Is time an ally of the invader? Time-binding the future of invasive alien species

Abstract

Invasive alien species, when perceived as an environmental problem, are a typical example of a problem that necessitates action before the full effects can be seen. This temporal gap has led to an increased focus on the future and to reliance on practices that aim to make the future actionable, such as risk assessments. However, the discourse on invasive alien species also depends heavily on specific spatiotemporal understandings, established within the scientific field of invasion biology. This article develops two analytical concepts for exploring the spatiotemporal relations in invasion biology and their role in risk assessments of invasive alien species: ‘The chronotope of evolution’ informs the understanding and valuation of species on basis of co-evolution as a normative idea, while the concept ‘time-binding practices’ describes practices through which the future is addressed and made available in risk assessments of invasive alien species. A close reading of four Norwegian guidelines for risk assessment of invasive alien species produced in the period from 2007 to 2023, shows a shift from a qualitative to a quantitative assessment methodology and from assessing species on the basis of observed effects to assessing them on the basis of observed and expected effects. These shifts are accompanied by a number of different time-binding practices, such as mathematical calculation of future ecological impact, an increased timeframe of the assessment, a clear methodology for selecting species that may become invasive aliens, and a recommendation to use climate predictions from a high-emission scenario. Being informed by the chronotope of evolution, which does not include human actions and their consequences as part of evolution, the risk assessments play an important part in increasing the killability of individuals of invasive alien species, making time an ally, not of the invader, but of the humans assessing it.

The arrival of an invasive alien

Exported as oyster spat and cultured all over the world by humans, Pacific oysters have been transported from their native coastal waters in the Northern Pacific to all continents except the Antarctic (Global Invasive Species Database, 2021). As such, the species they belong to is considered part of the category ‘invasive alien species’ – species that have been introduced by humans into places outside of their natural range with serious negative consequences for their new environment (IPBES, 2023). In 2007, Pacific oysters reached Norwegian waters, and in 2016 the Norwegian government launched a national Action plan against them. However, the actions planned in the Action plan were relatively restricted. Although arguing for local eradication projects, the environmental authorities also stated rather dryly that it ‘…is not possible to get rid of the species’ and that ‘the species’ enormous reproductive potential indicates that it is not realistic to eradicate the species completely from Norwegian waters’ (Miljødirektoratet, 2016: 1, 4). It was too late, a situation that is quite typical of the management of these so-called invasive alien species, and especially those who live in the ocean. They are often impossible or at least extremely expensive to remove once they have become established (IPBES, 2023: XIX). This brings to mind a statement made by the chair of a UN Conference on Alien Species held in Norway in 1996: ‘Time is an ally of the invader’ (Schei, 1996: 13). But is this always true?

The short story about Pacific oysters in Norway and the statement made at the 1996 UN Conference show invasive alien species to conform to Barbara Adam's claims about temporality and environmental problems in her book Timescapes of Modernity (1998). Adam held that two of the main obstacles when attempting to do something about environmental problems are the fact that most environmental problems emerge gradually over a long period of time and that they necessitate action before the full effects can be seen. This temporal gap has led to reliance on practices that aim to make the future actionable within a number of environmental fields, as well as to the wide use of the precautionary principle in environmental policy (Anderson, 2010; Beck, 2000; Braverman, 2017; Morin et al., 2024; Muiderman et al., 2020). With regards to invasive alien species, the main approaches to making the future actionable are risk assessments and the production of lists, like ‘100 of the World's Worst’ and ‘the Global Invasive Species Database’ (Global Invasive Species Database, 2023). Although a unified classification method for alien taxa, EICAT, was approved by the IUCN Council in 2020 (IUCN, 2020), there is still no internationally agreed-upon method for risk assessment. A large number of different risk assessment methodologies are presently in use for assessing invasive alien species across the world, some assessing only the environmental impact of a species, others including socio-economic impact as well (IPBES, n.d.: chapter 5). One of the methodologies that has been actively promoted internationally, is a methodology for the assessment of ecological impact, developed for the Norwegian Biodiversity Information Centre (NBIC) by a group of scientific experts from different Norwegian research institutions (Sandvik et al., 2019; Sandvik et al., 2020). ¹

Risk assessments are intrinsically dealing with the future, aiming to produce knowledge that makes it possible to avoid or reduce risk (Hardy and Maguire, 2016). Although such future-oriented practices are considered necessary for making good policy and management decisions, there is always the danger that they may contribute to cementing the future in specific ways (Anderson, 2010; Hulme, 2011; Muiderman et al., 2020). Unlike most of the environmental problems Adam discusses in Timescapes of Modernity (1998), the problem of invasive alien species consists of living organisms. Risk assessments of invasive alien species assess the risk presented by the species themselves, not for instance the risk produced by the humans who move them. This means that the ways in which they are produced may have large consequences for individuals belonging to the species defined as invasive aliens.

