Journal of Agricultural and Environmental Ethics

, Volume 25, Issue 4, pp 597–606

EU DAISIE Research Project: Wanted—Death Penalty to Keep Native Species Competitive?



DOI: 10.1007/s10806-011-9323-5

Cite this article as:
Zisenis, M. J Agric Environ Ethics (2012) 25: 597. doi:10.1007/s10806-011-9323-5


Neobiota as non-native species are commonly considered as alien species. The Convention on Biological Diversity (CBD) intends to “prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species”. The European Union has financed the DAISIE research project for the first pan-European inventory of Invasive Alien Species (IAS), which is supposed to serve as a basis for prevention and control of biological invasions. This paper discusses the evaluation approach for classifying “100 of the Worst” IAS in Europe by the EU DAISIE research project. The main impact categories used by DAISIE for assorting “100 of the Worst” IAS are investigated and the texts of the “Wanted” species factsheets are examined. Two examples from the DAISIE factsheets of the “100 of the Worst” IAS [Tree of Heaven (Ailanthus altissima) and the Raccoon (Procyon lotor)] are discussed to illustrate DAISIE’s biodiversity evaluation approach in more detail. However, the classification criteria used by DAISIE do not allow for sufficiently differentiating these neobiota from an ecological behavior of native species with a similar ecological niche. In conclusion, neobiota evaluations are not comprehensive when they refer mainly to the successful expansion and competition with native species into available ecological niches. A comprehensive assessment of the impacts of neobiota on biodiversity and humans needs to take into account the different values of biodiversity as mentioned in the preamble of the CBD.


Biodiversity evaluationCBD valuesEnvironmental impact assessmentEuropean biodiversity policyInvasive alien speciesNeobiota


Neobiota as non-native species are commonly considered as alien species. The Convention on Biological Diversity (CBD) urges its member states in Article 8 (h) to “prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species” (CBD 1992). Thus, Invasive Alien Species (IAS) means an alien species whose introduction and/or spread threaten biological diversity according to decision VI/23 of the Conference of the Parties (CBD 2005). Biological diversity includes the diversity within species, between species and of ecosystems as defined in Article 2 paragraph 1 of the Convention on Biological Diversity (CBD 1992). It ranges from global earth level via ecosystem complexes, ecosystems, landscapes, metapopulations, populations, species, subspecies, individuals, parts of individuals, cells, gene nets, alleles, to genes.

In line with international initiatives to address IAS (Clout and De Poorter 2005), the European Union has taken steps towards tackling IAS by the EU Council of Environmental Ministers in their conclusions in June 2009, March 2010, and June 2011 (EU 2009, 2010, 2011). The EU Biodiversity Action Plan intends to prevent and to minimize the impacts of IAS on biodiversity in the EU and to encourage the EU Member States to equally prepare national strategies and plans to reduce impacts from IAS (EC 2010). The EU Biodiversity Strategy to 2020 urges to identify and to prioritize IAS and their pathways for prevention, control, and eradication (EC 2011). From 1992 to 2006, the EU has already spent more than 132 million EUR for almost 300 projects dealing with IAS within their financial instruments of the LIFE Programme and the Framework Programmes for Research and Technological Development (Scalera 2010).

For halting the loss of biodiversity by 2010 and beyond in Europe (EC 2006), an indicator should be established that quantifies responses to IAS, e.g., the number and cost of national management activities against IAS (Hulme et al. 2009a). Legally binding blacklists are needed of a wide range of invasive pests in aquatic and terrestrial environments to be prohibited from import and sale in Europe (Hulme et al. 2009a).

There are several attempts globally to list and to describe IAS and their impacts on biological diversity (Sellers et al. 2010). The Global Invasive Species Database provides information on worldwide examples of successfully invasive non-native species (e.g., Lowe et al. 2004). On the European level, the Sixth EU Research Framework Programme (FP6) has financed the Delivering Alien Invasive Species Inventories for Europe (DAISIE) database (Hulme et al. 2009b) for delivering the first pan-European inventory of IAS (EC 2008). According to the European Commission, a regularly updated DAISIE inventory of IAS could serve for species eradication plans supported by national funds (EC 2008).

