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Accepted manuscript

A global census of weed risk assessment standards

Published online by Cambridge University Press:  26 September 2025

William G. Pfadenhauer*
Affiliation:
PhD Candidate, Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst, MA, 01003
Benjamin B. Kesler
Affiliation:
Undergraduate student, Biology, University of Massachusetts Amherst, Amherst, MA, 01003
Justin Salva
Affiliation:
Undergraduate student, University of Massachusetts Amherst, Amherst, MA, 01003
Luca Pillidge
Affiliation:
Undergraduate student, University of Massachusetts Amherst, Amherst, MA, 01003
Taesung Smith
Affiliation:
Research Intern, Economics, Information Technology, and Business, University of Massachusetts Amherst, Amherst, MA, 01003
Charles Chimera
Affiliation:
Weed Risk Assessment Specialist, Hawai’i Invasive Species Council, Honolulu, HI, 96813
Bethany A. Bradley
Affiliation:
Professor of Biogeography and Spatial Ecology, Environmental Conservation, University of Massachusetts Amherst, Amherst, MA, 01003
*
Author for correspondence: William G. Pfadenhauer, Email: pfadenwill@gmail.com
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Abstract

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Weed Risk Assessments (WRAs) aim to distinguish potentially invasive plants from non-invasive plants using traits including the likelihood that the species will be introduced, establish, spread, have negative impacts, and (sometimes) whether it can be managed effectively. International standards for the criteria used to assess risk have been proposed to improve the sharing and transferability of WRA results. However, it is unclear whether existing WRAs follow these standards. Here, we compiled a global database of national-level and subnational-level (state/province) WRAs and evaluated their assessment criteria relative to an amended list of proposed minimum standards. We searched for WRAs in 240 countries and retrieved 20 unique assessments associated with 81 countries. The most comprehensive WRA was the “Guidelines for the Generic Ecological Impact Assessment of Alien Species” created by Norway, which satisfied 23 of 24 standards. The International Plant Protection Convention (IPPC) Pest Risk Analysis Framework and the European and Mediterranean Plant Protection Organization (EPPO) Express Pest Risk Analysis were also comprehensive, fulfilling 21 of 24 standards. All national-level WRAs included a description of the focal species’ taxonomy, a description of risk assessment area, an assessment of the likelihood of spread of the focal species, and an assessment of the likelihood of impact of the focal species. Conversely, it was rare for WRAs to include a history of spread of the focal species or an evaluation of the possible effects of climate change. States/provinces showed a similar pattern (i.e. rarely discussed climate change), but also frequently lacked assessment of impact on ecosystem services and metrics of uncertainty. Many WRAs are shared between countries, but few are shared between states/provinces. Adopting similar WRA standards would allow policy makers and governing bodies to more effectively share information and results from completed weed risk assessments, improving consistency of regulated plants across jurisdictional borders.

Information

Type
Research Article
Creative Commons
Creative Common License - CCCreative Common License - BYCreative Common License - NCCreative Common License - ND
This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is unaltered and is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use or in order to create a derivative work.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Weed Science Society of America