Invasive species in Basel: a critical look at discourses of belonging

#invasive_species #Basel #Switzerland

1 June 2023


Our world is marked by volatility and movement. Change seems to be the only constant. The current debate around protecting ‘native species’ from so-called ‘invasive species’ raises the question how to embrace newness and change as inevitable aspects of our time, while protecting and maintaining other aspects. In the mainstream discourse invasive species are mainly framed as a threat to local harmony and equilibrium. However, this discourse and the practice it leads to are based on politically charged definitions of ‘nativeness’ against which the ‘invasive’ is demarcated and depicted as enemy. This article critically assesses the public discourse around invasive species in Basel, drawing on de-colonial ecology, and focuses on the Basel Botanical Garden and the Stadtgärtnerei. The latter is responsible for all public green and open spaces in the city.

by Pina Haas

Student of MA: Changing Societies: Migration - Resources - Conflicts,
supervision by Claske Dijkema, University of Basel

Today, the scientific and popular discourse on invasive species often centers around the danger of uncontrolled species spread and the threat of “nature ‘out of place’” [1]. This discourse is based on culturally and politically charged ideas of a ‘state of nature’ and ‘nativeness’. This makes it a contested field where political and ideological opinions on the management of migration, borders and changing communities become entangled with biological concerns around biodiversity loss and ecosystem degradation.

The scientific background

In conservation sciences there is a historically based classification of introduced species into the categories archeobiota and neobiota (the Latin ending biota is an umbrella term referring to plants, animals, and fungi, while the ending zoa refers to animals and phyte to plants only). Archeobiota are classified as those species that have been introduced (willfully or as a side product of globalization) to foreign ecosystems before 1492, this includes species that have been introduced as far back as 10.000 years BC.

Neophytes and neozoa are thus all plants and animals that were introduced after 1492 which is the year of the so-called ‘discovery’ of the Americas by Christopher Columbus and thus the beginning of European colonization [2]. The adjective invasive is used to refer to those introduced species that spread quickly, change and impede biodiversity across the planet [3].

According to Vogelaar (2021) the question of a plant’s nativity (or not) became a topic of concern in the natural sciences since the 1800s and has since then found wide-spread resonance. Many fields such as agriculture, biogeography, botany, entomology, forestry, natural history, pathology, and zoology are concerned with the issue of native and invasive species. At their intersection the field of invasion ecology was formed. However, it was Charles Elton’s essay The ecology of invasions by animals and plants in 1958 only that “marks the official birth of the discipline dedicated solely to the definition, identification, codification and management of ‘nativeness’” [4].

Importantly however, non-nativeness and invasion or quick spread are not causally related. Firstly, there are non-native species which have not spread uncontrollably and are not viewed as a threat to the local ecosystems [5]. And secondly, there are native plants that can spread very quickly and persistently and cause similar problems as invasive species, these are then referred to as expansive species (Möllerová 2005).

The issue with invasive species

The issue of invasive neophytes and neobiota is an issue of increasing concern to climate scientists and policy makers worldwide. According to the Swiss zoologist Urs Schaffner for example, invasive species are one of the major causes of global biodiversity loss and contribute fundamentally to the degradation of ecosystems and loss of ecosystem-services [6]. With increasing global connectivity, especially water and train transport, and the vulnerability of ecosystems across the globe due to climate change, the spread of invasive species is accelerating drastically; more and more species are being moved into new ecosystems either accidentally or on purpose.

Introduced into these new ecosystems, some species have a competitive advantage over the local species due to inherent traits leading to increased resiliency, adaptability, or effective procreation or due to the lack of natural predators in their new habitat [7]. The nation-wide association of Swiss Botanical gardens and plant collections – Hortus Botanicus Helveticus- states that climate change is a big driving factor in increasing the risks of invasive species as it makes ecosystems more vulnerable by impeding biodiversity and changing climatic conditions across the entire planet and supporting the spread of single species. In addition to the fact that many invasive species have been introduced into new ecosystems accidentally as a by-product of increasing globalization, there are also examples of purposefully introduced species for example for timber production or other economic uses which became invasive and cause harm to people, the environment and economy by colonizing whole areas [8]. In the light of these discourses, the fight against invasive species is being promoted internationally [9], and recently increasingly so also in Switzerland.