This paper shall neither provide a review of the discussed impacts of IAS in general (e.g., Pejchar and Mooney 2010; Pyšek and Richardson 2010; Vilà et al. 2009a) nor add to the long list of debates on defining the term “invasive” (e.g., Colautti and Richardson 2009; Valéry et al. 2008) while referring to the CBD definition of IAS mentioned above. It intends to enrich the discussion by providing a scientific and politically relevant example from Europe on how species characteristics are used to classify non-native species as one of the Worst IAS as a basis for urgent political action on European level by the EU FP6 DAISIE research project. First, the main impact categories were analyzed that were used by DAISIE for assorting “100 of the Worst” IAS in Europe. Second, the text descriptions of the “Wanted” species factsheets of “100 of the Worst” IAS defined by DAISIE were analyzed to see if they allow distinguishing them from the ecological behavior of native species. Third, two examples of the DAISIE database list on “100 of the Worst” IAS were discussed in more detail to illustrate DAISIE’s biodiversity evaluation approach. Finally, conclusions are drawn for an interdisciplinary evaluation framework of biodiversity that can be used to evaluate neobiota as part of biodiversity comprehensively, transparently, and comparably for risk assessments and management decisions of IAS.

100 Non-Native Species Evaluated by DAISIE as Among the Worst IAS in Europe

DAISIE lists ecological impacts for 1,094 species and economic impacts for 1,347 species out of a gathered database of more than 10,000 fungi, plant, and animal species alien to Europe that involved contributions from more than 1900 European experts on biological invasions (Vilà et al. 2009a; DAISIE 2008). The DAISIE database considers only alien species introduced to Europe after the discovery of America by Columbus in 1492 (Vilà et al. 2009a), so called neobiota (Kowarik 2003). “Verified by experts”, factsheets were produced of the ecological and economic impacts of alien species (Vilà et al. 2009a). “100 of the Worst” IAS were nominated by experts working within the DAISIE research project (Vilà et al. 2009b). A short description of the ecological characteristics of each neobiota species is presented on every “Wanted” factsheet together with the current distribution in Europe and their impacts on ecology, socio-economic values, and human and animal health. Furthermore, management measures are recommended to prevent and to treat the invaders (DAISIE 2008; Vilà et al. 2009b).

The following analysis of all 97 “Wanted” neobiota factsheets shows the categorized impact classes that were used as criteria for qualifying them as “100 of the Worst” IAS in Europe by DAISIE (Fig. 1).
Fig. 1

Categorized impacts of ‘100 of the Worst’ Invasive Alien Species in Europe (adapted from DAISIE 2008)

Competition with native species (77) is the major reason to put neobiota on the “Wanted” list of “100 of the Worst” IAS in Europe. However, additional neobiota characteristics including decrease of productivity (52), mechanical destruction (38), as well as pathological reaction (34) classify them as an urgent threat to biodiversity and humans according to DAISIE.

Looking into the text descriptions of the DAISIE database list on “100 of the Worst” IAS in more detail, it turns out that quite a lot of the quoted impacts on biodiversity and humans are based on an ecological behavior that cannot be distinguished from native species in Europe (Table 1).
Table 1

Quotations of selected text examples of Invasive Alien Species’ (IAS) impacts on biodiversity and humans in Europe (adapted from DAISIE 2008)

“100 of the worst” IAS name

Impact according to DAISIE’s database

Bay Barnacle (Balanus improvisus)

Sharp shells on the beach may cause human injuries

Canada Goose (Branta canadensis)

Some threat to air safety from collisions with aircraft have been noted. It is also a minor feeder on crops

New Zealand Pigmyweed (Crassula helmsii)

Floating mats can be mistaken for dry land

Himalayan Balsam (Impatiens glandulifera)

It is also expected to successfully compete for pollinators, e.g., with Stachys palustris. The species is capable of changing the appearance of riverbanks completely, especially when in bloom

American Mink (Mustela vison)

Can inflict damage to free ranging chickens, reared game birds, fisheries (salmon farming) and the eco-tourist industry through predation on ground nesting birds

Nutria (Myocastor coypus)

The impact on wetlands through feeding on aquatic vegetation could be severe. Selective feeding by coypu caused massive reduction in reedswamp areas, and eliminated plants of Rumex spp. and Nuphar lutea over large areas. It destroys nests and preys on eggs of several aquatic birds, including some endangered species

Round Goby (Neogobius melanostomus)

It often eats bivalves that filter the water, and is a vector for bioaccumulation of many contaminants. The contaminants that build up are passed on to larger game fish that prey on this species and then possibly on to humans

Red Swamp (Procambarus clarkia)

It accumulates heavy metals and toxins produced by Cyanobacteria, such as Microcystis aeruginosa, and can transfer them to its consumers, including humans. It is an intermediate host of trematodes of the genus Paragonimus, which are potential pathogens of humans if undercooked crayfish are consumed

Rose-ringed Parakeet (Psittacula krameri)

Some noise disturbance from loud squawking and screeching at large roost sites. Parakeets, which begin breeding prior to most other secondary cavity-nester species, may limit resources available for species such as House Sparrow (Passer domesticus), Stock Dove (Columba oenas), European Nuthatch (Sitta europaea) and European Starling (Sturnus vulgaris)

Robinia (Robinia pseudacacia)

The large blossoms of black locust compete with native plants for pollinating bees

However, native species also feed on plants and animals, respectively. They can carry diseases, accumulate toxic substances, and might be harmful in direct contact to humans. Native species may as well be perceived as being noisy, and they may dominate landscapes in high abundance. It becomes obvious that the cited text examples by the DAISIE research project for classifying them as “100 of the Worst” IAS do not sufficiently indicate the differentiating characteristics of neobiota, which separate them from native species with a similar ecological niche.