In the following, I will first develop two analytical concepts for exploring the spatiotemporal relations in invasion biology and their role in risk assessments of invasive alien species. ‘The chronotope of evolution’ informs the understanding and valuation of species on basis of co-evolution as a normative idea, while the concept ‘time-binding practices’ describes practices through which the future is addressed and made available in risk assessments of invasive alien species. Second, I will close-read four Norwegian guidelines for risk assessment of invasive alien species produced in the period from 2007 to 2023 through the lens of time-binding practices, and explore what understandings of the future are activated in the production of alien species knowledge. I will explore what temporal scales are in use, how the future is expressed, and what changes have occurred in the successive guidelines. I will then use my findings for a discussion of how the relation between time, space and evolution in invasion biology influences the knowledge produced through risk assessments.

Although concepts such as alien and native species have been contested for a long time, the understanding of invasive alien species as an environmental problem has been strengthened rather than weakened during recent years, especially with IPBES’ thematic assessment report on Invasive Alien Species from 2023 (IPBES, 2023). As I will argue later, the risk assessments of invasive alien species, and more specifically the time-binding practices included in them, play an important part in making the individuals of the invasive alien species killable (cf. Haraway, 2008: 80). Thus, addressing how the future is expressed in risk assessments of invasive alien species, what temporal scales are taken into account, and what information is included as relevant, has important ethical as well as practical consequences. This underscores the importance of developing a more profound understanding of spatiotemporal understandings within this discourse, as well as their normative effects.

The chronotope of evolution

Presently, the Intergovernmental science-policy platform on biodiversity and ecosystem services, IPBES, defines an alien species as ‘a species whose presence in a region is attributable to human activities that have enabled it to overcome the barriers that define its natural range’, and invasive alien species as ‘a subset of established alien species that spread and have a negative impact on biodiversity, local ecosystems and species’ (IPBES, 2023: 3). The war-inspired terminology of ‘invasive species’ was introduced to the biological sciences in the late 1950s, with Charles Elton's book The Ecology of Invasions by Animals and Plants (Davis, 2009; Elton, 1958). In the book, Elton described what he termed ‘ecological explosions’ – huge, out-of-control increases in the number of some kind of living organism, which is very often a ‘foreign species successfully invading another country’ (Elton, 1958: 17–18). In the decades following Elton's book, invasion biology became gradually more popular, and since the 1990s, it has been considered a separate scientific field, with journals such as Diversity and Distribution and Biological Invasions (Davis, 2009: 10).

Past distributions of plants and animals play an important role in invasion biology. Elton underlined in his book that examining the past was one of the most important themes ‘if we are to understand what is likely to happen to the ecological balance in the world’ (Elton, 1958: 33). Humanistic and social science scholarship on the temporalities of invasive alien species has also, to a large degree, focused on the consequences of how the past is understood within the discourse on invasive alien species, and a number of researchers have argued that categories such as ‘native’ and ‘alien’ are flawed, as species are always alien with respect to a certain place and a certain time (e.g., Chew and Hamilton, 2009; Everts, 2015; Head, 2017; Lidström et al., 2015). In the same vein, invasion biology has also been criticised for relying on the supposition that past landscapes can be kept unchanged (e.g., Frawley and McCalman, 2014; Qvenild and Setten, 2020; Setten, 2016). With regard to the future, temporalities scholarship has challenged the discourse's ideas of predictability and a priori stability, instead highlighting how relationships between humans and invasive alien species are emergent and part of ongoing processes of co-production (e.g., Atchinson, 2019; Everts, 2015; Head, 2014). None of these, however, provide more in-depth conceptual studies of the temporalities within invasion biology. Thus, to be able to discuss how the future is conceptualised in the empirical material of this study, I find it necessary to first elaborate on the understandings of time and the relationship between space and time within the field of invasion biology and second to develop a set of analytical concepts for exploring both the spatiotemporal relations the field rests on and how these play out in the empirical material.

In the IPBES definition, the past is mainly activated through the idea that there exists a certain ‘natural range’ for species. Although ‘range’ is primarily a spatial concept, ‘natural range’ is imbued with a specific temporality, namely a geological one. According to the first editorial of Biological Invasions, ‘natural range expansions of organisms, extended over vast sweeps of geological time, stand in dramatic temporal contrast to the rapid reorganization of the biotic world that has attended the flood of humans across the face of the Earth in the past 10,000 and more years’ (Carlton, 1999). While the ‘natural range’ of a species is produced through major geological events such as the movement of continents, which give different groups of species millions of years together or apart before the barriers change, human transport of organisms happens quickly and across these long-term barriers.