Fighting invasion in Basel

In Basel the issue is widely framed as a threat to local ecosystems and the Stadtgärtnerei - the public institution responsible for all green areas in the city - is collaborating with the municipality and other institutions to fight the spread of invasive species. There are several efforts to inform the public about the danger posed by invasive species and call for participation in the fight against them. The rhetoric and aesthetics in this discourse can however be criticized for relying on xenophobic tropes of vilifying newcomers and the need for protecting the native at all costs and is thus serving specific concepts of belonging and the management of protection and exclusion.

PNG - 321.5 KiB
Screenshot of the Website Stadtgärtnerei
It reads: Alien plants and animals – so called neobiota - can become a problem when they not only become established but also displace native species. So called invasive neophytes are non-native plants which disturb and change ecosystems (Invasive Neophyten n.d.)

On the website of the Stadtgärtnerei, the issue is informed about with the following words: “Alien plants and animals – so called neobiota - can become a problem when they not only become established but also displace native species. So called invasive neophytes are non-native plants which disturb and change ecosystems [10]” (‘Invasive Neophyten’ n.d.).

PNG - 1.1 MiB
Excerpt from the brochure
oekomobil, Environment and Communication. Published by Canton Basel-Landschaft and Basel-Stadt. January 2017

In addition to general information, the municipality also counts on the public to help in the prevention of the spread.

A brochure designed by the Kanton appeals to the readers with the words “Do not use exotic problem plants in the garden, there are enough attractive alternatives! [11]" [12]

JPEG - 268.8 KiB
Informative sign of the Stadtgärtnerei Basel in August 2021
Photo by Pina Haas

In allotment gardens the Stadtgärtnerei calls on garden owners to actively support the decimation of specific invasive species by putting up signs like the following which reads:

“!!Attention Urgent!! Massive occurrence of the neophyte “American fleabane” in the recreational gardens. This plant multiplies explosively! Now absolutely prevent it from multiplying: pull out the whole plant with the root and dispose of it in the rubbish, do not compost the flowers!!!! Thank you for your help! [13]

These examples speak for an issue that has been a topic of strong controversial debate within the natural sciences but also the public. The main problematic is the reliance on the native/alien dichotomy which the scholars Chew and Hamilton found out to be based on an “olio of ideas from pre-Darwinian botany and pre-Victorian English common law” [14], but not on scientifically conclusive and tenable knowledge about biotic characteristics of plants. They thus highlight that unlike the dominant scientific focus on biotic nativity suggests, “it is important […] to understand that those findings express some common beliefs about humans, but nothing about the essences of biota or of particular taxa” [15]).

Many ecologists themselves are alarmed about the widespread practice of basing scientific interventions and research on this dichotomy. A group of scientists stated in a joined publication that this practice has “helped to create a pervasive bias against alien species that has been embraced by the public, conservationists, land managers and policy-makers, as well by as many scientists, throughout the world” [16]. In a wider context even, the unquestioned reproduction of these contested concepts has been criticized in political and cultural debates for fueling xenophobia and mobilizing nationalist sentiments and militarist language by calling for the protection of proper native homelands by eradicating vilified foreign species [17].

These aspects are visible in the discourse in Basel. The rhetoric and language used in the above mentioned examples is based on ideas of nativist homeland protection which speaks of “our ecosystems” (‘Invasive Neophyten’ n.d.) and the displacement of “attractive native plants” [18] by individual invasive organisms which are framed as “problem plants” [19]. Further, the sign in the allotment garden carries the reminiscence of a ‘wanted poster’ and portrays this invasive neophyte much like a foreign criminal on the loose that must be caught and eradicated to protect the local population from the dangers posed by these quickly spreading alien species which must be prevented from propagating.

The biopolitics of monitoring species migration

In addition to this public information material, the spread of invasive species is combatted nation-wide with the help of several monitoring tools. The municipality of Basel keeps an online map on which the populations of invasive species found in the city are registered and traced.

JPEG - 470.1 KiB
Screenshot of the online map tracing populations of invasive species in the city of Basel

In addition to that, in commercial contexts such as plant markets some plants are tagged with warning signs (see image 5) about the imminent threat they pose if planted against the national ‘release ordinance’. This ordinance “regulates the handling of organisms and their metabolic products and waste in the environment, in particular genetically modified, pathogenic or alien organisms [20]" [21].

