|Les articles de Loïc Willm||https://tourduvalat.centredoc.fr/rss.php?id=47|
Les articles de Loïc Willm
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.
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.
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[...]
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.
de Manon Célia Morgane 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.
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.
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.
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.