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 threatenbiological 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).
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 semi-natural 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.
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 thatthe 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.