Biological Invasions

, Volume 20, Issue 10, pp 2723–2729 | Cite as

Invasive species denialism: a reply to Ricciardi and Ryan

  • Mark SagoffEmail author
Invasion Note


This paper offers a defense against ad hominem aspersions cast in this journal by Ricciardi and Ryan (Biol Invasions 20(3):549–553, 2018) who allege that several articles I wrote represent “invasive species denialism” and “science denialism.” I summarize the arguments found in those articles. They are (1) science cannot define ecological “harm” and thus cannot measure its risk; (2) invasion biologists rely on tautologies, i.e., definitions of concepts like “biodiversity” and “ecosystem intactness,” that exclude exotic species; (3) no empirical evidence shows that introduced plants have been significant causes of extinction; (4) biologists cannot tell by observing a species whether it is native or a naturalized alien; and (5) debates over the meanings and measurements of key concepts in invasion biology have passed the point of diminishing returns. These arguments may be wrong but none is “similar to the denialism that has affected climate science and medical science” as Ricciardi and Ryan aver.


Invasive species denialism Ecological harm Native-alien distinction Biodiversity Definitions in invasion biology 


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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Institute for Philosophy and Public PolicyGeorge Mason UniversityFairfaxUSA

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