[Invasive-species] criteria for a list ofinvasive species

[DE BRUYN, Luc]

Hello,

Sorry for my late response. I think we have to stick as much as possible
to scientific, well defined definitions. My definitions (which I try to
follow in the Flemish Nature Reports) are (very) simple:

Alien species: all (with emphasis on all) species that occur on our
territory and arrived here due through human intervention. This is in
agreement with the definition used in the Netherlands and many other
countries which had severe problems (e.g. New Zealand, Australia). For
most species this is simple because it is known they arrived here by
boat, airplane, ... I hve to admit it is not so clear for other species.
Some fish species could arrive here because (new) canals form corridors
between river catchments which were not connected earlier. Most (all?)
people consider them as aliens. But what about man made changes that
occurred much longer ago, and or are more gradual. For example, take
species like the pigeon Streptopelia decaocto or ferns that grow on
(city) walls. These species arrived in Belgium on there own power, but
only because we changed the environment.

Invasive alien species: species that colonise(d) (semi)natural habitats
and some of these invasive species can have detrimental effects. The
problem with the discrimination of both categories is that there is a
lack of sound scientific studies. Most of the time it is based on
subjective "gut feeling", coincidental observations or superficial
correlative research.

I think "assimilated" or "archeophyta" species are not a good terms in
the scope of alien species. They are too arbitrary. First some of these
species might become invasive/detrimental in the future (see also
further). Second, some of these species are indeed detrimental or at
least have important impact on our natural ecosystems. The rabbit
changes the environment and species composition through grazing.
Pheasants are supposed to be detrimental for our indigenous herpetofauna
(although I do not know a scientific paper that actually proofs this,
maybe somebody can point me to one?). We only learned to live with that
(or we do/did not care).

I also think it should be emphasised that all alien species are
potential time bombs. It has been shown that species can be present for
a long time and suddenly become invasive/detrimental due to adaptation
of the species in question and/or changes in the environment. For
instance, many species now confined to urban environments may become
invasive due to climate change. It is also very important to point out
that it is far more important to prevent the introduction of new alien
species, than to start eradication and/or control programs for the
(invasive) aliens present.

Best wishes,

Luc

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Luc De Bruyn
Instituut voor Natuur- en bosonderzoek (INBO)
Research Institute for Nature and Forest
Kliniekstraat 25
1070 Brussel
tel.: ++32(0)494/89.99.50
web: www.nara.be
     www.natuurindicatoren.be
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