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Correction to: Managing Urban Plant Invasions: a Multi-Criteria Prioritization Approach

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The original version of the article unfortunately contained an error with the figure captions. The appropriate captions for Fig. 3-6 are published accordingly. The original article has been corrected.
Environmental Management (2018) 62:11861189
Correction to: Managing Urban Plant Invasions: a Multi-Criteria
Prioritization Approach
Luke J. Potgieter1Mirijam Gaertner1,2 Ulrike M. Irlich1,3 Patrick J. OFarrell4,5 Louise Stafford3Hannah Vogt3
David M. Richardson1
Published online: 30 August 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
Correction to:Environmental Management https://doi.
The original version of the article unfortunately contained
an error with the gure captions. The appropriate captions
for Figs. 36are published accordingly. The original article
has been corrected.
The original article can be found online at
*Luke J. Potgieter
1Centre for Invasion Biology, Department of Botany and Zoology,
Stellenbosch University, Private Bag X1, Matieland 7602, South
2Nürtingen-Geislingen University of Applied Sciences (HFWU),
Schelmenwasen 4-8, 72622 Nürtingen, Germany
3Invasive Species Unit, Environmental Resource Management
Department, City of Cape Town, Westlake Conservation Ofce,
Cape Town, South Africa
4Natural Resources and Environment CSIR,
P. O. Box 320, Stellenbosch 7599, South Africa
5Percy FitzPatrick Institute of African Ornithology, University of
Cape Town, Rondebosch, South Africa
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... A trend in human preferences for particular plant traits has led to an increase in the proportion of alien trees in many urban areas around the world ( Dickie et al. 2014), compounded by escaped woody ornamentals ( Potgieter et al. 2017). Many alien tree taxa have subsequently spread and become invasive, threatening the delivery of ES (van Wilgen et al. 2008;van Wilgen 2012) and creating novel suites of EDS such as increased safety and security risks (Potgieter et al. 2018(Potgieter et al. , 2019a). Understanding the ES-EDS dichotomy in the context of urban landscapes is important for promoting the development of resilient and sustainable cities (Carpenter et al. 2006; Liu et al. 2007). ...
... Understanding the ES-EDS dichotomy in the context of urban landscapes is important for promoting the development of resilient and sustainable cities (Carpenter et al. 2006; Liu et al. 2007). Decisions around managing invasive alien plants (IAPs) (sensu Richardson et al. 2000) in urban areas are fundamentally determined by their capacity to create negative impacts (EDS) and provide benefits (ES) ( Vaz et al. 2017;Potgieter et al. 2018). Managing urban ecosystems to enhance the provisioning of ES while reducing EDS is a major challenge. ...
... The ISU conducts clearing operations in areas managed by multiple departments within the city, including many conservation areas. At each area identified as a priority for control operations, the ISU conducts a site assessment in which management units (MU) are delineated and surveyed and baseline Increased water consumption Increased water consumption by alien and invasive trees such as Acacia sp. and Eucalyptus sp. a Ecosystem disservices resulting from a reduction in ecosystem services information captured (see Potgieter et al. 2018). All IAPs present within each MU are listed and categorised according to predefined size categories used to describe the age of plants. ...
Full-text available
Background Natural resources within and around urban landscapes are under increasing pressure from ongoing urbanisation, and management efforts aimed at ensuring the sustainable provision of ecosystem services (ES) are an important response. Given the limited resources available for assessing urban ES in many cities, practical approaches for integrating ES in decision-making process are needed. Methods We apply remote sensing techniques (integrating LiDAR data with high-resolution multispectral imagery) and combined these with supplementary spatial data to develop a replicable approach for assessing the role of urban vegetation (including invasive alien plants) in providing ES and ecosystem disservices (EDS). We identify areas denoting potential management trade-offs based on the spatial distribution of ES and EDS using a local-scale case study in the city of Cape Town, South Africa. Situated within a global biodiversity hotspot, Cape Town must contend with widespread invasions of alien plants (especially trees and shrubs) along with complex socio-political challenges. This represents a useful system to examine the challenges in managing ES and EDS in the context of urban plant invasions. Results Areas of high ES provision (for example carbon sequestration, shade and visual amenity) are characterized by the presence of large trees. However, many of these areas also result in numerous EDS due to invasions of alien trees and shrubs – particularly along rivers, in wetlands and along the urban edge where tall alien trees have established and spread into the natural vegetation (for example increased water consumption, increased fire risk and reduced soil quality). This suggests significant trade-offs regarding the management of species and the ES and EDS they provide. Conclusions The approach applied here can be used to provide recommendations and to guide city planners and managers to fine-tune management interventions at local scales to maximise the provision of ES.