The difference between the two different ‘ranges’ – the natural and the unnatural – and their connected timescales of movement can thus be boiled down to the difference they produce in the possibility of co-evolution. The species that live within the same natural range have evolved together over millions of years and formed specific biogeographic regions, with different sets of species occupying similar ecological niches. The species that are moved by humans, on the other hand, cross the barriers that have produced these separately evolved floras and faunas and meet species with whom they have not co-evolved. As the first editorial of Biological Invasions continued: ‘As a result of instantaneous human-assisted transport, species are abruptly faced with interacting with new species and new environments with which they have had no evolutionary history’ (Carlton, 1999). The lack of an evolutionary relationship is thus the main reason why species moved by humans are per se considered to pose significant risks to biodiversity. Although Davis (2009: 10) has underlined that the scientific field of invasion biology has increased in maturity and now includes more complexity and ambiguity, this understanding of the role of evolution still holds sway within the discourse (e.g., Cuthbert et al., 2020; Ricciardi and Ryan, 2018).

Bakhtin (1981: 84) has described different ways of merging time and place into a unity in literature as chronotopes. Chronotopes come in a number of different forms and exist on different levels, from literary tropes to the specific spatiotemporal relationships associated with different genres. Agha (2007) has argued for the concept ‘cultural chronotopes’ as a more general term for all representations linking time, place, and personhood. Drawing on Agha's (2007) version of the concept, I understand the specific spatiotemporal ideas underlying invasion biology as a specific cultural chronotope, which I will term the chronotope of evolution. The chronotope of evolution informs the understanding of species within invasion biology, producing a fundamental difference between species that have evolved together over time in a specific place – and thus acted according to the chronotope of evolution – and species that have been transported to new places by humans.

There is only one species that is excepted from the chronotope of evolution within invasion biology, and that is humans. Human travel and transport of other organisms, or other organisms’ evolutionary adaptions to human transport, are not considered to be part of the chronotope of evolution. Instead, humans are presented as distorters of the chronotope: they make other species move too fast and settle in the wrong places. Elton (1958: 30–32) underlined that with regard to invasive alien species, the relevant segment of evolutionary history was the geological period then called Tertiary (66 to 2.6 million years ago). ² In this period, the continents that exist today had been formed, the dinosaurs had been wiped out, and our present floras and faunas were evolving. When what is at stake is the evolution of different floras and faunas over 66 million years, the role of humans in invasion biology has clearly seemed of little relevance other than in producing societies that disrupt the process of evolution. A deep, chronotopic split between humans and all other species thus lies at the core of invasion biology.

It is, however, important to point out that this understanding of humans as ‘outside’ evolution is not a general one in biology. As evolution can happen on a number of different timescales, and understandings of evolution are themselves historical products, understandings of the role of humans in evolution (and following that, in chronotopes based on evolution) vary among subdivisions of the biological sciences. Nordblad (forthcoming) for instance, describes a discourse where humans in their societal capacity are instead seen as taking an active part in the evolution of different plants through the development and use of breeding techniques. Another variation on the role of humans in evolution can be found in the discourse of what is termed ‘the sixth extinction’. Within this discourse, humans are often presented as a species whose evolutionary produced characteristics have made them bound to exterminate other species (Bjærke, 2021). Homo sapiens is thus included as an evolving species, as well as in their societal capacity. The fact that such different ways of approaching humans when evoking the concept of evolution exist in the context of quite closely related fields, highlights the importance of also exploring the third aspect entailed in Agha's (2007) concept of chronotope (in addition to time and place) – personhood. Making humans into disrupters of evolution, moving them outside, so to speak, produces a separation between humans and other species, which is specific to invasion biology.