JPEG - 464.8 KiB
Warning sign on plant sold on market in Basel informing about the dangers of the uncontrolled cultivation and directing to the nation-wide release ordinance
Photo by Pina Haas, April 2021

Some plants are further equipped with a ‘plant passport’ in form of a QR code which directs to the EU-wide plant passport system which is an “attestation for the supply (commercial or non-commercial) of regulated plant goods within Switzerland and for exchanges with the EU. It certifies that the goods meet plant health requirements and are subject to regular official controls”, the plant passport system promises to ensure the “traceability” of plant species. [22].

JPEG - 331.5 KiB
QR-code on plant sold on market in Basel directing to the EU Plant Passport system
Photo by Pina Haas, April 2021

These examples of monitoring speak to what Lorimer [23] calls an approach of “biosecurity” in the dealing with invasive species. Based on the anxiety over the threat of invasion and the uncontrolled mobility of non-native species, an alarming tendency occurs “in which nations, nature reserves, and other politicalized units become the bounded containers for Nature” and their “[m]anagement [tends] toward fixity, pre-empting and forestalling ecological processes in the interests of preservation and/or biosecurity” [24]. Reading these developments through a Foucauldian lens Lorimer is critical of this form of biopower in which control, policing and monitoring are answers to managing life and mobility [25].

The online-map of invasive species and the QR-plant-passport-system are expressions of such a biosecurity approach. Using the tools of tracing and scientific mapping - which have been argued to be colonial practices intricately related to power and domination. [26] –invasion ecologists are superimposed as rightful institutions for deciding over belonging and policing, controlling and publicly exposing individualized species as problematic and culpable for the ecological degradation of a passive and fixed local landscape. Such an approach is not only discursively problematic but might also ecologically not be a most sustainable and future-oriented approach. Lorimer [27] warns that in many instances an approach of biosecurity “proves practically difficult and can have pathological consequences when conditions of isolation foreclose on resilience or the fluidity necessary for adaptation”.

He continues that “some degree of spatial invasiveness is necessary for basic ecological function, not to mention adaptation to a changing climate” [28]. Hence, these attempts of biosecurity and territorial fixations seem particularly unfit for “naturalcultural” [29] networks in urban landscapes. Cities are fast-changing and dynamic hubs for exchange of resources, knowledge, values, money, people, and non-human species. Attempting to foreclose ‘invasion’ and change in the name of protecting a “natural” order in cities seems like a paradoxical and impossible task [30].

Accounting for complexity

While critically reflecting on the discourse on invasive species is important for drawing attention to elements like xenophobic rhetoric and biosecurity approaches of control, there is also the danger to jump to simple conclusions. Mastnak et al. for example, warn us from hastily equating the foreign plants with the figure of the “undocumented migrant” [31] and promoting something like a “botanical cosmopolitanism” [32] in which plants and animals should be able to roam freely and ‘chose’ their preferred habitat [33].

Such an approach is not only possibly downplaying the dramatic consequences of fast species spread, but it also simplifies the issue and forecloses a deeper and more systematic engagement with geological, sociological, and ecological change. What is likely overlooked in these debates is the way in which species mobility intersects with political and cultural processes of human expansion and displacement. With the growing acceptance and adoption of the concept of the Anthropocene, a consensus is formed that we live in a world in which ecological changes are primarily fueled by human behavior. [34].

This reality is not a neutral phenomenon in which all humans are equally responsible or equally bearing the costs, but it is imbued with questions of power and domination. Especially the history of European colonization is seen as responsible for the “production of a landscape” and a “literal planting and displanting of peoples, animals, and plants, (...) inscribing a domination into blood and soil founded in the fantasy of molding ecosystems with godlike arrogance” [35]. It is thus important to highlight that, in some contexts, instead of resembling immigrants and cosmopolitan subjects, neophytes are an expression of or even a constitutive factor in the human-led processes of settling and opportunistically occupying land and wiping out or dominating other species.

Given these complexities I suggest taking seriously Robbins’ reminder that “it is not species but sociobiological networks that are invasive” [36]. This might mean focusing less on making individualized species culpable for ecosystem degradation but broadening the view and understanding how the interaction between human processes and ecological adaptation produces myriad forms of migration and conditions for the quick spread of some and the vulnerability of other species. Separating the human from nature and installing a specific version of the human as the rightful dominating master of managing belonging and exclusion has not proven to contribute to the cultivation of a regenerative and respectful co-inhabitation on this planet. Ecological and human processes can no longer be viewed and managed apart.


