Invasive alien species in Switzerland - Schweizer ...

An inventory of alien species and their threat to biodiversity and economy in Switzerland FOEN 2006 138
With respect to plant life form, the composition of the ecological plant groups of the
alien flora differs from the native one, and it changes during the process of naturalization
and invasion. The proportion of ruderal species in the alien flora is much higher
than in the native one but this discrepancy is reduced during the naturalization process.
In contrast, the proportion of alien forest plant species is lower than that of native
forest plant species but proportions of invasive and native forest plant species are fairly
similar.
10.8 Invasive plant species in Europe
Up to 2003, only a few European countries had compiled data on their alien and invasive
floras at a national level. However, information from several countries is quite
informative about invasive species elsewhere in Europe that could be a threat to Switzerland.
Countries usually make explicit distinctions between invasive species, moderately
or potentially invasive species, and species for which special attention is needed
(usually the so-called ‘Watch List’). We had to interpret some data to a certain extent
to obtain a more consistent result. Austria includes an assessment of economic impact,
which we have reproduced in Table 10.8 (Essl and Rabitsch, 2002). Also, the European
and Mediterranean Plant Protection Organization (EPPO) is preparing a list of invasive
and potentially invasive alien plants for the EPPO region. This information is still
partial and it has not been used for the present review.
Plant species declared invasive or potentially invasive in nine European countries and
occurring in Switzerland are presented in Table 10.8. The list includes over 130 alien
plant species of concern in Europe. Quite obviously, not all of them are sufficiently
pre-adapted to the eco-climatic conditions of Switzerland to present a threat in this part
of Europe. On the other hand, some invasive species in northern European countries,
for example, which are not listed in Table 10.8, could become a problem in Switzerland.
Unfortunately, no detailed list of alien plants in Germany for each of the three
categories defined was available at the time of this review. In contrast, the detailed
information on the status of alien plants in France is highly relevant to Switzerland
(Muller, 2004).
The list of invasive species (‘Black List’) and ‘Watch Species’ in Switzerland is taken
from the CPS-SKEW working group (http://www.cps-skew.ch/index.htm). A few
species in these two categories do not have this status in the other European countries
from which information could be collected (Table 10.8). However, they are invasive on
other continents, e.g. Pueraria lobata (Willd.), and Lonicera japonica Thunberg
(Cronk and Fuller, 1995; Weber, 2003) or their taxonomy is complex and their invasive
status may not yet have been recognized (e.g. Rubus armeniacus).
Fact Sheets have been prepared for 48 plant species. They include 19 invasive species
and 11 ‘Watch Species’ of the CPS-SKEW working group. In this report, another 18
species to which special attention should be given in the future are also presented in
Fact Sheets. These species have been selected according to their status in neighbouring
countries and a previous list of potentially invasive species prepared by the CPS-
SKEW working group (Table 10.8).