Risk assessments and time-binding practices

My main analytical tool in the close reading of the Norwegian guidelines for the risk assessment of alien species is the concept of ‘time-binding practices’. The concept is based on the concept ‘time-binding technique’ as defined by Bergwik and Ekström in their book Times of History, Times of Nature (2022). Time-binding usually refers to the human capacity of transmitting experience from one generation to another (Merriam-Webster, n.d.). Bergwik and Ekström (2022: 6), however, use it to describe technologies and genres that enable ways of ‘connecting and visualizing different frames, layers, and durations of time’. With Bergwik and Ekström's definition, risk assessment can be understood as a time-binding technique. As a genre, risk assessment represents a specific way of binding past, present, and future together: past experiences are used for predicting the future and recommend present actions. This binding together of past, present and future through risk and understandings of risk, has been noted and discussed broadly, and is part of what Beck (1992) termed the ‘risk society’. However, what concrete practices a risk assessment includes and what underlying understandings of past, present and future it draws upon, still varies from assessment to assessment. In addition to using Bergwik and Ekström's ‘time-binding technique’ as a label for the genre of risk assessment, I have therefore added the concept ‘time-binding practices’ to describe the set of practices through which the future is addressed and made available in the specific risk assessment of invasive alien species. While these practices partly depend upon the temporal logic of the risk assessment (the time-binding technique), they are also influenced by the underlying understanding of time and space within the discourse, in this case, the chronotope of evolution in invasion biology. Thus, the time-binding practices within the risk assessment of invasive alien species are chosen and implemented in a field of tension between the temporality of the time-binding technique (the risk assessment) and underlying assumptions of the relationship between time and space, and between humans and more-than-humans.

An increased formalisation of the future

In Norway, the process of risk-assessing alien species is led by the state-owned NBIC and has been so since 2005 (NBIC, 2018). NBIC produces guidelines for the risk assessment of alien species, establishes the expert groups who assess the alien species, and supervises the process. The final assessments are published as an Alien Species List, launched approximately every fifth year. ³ I have examined four versions of guidelines for the risk assessment, produced for the four risk assessment processes that have been organised by NBIC so far: 2007, 2012, 2018, and 2023 Alien Species Lists (Artsdatabanken, 2011; Artsdatabanken, 2023; Gederaas et al., 2007; Sandvik et al., 2017). ⁴ Although the methodology of the risk assessment has changed, the guidelines for the assessments are quite similar throughout the whole period. They are text-heavy documents, with explanations of how to perform the different steps of the analysis and descriptions of what kinds of data and knowledge to include. Thus, all the guidelines lend themselves to a strategy of close reading for time-binding practices.

From 2007 to 2023, there has been an increase in the number of assessed species, an increase in the time spans over which these species are evaluated, and an increased formalisation of how the future is to be included in the process. When the first Norwegian Alien Species List was published in 2007, it was based on a risk assessment of only 217 species, most of which were already expected to have severe ecological effects. Species were categorised into three groups: Low risk, Unknown risk, and High risk. When the latest Alien Species List was published in 2023, it contained risk assessment of more than 2300 species. These were separated into the categories Severe impact (SE), High impact (HI), Potentially high impact (PH), Low impact (LO) and No known risk (NK), based on their estimated degree of both present and expected impact on the native ecology.

The assessment guidelines from 2007 held no details on how the future was to be included in the assessment other than stating that ‘The risk analysis of alien species in Norway is an evaluation of whether the species may have negative impacts on natural ecosystems, habitats, species, genotypes or may be a vector for species (parasites and diseases) that may have negative impacts on indigenous biological diversity’ (Gederaas et al., 2007: 51, my italics). However, already in the 2012 guidelines, the role of the future in the assessment had become more formalised. Now the risk assessment consisted of two steps: First, the assessment of invasion potential, which is the species’ expected population lifetime combined with its expected expansion. Second, the assessment of ecological effects. ⁵ Both these steps were to be assessed for the next 50 years (Artsdatabanken, 2011: 11, 13). In 2018, the temporal frame was increased even further. The guidelines now operated with three separate time spans of species survival in Norway: 10 years, 60 years and 650 years (Sandvik et al., 2017: 34). A population expected to survive in Norway for more than 650 years, was considered to have a high invasion potential.

A major change during the period is that the risk assessment has been developed from a qualitative (2007), into a semi-quantitative (Sandvik et al., 2013), and later into a fully quantitative assessment of ecological impact (Sandvik et al., 2019). An important aspect of the new quantitative method, according to its designers, is that its aim is ‘a purely ecological and normatively neutral impact assessment’ (Sandvik et al., 2019). No effects on humans – societal or economic – are included in the assessment, in order for the ensuing list to provide only ecological knowledge and to leave all normative decisions to the authorities (Sandvik et al., 2013; Sandvik et al., 2019). The designers also argue that their quantitative method makes for comparability across taxonomic groups and ecosystems, transparent prioritisation of management efforts, testability and high repeatability (Sandvik et al., 2020). The Norwegian risk assessments of alien species since 2018 thus share a feature of many risk assessments: they are understood by their designers to be fact-based and value-free, through ‘the application of widely recognized and highly institutionalized procedures and techniques’ (Hardy and Maguire, 2016: 84). However, the understanding that risk can be objectively assessed once the choice to risk assess something has been made, under-communicates the fact that through such processes certain kinds of knowledge are made relevant, while other kinds of knowledge are not (Hardy and Maguire, 2016).