The critical interpretation of the dominant institutional discourse on invasive species in Basel has shown that there is not much room for engaging with such complexities and ambivalences. The discourse interpreted above rather serves the stereotypical and xenophobic tropes of the vilification of the newcomer and promotes the installation of human dominance and control in managing species mobility.

Through my deeper engagement with how this issue is dealt with in Basel I want to propose a different approach: Instead of fighting around the issue of invasive species we can change our perspective and take their arrival as an invitation to open ourselves up for deeper questions. A transdisciplinary exchange platform could engage around such topics as the need to reconsider language used in speaking or writing about species mobility and ecological transformation, the questions around how things move across the globe, who is responsible and who benefits from the global displacement and marginalization of the ‘native’, and how to avoid that the protection of the native becomes imbued with nationalist and xenophobic ideology but a practice of conserving fruitful biodiversity and cultural knowledges and practices.


 Chew, M., and A. Hamilton. 2010. ‘The Rise and Fall of Biotic Nativeness: A Historical Perspective’. In Fifty Years of Invasion Ecology: The Legacy of Charles Elton, edited by David M. Richardson. Blackwell Publishing.

 Cooper, Davina. 2020. ‘Biodiversity and the Use of Nativist Language’. The Guardian, 16 July 2020, sec. Environment.

 Crawford, Amy. 2018. ‘Why We Should Rethink How We Talk About “Alien” Species’, Smithsonian Magazine, 1 September 2018

 Crutzen, Paul J. 2006. ‘The “Anthropocene”’. In Earth System Science in the Anthropocene, edited by Eckart Ehlers and Thomas Krafft, 13–18. Berlin, Heidelberg: Springer.

 Davis, Mark A., Matthew K. Chew, Richard J. Hobbs, Ariel E. Lugo, John J. Ewel, Geerat J. Vermeij, James H. Brown, et al. 2011. ‘Don’t Judge Species on Their Origins’. Nature 474 (7350): 153–54.

 Federal Office for Agriculture (FOAG). 2022. ‘Plant Passport’. Schweizerische Eidgenossenschaft. 14 April 2022.

 Haraway, Donna Jeanne. 2008. When Species Meet. Posthumanities 3. Minneapolis: University of Minnesota Press.

 Hellrigl, Klaus. 2022. ‘Rasche Ausbreitung Eingeschleppter Neobiota (Neozoen Und Neophyten)’, August.

 Hortus Botanicus Helveticus. 2020. Botanica, Garten- und Pflanzenführer. Klimawandel im Pflanzenreich: Invasive Neophyten Im Fokus. Edition 2020/2021. Vol. 1.

 ‘Invasive Neophyten’. n.d. Bau und Verkehrsdepartment des Kantons Basel-Stadt: Stadtgärtnerei. Accessed 18 September 2021.

 Lambert, Léopold. 2018. ‘Cartography & Power: Introduction’. The Funambulist Magazine, 7 July 2018.

 Lorimer, Jamie. 2015. Wildlife in the Anthropocene: Conservation after Nature. Minneapolis: University of Minnesota Press.

 Mastnak, Tomaz, Julia Elyachar, and Tom Boellstorff. 2014. ‘Botanical Decolonization: Rethinking Native Plants’. Environment and Planning D: Society and Space 32 (2): 363–80.

 Mehari, Zeraye H. 2015. ‘The Invasion of Prosopis Juliflora and Afar Pastoral Livelihoods in the Middle Awash Area of Ethiopia’. Ecological Processes 4 (1): 13.

 Möllerová, J. 2005. ‘Notes on Invasive and Expansive Trees and Shrubs’. Journal of Forest Science 51 (Special Issue): 19–23.

 Ökomobil, Umwelt & Kommunikation. 2017. ‘Problempflanzen im Garten- Was tun?’. Kanton Basel-Stadt und Kanton Basel-Landschaft.

 Schaffner, Urs. 2022. “Invasive Pflanzen können ganze Ökosyseme verändern” – Botanica Interview by Beat Fischer.

 Schweizerischer Bundesrat. 2008. ‘Verordnung über den Umgang mit Organismen in der Umwelt (Freisetzungsverordnung, FrSV)’.

 Shiferaw, Hailu, Tena Alamirew, Sebinasi Dzikiti, Woldeamlak Bewket, Gete Zeleke, and Urs Schaffner. 2021. ‘Water Use of Prosopis Juliflora and Its Impacts on Catchment Water Budget and Rural Livelihoods in Afar Region, Ethiopia’. Scientific Reports 11 (1): 2688.