Cultural
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Recreation
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Picnicking under tall shade-providing trees (e.g. Pinus pinea)
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Potgieter et al. (2019b)
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Physical, intellectual and spiritual interactions with nature, including aesthetic values, inspiration and cognitive development, and spiritual enrichment
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Well managed urban green spaces with abundant vegetation
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Bastian et al. (2012); Dobbs et al. (2011)
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Visual amenity, ornamental purposes and landscape re-greening
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Private residential gardens
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Dickie et al. (2014); Carruthers et al. (2011); Kull et al. (2011); Le Maitre et al. (2011); Shackleton et al. (2016)
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Provision of a ‘sense of place’
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Dickie et al. (2014)
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Heritage
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Pinus pinea trees planted in the seventeenth century by the early settlers, have significant heritage value
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Gaertner et al. (2016)
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Increased property values
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Soares et al. (2011)
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Provisioning
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Firewood
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Trees such as Acacia sp., Eucalyptus sp. or Pinus sp. can be used for firewood
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Dickie et al. (2014)
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Construction material
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Trees such as Eucalyptus sp. or Pinus sp. can be used for poles
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Dickie et al. (2014)
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Medicinal value
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Essential oils provided by Eucalyptus sp.
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Fodder
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Eucalyptus camaldulensis used as fodder
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Bernholt et al. (2009)
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Food
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Eucalyptus sp. (especially E. cladocalyx) are important for honey production
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Regulating
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Shade
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Shade from tall trees with wide canopy such as Pinus pinea
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Potgieter et al. (2019b);
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Climate regulation
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Cooling effects (by transpiration) of street trees such as Platanus × acerifolia
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Jim and Chen (2009)
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Air quality
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Reduced emissions of air pollutants by Platanus × acerifolia
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McPherson (2003)
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Flood attenuation
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Wetlands
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Barrier
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Pinus sp. used as a barrier plant
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Carbon sequestration
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Trees such as Platanus × acerifolia sequester carbon
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Potgieter et al. (2017)
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Nitrogen fixation
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Acacia sp. fix nitrogen, enriching the soil
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Qiu (2015); Dickie et al. (2014); van Wilgen and Richardson (2014); de Wit et al. (2001)
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Erosion control
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Erosion control by trees such Ailanthus altissima
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Sladonja et al. (2015); Kowarik and Säumel (2007)
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Energy saving
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Changes in building energy use from shade trees such as Platanus × acerifolia
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McPherson (2003)
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Stormwater runoff mitigation
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Supporting
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Habitat provision
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Tall alien trees such as eucalypts and pines provide nesting sites for birds with which many urban dwellers can enjoy encounters.
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McPherson et al. (2011)
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Nutrient cycling
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Pollination
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Robinia pseudoacacia in urban areas provides resources for honey producing bees
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Hausman et al. (2015)
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Primary production
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Soil formation
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Cultural and Aesthetic
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Loss of sense of place and aesthetic valuesa
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Loss of sense of place and aesthetic values due to the presence of invasive alien plant species
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de Wit et al. (2001); Le Maitre et al. (2011)
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Unattractive species or landscapes
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Ugly’ landscapes dominated by Acacia species. Neglected vacant lots overgrown with ‘weedy’ vegetation
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Carruthers et al. (2011)
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Obscuring good views
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Tall trees such as Pinus sp. can block good views
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Roy et al. (2012)
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Economic Problem
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Increased maintenance costs
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Grooming of street trees or sweeping up of leaf litter in streets
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Roy et al. (2012)
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Cost of irrigation
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Alien plants in gardens require supplementary irrigation during the dry season
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Roy et al. (2012)
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Reduced property valuea
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Invasive plants blocking good views can reduce property prices
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Roy et al. (2012)
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Environmental Problem
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Generating green waste
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Increased green waste from gardens
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Roy et al. (2012)
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Increased water consumption
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Increased water consumption by alien and invasive trees such as Acacia sp. and Eucalyptus sp.
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Carruthers et al. (2011); Kull et al. (2011); Le Maitre et al. (2002, 2011); van Wilgen and Richardson (2014)
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Reduced soil qualitya
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Modification of soil quality and promotion of soil erosion
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de Wit et al. (2001); Shackleton et al. (2016)
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Disruption of soil-nutrient cycling, carbon and nitrogen fixationa
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Invasive alien trees and shrubs such as Acacia sp. fix nitrogen
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Yelenik et al. (2004); Gaertner et al. (2014); Qiu (2015)
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Displacement of native plant species / Reduced species richnessa
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Invasive alien trees and shrubs spreading into natural areas can disrupt native fynbos plant species and continued spread may reduce native species richness
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Carruthers et al. (2011); Dickie et al. (2014); Kull et al. (2011); Le Maitre et al. (2011); Shackleton et al. (2016); van Wilgen and Richardson (2014); Vicente et al. (2013)
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Health
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Reduced air qualitya
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Emissions of Biogenic Volatile Organic Compounds reducing air quality
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Potgieter et al. (2017)
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Increasing attack by associated insects and other animals
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Areas with dense vegetation can harbour potentially dangerous animals such as venomous snakes
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Roy et al. (2012)
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Pollen allergies
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Pollen allergy and/or dermatitis caused by A. altissima, Acacia dealbata, Cortaderia selloana, and Schinus terebinthifolius
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Pyšek and Richardson (2010)
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Poisoning
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Cardiac problems and poisoning from Echium plantagineum
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Pyšek and Richardson (2010)
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Leisure and Recreation
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Reduced recreationa
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Presence of invasive species considered unpleasant for recreation
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Vaz et al. (2017)
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Physical injury
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Physical injury through contact with plant spines or thorns
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Pyšek and Richardson (2010); Shackleton et al. (2016)
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Material
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Infrastructural damage
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Roots of Ailanthus altissima damaging paved surfaces and boundary walls
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Celesti-Grapow and Blasi (2004); Potgieter et al. (2019b)
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Safety and Security
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Fears of insects and other animals
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Areas with dense vegetation can be invoke fear due to the possible presence of distasteful animals such as insects or snakes
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Vaz et al. (2017)
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Increased crime risk
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Criminal activity in dense vegetation close to informal settlement
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Potgieter et al. (2019a)
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Safety and Security / Environmental Problem
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Increased fire risk (safety risk to infrastructure, but also impacting on native plants due to increased frequency and intensity of fires)
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Increased fire risk due to tree invasions along the urban edge
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Gaertner et al. (2014); Le Maitre et al. (2011); van Wilgen and Richardson (2014); Potgieter et al. (2018)
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Safety and Security / Material
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Safety hazard
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Tall trees blown over in strong winds
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Potgieter et al. (2019b)
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