Boutron, Loic Willm, Stephan Arnassant, Arnaud Béchet
In Sustainability, 13(12) (June 2021), 6827
En ligne : www.mdpi.com[...]

Sustainable conservation planning depends on understanding local context including the way social values impact a landscape. Flamingos are used here as a ﬂagship species to focus the social values of a broad range of people living in and working in the Camargue in France. A survey questionnaire (n = 87) was used to identify the range of ways in which people value the landscape and their perception of effectiveness of ﬂamingo management strategies. Survey analysis was conducted through a multi-method approach, triangulating standard descriptive statistics, qualitative data analysis, and multivariate analysis applying numerical taxonomy. Applying numerical taxonomy allowed us to identify and deﬁne six social assemblages. Each assemblage had geographical characteristics with distinct values and perceptions in relation to management. The primary residence and geographic identity of the participants was deﬁning, showing clear value differences from participants living in different parts of the delta. The participants most frequently agreed that ﬂamingos contributed to the aesthetic, economic, biodiversity, and recreational values of the landscape. We show how identifying points of consensus and points in contest is necessary for navigating differences in values for conservation planning. This research shows the importance of the local social context in sustainably managing landscape change. /La planification d'une conservation durable dépend de la compréhension du contexte local, notamment de l'impact des valeurs sociales sur un paysage. Les flamants roses sont utilisés ici comme une espèce phare pour mettre l'accent sur les valeurs sociales d'un large éventail de personnes vivant et travaillant en Camargue. L'analyse de l'enquête montre que la résidence principale et l'identité géographique des participants ont été déterminantes, montrant des différences de valeurs claires entre les participants vivant dans différentes parties du delta. Les participants ont le plus souvent exprimaient que les flamants roses contribuaient aux valeurs esthétiques, économiques, de biodiversité et récréatives du paysage. Nous montrons comment l'identification des points de consensus et des points de contestation est nécessaire pour naviguer dans les différences de valeurs pour la planification de la conservation. Cette recherche montre l'importance du contexte social local dans la gestion durable du changement de paysage.

Assessing Management Perceptions Linked to a Flagship Species: A New Approach to Increase Landscape Management Legitimacy and Support

Tue, 8 Jun 2021 10:32:39

de Lisa Ernoul, Angela Wardell-Johnson, Raphael Mathevet, Alain Sandoz, Olivier Boutron, Loic Willm, Stephan Arnassant, Arnaud Béchet
In Coastal Management, 49(4) (June, 2021), 1-13
En ligne : www.tandfonline.com[...]

Integrated socio-ecological decision-making is important in improving legitimacy in management decisions through effective solutions that avert conflicts. This research examined social perceptions in landscape planning and management with regard to the Greater flamingo, a flagship species along the southern French Coast. A strategic delivery to a cross-section in a social catchment (n = 87) captured the perception and the recognition of management strategies through a survey questionnaire. Analysis was conducted through a multi-method approach, triangulating qualitative and quantitative results. Results show the importance of the attachment to flamingos in local landscapes. Knowledge on flamingo ecology was relatively high and participants perceived some of the regional management options to be unfavorable for flamingos. Participants identified threats to the species and expressed concern for the future of the flamingos, challenging the legitimacy of some landscape management decisions and planning policies. This research demonstrates the role of flagship species in stimulating reflection on landscape management, addressing both the ecological and human dimensions. Understanding social perceptions of biodiversity management objectives is fundamental for effective coastal conservation.

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.

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.

Integrative science to achieve long-term impact in conservation

Thu, 22 Nov 2018 10:23:32

de Lisa Ernoul, Raphael Mathevet, Angela Wardell-Johnson, Alain Sandoz, Loic Willm, Olivier Boutron
In Frontiers in Ecology and Evolution, 6 (2018)
En ligne : www.frontiersin.org[...]

Participatory mapping: Exploring landscape values associated with an iconic species

Fri, 4 May 2018 11:12:57

de Lisa Ernoul, Angela Wardell-Johnson, Loic Willm, Arnaud Béchet, Olivier Boutron, Raphael Mathevet, Stephan Arnassant, Alain Sandoz
In Applied Geography, 95 (June 2018), 71-78
En ligne : www.sciencedirect.com[...]

Participatory mapping provides a way to collate a wide range of landscape values providing a visual representation to inform conservation planning. We tested the use of an iconic species, the Greater Flamingo, as a lens for participatory mapping to render explicit the socio-cultural values attributed in a landscape. Spatial information on six landscape values in a biodiversity hotspot, the Camargue Biosphere Reserve (southern France) was collected from 113 participants through surveys, interviews and workshops. This data was geo-located through a SoftGIS methodology to map and quantify the overlap of bivariate hotspots identifying value concurrence. The most frequent values recorded through total number of polygons and surface areas were wilderness and recreation. The least frequently mapped values were economic loss and biodiversity. There was frequent concurrence between biodiversity and aesthetic values especially in wetlands (lagoons, salt flats and sea). There was also frequent concurrence between biodiversity and recreational values with more overlap in sites with easy access (along roads and public areas). Our results show that using an iconic species is an effective way to render explicit spatial variations in the values attributed to a landscape and to identify concurrence of values, thus enabling integration of multiple landscape values in conservation planning.

