[Invasive-species] criteria for a list of invasive species

[BRANQUART Etienne]

Dear all,

The reference date for Category D is indeed a critical issue. I have to
acknowledge that 'naturalised species' is maybe not the right term for it as
the idea is to have a category including archeophytes and 'archeo animals'
that were introduced in Belgium a long time ago and are supposed not to be
detrimental to native species today. Maybe can we use the term 'assimilated
as indigenous' used in the Belgian flora ? Any other idea ?

Etienne

PS : note that some species that were introduced in Belgium quite a long
time ago as Prunus serotina (1890) or Ondatra zibethicus (?) have really
become invasive several decades after introduction (lag time concept) and
are still very problematic today. Such species are of course not covered by
Category D.

----- Original Message ----- 
From: "Roger Cammaerts" <rcammaer at ulb.ac.be>
To: <Invasive-species at biodiversity.be>
Sent: Sunday, January 22, 2006 6:57 PM
Subject: [Invasive-species] criteria for a list of invasive species


> Dear all,
>
> The critera you suggest for the building up of a list of invasive exotic
species in Belgium sound fair, but I want to add a remark.
>
> For animals, the date criterium for naturalized species (category D) could
be taken shorter than for plants (1500). For instance, the Amphipod Gammarus
roeseli is considered to be a naturalized species, although it was only
encountered for the first time in 1931 in Belgium, this is not yet a century
.But for the Amphipod specialists, it is established "since long" in our
country and it seems to be in balance with its environment. Moreover, it is
apparently restricted to some portions of turbid rivers and do not appear to
be invasive.
>
> May I add that, according to a decree of the Flemish Government of 31
April 1993, animals present for more than 50 years in Flanders are not more
considered to be exotic to the fauna. As a consequence to this arbitrary
decree, Orconectes limosus, seen for the first time in Belgium in 1962,
might soon receive the status of  naturalized crayfish. It is possibly is in
balance with its environment (large turbid rivers as well as smaller waters
of good quality) and we may suspect that it has taken the place of our
native Astacus astacus, long ago ruled out of these rivers by pollution and
pleague.
>
> What I want to say is that we never should lose sight  that all
classifications are somewhat arbitrary.
>
> Dr Roger Cammaerts,
> Laboratoire de Systématique et d'Ecologie Animales,
> Université Libre de Bruxelles,
> CP 160/13
> av. F.D. Roosevelt 50
> B-1050 Bruxelles
> Belgique
>
>
>
>
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