Two neobiota examples of the DAISIE database list on “100 of the Worst” IAS underline these overview results in putting the DAISIE evaluation approach of IAS into question.

Tree of Heaven (Ailanthus altissima)

The Tree of Heaven, which is native to China and Northern Korea, was introduced by the Jesuit Pierre d’Incarneville to Paris in 1740. It was rapidly distributed as a decorative tree in the Old and New World, respectively (Kowarik 2003). Today, the Tree of Heaven is widely spread in Western, Central, parts of Southern and Eastern Europe, as well as adjacent Asia (DAISIE 2008). It is a fast growing tree forming dense thickets, which compete with the native vegetation. In addition, it has allelopathic effects, principally due to ailanthone. Contact with plant sap can produce dermatitis. Long exposure to the sap (i.e., team clearing people) can produce myocarditis due to plant quassinoid proteins. Can be a tree-fall hazard along roads. The root system can damage pavements, archaeological remains, walls, etc. (DAISIE 2008).

However, the Tree of Heaven has similar ecological functions in producing fresh air, clean water, and shadow to native tree species. It has become a characteristic (typical) urban tree (Kowarik 2003), which reproduces naturally in the wild. The Tree of Heaven supports the life of several insect, mammal, and fungi species (Kowarik and Säumel 2007). Health risks due to direct contact and long exposure to plant sap seem to be caused by rather unusual human contact behavior. Tree roots and falling branches or stems are also common with natives.

Raccoon (Procyon lotor)

Intentionally released for hunting for its fur in Germany, the Raccoon escaped also from fur farms, zoological gardens, and animal husbandries in several European countries. It is now widespread in Germany with a strong tendency of range expansion (DAISIE 2008). The Raccoon can occasionally predate on birds (nests) and amphibians decreasing nesting success and/or population sizes. Due to the raccoon roundworm (Baylisascaris procyonis) there is a high potential of zoonosis for humans and its animal vectors. The cerebral larva migrans in humans caused by the raccoon roundworm can be lethal. But at the moment there have not been any lethal cases nor serious raccoon rabies cases in Europe (DAISIE 2008). Like with other wild animals, we must be aware of such health risks (Boye 2003). Furthermore, Raccoons can disturb boundary areas of settlements when rifling through bins or when using garrets as sleeping quarters (Boye 2003).

However, these characteristics do not seem to distinguish Raccoons significantly from the habitat requirements of native mammal species, such as the Beech Marten (Martes foina), which has coadapted to human settlements as a cultural follower (see Klausnitzer 1993). The Raccoon just fills an ecological niche and has become a naturally reproducing and established species in Central Europe.

Neobiota Need to be Comprehensively Evaluated

Successful expansion of neobiota does not necessarily imply it has negative impacts on biodiversity. It depends on the particular evaluation case if certain neobiota species can be assessed as being a threat to the different functions and values of biodiversity (Brown and Sax 2004, 2005; Sagoff 2005, 2009; Warren 2007, 2009).

For instance, it seems to be arbitrary to evaluate the assumed negative impacts on (ordinary) scales of the reduction of the abundances of other taxa by non-native species, for instance, generally as high >50%, as medium 20–50%, and as low <20 (Kowarik et al. 2003a, b; see also Ricciardi and Cohen 2007), because there can be more or less severe impacts on the different components of biodiversity on lower or higher degrees of occurrence of non-native species depending on the particular evaluation case at a certain area and time-scale (e.g., Strayer et al. 2006). Competing native species might be driven out below a certain level of their Minimum Viable Metapopulations. This can be estimated by Population Vulnerability Analyses on certain spatial- and time-scales (Gilpin 1987), but not derived from a generalized rule of a certain abundance or expansion rate of neobiota.

