Download files
Abstract
In this thesis, I discuss the global mammal extinction crisis and the role of rewilding programs in restoring ecological function to landscapes (Chapter 1). I draw attention to functional extinction and rewilding in an Australian context because the Australian arid zone mammal fauna has been decimated in the past 200 years. Consequently, our understanding of ecosystem function in Australian deserts is prone to shifting baselines because many paradigms were developed within depauperate mammal assemblages.
I used reserves to which functionally extinct mammals have been reintroduced to revisit paradigms about mammals being unimportant seed predators. I found that mammals were important seed predators, and that existing paradigms on seed fate (Chapter 2 & 3), shrub encroachment (Chapter 2) and myrmecochory (Chapter 3) are legacies of mammal functional extinction.
I used exclusion experiments to determine how rewilded and refuge populations of rare mammals influence the vegetation community (Chapter 4 & 5). I found that interactions between mammals and vegetation were more complicated than predicted from prior knowledge of these species’ functional roles (Chapter 4) and that omnivores had unexpectedly strong effects on multiple food resources of varying protein content (Chapter 5).
Overall, I found that paradigms describing the function and organisation of Australia’s deserts are legacies of mammal extinction and that the flow-on effects of mammal decline on vegetation and ecosystem function have been overlooked. However, I also found that the interactions between mammals, vegetation and the seedbank were complex.
To synthesise the findings within this thesis, I introduce the Resource-Pulse-Consumer-Compartment model to describe the multiple pathways by which omnivorous consumers influence resources, especially vegetation, in the Australian arid zone (Chapter 6). I recommend that future research investigating consumer – vegetation interactions do so across a variety of mammal assemblages and densities.
It is impossible to discuss the functional roles of mammals without considering the role that shifting baselines have played in our understanding of arid Australian ecosystems. With this in mind, I suggest that rewilding and other ecosystem restoration programs embrace the novel ecosystems that they are creating, instead of seeking a past for which there is no baseline.