Un indice écologique pour la surveillance des zones humides basé sur l’avifaune aquatique : cas de la Tunisie

Hamdi, N. & Ismail-Hamdi, S. (2015). Un indice écologique pour la surveillance des zones humides basé sur l’avifaune aquatique : cas de la Tunisie. Revue d’Ecologie (Terre et Vie): 328–342.

Resumé :

Nous proposons dans ce travail un indice écologique pour la surveillance des zones humides tunisiennes, basé sur la variation des effectifs annuels moyens d’oiseaux d’eau. Ce nouvel outil offre une méthode applicable à la surveillance de toutes les catégories de zones humides du Nord de l’Afrique ayant des similitudes avifaunistiques et hydrologiques. Cet indice écologique se calcule en quatre étapes : (1) discriminer les zones humides en associations partageant des caractéristiques hydro-écologiques communes ; (2) déterminer la valeur indicatrice de chaque espèce sur ces différentes associations, quantifiant la relation d’une espèce à l’une des associations ; (3) calculer les variations temporelles des effectifs moyens de chacune de ces espèces entre deux périodes de suivi (dans notre cas 1970/2000 et 2001/2013) ; (4) calculer la somme pondérée des produits des deux métriques de toutes les espèces indicatrices pour chaque association. L’application de notre indice aux zones humides tunisiennes suggère une dégradation des conditions d’hivernage des lagunes et des sebkhas ainsi que des milieux côtiers. À l’inverse, les conditions d’hivernage dans les plaines inondées et les garaets semblent s’améliorer, notamment pour les espèces anthropophiles. Cette méthode de surveillance des zones humides constitue un nouvel outil de travail simple et efficace pour les professionnels de l’environnement.

Abstract:

Waterbirds as an ecological indicator for monitoring wetlands: an application to Tunisia.

We propose a simple ecological index to monitor wetlands, based on interannual changes in waterbird numbers and the hydro-ecological characteristics of their wintering sites. This new method provides a simple tool applicable to most types of wetlands in northern Africa with comparable waterbird species and hydrological attributes. Scores of this ecological index are calculated through a four-steps approach: (1) discriminate prospected sites into different associations based on their hydro-ecological characteristics; (2) compute indicator values for each waterbird species considered to quantify the strength of species-habitat relationships in each wetland associations; (3) calculate the relative rate of temporal change in indicator species abundances between two sampling events (in our example 2001-2013 and 1970/2000); (4) compute the weighted sum across species of the product of these two metrics within a given wetlands association. The application of our index to the monitoring of Tunisian wetlands suggests the degradation of wintering lagoons and salt pans and coastal environments. Nevertheless, applying the index in floodplains and garaets tends to indicate improved overwintering conditions, especially for man-tolerant waterbird species. Our new index targets environmental stakeholders seeking for an efficient tool for biodiversity monitoring.

 

Monitoring Mediterranean Lesser Crested Terns (Thalasseus bengalensis emigratus) in Libya

RAC/SPA-UNEP/MAP, 2014. Monitoring Mediterranean Lesser Crested Terns Thalasseus bengalensis emigratus. By Baccetti N. and Zenatello M. (Ed.), RAC.SPA, Tunis. 26p + Appendices. PDF

Summary:

The Mediterranean Lesser Crested Terns, Thalasseus bengalensis emigratus, is a Mediterranean endemic seabird, potentially vulnerable to many sources of threat. In 2012, within the framework of the MedMPAnet Project, a study was conducted on this species in Libya, especially in Garah, a potential future MPA where the largest fraction of the seabird global population is concentrated.

Actions and methods are described to monitor the breeding population of the Mediterranean Lesser Crested Tern, which is currently confined to Libya. The aim is providing a tool which will allow a coherent and safe approach to a population of extremely high conservation value, which is potentially vulnerable to many sources of threat, not least monitoring itself.

Assessing changes in population size, distribution and breeding success is crucial for conservation. We attempted to gather recent experiences carried out under the RAC-SPA umbrella to produce a document available for further sharing, that may ensure a correct continuation of activities in the next future. The monitoring guide of the Mediterranean Lesser Crested Tern population is now available on-line at the RAC-SPA website.

 Adult Mediterranean Lesser Crested Tern (Thalasseus bengalensis emigrates) and ringed juvenile at Garah, Libya

Adult Mediterranean Lesser Crested Terns (Thalasseus bengalensis emigrates) and ringed juvenile (c. 10 days old) at Garah, Libya. (photo: J. Sultana).

Breeding colony of the Mediterranean Lesser Crested Terns (Thalasseus bengalensis emigrates) at Garah, Libya

Breeding colony of the Mediterranean Lesser Crested Terns (Thalasseus bengalensis emigrates) at Garah, Libya. (photo: J. Sultana).