Norsk svarteliste 2007

Norsk svarteliste 2007
Spredning og effekter av fremmede arter Dispersal and effects of alien species
combating them as soon as possible after their arrival
(see Box 12 on the pinewood nematode). This calls for
international cooperation and good monitoring systems
and routines which can reveal newcomers as early as
possible.
Climate change and alien species
One of the most important factors offering alien species
the possibility to become established in Norway is the
climate. Species that are not adapted to boreal (northerly)
or arctic/alpine conditions will naturally not be able
to survive several months of snow and cold. The global
changes in climate, which, here, are expected to result in
more precipitation, longer growing seasons and shorter,
milder winters, may have substantial consequences for
the opportunities for alien species to establish themselves,
particularly those that come from southerly
latitudes. It is expected that species which are nowadays
prevented from becoming established due to a relatively
severe climate will have more opportunity to do so, and
some of these may become invasive (Stachowicz et al.
2002). Some scenarios seem to be quite obvious, for
instance that some of the alien species that are only able
to survive indoors now will be able to establish themselves
outside. Alien insect species that exploit the stable
microclimate in compost heaps to survive the winter in
Norway will be able to become established elsewhere
outdoors (Ødegaard 1999, Ødegaard & Tømmerås
2000). Plants that have so far only survived or thrived
in southern parts of the country will be able to expand
northwards and upwards, provided there are suitable
habitats where they can establish themselves. Many species
of plants are already spreading in Norway (Fremstad
& Elven 1997) and the current climate scenarios make
it likely that several of these will not only expand northwards
and further inland, but also become increasingly
common where they have already become established.
Not all expansion can be ascribed to climate change;
changes in land use (both areas becoming overgrown
and more areas being disturbed) will promote the dispersal
of alien species.
An already important group of species that will
become even more prominent is garden plants that have
run wild or been thrown out, and trees that have run
wild from plantations (Fremstad 1999). Many of the
numerous species that are grown in Norwegian gardens
and green spaces, or in forestry, are so well adapted
to Norwegian conditions that they have already been
found in the wild. Some have been grown for a long
time and have had good opportunities to spread. Oth-
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