Desarrollo de un indicador para el seguimiento de los niveles de inundación en humedales Mediterráneos

Los humedales representan ecosistemas sensibles que son objeto de amenazas antropogénicas. En las últimas décadas, los humedales costeros en el Mediterráneo han sufrido presiones considerables por el crecimiento urbano y la intensificación de prácticas agrícolas. Las técnicas de teledetección y Sistemas de Información Geográfica (SIG) son herramientas eficientes que pueden apoyar el seguimiento de humedales costeros del Mediterráneo. Estas técnicas han sido utilizadas para desarrollar un indicador de inundación para apoyar el seguimiento y control de humedales costeros en el sur de Francia. El indicador se basa en series temporales de imágenes del satélite Landsat, que cubren los años 2000, 2007 y 2012; y capas de referencia de usos del suelo para identificar y mapear los niveles de inundación anuales. La metodología combina el uso de índices de vegetación con un árbol de decisión para detectar la masa de agua que cubre los humedales en diferentes fechas dentro de un ciclo anual. Un proceso de validación es implementado para comprobar la fiabilidad del indicador comparándolo con los inventarios de humedales. Los resultados indican que el área de estudio presenta un alto nivel de inundación a lo largo de todo el año. Durante el periodo de estudio, el 40% del área se encuentra permanentemente inundada. El nivel de inundación aumenta hasta el 56- 62% cuando las inundaciones estacionales son consideradas. Los niveles más altos son detectados durante el invierno (lluvias) y en primavera (inundación de campos de arroz). Las comparaciones temporales en los niveles de inundación muestran que hay una tendencia decreciente con los años (62% en 2000; 59% en 2007; y 56% en 2012).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Multitemporal optical and radar metrics for wetland mapping at national level in Albania

Wetlands are highly dynamic, with many natural and anthropogenic drivers causing seasonal, periodic or permanent changes in their structure and composition. Thus, it is necessary to use time series of images for accurate classifications and monitoring. We used all available Sentinel-1 and Sentinel-2 images to produce a national wetlands map for Albania. We derived different indices and temporal metrics and investigated their impacts and synergies in terms of mapping accuracy. Best results were achieved when combining Sentinel-1 with Sentinel-2 and its derived indices. We reduced systematic errors and increased the thematic resolution using morphometric characteristics and knowledge-based rules, achieving an overall accuracy of 82%. Results were also validated against field inventories. This methodology can be reproducible to other countries and can be made operational for an integrated planning that considers the food, water, and energy nexus

A More Effective Ramsar Convention for the Conservation of Mediterranean Wetlands

The Ramsar Convention is the multilateral agreement aimed at protecting wetlands globally. Wetlands are particularly recognized for their role in the Mediterranean biodiversity hotspot by providing key habitats for endemic and migratory species, directly contributing benefits to the lives of people and being an integral part of their culture. In response to this importance, the Mediterranean Wetlands Observatory publishes Mediterranean Wetland Outlooks (MWOs) on the state and trends of Mediterranean wetlands; the first edition in 2012 (MWO1) and the second edition in 2018 (MWO2). In this paper, we used the results of the two Mediterranean Wetland Outlooks to highlight ways to increase the impact of the Ramsar Convention by identifying the spatial dimensions of detected biodiversity trends as well as the societal developments and estimated impacts of global change and protection status

Cartographie des forêts humides dans la région d’El Kala (Algérie) à l’aide des outils d’observation de la Terre

