Impact des activités anthropiques sur la dynamique et l'état de conservation d'un habitat naturel : exemple de la chenalisation des Rivières à renoncules (UE 3260)

Abstract : Since the publication of the Habitat Directive, France must evaluate the conservation status of natural habitats and species in its territory. With this perspective, we chose the habitat – EU-3260 - “Running chalk streams with Water Crowfoot (Ranunculus spp.)” to test the impact of human pressure such as channelization on the conservation status of this habitat. Our objective was to determine which environmental and biological structures and functions were affected by channelization and could introduce possible impairments of the habitat. Seventeen reaches, in four rivers with similar geomorphology, were monitored in several seasons during two successive years (2006 and 2007). Among these reaches, 6 were considered as reference reaches and 11 as channelized reaches. The latter were distinguished by the method of channelization which could be an embankment, a straightening, or the presence of rigid structures in the stream bed. On the 17 reaches, we then measured several physical and chemical variables, monitored three biological communities (birds, aquatic plants, benthic macroinvertebrates), and tested different biological indices often used in river evaluation. Results showed that channelization led to physical changes of the habitat in several spatial scales: the reach, the riffle-pool sequence, and the microhabitat. For biological communities, taxonomic richness was lower in channelized reaches than in control reaches whatever the community. Dominant taxa were ubiquitous and resistant to environmental stresses. Tested biological indices, and notably IMBR, then showed more debased values in the presence of channelization. Aquatic vegetation was the most interesting biological community to study channelization impact because plants were linked to the different spatial scales, and especially to that of the riffle-pool sequence. Adaptive strategies linked to biological traits of plant taxa were more diverse in channelized reaches in response to the modifications of the spatial and temporal dynamics of the EU 3260 habitat. Our whole study stresses the most appropriate environmental and biological tools for providing information on the impact of channelization. These tools allow us to recommend certain management measures for conserving habitat EU 3260.
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Maëlle Rambaud. Impact des activités anthropiques sur la dynamique et l'état de conservation d'un habitat naturel : exemple de la chenalisation des Rivières à renoncules (UE 3260). Ecologie, Environnement. Museum National d'Histoire Naturelle (MNHN), 2008. Français. ⟨tel-02263254⟩

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