Table 2 Ecosystem services and disservices associated with urban vegetation within the study area

Cultural

Recreation

Picnicking under tall shade-providing trees (e.g. Pinus pinea)

Potgieter et al. (2019b)

Physical, intellectual and spiritual interactions with nature, including aesthetic values, inspiration and cognitive development, and spiritual enrichment

Well managed urban green spaces with abundant vegetation

Bastian et al. (2012); Dobbs et al. (2011)

Visual amenity, ornamental purposes and landscape re-greening

Private residential gardens

Dickie et al. (2014); Carruthers et al. (2011); Kull et al. (2011); Le Maitre et al. (2011); Shackleton et al. (2016)

Provision of a ‘sense of place’

Dickie et al. (2014)

Heritage

Pinus pinea trees planted in the seventeenth century by the early settlers, have significant heritage value

Gaertner et al. (2016)

Increased property values

Soares et al. (2011)

Provisioning

Firewood

Trees such as Acacia sp., Eucalyptus sp. or Pinus sp. can be used for firewood

Dickie et al. (2014)

Construction material

Trees such as Eucalyptus sp. or Pinus sp. can be used for poles

Dickie et al. (2014)

Medicinal value

Essential oils provided by Eucalyptus sp.

Fodder

Eucalyptus camaldulensis used as fodder

Bernholt et al. (2009)

Food

Eucalyptus sp. (especially E. cladocalyx) are important for honey production

Regulating

Shade

Shade from tall trees with wide canopy such as Pinus pinea

Potgieter et al. (2019b);

Climate regulation

Cooling effects (by transpiration) of street trees such as Platanus × acerifolia

Jim and Chen (2009)

Air quality

Reduced emissions of air pollutants by Platanus × acerifolia

McPherson (2003)

Flood attenuation

Wetlands

Barrier

Pinus sp. used as a barrier plant

Carbon sequestration

Trees such as Platanus × acerifolia sequester carbon

Potgieter et al. (2017)

Nitrogen fixation

Acacia sp. fix nitrogen, enriching the soil

Qiu (2015); Dickie et al. (2014); van Wilgen and Richardson (2014); de Wit et al. (2001)

Erosion control

Erosion control by trees such Ailanthus altissima

Sladonja et al. (2015); Kowarik and Säumel (2007)

Energy saving

Changes in building energy use from shade trees such as Platanus × acerifolia

McPherson (2003)

Stormwater runoff mitigation

Supporting

Habitat provision

Tall alien trees such as eucalypts and pines provide nesting sites for birds with which many urban dwellers can enjoy encounters.

McPherson et al. (2011)

Nutrient cycling

Pollination

Robinia pseudoacacia in urban areas provides resources for honey producing bees

Hausman et al. (2015)

Primary production

Soil formation

Cultural and Aesthetic

Loss of sense of place and aesthetic values^a

Loss of sense of place and aesthetic values due to the presence of invasive alien plant species

de Wit et al. (2001); Le Maitre et al. (2011)

Unattractive species or landscapes

Ugly’ landscapes dominated by Acacia species. Neglected vacant lots overgrown with ‘weedy’ vegetation

Carruthers et al. (2011)

Obscuring good views

Tall trees such as Pinus sp. can block good views

Roy et al. (2012)

Economic Problem

Increased maintenance costs

Grooming of street trees or sweeping up of leaf litter in streets

Roy et al. (2012)

Cost of irrigation

Alien plants in gardens require supplementary irrigation during the dry season

Roy et al. (2012)

Reduced property value^a

Invasive plants blocking good views can reduce property prices

Roy et al. (2012)

Environmental Problem

Generating green waste

Increased green waste from gardens

Roy et al. (2012)

Increased water consumption

Increased water consumption by alien and invasive trees such as Acacia sp. and Eucalyptus sp.

Carruthers et al. (2011); Kull et al. (2011); Le Maitre et al. (2002, 2011); van Wilgen and Richardson (2014)

Reduced soil quality^a

Modification of soil quality and promotion of soil erosion

de Wit et al. (2001); Shackleton et al. (2016)

Disruption of soil-nutrient cycling, carbon and nitrogen fixation^a

Invasive alien trees and shrubs such as Acacia sp. fix nitrogen

Yelenik et al. (2004); Gaertner et al. (2014); Qiu (2015)

Displacement of native plant species / Reduced species richness^a

Invasive alien trees and shrubs spreading into natural areas can disrupt native fynbos plant species and continued spread may reduce native species richness

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)

Health

Reduced air quality^a

Emissions of Biogenic Volatile Organic Compounds reducing air quality

Potgieter et al. (2017)

Increasing attack by associated insects and other animals

Areas with dense vegetation can harbour potentially dangerous animals such as venomous snakes

Roy et al. (2012)

Pollen allergies

Pollen allergy and/or dermatitis caused by A. altissima, Acacia dealbata, Cortaderia selloana, and Schinus terebinthifolius

Pyšek and Richardson (2010)

Poisoning

Cardiac problems and poisoning from Echium plantagineum

Pyšek and Richardson (2010)

Leisure and Recreation

Reduced recreation^a

Presence of invasive species considered unpleasant for recreation

Vaz et al. (2017)

Physical injury

Physical injury through contact with plant spines or thorns

Pyšek and Richardson (2010); Shackleton et al. (2016)

Material

Infrastructural damage

Roots of Ailanthus altissima damaging paved surfaces and boundary walls

Celesti-Grapow and Blasi (2004); Potgieter et al. (2019b)

Safety and Security

Fears of insects and other animals

Areas with dense vegetation can be invoke fear due to the possible presence of distasteful animals such as insects or snakes

Vaz et al. (2017)

Increased crime risk

Criminal activity in dense vegetation close to informal settlement

Potgieter et al. (2019a)

Safety and Security / Environmental Problem

Increased fire risk (safety risk to infrastructure, but also impacting on native plants due to increased frequency and intensity of fires)

Increased fire risk due to tree invasions along the urban edge

Gaertner et al. (2014); Le Maitre et al. (2011); van Wilgen and Richardson (2014); Potgieter et al. (2018)

Safety and Security / Material

Safety hazard

Tall trees blown over in strong winds

Potgieter et al. (2019b)