Mapping of wet forests using Earth Observation tools in El Kala area (Algeria). Wet forests are among the most threatened and degraded wetland ecosystems in the world. In Algeria, they are mainly represented by specific, fragile and rare forest habitats. The region of El Kala (North-East of Algeria) hosts many unique wetlands (e. g. lakes, marshlands, wet meadows, lagoons, etc.) but also some of the most extended wet forests in North Africa. The main objective of this study is to develop a new mapping approach for the location and the delineation of these ecosystems using Earth Observation (EO) tools. This methodology is based on a combination of topographic and hydro-geomorphological indices derived from Digital Elevation Models (DEMs), with spectral variables extracted from Landsat-8 satellite images and in-situ data collected from the field. The final result showed that the studied area hosts more than 3900 ha of wet forests (alder and riparian forests), with an overall accuracy, estimated using field observations, higher than 85 %. This new approach allows mapping the spatial distribution of wet forests at large geographic scales and could be used as a support to facilitate their monitoring, using EO time series, but also to better implement management and conservation measures.Les forêts humides sont parmi les écosystèmes humides les plus dégradés et les plus menacés dans le monde. En Algérie, elles représentent un ensemble d’habitats forestiers singuliers, fragiles et rares. La région d’El Kala, à l’extrême nord-est du pays, abrite de nombreuses zones humides uniques (lacs, marais, prairies humides, lagunes, etc.), parmi lesquelles quelques-unes des plus importantes formations de forêts humides en Afrique du Nord. L’objectif de cette étude est de développer une nouvelle approche cartographique afin de localiser et de délimiter ces formations à l’aide des outils d’observation de la Terre. Elle se base sur une combinaison d’indices topographiques et hydro-géomorphologiques, issus des Modèles Numériques de Terrain (MNT), de variables spectrales calculées à partir des images Landsat-8 et de données collectées sur terrain. Le résultat final a permis de mettre en évidence l’existence de plus de 3900 ha de forêts humides (aulnaies plus ripisylves) sur l’ensemble des bassins versants de la région d’El Kala, avec un niveau de fiabilité, estimé à partir d’observations terrain, supérieur à 85 %. Ainsi, la méthodologie développée ici permet de définir la distribution spatiale des forêts humides sur de grandes échelles territoriales, ce qui pourrait grandement faciliter leur suivi diachronique, avec des analyses rétrospectives rendues possible grâce aux outils de télédétection, mais aussi une meilleure implémentation des outils dédiés à leur gestion et à leur conservation.Kahli Asma, Belhadj Ghania, Gaget Élie, Merle Clément, Guelmami Anis. Cartographie des forêts humides dans la région d’El Kala (Algérie) à l’aide des outils d’observation de la Terre. In: Revue d'Écologie (La Terre et La Vie), tome 73, n°4, 2018. pp. 431-445

Coupling future climate and land‐use projections reveals where to strengthen the protection of Mediterranean Key Biodiversity Areas

International audienceIdentifying sites that are both important for biodiversity and likely to be heavily affected by anthropogenic pressures in the future is crucial to settle priorities in the implementation of conservation measures, such as the designation of new protected areas. Although assessing the exposure of terrestrial Key Biodiversity Areas to global change would support such identification, it has never been performed to our knowledge. In addition, previous exposure assessments have been limited to few metrics of climate change and have not considered other global change components. Here, we assess the extent to which terrestrial (including inland water) Key Biodiversity Areas are exposed to future climate change and land-use modifications in 29 countries of the Mediterranean region, and identify countries where additional protection efforts are most needed. To this end, we calculated two local and two regional exposure metrics using projections of climate and land-use for late 21st century under four scenarios that were used in the sixth assessment report of the Intergovernmental Panel on Climate Change (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). These four exposure metrics were subsequently combined into an exposure index ranking sites from least to most exposed to climate and land-use changes. We highlight that the most exposed non-protected Key Biodiversity Areas are located in countries where the protection of this network is lowest (i.e., high number and percentage of non-protected sites). We also found that Key Biodiversity Areas were overall more exposed than the rest of the study zone and that the sites most in need of conservation actions were similar across future scenarios. Our study reinforces the pressing necessity to strengthen and extend conservation measures in Mediterranean Key Biodiversity Areas, especially in Middle-East and Maghreb countries whose Key Biodiversity Areas are both at risk to be strongly affected by anthropogenic pressures and insufficiently protected

