Spatial conservation prioritisation under global threats

Species extinction is one of the world’s major environmental problems. Biodiversity conservation planning aims to provide tools and knowledge to assist solving this problem. Historically, conservation planning has accounted for threats from human activity at a local scale (e.g. land conversion or hunting). However, the emergence of global-scale environmental threats demands novel techniques. Here, I develop new tools for global biodiversity conservation in two emerging areas: global-scale conservation planning in a changing climate and conservation of migratory species under sea level rise. Climate change is affecting, or will affect, every place in the world. Researchers interested in predicting and managing the impact of climate change on species have generally focused on the predictions of future species ranges to determine actions and priorities. However, the predicted shifts in the ranges of species are expected to be very uncertain because of issues such as dispersal distances, population dynamics and interactions with other species. To overcome these problems surrounding the prediction of species range shifts, one would need to develop very detailed species distribution models based on a great deal of data for each species. It is thus not practical to apply techniques for predicting future species range shifts for global-scale conservation prioritisation, where uncertainty is too great to predict the future distributions of all the species in the world. In this thesis, I tackle this problem by incorporating climate stability and effectiveness of habitat as climatic refugia into analyses for global conservation planning under climate change. Sea level rise is one of the most prominent consequences of climate change: global mean sea level is predicted to rise between 75 and 200 cm by 2100. This will impact coastal species, of which migratory shorebirds are a particularly sensitive exemplar. These birds undertake annual long distance flights from their Arctic breeding grounds to coasts around the world. Most shorebirds interrupt their journeys to rest and feed, and such staging areas can constitute significant bottlenecks. The dependency of the entire population on these local bottlenecks can cause much higher population loss than when the impact is simply calculated by summing total habitat loss. However, previous studies on the impacts of habitat loss have typically taken this latter approach. For migratory species, conservation planning based on spatially explicit modelling is clearly required to solve this problem. Underpinning my thesis is the need to spend scarce conservation resources wisely. Most international conservation organizations (e.g. World Wildlife Fund, Conservation International, The Nature Conservancy) have developed global conservation priorities to guide expenditure at a global scale. Such global conservation prioritisations influence the allocation of 1.5 billion USD annually. Despite this, no existing prioritisation schemes consider the impacts of climate change. In Chapter 2, I examine the robustness of eight global conservation prioritisation schemes to climate change and statistically analyse which prioritizing criteria correlate with this robustness. I discover that global conservation priorities that invest in areas with high endemic species richness and high irreplaceability are more robust to a changing climate. At the same time, investment in more intact regions proved less robust under a changing climate. Conservation prioritisation based on predicting the future distributions of individual species is simply not realistic for global-scale conservation priority setting due to data limitations. In Chapter 3, I develop a novel resource allocation algorithm for conservation investment that incorporates the ecological stability of ecoregions under climate change. I discover that allocating funds in this way changes the optimal schedule of global investments both spatially and temporally. To maximise the resilience of global biodiversity to global climate change, my analysis concludes that funding be increased in ecoregions located in the tropics and/or mid-elevation habitats, where climatic conditions are predicted to remain relatively stable. The distributions of many species are dynamic over time and space, and this presents serious challenges for conservation prioritisation because the conservation target is continually moving. Past research has typically assumed that the impacts on a species or ecosystem equal the sum of local habitat change, an assumption that is invalid if species distributions are changing. In Chapter 4, I explicitly model the network structure for an assemblage of migratory birds using the East Asian-Australasian Flyway (EAAF). Using this model, I estimate the impacts of sea level rise on the carrying capacity for each population using a graph theoretic framework. I discover that the loss of flyway capacity is much higher when we consider the connectedness of the network than simply considering the extent of habitat loss alone. I also find that much of the variation in impact among taxa can be explained by the identity of the sites acting as bottlenecks in the migratory networks for each species. In Chapter 5, I design a resource allocation algorithm to guide conservation efforts in sites along the migratory routes of shorebirds. The objective is to maximise flyway capacity after sea level rise for all taxa in the assemblage. I find that allocating resources based on a spatially explicit model of the flyway network is much more efficient that simply directing conservation effort to sites that will suffer the greatest local impact. However, the resulting conservation schedule is preliminary and can be subject to iterative improvement as our knowledge of the structure of migratory networks improves. This highlights the importance of understanding connectivity for migratory species in a changing world. My work has discovered the extent and dynamics of two novel global threats to biodiversity, namely global climate change and sea level rise. I have developed novel tools to allocate conservation effort in the face of these problems, and have shown that the solutions are frequently counterintuitive