... urban areas, Box 4.1). (Holmes et al. 2018); and decision support tools to assist with management planning (Gaertner et al. 2017b) and prioritisation have been developed (Potgieter et al. 2018). ...
... Moreover, we now have a better understanding of the role of urban areas as hotspots and sentinel sites for invasions (Paap et al. 2017), and of both perceived and realised impacts (Potgieter et al. 2018(Potgieter et al. , 2019a(Potgieter et al. , 2019b(Potgieter et al. , 2020. There have also been significant investments in control operations (in particular by the City of Cape Town and eThekwini) focusing on both plants and animals (Davies et al. 2020). ...
Technical Report
Full-text available
Biological invasions are a major threat to South Africa’s biodiversity, economy, and sustainable development. This report is a part of South Africa’s commitment to alleviating these impacts. It is a comprehensive national-scale assessment with contributions from 36 experts from 16 institutions. Drafts of the report were available for comment in two substantive rounds of review, with over 350 comments received from 17 institutions. This report is unique in the world in focussing specifically on invasions and is an important part of South Africa’s global leading position on the issue (the government invests over 1 billion ZAR a year to deal with the problem). The report is based around a suite of 20 indicators that provide details on: 1) how alien species are introduced and move around the country; 2) the status and impacts of 1880 alien species of which 776 are invasive; 3) the degree to which sites are invaded and impacted; and 4) the effectiveness of the full range of interventions that South Africa has used to address the problem. This report provides valuable insights into how South Africa can reduce the negative impacts of biological invasions on ecosystems, the economy, and people while retaining the benefits alien species provide where this is possible and desirable. It collates foundational information essential for researchers of the topic and an assessment of interventions that is vital for policy makers and managers.
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Urban areas have unique assemblages of species which are governed by novel ecological processes. People living in these environments have specific needs and demands in terms of ecosystem services (ES). Urban ecosystems are transformed in many ways by human activities and their floras comprise a high proportion of alien plant species, many of which were intentionally introduced to provide, augment or restore ES. Urban environments also have novel disturbance regimes and provide colonization sites for the establishment, dispersal and proliferation of alien plant species; such conditions often generate biological invasions which may cause marked changes to ES. We review the roles that alien plants play in providing urban ES and ecosystem disservices (EDS) globally. We identify the main ES and EDS associated with alien plants, and highlight the key species involved. A literature search revealed 335 papers, representing studies in 58 cities or urban areas in 27 countries. These studies recorded 337 alien plant species, contributing to 39 different ES and 27 EDS–310 species were recorded s contributing to ES and 53 species to EDS. A small number of alien plant taxa were frequently recorded as providing multiple ES in many urban ecosystems; the 10 most recorded species accounted for 21% of the ES recorded. Some of these species also result in significant EDS; three species accounted for 30% of the EDS recorded. Cultural services (notably aesthetics) are the most reported ES provided by alien plants in urban areas of developed countries, while provisioning services (notably food production) are most reported in developing countries. The most commonly studied EDS provided by alien plants is the impact on human health (notably allergic reactions). Eighty percent of studies on alien plants and ES and EDS have been done in developed countries. To elucidate the full range of effects of alien plants, more work is needed in developing countries. Urban planners and managers need to be mindful of both the positive and negative impacts of alien plant species to maximise the provision of ES.
