Biological Invasions

, Volume 12, Issue 12, pp 4085–4098 | Cite as

Evaluation of the Australian weed risk assessment system for the prediction of plant invasiveness in Canada

  • Alec McClay
  • Andrea Sissons
  • Claire Wilson
  • Sarah Davis
Original Paper


The Australian Weed Risk Assessment system has been tested in a number of countries and geographical areas since its introduction in 1997, and is widely considered to be an accurate method of predicting the risk of invasiveness of new plant introductions. We evaluated the system against 152 plant species with at least a 50-year introduction history in Canada, including major and minor weeds and species which have not naturalized. Four questions that referred explicitly to Australian conditions were replaced with appropriate equivalent questions for Canada. The weediness of each species was independently rated by a panel of Canadian agricultural, botanical, and conservation experts. Using the standard cut-off scores, the system correctly rejected all major and 86% of minor weeds. However, it also incorrectly rejected 44% of non-weedy species. The diagnostic power of the system, as measured by the receiver operating characteristic curve, was similar to but somewhat lower than that found in other regions where the system has been evaluated. Answers to 23 of the 49 questions were not significantly associated with experts’ weediness ratings, indicating that a simplified system could give equally reliable results for Canada. Experts’ ratings were strongly related to cold-hardiness, suggesting that the system could be improved by making better use of data on climatic tolerances. We suggest that performance would also be improved by combining likelihood- and consequence-related scores in a multiplicative rather than additive way.


Weed risk assessment Weeds Introduced plants ROC curve Screening system Invasive species Alien plants Canada 



We thank CFIA staff Ken Allison, Karen Castro, and Cheryl Corbett for species assessments; Doria Gordon (The Nature Conservancy) for access to Florida species data, the guidance document, and the spreadsheet; Roger Magarey (USDA-APHIS) for information on the NAPPFAST plant hardiness zones; and Anthony L. Koop (USDA-APHIS) for helpful discussions on risk assessment approaches. We are also grateful to the experts who assessed the weed status of the plant species in Canada: Hugh Beckie (Agriculture and Agri-Food Canada, Saskatoon Research Centre), Bruce Bennett (Environment Yukon), Sean Blaney (Atlantic Canada Conservation Data Centre), Luc Brouillet (Université de Montréal), Joe Calder (Nova Scotia Department of Agriculture), David Clements (Trinity Western University), Stephen Darbyshire (Agriculture and Agri-Food Canada, Eastern Cereal and Oilseeds Research Centre), Bruce Ford (University of Manitoba), Linda Hall (University of Alberta), Susan Meades (Northern Ontario Plant Database), Val Miller (British Columbia Ministry of Forests and Range), Romain Néron (Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec), Michael Oldham (Ontario Ministry of Natural Resources), Rafael Otifnowski (University of Manitoba), and Suzanne Warwick (Agriculture and Agri-Food Canada, Eastern Cereal and Oilseeds Research Centre).


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Copyright information

© Her Majesty the Queen in Right of Canada 2010

Authors and Affiliations

  • Alec McClay
    • 1
  • Andrea Sissons
    • 2
  • Claire Wilson
    • 3
  • Sarah Davis
    • 2
  1. 1.McClay EcoscienceSherwood ParkCanada
  2. 2.Canadian Food Inspection AgencyOttawaCanada
  3. 3.Canadian Food Inspection AgencyDartmouthCanada

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