Browsing by Author "Potgieter, Luke J."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Does vegetation structure influence criminal activity? insights from Cape Town, South Africa
    (International Biogeography Society, 2019) Potgieter, Luke J.; Gaertner, Mirijam; O’Farrell, Patrick J.; Richardson, David M.
    ENGLISH ABSTRACT: Dense vegetation, especially thickets of trees or shrubs, has been associated with actual and perceived crime risk in several parts of the world. In some contexts, invasive alien trees and shrubs can create a habitat structure that is very different from that provided by native vegetation. The role of alien and native plant species at different stages of invasion/densification in mediating criminal activity within a managed landscape remains poorly documented and elaborated. Using the South African city of Cape Town (a rapidly growing metropolitan centre within a global biodiversity hotspot) as a case study, we discuss the role of alien, invasive and native vegetation in mediating criminal activity in urban areas, particularly in a developing-country context. We argue that the incidence of crime may not always be determined by the biogeographical status of dominant plants (i.e., whether vegetation is dominated by native, alien, or invasive alien species), but rather on the structure/habitat they provide. A stronger link between crime and vegetation is likely in areas where tree invasions have drastically altered vegetation structure. This paper draws attention to a novel interaction between humans and vegetation and highlights the need for context-specific approaches when managing plant invasions, particularly in urban areas.
  • Thumbnail Image
    Item
    A fine-scale assessment of the ecosystem service-disservice dichotomy in the context of urban ecosystems affected by alien plant invasions
    (SpringerOpen (part of Springer Nature), 2019) Potgieter, Luke J.; Gaertner, Mirijam; O’Farrell, Patrick J.; Richardson, David M.
    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.
  • Thumbnail Image
    Item
    Global effects of non-native tree species on multiple ecosystem services
    (Wiley, 2019-04-19) Castro-Diez, Pilar; Vaz, Ana Sofia; Silva, Joaquim S.; Van Loo, Marcela; Alonso, Alvaro; Aponte, Cristina; Bayon, Alvaro; Bellingham, Peter J.; Chiuffo, Mariana C.; DiManno, Nicole; Julian, Kahua; Kandert, Susanne; La Porta, Nicola; Marchante, Helia; Maule, Hamish G.; Mayfield, Margaret M.; Metcalfe, Daniel; Monteverdi, M. Cristina; Nunez, Martin A.; Ostertag, Rebecca; Parker, Ingrid M.; Peltzer, Duane A.; Potgieter, Luke J.; Raymundo, Maia; Rayome, Donald; Reisman-Berman, Orna; Richardson, David M.; Roos, Ruben E.; Saldana, Asuncion; Shackleton, Ross T.; Torres, Agostina; Trudgen, Melinda; Urban, Josef; Vicente, Joana R.; Vila, Montserrat; Ylioja, Tiina; Zenni, Rafael D.; Godoy, Oscar
    Non-native tree (NNT) species have been transported worldwide to create or enhance services that are fundamental for human well-being, such as timber provision, erosion control or ornamental value; yet NNTs can also produce undesired effects, such as fire proneness or pollen allergenicity. Despite the variety of effects that NNTs have on multiple ecosystem services, a global quantitative assessment of their costs and benefits is still lacking. Such information is critical for decision-making, management and sustainable exploitation of NNTs. We present here a global assessment of NNT effects on the three main categories of ecosystem services, including regulating (RES), provisioning (PES) and cultural services (CES), and on an ecosystem disservice (EDS), i.e. pollen allergenicity. By searching the scientific literature, country forestry reports, and social media, we compiled a global data set of 1683 case studies from over 125 NNT species, covering 44 countries, all continents but Antarctica, and seven biomes. Using differentmeta-analysis techniques, we found that, while NNTs increase most RES (e.g. climate regulation, soil erosion control, fertility and formation), they decrease PES (e.g. NNTs contribute less than native trees to global timber provision). Also, they have different effects on CES (e.g. increase aesthetic values but decrease scientific interest), and no effect on the EDS considered. NNT effects on each ecosystem (dis)service showed a strong context dependency, varying across NNT types, biomes and socio-economic conditions. For instance, some RES are increased more by NNTs able to fix atmospheric nitrogen, and when the ecosystem is located in low-latitude biomes; some CES are increased more by NNTs in less-wealthy countries or in countries with higher gross domestic products. The effects of NNTs on several ecosystem (dis)services exhibited some synergies (e.g. among soil fertility, soil formation and climate regulation or between aesthetic values and pollen allergenicity), but also trade-offs (e.g. between fire regulation and soil erosion control). Our analyses provide a quantitative understanding of the complex synergies, trade-offs and context dependencies involved for the effects of NNTs that is essential for attaining a sustained provision of ecosystem services.