Two other practices directly concerning future invasions have emerged along the way. The first is the assessment of ‘door knocker species’ or just ‘door knockers’, as they are referred to in the guidelines. Door knockers are species that have not yet reproduced independently in Norway, but are believed to be able to do so within 50 years. In 2007, door knockers were not included in the Alien Species List, although NBIC stated their intention to include them in lists to come (Gederaas et al., 2007: 17). In 2018, 319 door knockers were assessed, and in the risk assessment for the 2023 Alien Species List, more than 800 new door knocker species were considered (Artsdatabanken, 2023). The second practice is a method for the initial selection of door knockers for assessment, the ‘horizon scan’ (NBIC, 2022: 23). The horizon scan consists of a preliminary assessment of a species’ potential for establishment and ecological effects, allowing for the evaluation of a large number of species before deciding which ones to submit to a complete risk assessment as door knockers (NBIC, 2022: 24).

The increased formalisation and the choice of including increasingly long timespans have gradually stretched the category of invasive alien species in Norway further and further into the future. Rather than focusing only on the present, the risk assessment process increasingly also highlights future effects, both of alien species that are already present in Norway and of alien species that are expected to be present in the future. Thus, one of the features of the development of the risk assessment guidelines is that they have served to gradually increase the importance of and the length of the future, and that there is no indication that the alien species will at some point stop being considered alien.

The replacement of time with place

The guidelines for the 2018 and 2023 risk assessments state that ‘[a]s far as ecological effects are concerned, assessments are not only to take account of historical and current effects but also of effects that, based on documented evidence, can be expected to occur in the future’. (NBIC, 2022: 41; Sandvik et al., 2017: 42). The guidelines explicitly mention three kinds of documented evidence of expected future effects: the expected expansion of the area of occupancy, age-dependent, density-dependent or frequency-dependent effects, and effects that become more likely under a changed climate (Sandvik et al., 2017: 42). In both the second and the third case, the guidelines detail that they concern effects that ‘have not yet been observed in Norway’, and which should either be documented in places with similar bioclimatic conditions to the ones in Norway or documented in countries with a climate comparable to the one Norway may get in the future (Sandvik et al., 2017: 42). What is to be documented is thus either phenomena that have not had time to occur in Norway yet, or that have not occurred in Norway yet because the climatic conditions must change first. The first is based on an idea of a stable climate, but an increasing number of individuals of a species. The other on changing climatic conditions, which will then lead to an increasing number of individuals. The guidelines provide a table showing the total area of different bioclimatic zones in Norway (NBIC, 2022: 30; Sandvik et al., 2017: 29), but do not provide lists of other countries with similar bioclimatic conditions to Norway. Finding the relevant places is thus a task for the experts doing the assessment.

Binding the future to specific places, which are possible to observe and represent visually, is a powerful way of concretising the expected future (Doyle, 2011; Setten, 2016). While the real future always has to be imagined, an existing place is visible. It is possible to travel there, to take photos of it, all in all to gain information from it in ways that seem more real than probabilities, statistics or models. Binding the future to specific places also narrows down the number of futures that are possible to imagine. The assortment becomes limited to phenomena that already exist – which can then work as examples or analogies of what is to come.

Describing the future by referring to a different geographical place is a recurring literary trope from 18th-century works like Gulliver's travels by Jonathan Swift (published 1726) and Niels Klims underground travels by Ludvig Holberg (published 1741) to contemporary science fiction. The use of this trope in the risk assessment guidelines relies heavily on two aspects: First, that the future can be documented through the present. Second, that places with the necessary features – here; similar bioclimatic conditions and the presence of the invasive alien species in question – already exist. In writing on Silicon Valley innovation, Suchman (2010) cited a technologist stating that ‘the future arrives sooner here’. She used the citation to call attention to the idea that some places are origins of change, from where knowledge or technology spreads outward towards the periphery. The idea that one can obtain knowledge of the future from another place relies heavily on the reverse – an idea of the future arriving later. Embedded in the Norwegian risk assessment is thus an idea of Norway being a late stage in an ongoing process of dispersal of invasive alien species. The end point, so to speak. This idea is enhanced by the fact that the risk assessment is a national endeavour, assessing ecological risk for what the guidelines term ‘Norwegian nature’, so that the possibility of species moving on to other countries is not part of the risk assessment. ⁶ However, the idea also indicates that the alien species assessed is bound to arrive, since it has already done so in other comparable countries.

