Download 25. invasive non

Invasive non-native species
‘Invasive non-native species’ formed the second
group of species for which management was
deemed necessary to benefit nature. Here,
targeted action is focused on species that are
not native, and which are harmful to the wider
biodiversity of a given area.
The hierarchy of action in dealing with such
invasive species is: prevention, containment
and then control. The most effective action is to
prevent the spread of invasive non-native species
into Scotland in the first place - those species
that present a recognised but imminent threat
need to be targeted in particular. In Scotland
the Non-Native Species Action Group currently
provides a lead in coordinating necessary action
for such species. However, the SAF concentrated
on species that had already established themselves
in Scotland. Actions for invasive non-native species
can include control measures to reduce their
population or limit their spread, or efforts to modify
the human activity contributing to their spread
(through enactment and enforcement of legislation,
voluntary agreements or through education and
promotion of codes of practice).
SNH’s priorities related mainly to the control of
such species where they affected sites, habitats and
species of high nature conservation importance,
including genetic as well as ecological threats.
Six out of the 32 SAF species were included here.
These became the focus of new, targeted effort and
resources over the five year project. These met the
SAF criterion of being ‘non-native species present in
Scotland and assessed as presenting the greatest risk
to biodiversity of high conservation value.’
The following species became the focus of new
action under this heading:
Plants
• New Zealand pygmyweed
• Rhododendron ponticum and its invasive
hybrids
• Wireweed
American mink
© John MacAvoy
Grey squirrel
© Laurie Campbell
North American signal crayfish
© Lorne Gill/SNH
Wireweed
© Lorne Gill/SNH
Vertebrates
• American mink
• Grey squirrel (see chapter 8)
Invertebrate
• North American signal crayfish