©2023 International Society of Arboriculture Arboriculture & Urban Forestry 49(4): July 2023 191 unsuitable for 10 out of 60 tree species assessed. Sim- ilarly, Burley et al. (2019) predicted that suitable urban habitat might decline for 73% of native tree species planted across Australia’s urban areas by 2070. On a global scale, more than 13,000 species will be at risk from projected changes in temperature by the year 2050 (Esperon-Rodriguez et al. 2021). However, the deleterious effects of climate change on urban vegetation are already beginning to be observed. For example, Zhang and Brack (2021) found that only 37% of street trees surveyed in Canberra, Australia showed no visible stress symptoms (e.g., dead branches, crown dieback, etc.) compared with 80% of trees sur- veyed in 1999. Other street tree surveys have also found significant damage to foliage following increases in the intensity and frequency of droughts and heat- waves in urban areas associated with climate change (Tabassum et al. 2021a; Haase and Hellwig 2022). Despite these negative impacts, some species are expected to benefit by gaining climatically suitable habitats in urban areas in the future (Yang 2009; Bur- ley et al. 2019). Identifying which species are likely to thrive in future climates is paramount to increasing the resilience and sustainability of urban green spaces. Although choosing climate-ready species is import- ant for increasing the resilience of urban green spaces to threats such as climate change, ensuring that we plant a diverse range of climate-ready species is also critically important (Kendal et al. 2014). However, most urban green spaces are characterised by low diversity (Nowak 1994; Bourne and Conway 2014; Tabassum et al. 2020). Urban green spaces with low plant diversity are more vulnerable to climate change due to a reduced capacity for adaptation and an increased vulnerability to species-specific threats such as pests and pathogens. For example, the popu- larity of the American elm (Ulmus americana) as a street tree in several regions of the USA and Canada led to significant canopy loss when Dutch elm dis- ease (Ophiostoma ulmi) spread throughout the region during the 20th century, with canopy cover in some regions only recovering to pre-disease levels after 40 years (Roman et al. 2018). Climate change is pre- dicted to impact the distribution and abundance of many pests and pathogens (Tubby and Weber 2010; Ramsfield et al. 2016), potentially making devastat- ing losses of urban vegetation cover more prevalent. Despite advocating for change to how urban green spaces are designed, there are still many challenges to overcome such as limited nursery stock and a ten- dency to rely on a handful of well-known species (Sjöman and Nielson 2010; Conway and Vecht 2015; Khan and Conway 2020). Many urban forestry practitioners have identified climate change as an important challenge for the sur- vival of urban green spaces (Živojinović and Wolfslehner 2015). However, there is often uncer- tainty regarding which species will thrive under future climates (Khan and Conway 2020). There may also be a mismatch between what practitioners would like to plant and what is available for purchase at nurseries (Sydnor et al. 2010; Khan and Conway 2020). This is because nurseries may need 5 to 10 years to produce stock to be sold, therefore, favouring species which are already in demand (D’Amato et al. 2002). Even if practitioners took a proactive approach to planting species suited to future climates, this may not be possible due to the limited supply of plants available in the present market. Many species which are planted in urban areas now can survive for decades into the future and potentially be exposed to a signifi- cantly different climate. Therefore, it is imperative that we predict which species may be able to survive in future climates, with a high degree of confidence. Current urban planning and management decisions need to consider future climates to ensure that urban green spaces remain functional and healthy, deliver- ing the desired benefits for years to come. Numerous stakeholder workshops were conducted before the creation of Which Plant Where, to identify functionality that would be most beneficial for end users. Participants at these workshops identified that the end users of this tool would be Australian urban planners, practitioners, and specifiers (e.g., profes- sionals working in local and state government, roads and transport services, the nursery industry, land- scape architecture and development). During these workshops, barriers and knowledge gaps for species selection for urban planting projects were identified. These include identifying climate-ready species for urban landscapes, the ability to make informed deci- sions regarding species substitutions, the ability to quantify co-benefits to assess the success of urban plantings, the need to create a central hub for infor- mation on plant traits and tolerances, as well as designing best-practice, urban-greening guidelines. Many plant selection tools have been created to aid practitioners in choosing species for urban
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