Microwave soil heating reduces seedling emergence of a wide range of species including invasives

Wed, 31 Jan 2018 00:00:00

de Manon C.M. Hess, Melissa De Wilde, Nicole Yavercovski, Loic Willm, François Mesléard, Elise Buisson
In Restoration Ecology, 10.1111/rec.12668 (2018), 10 pp.
En ligne : onlinelibrary.wiley.com[...]

A microwave-based process to control invasive species (seeds and adult stages) in the field prior to plant community restoration is currently under development. We investigated the effect of four microwave treatment pairings of Power × Duration (2kW4min, 4kW2min, 2kW8min, and 4kW4min) on seedling emergence of (1) an abandoned field seed bank used as a model for various plant species and (2) seeds of three species invasive in Europe: Datura stramonium (Jimson weed), Reynoutria × bohemica (Bohemian knotweed), and Solidago gigantea (Giant goldenrod). In addition, we assessed whether nontreated seeds of these three invasive species could germinate on microwave-treated soils. As microwave soil heating usually leads to nonhomogeneous temperatures within a sample, we also assessed whether the position of seeds in the soil during microwave treatment (center vs. edges) impacted seedling emergence. Results show that the most intensive microwave treatments (2kW8min and 4kW4min), enabling the soil to reach 85°C, are highly effective in inhibiting seedling emergence of invasive species and the seed bank. The 2kW8min treatment, combining lowest power and longest exposure, is the most effective, reducing seed bank seedling emergence by 98% compared to control. The results also reveal a species-specific response to heat, and lower microwave effectiveness on seeds located at the soil surface, which may explain the incomplete effectiveness of intensive treatments. Our results also suggest that prior microwave soil treatment does not prevent a considerable proportion of newly arrived invasive species seeds from germinating, suggesting that this method should be followed by restoration of native plant cover.

Using microwave soil heating to inhibit invasive species seed germination

Fri, 1 Sep 2017 00:00:00

de Melissa De Wilde, Elise Buisson, Nicole Yaverkovski, Loic Willm, Livia Bieder, François Mesléard
In Invasive Plant Science and Management, 10(3) (July-September 2017), 42-51
En ligne : doi.org[...]

Successful invasive plant eradication is rare, because the methods used target the adult stage, not taking into account the development capacity of a large seedbank. Heating by microwave was considered, because it offers a means w quickly reach the temperature required for loss of seed viability and inhibition of germination. Previous results were not encouraging, because homogeneous and deep-wave penetration was not achieved, and the various parameters that can affect treatment effectiveness were incompletely addressed. This study aimed to determine, under experimental conditions, the best microwave treatment to inhibit invasive species seed germination in terms of power (2, 4, 6kW) and duration (2, 4, 8 min) of treatments and depending on soil moisture (10%, 13%, 20%, 30%) and seed burial depth (2, 12cm). Three invasive species were tested: Bohemian knotweed, giant goldenrod, and jimsonweed. The most effective treatments required relatively high power and duration (2kW8min, 4kW4min, 6kW2min, and 6kW4min; 4kW8min and 6kW8min were not tested for technical reasons), and their effectiveness diminished with increasing soil moisture with germination percentage between 0% and 2% for the lowest soil moisture, 0% and 56% for intermediate soit moisture, and 27% and 68% in control treatments. For the highest soil moisture, only 2kW8min and 4kW4min reduced germination percentage between 2% and 19%. Occasiona1ly, germination of seeds located at the 12-cm depth was more strongly affected. Giant goldenrod seeds were the most sensitive, probably due to their small size. Results are promising and justify further experiments before developing a field microwave device to mat large volumes of soil infested by invasive seed efficlently and with reasonable energy requirements. Other types of soil, in terms of texture and argutie matter content, should be tested in future capermonts, because these factors influence soil water content and, consequently, microwave heating.

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.

Trends in management plans and guides: 25 years of experience from Southern France

Wed, 27 Apr 2016 14:20:30

de Lisa Ernoul, Nicolas Beck, Damien Cohez, Christian Perennou, Marc Thibault, Loic Willm, Brigitte Poulin
In Journal of Environmental Planning and Management, 58(6) (June 2015), 1096-1112
En ligne : dx.doi.org[...]

This study analysed 14 management plans and guidelines from a 25-year period to understand trends in conservation planning. A Rosetta Stone Analysis was used for the systematic comparison of plans and guidelines. Management plans incorporated management philosophies, management scenarios, opportunities for infrastructure, and plans for data collection by 2000. As of 2010, they incorporated ecosystem services, stakeholders’ objectives and methods for storing and analysing data. The results demonstrate the complex nature of management plans, with an important workload for site managers. Recommendations for future planning include adjustments in planning timeframes and a better identification of conservation targets from initial stages.