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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. in 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. 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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Alien species are often first introduced to urban areas, so it is unsurprising that towns and cities are often hotspots for invasions. However, while large cities are usually the first sites of introduction, small towns are more numerous and have a greater chance of launching invasions into natural areas as they have proportionally larger interfaces with their surroundings. In this paper we develop a set of scenarios as hypotheses to explore the role of small towns in facilitating within-country dispersal of alien plants. In particular, we developed ten scenarios for how introductions to small towns, agricultural and natural areas can lead to landscape-scale invasions. We tested a part of these scenarios using a case study of a highly invaded region in South Africa (the Berg River catchment area in the Western Cape). We specifically investigated the main plant invasion routes between 12 small towns and their surrounding agricultural and natural areas. This was accomplished by conducting urban-specific alien plant surveys in towns, then comparing these results to regional databases of naturalized and/or invasive plants. Many of the alien plants found in urban areas were listed as invasive or naturalized in the catchment (over 30% of the total alien pool). Despite marked environmental gradients across the study area, we found no relationships between the alien plant species richness in towns and climatic variables or with levels of anthropogenic disturbances. All towns hosted large numbers of invasive plant species and nearly half of the alien species found in towns were naturalized or invasive in surrounding areas. The likelihood of alien plants being naturalized or invasive outside urban areas increased in proportion to their local abundance in towns and if they were tall and woody. Ornamental horticulture was the main reason for introduction of these alien species (69%). Small towns can and do harbour significant populations of plant taxa that are able to spread to surrounding natural areas to launch invasions. Comparing lists of species from urban alien plant surveys with those from naturalisation records for the region is a useful protocol for identifying species which may be moving along the introduction-naturalization-invasion continuum.
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Alien species can have major ecological and socioeconomic impacts in their novel ranges and so effective management actions are needed. However, management can be contentious and create conflicts, especially when stakeholders who benefit from alien species are different from those who incur costs. Such conflicts of interests mean that management strategies can often not be implemented. There is, therefore, increasing interest in engaging stakeholders affected by alien species or by their management. Through a facilitated workshop and consultation process including academics and managers working on a variety of organisms and in different areas (urban and rural) and ecosystems (terrestrial and aquatic), we developed a framework for engaging stakeholders in the management of alien species. The proposed framework for stakeholder engagement consists of 12 steps: (1) identify stakeholders; (2) select key stakeholders for engagement; (3) explore key stakeholders' perceptions and develop initial aims for management; (4) engage key stakeholders in the development of a draft management strategy; (5) re-explore key stakeholders' perceptions and revise the aims of the strategy; (6) co-design general aims, management objectives and time frames with key stakeholders; (7) co-design a management strategy; (8) facilitate stakeholders' ownership of the strategy and adapt as required; and (9) implement the strategy and monitor management actions to evaluate the need for additional or future actions. In case additional management is needed after these actions take place, some extra steps should be taken: (10) identify any new stakeholders, benefits, and costs; (11) monitor engagement; and (12) revise management strategy. Overall, we believe that our framework provides an effective approach to minimize the impact of conflicts created by alien species management.
Aim Decision-support models have considerable potential for guiding management strategies when problems are complex. The robustness of such decision-making processes is rarely evaluated, and the influence of decision criteria (or factors) in management decisions is seldom considered. We present a framework for a spatially-explicit sensitivity analysis by using a scheme developed to provide objective guidelines, in the form of static priority maps, for managing woody invasive alien plants (IAPs).
Human perceptions of nature and the environment are increasingly being recognised as important for environmental management and conservation. Understanding people's perceptions is crucial for understanding behaviour and developing effective management strategies to maintain, preserve and improve biodiversity, ecosystem services and human well-being. As an interdisciplinary team, we produced a synthesis of the key factors that influence people's perceptions of invasive alien species, and ordered them in a conceptual framework. In a context of considerable complexity and variation across time and space, we identified six broad-scale dimensions: (1) attributes of the individual perceiving the invasive alien species; (2) characteristics of the invasive alien species itself; (3) effects of the invasion (including negative and positive impacts, i.e. benefits and costs); (4) socio-cultural context; (5) landscape context; and (6) institutional and policy context. A number of underlying and facilitating aspects for each of these six overarching dimensions are also identified and discussed. Synthesising and understanding the main factors that influence people's perceptions is useful to guide future research, to facilitate dialogue and negotiation between actors, and to aid management and policy formulation and governance of invasive alien species. This can help to circumvent and mitigate conflicts, support prioritisation plans, improve stakeholder engagement platforms, and implement control measures.