The future as climate change

Climate change is addressed already in the first risk assessment guidelines from 2007, but only in a general way. There is a subchapter on climate change and alien species, which states that a future warmer climate is expected to lead to a greater need for information on alien species, but gives no concrete information on how climate change is to be included in the risk assessment process (Gederaas et al., 2007: 3). In the guidelines from 2011, a set of climate prognoses are listed as part of the documentation the expert groups should use when ‘assessing the effect of future climate change’ (Artsdatabanken, 2011: 26). From 2017 onwards, however, effects of climate change form an explicit part of the risk assessment process. The guidelines state that documentation should come from ‘countries with a climate comparable to the one Norway may get in the future’ (Sandvik et al., 2017: 42). Experts doing the risk assessments are advised to first use a certain climate model to predict future climatic conditions in Norway. Then, based on the predictions, they must find countries with a climate similar to the one predicted for Norway, and in which the invasive alien species in question is already present. From such geographical places, the ecological effects of the alien species in a future climate-changed Norway can be attained. Again, the process depends on a change from time to place as well as some sort of downstream understanding. For the effects of the invasive alien species to be documented, it is necessary that the climatic conditions expected in Norway in the future already exist somewhere else.

It is worth noting that the two ways of replacing the future with a place described in the guidelines represent two slightly different versions of the relationship between time and space. The one concerning density and time-dependent factors of the alien species depicts the future through places with bioclimatic conditions similar to present-day Norway. The one concerning climate change depicts the future through places with similar bioclimatic conditions to a future Norway. Thus, ‘documented evidence of future effects’ can be found in two different sets of places, probably partly, but not completely, overlapping.

No other expected future changes are included explicitly in the risk assessment for alien species in the same way as climate change. This means that neither expected future land/sea use changes, pollution or harvesting nor combination effects between these are included. Neither are any expectations of future societal changes that might influence the spread of alien species in a general manner. One reason for this might be what Mike Hulme (2011) has termed ‘climate reductionism’. Hulme has argued that climate models and predictions now hold hegemony over visions of the future to such a degree that it leads to a tendency to ‘reduce the complexity of interactions between climates, environments, and societies’ to climate. He pins this on the fact that climate research has such good models and predictions compared to other social conditions, that these other conditions, which cannot be quantified in the same way as climate change, become difficult to incorporate into future scenarios and are thus in danger of being forgotten. Although Hulme coined the term ‘climate reductionism’ with regard to cultural and societal aspects, similar tendencies have been noted between different environmental discourses as well (Bjærke, 2019). Climate predictions, presenting temperatures and average rainfalls that are easily compared with data from other countries or regions, are easily adapted to an idea of documenting the future through place. Expected future changes in land use would, for instance, be difficult to include in a similar manner.

The guidelines recommend using climate predictions from the Norwegian Centre for Climate Services for finding countries with a similar climate to future Norway, and also recommend using RCP8.5 ⁷ , a high emission scenario based on ‘continuous growth in climate gas emissions’, for the assessment (NBIC, 2022: 30; Sandvik et al., 2017: 28–29). In this high emission scenario, it is ‘very likely that the global temperature increase at the end of the century will be more than 4 degrees Celsius relative to the period 1850–1900’ (Norwegian Centre for Climate Services, 2022). The choice of climate scenario represents an interesting difference to guidelines on invasive alien species from EU, as well as to the guidelines for producing the Norwegian Red List for threatened species. EU recommends the use of RCP2.6 or RCP4.5 (European Commission, 2019). With regard to threatened species, NBIC recommends using RCP4.5, among other things to ‘avoid accusations of doomsday prophecies’ (Artsdatabanken, 2020: 18). Choosing RCP8.5 also represents an interesting form of compartmentalisation. It is not in line with either national or international climate goals. A climate scenario leading to a 4°C increase in global temperatures before the end of the century would be expected to have a number of serious consequences for human societies as well as biodiversity, and these will probably also affect the work on risk assessing invasive alien species (and the people doing the work) in a number of different and unpredictable ways.