Mapping of wet forests in El Kala area (Algeria) using Earth Observation tools

Les forêts humides sont parmi les écosystèmes humides les plus dégradés et les plus menacés dans le monde. En Algérie, elles représentent un ensemble d’habitats forestiers singuliers, fragiles et rares. La région d’El Kala, à l’extrême nord-est du pays, abrite de nombreuses zones humides uniques (lacs, marais, prairies humides, lagunes, etc.), parmi lesquelles quelques-unes des plus importantes formations de forêts humides en Afrique du Nord. L’objectif de cette étude est de développer une nouvelle approche cartographique afin de localiser et de délimiter ces formations à l’aide des outils d’observation de la Terre. Elle se base sur une combinaison d’indices topographiques et hydro-géomorphologiques, issus des Modèles Numériques de Terrain (MNT), de variables spectrales calculées à partir des images Landsat-8 et de données collectées sur terrain. Le résultat final a permis de mettre en évidence l’existence de plus de 3900 ha de forêts humides (aulnaies plus ripisylves) sur l’ensemble des bassins versants de la région d’El Kala, avec un niveau de fiabilité, estimé à partir d’observations terrain, supérieur à 85 %. Ainsi, la méthodologie développée ici permet de définir la distribution spatiale des forêts humides sur de grandes échelles territoriales, ce qui pourrait grandement faciliter leur suivi diachronique, avec des analyses rétrospectives rendues possible grâce aux outils de télédétection, mais aussi une meilleure implémentation des outils dédiés à leur gestion et à leur conservation.Wet forests are among the most threatened and degraded wetland ecosystems in the world. In Algeria, they are mainly represented by specific, fragile and rare forest habitats. The region of El Kala (North-East of Algeria) hosts many unique wetlands (e.g. lakes, marshlands, wet meadows, lagoons, etc.) but also some of the most extended wet forests in North Africa. The main objective of this study is to develop a new mapping approach for the location and the delineation of these ecosystems using Earth Observation (EO) tools. This methodology is based on a combination of topographic and hydro-geomorphological indices derived from Digital Elevation Models (DEMs), with spectral variables extracted from Landsat-8 satellite images and in-situ data collected from the field. The final result showed that the studied area hosts more than 3900 ha of wet forests (alder and riparian forests), with an overall accuracy, estimated using field observations, higher than 85 %.This new approach allows mapping the spatial distribution of wet forests at large geographic scales and could be used as a support to facilitate their monitoring, using EO time series, but also to better implement management and conservation measures

Existing areas and past changes of wetland extent in the Mediterranean region: an overview

We quantified the amount of existing wetlands in the Mediterranean region as well as their losses in the past century. An estimated 18.5 ± 3.5 million ha of wetlands existed in c. 2000, one quarter of them consisting of artificial wetlands, including primarily reservoirs and ricefields. Past losses were estimated to represent c. 50% over the 20th century. Land-cover maps derived from the CORINE Land-Cover system were also used to test whether they could monitor total surface areas, surfaces by wetland types, or wetland losses, at the required scale.Nous avons quantifié la surface de zones humides existant en Méditerranée, ainsi que leurs pertes au cours du siècle passé. Environ 18,5 millions d’hectares (± 3,5 millions) existaient vers l’an 2000, dont environ un quart de zones humides artificielles, principalement des réservoirs et des rizières. Les pertes sont estimées à environ 50 % au cours du XXe siècle. Les cartes d’occupation du sol tirées de CORINE Land-Cover ont aussi été utilisées, afin de tester si elles permettraient de suivre, à l’échelle requise, la surface totale, la surface par type de zones humides, et la perte de ces milieux.Perennou Christian, Beltrame Coralie, Guelmami Anis, Tomàs Vives Pere, Caessteker Pierre. Existing areas and past changes of wetland extent in the Mediterranean region: an overview. In: Ecologia mediterranea, tome 38 n°2, 2012. pp. 53-66

Example of the layer union process for Dep. 13.

<p>Water bodies, wetland vegetation and rice fields are combined to obtain the wetland indicator layer.</p

Map of wetlands of the PACA region.

<p>To the left, surface detected by the wetland indicator; to the right, inventory of wetlands.</p

Anthropogenic stressors are driving a steep decline of hemipteran diversity in dune ponds in north-eastern Algeria

International audienceIn arid North Africa, dune ponds qualify as hotspots of aquatic biodiversity, offering numerous sustainable ecosystem services. Despite mounting anthropogenic pressures that threaten their integrity, the overall consequences of these changes have yet to be documented and no strategy to mitigate potential impacts is being implemented. We monitored four dune ponds in northeast Algeria during five hydrological cycles spanning the period 1996–2013. The analysis revealed a steep decline in species richness (47%) and abundance (94%) over the study period. Remote sensing-based data indicated that marked human-induced changes in and around these dune ponds have over time led to a substantial expansion of built areas and cultivated plots and a reduction in both natural wet- and dry-land habitats. Fish predation by the introduced fish, Gambusia holbrooki, may have had both direct and indirect impacts on notonectids. We argue that aquatic hemipterans have undergone an alarming reduction driven by a combination of invasive species, human encroachment, agricultural runoffs, and possibly, climate change