Gebietsfremde Arten der Schweizer Flora – Ausmass und Bedeutung

Abstract

The species composition of the flora of any region changes with time as some species decline and new species immigrate. Within the last 150 years, we witnessed a rapid decline of rare species due to habitat destruction and a rapid increase in the number of non-native species introduced and becoming naturalized. The spread of non-native species into natural and semi-natural habitats is an important issue in conservation biology and will increase in its significance as more and more alien species are becoming naturalized. The presence of alien species changes the taxonomic and ecological composition of a flora, making different floras more similar, and leads to the spread of invasive species – fast growing species that become dominant where established and supress native vegetation. Whereas the extent of declining species is rather well documented, data on the extent of the alien flora are lacking for Switzerland. This paper gives an overview on the alien flora of Switzerland and explores trends in the taxonomic composition and geographic origins.