The assessment guidelines justify the choice by referring to the precautionary principle (NBIC, 2022: 30; Sandvik et al., 2017: 29). Outlined in the Rio Declaration and adopted as part of the Convention on Biological Diversity in 1992, the precautionary principle, although contested, has spread into a number of other international environmental agreements and national legislations (Morin et al., 2024). ⁸ A version of the principle was included in Norwegian environmental law in 2009, with the implementation of the Nature Diversity Act. This version states that ‘when a decision is made in the absence of adequate information on the impacts it may have on the natural environment, the aim shall be to avoid possible significant damage to biological, geological or landscape diversity’ (§ 9). By using this principle as a justification for their choice of climate scenario, the guidelines thus imply that choosing a low or medium-emission scenario might lead to significant damage to biological diversity. This is because many of the alien species in Norway are at the northern edge of their distribution, and that the higher the predicted future temperature, the more likely they are to establish themselves and have ecological consequences. Choosing a climate scenario that turns out to be too low, would thus increase the chance than an alien species is assessed as posing less future risk than it actually does. On the other hand, choosing a climate scenario that turns out to be too high, would assign too many alien species to high-risk categories and thus increase the possibility of subjecting them to management measures. Thus, although the risk assessment process and the ensuing list are considered neutral knowledge by NBIC, the choice of climate scenario shows a clear differentiation of value among species. While the existing biodiversity of the country is protected by the precautionary principle, the species that are assessed for the Alien Species List are not.

Time-binding practices and the chronotope of evolution

There are two almost parallel shifts occurring in the Norwegian risk assessment guidelines in the period from 2007 to 2023. The first is the shift from a qualitative to a quantitative assessment methodology, where the basis of the assessment changes from qualitative statements to quantitative calculations. The second is the shift from assessing species on basis of observed effects (the present) to assessing them on basis of observed and expected effects (the present and the future). These two shifts are closely intertwined and have over time led to the inclusion of a number of new time-binding practices in the risk assessment guidelines with an impact on how the future is conceptualised, such as descriptions of mathematical calculation of future ecological impact, an increased timeframe of the assessment, a clear methodology for selecting species that may become invasive aliens, and links to scenarios for a changing climate. The two shifts have also served to bring the Norwegian assessment of alien species closer to the spatiotemporal basis of invasion biology. The NBIC is an institution whose explicit goal is ‘bridging the gap between biodiversity, science and policy’ and producing neutral knowledge on nature diversity (NBIC, n.d.). When viewed in light of the chronotope of evolution, all alien species present an inherent threat of becoming what Elton termed ‘ecological explosions’. This means that to bridge the gap between science and policy, it was not sufficient for NBIC to provide knowledge on alien species that were already known to be invasive in Norway, as they did in 2007. They needed to develop their methodology to provide knowledge on species that are alien, but not yet invasive, as well as on species that are currently neither alien, nor invasive, but which may become so in the future.

In using a high emission scenario, with a 4°C increase in global temperature, the precautionary principle is used actively for erring in favour of native biodiversity rather than in favour of individuals belonging to the alien species. The consequences this might have for the alien species are not questioned or discussed in any way in the guidelines. The practice, however, makes perfect sense when the chronotope of evolution is taken as a starting point. When the underlying idea is that evolution is a slow process producing different floras and faunas in different biogeographic regions, and when this idea leads to normative claims as to where a species should be at a specific time, species travelling with the aid of human will never stop being in the wrong place. With the human as a distorter of (co-)evolution, rather than as a part of it, species travelling with humans will always be of less value than species that do not. It does not matter if a future world has changed in a number of other, unforeseeable ways. Effects on humans and human society are excluded from the risk assessment of invasive alien species. The same goes for effects from human societies and technological development, except for climate change. This choice and the idea that it makes the assessments more normatively neutral, can also be traced back to the chronotope of evolution. As humans are not included in the chronotope of evolution underlying invasion biology, their societies are not considered in terms of evolution, but as producing exceptions in other species’ distributions.

When a species is found to spread in a new place it is often portrayed as a dramatic turning point. When Elton called these events ‘ecological explosions’, he signalled both a suddenness and a compression of time followed by an expansion. The inclusion of door knockers and future-as-place in the risk assessment guidelines, can be seen as attempts to smooth out the dramatic violation of the chronotope of evolution by the invasive alien species. The inclusion of door knockers at the same time reintroduces an element of predictability and an element of control, while the future-as-place indicates that the invasion event in Norway a late one in a long series of invasions, itself forming a temporal rhythm of continuity.

As the future emerges more and more clearly through the risk assessment guidelines, the documentation requirements in the assessment process increasingly also affect what futures can be imagined. The time-binding practices concerned with obtaining knowledge of the future by turning it into a geographical place, and the combination of this with climate change suggests that both the invasion of the alien species and climate change are unavoidable factors. These time-binding practices are not only simple measures taken for the practical purpose of doing a risk analysis. They themselves act as ways of ‘closing’ the future, making it seem unavoidable. A fascinating aspect of this is that the risk assessment ends up presupposing an understanding of Norway as a place where invasive alien species arrive late, as well as a place where climate change will take the form of a bioclimate already existing in other countries – even when the global temperature rise is expected to be more than four degrees Celsius in the year 2100.

