Exotics and Invasions of Plants and Animals
The aim of this chapter is to provide an overview of the invasions of exotic biota to the Rhine–Meuse Delta. Invasions of non-native plants and animals to and from western Europe have occurred from prehistoric times onwards, and consequently drastic restrictions in the framework of this chapter are necessary. The focus is on recent (19th and 20th century) invasions in freshwater ecosystems. Estuarinemarine invasions are mainly left out, except for those species that penetrate the brackish environment from the freshwater habitat. Massive marine invasions changing the outlook of complete estuarine ecosystems, such as the Japanese oyster, Crassotrea gigas, and the American razor clam, Ensis americanus, belong to the domain of the environmental history of marine ecosystems (cf. Lotze et al., 2005). The question, what makes invasions successful, is particularly intriguing because disturbed river basins are coined as ecosystems most susceptible to the introduction of exotics. The evidence for causal factors underlying invasion phenomena is scanty, however, and only recently substantiated. Climate change has all too eagerly been coined as explanatory for various invasion patterns, induced by the recently aroused interest for that phenomenon. In this chapter data are given on migration routes and range extensions of tens of species, invertebrates and higher plants. The Ponto-Caspian connection will be highlighted, along which a considerable number of southeastern European and Asian invertebrates entered the western European lowland rivers. The chapter comprises four case studies, two bivalve mollusc species from the Black Sea and the Adriatic Sea, and two plant species from America. The contrast between two historic introductions from the 19th century, and two recent invasions, is worked out.
KeywordsBiomass Europe Phytoplankton Sewage Beach
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