Download Definitions of the terms alien species/plants and invasive

Document: ISPM2 EWG-12 Rev. 1
Agenda point: 8
Definitions of the terms alien species/plants and invasive alien species/plants (Rev. 1)
Discussion paper by Gritta Schrader and Uwe Starfinger
Introducing remark: We have strong doubts, that it is useful and necessary to include
the definitions for ‘invasive’ / ‘invasive alien plant’ or ‘invasive alien species’ into the list
of definitions / the IPPC glossary. To illustrate our doubts, we have put together existing
definitions and comment these in the following:
CBD:
Alien species refers to a species, subspecies or lower taxon, introduced outside its
natural past or present distribution; includes any part, gametes, seeds, eggs, or
propagules of such species that might survive and subsequently reproduce.
COMMENT:
Strictly speaking, this definition only includes organisms that are already introduced. If you
have a look at the statements by the OEWG on invasive alien species in Rome 2000 (which
were adopted by the ICPM in 2001):
RELATIONSHIP BETWEEN INVASIVE SPECIES AND QUARANTINE PESTS
…
15.
Notes that species that may be invasive and that directly or indirectly affect plants or plant products or
that may be used as biological control agents should be assessed, monitored and managed if necessary according
to IPPC provisions and standards.
16.
Notes that those species that are identified under paragraph 15 and that are absent (not present) from an
area (or if present, are limited in distribution and subject to official control) should be considered quarantine
pests and should be subjected to measures according to IPPC provisions and standards.)
you see that this is incompatible. An invasive alien species (which is by definition already
introduced – i.e. entry + establishment in IPPC language or – according to the CBD - moved
by human agency, indirect or direct, outside of its natural range) is only a quarantine pest, if
absent from an area (or limited in distribution).
Additionally, this definition does not include species which could enter on their own but
depend on indirect human help (e.g. change of habitats due to anthropogenic activities). Also,
according to this definition species that had once been present in an area are not alien, even if
they have long been extinct (e.g. Pseudotsuga or Ginkgo in Europe).
Cultivars and hybrids are not included, as they do not have a natural past or present
distribution.
Invasive alien species means an alien species whose introduction and/or spread threaten
biological diversity.
COMMENT:
Does biological diversity include crops and other cultivated plants? There is some dissent.
How does agricultural biodiversity fit in? What would the political implications be? Is it
necessary to include ‘whose introduction and / or spread’?
If 'spread' is included in the definition, a localised population cannot be called invasive even if
it has a large impact on biodiversity. If 'introduction' is in the definition, a species will cease
to be invasive after its introduction (because the introduction is the threat, not the impact).
Document: ISPM2 EWG-12 Rev. 1
Agenda point: 8
Proposal EPPO (first draft of standard for import of plants; has now been deleted):
Alien species: a species growing or under consideration to be grown outside of its
natural range and dispersal potential.
COMMENT:
This definition excludes cultivars and hybrids, as these do not have a natural range.
Dispersal potential should be deleted. If the species disperses naturally, this would be its
natural range. Before it does, there is only some estimation what the dispersal potential would
be.
The definition ties the alienness of a species to its (intended) occurrence in a region. That
implies that a species that is neither present nor considered to be grown in a region is not
alien.
Invasive alien species: an alien species, which becomes established in natural or seminatural ecosystems or habitats, is an agent of change, and threatens native biological
diversity.
COMMENT:
This is a very narrow definition. It excludes explicitly
- agricultural biodiversity
- habitats like intensively used pastures, highway sides, urban areas etc.
- non-native biological biodiversity (which may well be worthy of protection, cf. central
Europe)
(same definition as from IUCN Guidelines)
IUCN Guidelines for the Prevention of Biodiversity Loss Due to Biological Invasion:
Alien species (non-native, non-indigenous, foreign, exotic) means a species, subspecies,
or lower taxon occurring outside of its natural range (past or present) and dispersal
potential (i.e. outside the range it occupies naturally or could not occupy without direct
or indirect introduction or care by humans) and includes any part, gametes or
propagule of such species that might survive and subsequently reproduce.
COMMENT:
This definition is unnecessarily long. In addition see other comments above.
Alien invasive species means an alien species which becomes established in natural or
semi-natural ecosystems or habitats, is an agent of change, and threatens native
biological diversity.
COMMENT:
See comments above
Wittenberg et al. 2005
Alien species: a species introduced outside its natural distribution.
Invasive alien species (IAS): an alien species which threatens ecosystems, habitats and
species. These are addressed under Article 8(h) of the CBD.
Document: ISPM2 EWG-12 Rev. 1
Agenda point: 8
COMMENT: short and clear, but see above for "introduced". Cultivars and hybrids not
included etc.
Discussion
1.) It is important to notice that both words 'alien' and 'invasive' are always related to
organisms in a given area. This may be a continent, a region, a country or a part thereof, e.g.,
a city (as in "The alien flora of Salzburg") etc. This means that a species may be alien to one,
but indigenous to another part of the same geographical unit. The same holds for 'invasive':
areas where a species is invasive may be very close to areas with no invasive behaviour of the
same species.
2.) A consistent use of these terms cannot be reasonably aspired, since so many definitions
and uses are documented (e.g. Richardson et al. 2000, Colautti & MacIsaac 2004). It should in
particular be noted, that in the field of invasion ecology, the term 'invasive' is often tied to a
certain rate of spread rather than to a threat.
3.) As outlined in this discussion paper, existing definitions are inconsistent or incomplete (or
both). All of them include terms (e.g. biodiversity, threat…) that would need to be defined as
well, if definitions were put up.
4.) ISPM No. 11 uses the terms “invasive plant/weed”. The use of both terms underlines that
both cultivated and uncultivated areas are covered. It is not necessary and not intended to
have a clear separation between the two terms. Also, some contracting parties to the IPPC use
invasive plant and weed in different ways, sometimes even as synonyms.
The solution to this dilemma could be that the use of the terms ‘invasive’, ‘alien’ etc. was
accompanied by an explanation (e.g. invasive refers to threat to biodiversity), possibly in
an introducing sentence in the relevant section or in a note without having a glossary
definition.