Which tree where and why? Using urban street tree inventories to improve predictions of species’ sensitivities to climate change

Anthropogenic climate change has already altered species diversity, distributions and habitat. Niche based predictive studies are now widely used to inform our current understanding of the sensitivity and adaptive capacity of species to climate change. Species niche, the breadth of climatic conditions in which a species can maintain a viable population, is often estimated from native range records, assuming that the species' current distribution is in equilibrium with the environment. As such, the climate niche realised by native range should approximate the species' fundamental niche. However, a growing number of studies have found disequilibrium between species native and non-native climate niches. This thesis aimed to address such a gap and utilise the findings to direct a sustainable urban greening approach while incorporating species' functional contribution to the ecosystems of Australian Local government Areas (LGAs). My thesis consists of three analytical chapters. In the first chapter, I looked into how far beyond native niches do species' urban niches extend globally and whether the direction and magnitude of this shift are predictable based on native range characteristics. Overall I found that the urban niche of tree species are significantly larger and significantly different to their native niche. I also demonstrate that species with narrower native climate niches show greater differences with their urban niche. Chapter two extends my previous study by incorporating species distribution modelling (SDMs) to predict species native habitat suitability in current and future climate scenarios. The question we answer are i) does the inclusion of global urban tree inventory data expand future projections of habitat suitability? ii) does current scholarship/evidence overestimate the vulnerability of species in their native range? and iii) is the magnitude of difference between SDM predictions with and without urban records related to their climatic niche? In chapter three, I utilise a list of recommended species by local councils across Australia. Using the urban and native records, I evaluate if the recommended species can withstand future climate change in urban areas. To achieve these aims, I expressly ask- i) are the species currently suggested by LGAs in Australia's urban areas suitable for the future (2050 and 2070)? ii) can we recommend alternative species by ensuring better climate resilience and preserving the functional diversity of the most vulnerable urban areas? Finally, we recommended alternative climate-ready species for the main urban areas of Australia. As the importance of addressing non-native records in conservation initiatives has been gaining attention, findings from this thesis may help point out to decision-makers the more efficient conservation initiatives while considering alternative non-native records such as those from urban tree inventories. This thesis also assesses how the benefits that trees provide to urban environments may be eroded in the future with unknown consequences on the functionality of urban forests and cascading effects on urban ecosystem service provision to communities and the built environment.