In particular, Neobiota can endanger indigenous species with extinction in certain cases, for example, due to habitat competition, predation, introduced diseases, and genetic changes such as hybridizations (Hulme 2007). However, these impacts are often crucially based on habitat changes by the human species (Chytrý et al. 2008). Examples of faunal extinctions of endemic species by neozoa have been described on islands or island like ecosystems such as lakes, but a principal reason of extinction by introduced plants is rather doubtful (Sagoff 2005, 2009). There is no known case for Central Europe, when a non-native species has caused the dying out of a native species (Klingenstein et al. 2003; Kowarik 2003). On the other hand, neobiota can be considered as rare and endangered themselves, if they are currently established or if they were once. Naturalization is combined with a process of selection and adaptation to neobiota. It is just a question of time up to geological time scales until neobiota will have become an integrated part of ecosystems (Cox 2004).

From the historical point of view, neozoa, neophytes, and other neobiota introduced to Europe after 1492 are unnatural by definition (e.g., Klingenstein et al. 2003). However, neobiota can be considered as being natural from the point of view of natural developments at present time, when they have established themselves in an area for the first time neither by being conventionally bred, nor genetically modified, nor actively introduced, nor passively transported by humans. Nevertheless, the human species provides the ground for (re-)establishment of neobiota by land use impacts, especially in cultural landscapes like Central Europe. This refers also to climate change with global impacts, which becomes an increasingly important ecological factor in the reallocation of the distribution of neobiota in modified ecological niches that might overlap with those of native species (e.g., Kleinbauer et al. 2010; Walther et al. 2009). However, the extent of these expected climate change and other human induced species niche/distribution influences cannot be predicted precisely by modeling, for instance, climate envelopes (Thomas and Ohlemüller 2010) due to the complexity and unpredictability of future changes and evolutionary interactions (Lavergne et al. 2010).

The establishment abilities of neobiota depend, like for native species, on colonization possibilities, isolation barriers, and time durations of developments of similar habitats to their native range (Hejda et al. 2009). Obviously, the vulnerability of ecosystems to invasions by neobiota depends on the availability of free ecological niches and the competitiveness with species of already occupied ecological niches. On the other hand, neobiota can fulfil similar ecological functions as native species (Prévot-Juillard et al. 2011), because of the overlapping ecological niches with native species and the evolutionary adaptation process to the new environment. Furthermore, neobiota can also just fill up ecological niches, either when they arrive before native species can occupy them or will occupy these niches during evolutionary times of adaptation and selection processes, respectively (Cox 2004).

Therefore, impact assessments of neobiota cannot be mainly based on general rules of the extent of the expansion and competition with native species for similar ecological niches such as carried out by the EU FP6 DAISIE research project. The induced alterations by neobiota of certain elements, structures, and functions of biodiversity need to be assessed for their particular positive and negative impacts in a weighing up process of the different values to human beings and on their own (intrinsic value). They are just expressions of the surveyed and analyzed changes by neobiota, but do not imply a (normative) value itself. Many neobiota have already become typical parts of nature and landscapes (e.g., Kowarik 2003). In certain cases dominant non-native species might be desired by people. For example, colourful non-native flowers or conifers in the garden can have a positive psychological aesthetic and recreational value for them, while untypical native species might be eradicated by the garden owners, i.e., these gardens can have a high degree of human influences (hemeroby) and a low content of native species, but still a high value for the garden owners.

Conclusions: An Interdisciplinary Evaluation Framework for Neobiota as Part of Biodiversity

The occurrence of neobiota as part of biological diversity cannot be considered a priori as being negative. Assessments of neobiota need to comprehensively consider their impacts on the different values of biodiversity. They can be positive or negative depending on the particular circumstances in space and time. In general, neobiota are supported by natural or human habitat changes (Kowarik 2003; Didham et al. 2005; Pyšek et al. 2009). The human being is the dominant species on earth. An interdisciplinary evaluation framework of biodiversity is necessary for assessing comprehensively the different positive and negative values of neobiota for humans and biodiversity on its own in a weighting up process under participation of the public (Zisenis 2009).

Therefore, the application of Article 8 (h) of the Convention on Biological Diversity must be seen in the decisive light of paragraph 1 of its preamble, which points out the intrinsic value of biological diversity and the ecological, genetic, social, economic, scientific, educational, cultural, recreational, and aesthetic values of biological diversity and its components (CBD 1992). This is a shift from the sometimes emotional experts’ condemnation of the appearance and natural expansion of competitive neobiota as targeted “Wanted” enemies of historically native species (Brown and Sax 2004; Larson 2005; Falk-Petersen et al. 2006) towards a scientifically profound analysis and evaluation. An interdisciplinary evaluation framework of biodiversity allows comprehensive, transparent, and comparable consideration of the impacts of each neobiota on the different values of biodiversity for risk assessments and management decisions of IAS.


I would like to thank Staci McLennan and an anonymous reviewer for their helpful comments to this article.

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© Springer Science+Business Media B.V. 2011