Managing invasive species in cities: a decision support framework applied to Cape Town

Abstract

It has been suggested that existing frameworks for guiding management of invasive species in rural areas and protected areas are inadequate for dealing with invasions in urban settings. A framework for selecting appropriate goals for managing invasive species in urban areas was developed by Gaertner et al. (Landsc Urban Plan 151:1–9, 2016). This framework groups species into three management approaches (control priority, active engagement, and tolerance) depending on their real or perceived benefits and their potential to generate negative impacts. This study tests the practical application of the framework using the example of Cape Town. We assess the suitability of the framework to support decision-making for managing invasive species in urban ecosystems using a questionnaire-based survey of members of the public, and an e-mail-based survey and a workshop with invasion biology researchers and managers. Specifically, we (1) determine the differences in perceptions regarding the benefits and impacts of invasive species between the public, managers and researchers; (2) investigate how consistently managers and researchers group invasive species into the three management categories; and (3) identify, with the help of managers and researchers, issues linked to the framework and give suggestions to overcome the identified issues. We found no clear pattern in the perceptions of the public, managers and researchers regarding perceived benefits and negative impacts of invasive species. Instead, the answers were widely scattered among all groups for most of the species that were considered. However, using the framework leads to a higher consistency among managers in placing the species into management categories, compared to invasive species grouping without guidance of the framework. We conclude that decision-support frameworks can assist managers in placing invasive species into management categories. However, even more specific guidelines on the use of invasive species management frameworks in urban areas are needed.

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Acknowledgements

We acknowledge funding from the DST-NRF Centre of Excellence for Invasion Biology (M.G., A.N. and D.M.R), the National Research Foundation, South Africa (Grant 85417 to D.M.R), the South African National Department of Environment Affairs through its funding of the South African National Biodiversity Institute’s Invasive Species Programme (A.N.), the Project No. 14-36079G Centre of Excellence PLADIAS (A.N.; Czech Science Foundation) and the long-term research development project RVO 67985939 (A.N.; The Czech Academy of Sciences). We would also like to acknowledge funding from the EcoDry project (EcoDry— Sharing Best Agroecological Practice for Resilient Production Systems in Dryland and Drought Conditions), an EU FP7-PEOPLE-2013-IRSES project that enabled involved researchers (A.N., J.F.) to travel between South Africa and the UK. An early version of this paper was presented at a workshop on ‘Non-native species in urban environments’ hosted and funded by the DST-NRF Centre of Excellence for Invasion Biology (C·I·B) in Stellenbosch, South Africa, in November 2016. Comments and suggestions from participants at the workshop improved the paper. We thank Giovanni Vimercati for his help with the questionnaires and Brendon Larson for comments on the manuscript.

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Correspondence to Mirijam Gaertner.

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Guest Editors: Mirijam Gaertner, John R. U. Wilson, Marc W. Cadotte, J. Scott MacIvor, Rafael D. Zenni and David M. Richardson/Urban Invasions.

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Gaertner, M., Novoa, A., Fried, J. et al. Managing invasive species in cities: a decision support framework applied to Cape Town. Biol Invasions 19, 3707–3723 (2017). https://doi.org/10.1007/s10530-017-1587-x

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Keywords

  • Biological invasions
  • Management
  • Stakeholder engagement
  • South Africa
  • Tree invasions
  • Urban invasions