School of BioSciences - Theses
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ItemCost-effective methods in conservation( 2018)Conservation resources are scarce, whether it is time, money or effort. Therefore, wise spending is important and decisions need to be made on how to prioritise limited resources between different conservation actions. Effectively targeting declines in biodiversity requires monitoring and management, each of which contribute differently to improved conservation outcomes. Monitoring provides information about the system (whether it is about the state or the dynamics), while management aims to halt downward population trajectories. Often monitoring and management are competing for the same resources, creating trade-offs in how these resources should be spent. In this thesis, I examine trade-offs in conservation, by focusing on how alternative resource allocations within monitoring, and between monitoring and management, impact the ultimate conservation outcome. I illustrate this with two case studies: the endangered growling grass frog (Litoria raniformis) metapopulation around Melbourne, Australia, and the invasive yellow crazy ant (Anoplolepis gracilipes) on Christmas Island, Australia. The first chapter provides a general introduction to the role of monitoring and management in conservation and the trade-offs that exist within and between them. In the second chapter, I examine whether increasing the spatial coverage of a monitoring program for the growling grass frog can replace learning about metapopulation dynamics in terms of population persistence. The advantage of obtaining reliable estimates from spatial monitoring over temporal monitoring is that wasting invaluable time is avoided. In the third chapter, I explore management of the endangered growling grass frog metapopulation, and study how alternative resource allocations between monitoring and management affect the confidence about sufficient offsetting actions. Increasing urbanisation requires habitat offsetting to reduce further declines in the metapopulation. Investing in monitoring might result in more precise estimates of the metapopulation dynamics, and hence allow managers to be more confident about which management strategy might be best. More management, on the other hand, might reduce the extinction risk of the metapopulation directly, provided suitable actions are chosen. Determining the optimal allocation of resources between the two is important to ensure the metapopulation gains as much as possible from the implemented offsetting management. In the fourth chapter, I switch focus to an invasive species, the yellow crazy ant, and investigate how to optimally survey an island for high density super-colonies. I compare effectiveness of a survey strategy that explicitly accounts for the variation in survey cost across the island with alternative ones that ignore survey cost estimates. In the fifth chapter, I determine the amount of monitoring data that contains sufficient information to find the ant super-colonies. Using a habitat suitability model for the super-colonies, combined with survey cost estimates, I prioritise sites, and evaluate the impact of more monitoring data on the amount of super-colonies found. Monitoring a small part of the island is sufficient to find the maximum possible super-colonies for a particular budget, resulting in the effectiveness of the survey strategy levelling off. This suggests that the resources that are currently spent on monitoring the entire island, can be redirected towards management of the invasive species. Finally, in the last chapter, I summarise the main findings of this research and discuss some potential paths for future research.