Between approval and disapproval: Citizens’ views on the invasive tree Ailanthus altissima and its management

Abstract

While cities are invasion hotspots, the view of urban residents on non-native species is critically understudied – an important knowledge gap since strategies on biological invasions could gain power by integrating human values, attitudes and perceptions. How citizens perceive the non-native tree Ailanthus altissima (tree of heaven) is unknown despite its abundance in many cities globally and its classification as invasive in many countries. In a quantitative survey with closed questions, we analysed (i) whether residents of Berlin, Germany knew the widespread species, (ii) how they perceived it in different urban situations, (iii) how they accepted different management strategies of it, and (iv) how the sociodemographic background of respondents predicted their preference and acceptability ratings. In total, we surveyed 196 respondents. Most respondents recognized the tree in a photograph, but few provided its correct name. Citizens’ preferences differed significantly among four urban contexts in which the species was shown, with prevailing approval for trees as a component of designed green spaces and less pronounced preferences for wild-grown trees in other urban spaces. When respondents were asked to indicate how the tree should be managed (three options), we found the most support for removal in problematic cases (‘adaptive on-site’ strategy); some support was found for the ‘leave alone’ strategy and least support for the ‘complete removal’ management strategy. Practitioners with expertise in urban landscaping were more critical of Ailanthus than laypeople. Ordinal logistic regression analyses showed that respondents with a ‘close to nature’ behaviour and attitude had a more positive view on Ailanthus and expressed more support for ‘leave alone’ management. Results demonstrate the importance of citizens’ context dependent views about a widespread invasive species, spanning from approval to disapproval in different situations. We conclude that urban management strategies concerning Ailanthus would gain support from citizens when combining multiple approaches: (i) to control the species in case of realized negative impacts; (ii) to prevent the invasion of the species in areas of conservation concern; and (iii) to develop novel approaches of integrating wild Ailanthus trees into urban green spaces. These insights could support management measures that need to be established due to the EU-Regulation on Invasive Alien Species.

Streetscapes as Surrogate Greenspaces During COVID-19?

“…This is backed by previous studies in the context of spontaneous, wild growing vegetation in tree pits that people broadly supported species-rich vegetation (Fischer et al, 2018a). Also spontaneously growing, non-native tree species are widely accepted as greening element in streetscapes, especially when incorporated into a traditionally managed green street setting (Kowarik et al, 2021).…”

Novel Urban Ecosystems: Opportunities from and to Landscape Architecture

“…But mostly, it will be critical to consider people's interests, values, and preferences in this discussion, such as what they like or dislike, what they need, and the benefits they will mostly value in urban green spaces (e.g., beauty, biodiversity, well-being, health, or comfort) [52,54,57]. Understanding people's social values, preferences, and attitudes towards NUE can inform and support their design, planning, or management, thereby increasing their general acceptance and successful integration in political agendas [35,52,58,59]. To this end, studies using well-established approaches from the social sciences, such as questionnaires often assembled with photographs or photo-manipulations [60], are being implemented to understand urban dwellers' perceptions, preferences, or attitudes and then inform practitioners [58,[61][62][63][64].…”

“…Understanding people's social values, preferences, and attitudes towards NUE can inform and support their design, planning, or management, thereby increasing their general acceptance and successful integration in political agendas [35,52,58,59]. To this end, studies using well-established approaches from the social sciences, such as questionnaires often assembled with photographs or photo-manipulations [60], are being implemented to understand urban dwellers' perceptions, preferences, or attitudes and then inform practitioners [58,[61][62][63][64].…”

Physiochemical responses of Ailanthus altissima under the challenge of Verticillium dahliae: elucidating the decline of one of the world’s worst invasive alien plant species

“…Ailanthus altissima (Mill.) Swingle (Simaroubaceae; hereafter Ailanthus), also known as 'tree of heaven', is a tree species native to East Asia that has been designated as one of the "100 of the World's Worst Invasive Alien Species" by the IUCN Invasive Species Specialist Group (Kowarik et al 2021), after becoming an undesired plant in many world regions such as North America (Schall and Davis 2009a), South Africa (Walker et al 2017) and Europe (Kowarik and Säumel 2007;Nentwig et al 2018). Firstly, introduced to Europe in the 1740s (Hu 1979), mainly as ornamental species in several cities because of its tolerance to urban stressful conditions and its resistance to herbivory (Kowarik and Säumel 2007), Ailanthus has since spread so widely and uncontrollably that from August 2019 it has also been included among the Invasive Alien Species (IAS) of Union Concern (Kowarik et al 2021).…”