Une gamme d’îles de référence, un atout majeur pour l’évaluation de programmes de restauration dans l’archipel de Kerguelen

Résumé En Fr

The Kerguelen Archipelago is constituted by a main island (6 500 km²) and about sixty secondary islands (1-200 km²). Some of these islands are pristine, while some others have been colonized by introduced plants, invertebrate species and, in some cases, by one or several alien mammals. Programs of ecological restoration began in 1992 on three islands, Verte I., Guillou I. and Cochons I. (respectively 150, 145 and 165 ha) damaged by the presence of mammals (rabbits, rabbits-cats-mice, rabbits-mice). The management action was the eradication of rabbits by poisoning. Due to the existence of reference islands (with or without introduced mammals), and of control islands (presence of rabbits), the Kerguelen Archipelago offers an unusual opportunity to distinguish the effects of the management intervention from those of other factors. For example, synchronised vegetation monitoring of habitats on a control island (Cimetière I., colonized by rabbits) has shown the role of this mammal in controlling one introduced Asteraceae (Taraxacum officinale). After rabbit eradication, this plant drastically increased in cover on the three experimental islands. Moreover, results from Mayes I (without herbivores) and from the 4 other islands studied, emphasized the impact of the present climatic changes on the evolution of plant communities. This factor explains most of the decrease in cover of several native species, especially Acaena magellanica, with the timing of Dandelion’s success linked to open land appearance. These observations confirmed the value of contemporary reference sites to analyze the advantages of restoration programs and to conduct future actions.

L’archipel de Kerguelen est constitué d’une île principale (6 500 km²) et d’une soixantaine d’îles secondaires (1-200 km²). Certaines sont totalement indemnes d’espèces introduites, d’autres ont été colonisées par des espèces végétales et des invertébrés allochtones, et d’autres encore sont occupées, de plus, par un ou plusieurs mammifères introduits. Un programme de restauration écologique concernant trois îles (145 à 165 ha) dégradées par la