School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe ecological costs and benefits of urban stormwater wetlands to frogs( 2018)The speed and scale at which humans are altering natural systems creates novel challenges for many species. Some species can cope with human-induced rapid environmental change by exhibiting adaptive behavioural or phenotypic plasticity. Many others, however, respond maladaptively in ways that can impact individual fitness. When rapid environmental change triggers mismatches between perceived and actual habitat quality, animals can prefer inferior habitats, that are known as ecological traps. Using a meta-analysis, I show that ecological traps are an unexplored but potentially important conservation risk to animals within wetland habitats (Chapter 2). Focusing on urbanisation and stormwater wetlands as a case study, I assess how anthropogenic environmental change affects frogs, in terms of the environmental variables influencing species occurrence (Chapter 3), the capacity of individuals to make adaptive habitat selection decisions (Chapter 4), and the fitness and behavioural consequences of these decisions (Chapter 4 and 5). I show that frogs occupied wetlands across a broad spectrum of pollution levels, including even the most contaminated, and that pollution exposure reduced survival and impaired predator avoidance behaviours. Breeding frogs did not avoid wetlands where these fitness reductions occurred, demonstrating that stormwater wetlands can function as ecological traps. Collectively, my results highlight the need for a greater focus on individual-level metrics (e.g. fitness and habitat preferences) in addition to the more commonly measured population- and community-level metrics (e.g. richness and abundance). Based on my research, I propose three key recommendations to maximise biodiversity at wetlands within urban landscapes. Firstly, appreciate that poor water quality at stormwater wetlands may impact resident wildlife, and attempt to reduce the causal factors. Second, despite this, do not ignore the potential value of stormwater wetlands in providing habitat and enhancing connectivity amongst aquatic habitats, particularly when they are appropriately designed and managed. Finally, it is important to design and construct wetlands for wildlife that are not connected to stormwater networks, with their placement within the landscape carefully considered.