Many alien plant species are introduced to urban areas to create, augment or restore ecosystem services (ES). However, many of these species spread beyond original plantings, sometimes causing negative effects on existing ES or creating novel ecosystem disservices (EDS). An understanding of the perceptions of urban residents regarding invasive alien plants (IAPs) and the ES and EDS they provide is needed for the effective prioritisation of IAP management efforts in cities. Using the city of Cape Town, South Africa as a case study, we conducted questionnaire-based surveys (online and face-to-face) to determine the perceptions of urban residents regarding IAPs and their capacity to provide ES and EDS. Most urban residents perceive IAPs negatively (i.e. agreeing that they create EDS), but many recognise their importance in providing ES. Although most residents are not opposed to the management of IAPs, such actions are not perceived as a high priority relative to other environmental problems. Socio-demographic variables such as age, education, environmental awareness, and ethnicity shape urban residents' perceptions of IAPs. Older, more educated respondents were more likely to perceive IAPs negatively, while respondents with greater environmental awareness were aware of the benefits provided by IAPs. This study highlights the need to integrate public perceptions into the planning and management of IAPs and emphasises the importance of including ES assessments into the decision-making process, particularly in urban areas.
Although urban ecosystems are hotspots for biological invasions, the field of invasion science has given scant attention to invasion dynamics and the challenges facing managers in towns and cities. This paper provides an introduction to the growing challenges of understanding and managing invasive species in urban systems, and the context for a special issue of Biological Invasions, comprising 17 papers, that arose from a workshop on “Non-native species in urban environments: patterns, processes, impacts and challenges” held in Stellenbosch, South Africa, in November 2016. Contributions explore the following key questions: Are patterns and processes of urban invasions different from invasions in other contexts? Why is it important to manage non-native species in urban ecosystems? What are the special management needs in an urban context? How can we bridge the gaps between science, management, and policy with regards to biological invasions in urban ecosystems? The papers in this special issue show that patterns and processes of urban invasions differ in many ways from invasions in other contexts, and that managing invasive species in cities poses unique and increasingly complex challenges. Progress in urban invasion science requires further work to: (1) address key limitations that hinder our understanding of invasion dynamics in cities; (2) clarify whether fundamental concepts in the field of invasion science are appropriate for urban ecosystems; (3) integrate insights from invasion science with those from the burgeoning literature on the “Anthropocene biosphere”, novel ecosystems, social–ecological systems, human–wildlife conflicts, urban green infrastructure, urban planning and design, and ecosystem services/disservices.
1. Many alien taxa are known to cause socio-economic impacts by affecting the different constituents of human well-being (security; material and non-material assets; health; social, spiritual and cultural relations; freedom of choice and action). Attempts to quantify socio-economic impacts in monetary terms are unlikely to provide a useful basis for evaluating and comparing impacts of alien taxa because they are notoriously difficult to measure and important aspects of human well-being are ignored. 2. Here, we propose a novel standardised method for classifying alien taxa in terms of the magnitude of their impacts on human well-being, based on the capability approach from welfare economics. The core characteristic of this approach is that it uses changes in peoples’ activities as a common metric for evaluating impacts on well-being. 3. Impacts are assigned to one of five levels, from Minimal Concern to Massive, according to semi-quantitative scenarios that describe the severity of the impacts. Taxa are then classified according to the highest level of deleterious impact that they have been recorded to cause on any constituent of human well-being. The scheme also includes categories for taxa that are not evaluated, have no alien population, or are data deficient, and a method for assigning uncertainty to all the classifications. To demonstrate the utility of the system, we classified impacts of amphibians globally. These showed a variety of impacts on human well-being, with the cane toad (Rhinella marina) scoring Major impacts. For most species, however, no studies reporting impacts on human well-being were found, i.e. these species were data deficient. 4. The classification provides a consistent procedure for translating the broad range of measures and types of impact into ranked levels of socio-economic impact, assigns alien taxa on the basis of the best available evidence of their documented deleterious impacts, and is applicable across taxa and at a range of spatial scales. The system was designed to align closely with the Environmental Impact Classification for Alien Taxa (EICAT) and the Red List, both of which have been adopted by the International Union of Nature Conservation (IUCN), and could therefore be readily integrated into international practices and policies.