INTRODUCTIONS OF AQUATIC AND RIPARIAN MAC ROPHYTES INTO CONTINENTAL FRENCH HYDROSYSTEMS - AN ATTEMPT AT EVALUATION

Introductions of aquatic and riparian macrophytes into Continental Fra nce are difficult to evaluate because agents are numerous and the outc ome of these introductions is highly variable, from a rapid decrease t o a proliferation involving nuisances. Nevertheless, a preliminary eva luation is presented here for aquatic species. All categories of hydro systems and most biological types of macrophytes, from algae to trees, are potentially concerned by such introductions. The ecological proce sses that are responsible for large proliferations of introduced macro phytes are discussed in connection with the biological characteristics of the species and the ecological features of the receiving ecosystem s. When extensive growth occurs, the management of the ecosystems affe cted becomes difficult. The lack of administrative rules adapted to th ese environmental risks is obvious. It concurs to a deficiency in gene ral ecosystem investigation and to our limited means of checking proli feration, thus making management highly uncertain.