Migration is an incredible phenomenon. Across cultures it moves and inspires us, from the first song of a migratory bird arriving in spring, to the sight of thousands of migratory wildebeest thundering across African plains. Not only important to us as humans, migratory species play a major role in ecosystem functioning across the globe. Migrants use multiple landscapes and can have dramatically different ecologies across their lifecycle, making huge contributions to resource fluxes and nutrient transport. However, migrants around the world are in decline. In this thesis I examine our conservation response to these declines, exploring how well current approaches account for the unique needs of migratory species, and develop ways to improve on these. The movements of migrants across time and space make their conservation a multidimensional problem, requiring actions to mitigate threats across jurisdictions, across habitat types and across time. Incorporating such linkages can make a dramatic difference to conservation success, yet migratory species are often treated for the purposes of conservation planning as if they were stationary, ignoring the complex linkages between sites and resources. In this thesis I measure how well existing global conservation networks represent these migratory linkages, discovering major gaps in our current protection of migratory species. I then go on to develop tools for improving conservation of migratory species across two areas: prioritizing actions across species and designing conservation networks.
Protected areas are one of our most effective conservation tools, and expanding the global protected area estate remains a priority at an international level. Globally, about 12.9% of the landscape is covered by protected areas, and in Chapter 2 I examine how well migratory birds are represented within current protected areas, specifically taking into account their need for protection across the migratory cycle. I discover that just 9% of migratory birds meet standard protection targets across all parts of their migratory distribution, their breeding, non-breeding and passage distributions, in stark contrast to the 45% of non-migratory birds meeting the same targets. There is currently a major push to increase the size and comprehensiveness of the global protected area estate, and these findings highlight the need for greater emphasis on collaboration across nations to incorporate migratory connectivity into our approaches to protected area placement.
One of the challenges to incorporating migratory connectivity into systematic conservation planning is that often we have only a poor understanding of the patterns of movements of migrants in space and time. In Chapter 3 and 4 I develop a tool for discovering spatial dynamics in highly mobile yet data-poor species, unlocking valuable information for improved extinction risk assessment and conservation planning. Using Australian arid-zone nomadic birds as a case study, I reveal enormous variability in predicted spatial distribution over time. This variability has huge impacts on both our ability to estimate extinction risk accurately in migratory species; and the way that we plan conservation actions across the landscape. In Chapter 3 I discover that several species not currently classified as globally threatened contracted to very small areas during times of poor environmental conditions despite their normally large geographic range size, raising questions about the adequacy of conventional assessments of extinction risk based on static geographic range size (e.g. for IUCN Red Listing). I develop guidelines to better estimate extinction risk for nomadic species.
In Chapter 4 I examine how the spatial configuration of conservation actions changes when we incorporate these spatial and temporal movements of mobile species. Using the time series of predicted distributions of Australian nomadic birds developed in Chapter 3, I show that accounting for movements changes the spatial pattern of conservation investment and increases the overall area needed for conservation measures. This presents both a challenge and an opportunity for conservation practitioners, who will need to work with landholders to provide sustainable conservation outcomes in activities such as agriculture, grazing and mining. It suggests a need for a shift in the current paradigm of conservation happening in ‘special places’ such as protected areas to conservation being a whole-of-landscape activity.
Underpinning my thesis is the need to evaluate and rethink how we plan and apply conservation actions across the full migratory cycle. In Chapter 5 I summarise state-of-the-art advances in conservation planning for migrants, outline gaps and suggest new directions for research. I discover that very few large-scale conservation projects incorporate the needs of migrants, and yet incorporating migratory connectivity is essential to long-term success of conservation actions for these species. I describe some recently developed tools to incorporate migratory connectivity into conservation planning; and discover that several useful tools relevant to the problem of migratory species conservation already exist in other disciplines.
Throughout this thesis I use the terms ‘migratory’ and ‘mobile’ interchangeably. In doing so, I use the broadest definition of the term migratory, to encompass any species making cyclical or predictable movements, from the seasonally predictable movements of ‘to-and-fro’ migrants to the environmentally predictable movements of nomadic and irruptive species.
Migratory species use large geographic areas, and their effective conservation is undoubtedly a major challenge. While imperfect knowledge is often cited as a barrier to conserving migrants, I have shown that we can make considerable progress based on existing knowledge, and that substantial action is needed now to ensure that one of nature’s great phenomena remains for future generations.