No such thing as a neutral future

Presently, invasive alien species are considered a major direct driver of biological change by IPBES and their large range of experts, and as an environmental problem, they are considered to have contributed solely or alongside other drivers to 60% of recorded global animal and plant extinctions (IPBES, 2019, 2023). Although Head (2017) and others stress the absence of a fundamental biological meaning for the concept ‘nativeness’, and following that, for ‘alienness’, this group of species constitutes a large environmental problem that I do not wish to make light of. But my starting question was whether time really is an ally of the invader, as was stated at the UN Conference on Alien Species in 1996, and my answer to that is presently a no. As the timeframe of the risk assessment has gradually expanded, the number of evaluated species increased, and a rather intensely climate-changed future has been included, time has gradually been turned from an ally of invasive alien species into an ally of humans aiming to stop them.

As I mentioned previously, the NBIC presents the Norwegian risk assessment of alien species as normatively neutral, since it does not include economic or societal effects. They make a point of the fact that the political control and management of alien species is done by other governmental institutions, and that the risk assessments and ensuing Alien Species Lists only provide the knowledge necessary for management authorities, researchers and the public (NBIC, 2022: 5). However, time-binding techniques such as risk assessments are never neutral processes, even disregarding the choice to start doing them in the first place, which is obviously a political one. There are always choices to be made, and these choices always have normative aspects, whether it concerns who benefits from the precautionary principle or how long into the future a species is to be considered alien. As Beck (2000) writes: ‘Risk statements are neither purely factual claims nor exclusively value claims. Instead, they are either both at the same time or something in between, a “mathematicized morality” as it were’. In the case of the invasive alien species, the morality of the risk assessment is provided by the chronotope of evolution, with its normative spatiotemporal claims based on co-evolution. Uniting the two in the Norwegian risk assessment methodology does not seem to have been difficult. Rather, the chronotope of evolution and the temporal logic of the risk assessment seem to pull in the same direction, towards including longer future timescales, more species, and more quantitative assessment steps.

The fact that the chronotope of evolution and the risk assessment's aim to produce knowledge that can be acted upon pull the risk assessment guidelines in the same direction is bad news for the alien species. The further into the future each species is considered an alien, the more species one will find on the alien species list. The same is true for door knockers; the more possible invasive alien species one examines, the more one will find. In addition, the way the precautionary principle is used shows that the guidelines take their legally based responsibility to err in favour of the native biodiversity uncommonly far. Although NBIC underlines that the Alien Species Lists are neutral documents that do not directly trigger political action (Artsdatabanken, 2018), the list is used by environmental authorities as a knowledge base for deciding what species they will produce action plans for, what actions they will recommend, and for recommending which species to include in the government's financing schemes. Thus, being risk assessed into the category of Severe (Ecological) Impact will often indirectly lead to eradication of organisms belonging to the species, even if the risk assessment itself does not have direct political consequences.

The Pacific oyster with which I started this article is a species in this category. Although I described the helplessness of the authorities in the face of ‘eradicating the species completely from Norwegian waters’, removing oysters locally was one of the recommended measures in the Action plan (Miljødirektoratet, 2016: 46–47). This has resulted in a number of state and regionally funded oyster eradication campaigns, where individual oysters are smashed with hammers (e.g., Vestfold og Telemark Fylkeskommune, n.d.). As mentioned in the beginning of this article Donna Haraway has argued for the imperative to avoid practices that make other species killable (2008: 79–80). Although killing might be necessary in certain cases, for instance in cases where individuals belonging to an invasive alien species threaten local diversity, practices for making killable, for making the choice too easy, are the real problem. The way the chronotope of evolution is set up in invasion biology – making such a clear distinction between humans and all other species – as well as how it serves to inform certain time-binding practices, can be seen as doing just that. It produces three categories of beings with different degrees of killability: humans, individuals belonging to species that have not been moved by humans, and individuals belonging to species that have been moved (invasive aliens). This difference then allows for choices in the guidelines such as using the rarely used RCP8.5 for the sake of precaution and considering it a neutral choice. Both the category of invasive alien species itself and the time-binding practices used in the guidelines for the risk assessment of them thus participate in moving decisions of killing individuals belonging to species assessed as invasive aliens outside the realm of ethical responsibility. Thus, the time-binding practices obscured within seemingly neutral risk assessment guidelines show time to be an ally, not of the invader, but of the humans assessing it.