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An Interdisciplinary Perspective on Invasive Alien Species

A guest post from Susanna Lidström from the KTH Royal Institute of Technology and Simon West of the Stockholm Reslience Centre


Recently, Russell and Blackburn argued that critique of the invasive alien species (IAS) concept constitutes science denialism—the rejection of basic facts and concepts that are well-supported. While others have robustly challenged this claim (2, 3, 4), we situate the debate in the context of broader shifts in interdisciplinary environmental studies and associated understandings of science-society relations. The relationships between values and evidence are a classic point of conflict and misunderstanding in the natural sciences, and between the natural and social sciences and humanities. The way forward is not to play down the role of values in science, but to better understand their interaction.


Russell and Blackburn’s argument hinges on an imagined ability to clearly demarcate the definition of IAS and their impacts (both acknowledged to include ‘subjective’ elements), from the measurement of these impacts. Those who do not clearly establish this demarcation are derided as “science denialists,” motivated by laissez-faire free market ideologies.


However, research in the environmental social sciences and humanities has demonstrated the impossibility of definitively separating definitions of human-environment phenomena from measurement of impacts (5, 6, 7). The definition of a phenomenon colours what is measured, how it is measured, and how the results are interpreted. Rather than constituting science denialism, this research has enhanced our understanding of how ecological knowledge is produced and used in society. Far from having “disingenuous motivations,” scholars have largely been motivated by the need to understand how science – together with other sources of knowledge – may be better used to address complex socio-environmental issues like IAS (11).


The definition of invasive and alien species is shaped by values, metaphors and interests – as a large body of critical literature on IAS across the natural and social sciences and humanities has made clear (9, 10, 11). Values and metaphors do not undermine scientific rigour. They are an essential part of science – indeed, they are crucial for understanding anything at all. The critique of IAS is therefore generally not that IAS is a troubling concept because it is value-laden per se, but raises the question of whether it is a useful ‘lens’ for collecting and interpreting ecological data, and for framing our understanding of human-environment relations.


For some, including Russell and Blackburn, the answer to this question is ‘yes’ – predominantly because of the (presumed) power of the IAS metaphor to exert policy impacts. For others, however, the answer is ‘no.’ Many ecologists find that the metaphor poorly reflects the complexity of ecological relationships. Viewed from the social sciences and humanities the rhetoric surrounding IAS has uncomfortable resonances with xenophobic modes of thinking and acting that ascribe inherent and essentialist “good” and “bad” identities to different species, giving the impression that these are characteristics present in the natural world rather than value judgements made by people [9]. Whichever perspective on IAS is adopted, the relationships between values and evidence are inextricable and not easily parsed by the simple adoption of, e.g. decision science tools. Rather they require deeper, on-going discussions about how we know and act in relation to the environment, and honest, reflexive conversations about what motivates us and what we value.


These debates are tricky to navigate because different disciplines carry different assumptions, expectations of research, and understandings of the relationships between subjectivity and objectivity. Debates are often highly charged.


In very broad terms, natural science tends to progress within paradigms, while the social sciences and humanities proceed by debating the assumptions of paradigms. Russell and Blackburn acknowledge that questioning paradigms is “at times” important. We suggest that a continual critique of paradigms is essential to the progression of science. Russell and Blackburn state that when questioning paradigms “scientists must be mindful of their own underlying motivations and values” (5). We agree, but this is not only applicable to those making the critique, but to all scientists at all times, especially those in the normative ‘crisis discipline’ of conservation biology. Indeed, it is the uncomfortable questions of value and motivation in scientific knowledge raised by critiques of IAS that Russell and Blackburn appear unprepared to address – hence the rush to label those who raise them ‘science denialists.’


Superficial understanding of the relationships between evidence and values creates exactly the dichotomization between science ‘believers’ and ‘denialists’ that Russell and Blackburn ostensibly seek to avoid. Rather than ‘standing up for science’ such dichotomization undermines it, rendering aspects of scientific enterprise ‘off limits’ to the kinds of rigorous critical (self) examination fostered by science at its best. We suggest that instead of name-calling, Russell and Blackburn’s stated aim to foster “vibrant and robust dialogue” around IAS is best served by ‘opening up’ science through increased co-design and co-production of research, and involvement of experts and perspectives from a variety of disciplines and societal sectors (12). This will help build new models of science-society interaction that can effectively negotiate – rather than deny – the role of values in ecological science.


Susanna Lidström (

Simon West (
References (Hyperlinks in text)

  1. Russell, J.C. and Blackburn, T.M. (2016) The rise of invasive species denialism. Ecol. Evol. 32, 3–6
  2. Tassin, J. et al. (2017) Determining whether the impacts of introduced species are negative cannot be based solely on science: a response to Russell and Blackburn. Trends Ecol. Evol. 32(4), 230–231
  3. Crowley, S.L. et al. (2017) Disagreement about invasive species does not equate to denialism: a response to Russell and Blackburn. Trends Ecol. Evol. 32(4), 228–229
  4. Davis, A.D. and Chew, M.K. (2017) ‘The denialists are coming!’ Well, not exactly: a response to Russell and Blackburn. Trends Ecol. Evol. 32(4), 229–230
  5. Forsyth, T. (2003) Critical Political Ecology: The Politics of Environmental Science. London: Routledge
  6. Sarewitz, D. (2004) How science makes environmental controversies worse. Environmental Science & Policy 7(5), 385–403
  7. Leach, M. et al. (2010) Dynamic Sustainabilities: Technology, Environment, Social Justice. London and New York: Earthscan
  8. Funtowicz, S. and Ravetz, J. (1993) Science for the post-normal age. Futures 31(7), 735–755
  9. Lidström, S. et al. (2015) Invasive narratives and the inverse of slow violence: alien species in science and society. Environmental Humanities 7, 1–40
  10. Frawley, J., and McCalman, I. (2014) Rethinking invasion ecologies from the environmental humanities. London and New York: Routledge
  11. Larson, B. (2011) Metaphors for environmental sustainability: redefining our relationship with nature. New Haven: Yale University Press
  12. Mauser, W. et al . (2013) Transdisciplinary global change research: the co-creation of knowledge for sustainability. Current Opinion in Environmental Sustainability 5(3-4), 420–431





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