[UBEBLOCK HIT] Re: [Invasive-species] criteria for a list of invasive species

Filip Verloove filip.verloove at swc.be
Tue Jan 31 13:08:39 CET 2006

Dear all,

Herewith some suggestions, remarks,... from Leo Vanhecke and myself.

1. General remarks

In our opinion the distinction man-made habitats / (semi-)natural habitats
is very artificial. Even the so-called (semi-) natural ones are always in a
certain degree influenced by man (dunes, heathland, ponds,...; natural lakes
are totally absent). The question appears to be in which degree an habitat
is influenced by man rather than whether it is man-made or (semi-) natural.
As a consequence, for many habitats it is difficult to assess whether a
taxon is present in a man-made or semi-natural habitat and hence to decide
if it belongs to categorie A or B.

For the cat. A and B, once established, a limitative list of concerned taxa
should be presented. Moreover, it should be stated that the list is temporal
and regular updates are required.

Cat. C and D should be united (naturalized but non-invasive species) as they
only differ in time of introduction (archaeophytes vs. neophytes). For this
categorie (with countless taxa!) an enumeration of taxa is probably not
needed (or the enumeration of some examples will be sufficient).

2. Specific remarks

Several aquatic weeds are causing severe damage for waterrecreation and
waterhousehold. We guess this belongs to "damage to economy" but it should
probably be cited explicitely.

>From cat. A I believe Ambrosia artemisiifolia should be removed. On the one
hand it is surely not naturalized in Belgium, on the other hand I don't
think that health problems caused by this species have been registered from
Belgium (contrary to France, especially Rhône-valley, where it is, indeed, a
serious problem).

>From cat. B "colonise only man-made habitats" is perhaps better replaced by
"colonise chiefly..." (as far as the distinction man-made / semi-natural is
obvious; see above). Many taxa are found in various types of habitats and
can be ascribed to cat. A as well as cat. B. Ailanthus altissima for
instance is usely found in urban areas but also occurs in more natural
river-valleys. Buddleja davidii idem but also occurs in the seadunes. Idem
for Fallopia japonica,...

Finally, from my own experience, while compiling my checklist of non-native
vascular plants in Belgium, I must admit that it is sometimes very difficult
and arbitrary to judge whether a given taxon is invasive or not. For many
taxa intensive and long-time research is probably required to assess. The
American Lindernia dubia, for instance, produces crowded populations but
only very locally and in artificial habitats (fishing ponds) but it is found
along with (and outcompetes??) very vulnerable native taxa. Is it invasive
or not? I don't know...
Some exotics used to be more or less invasive (e.g. Juncus tenuis) but are
now perhaps well-integrated without causing damage.

For the moment, this will do. Sorry to be of so little help...

All best wishes,
Filip Verloove
National Botanic Garden of Belgium

-----Oorspronkelijk bericht-----
Van: invasive-species-bounces at biodiversity.be
[mailto:invasive-species-bounces at biodiversity.be] Namens BRANQUART Etienne
Verzonden: maandag 23 januari 2006 11:00
Aan: Invasive alien species in Belgium
CC: LM.Delescaille at mrw.wallonie.be
Onderwerp: [UBEBLOCK HIT] Re: [Invasive-species] criteria for a list of
invasive species

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 ?


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: [UBEBLOCK HIT] [Invasive-species] criteria for a list of invasive

> 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
> 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
> _______________________________________________
> Invasive-species mailing list
> Invasive-species at biodiversity.be
> http://www.biodiversity.be/cgi-bin/mailman/listinfo/invasive-species

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