The persistence of common wombats in road impacted environments

Abstract

There is growing global concern over the influence of road development on the conservation of biodiversity and on the functioning of ecosystems. Published reviews in the field of road ecology have identified that most research has examined the effects of roads linearly and have advocated for research at landscape scales. Among the many effects roads have, one of the most significant is the loss of animal life resulting from collisions with vehicles. Despite this, little is known of what toll this has on animal populations and how these impacts vary with scale. This stems from the perception that impacts are localised and that animals killed are typically considered common, and therefore not of great conservation concern. This thesis challenges this notion by showing that the impacts of fatalities can affect populations at landscape extents and that commonness is not a barrier to localised extinction risk. To achieve this I focus on the common wombat; an example of a common species for which road impacts have never been previously examined. Chapter 1 provides an overview of the importance of scale in quantifying road impacts and the debate surrounding common species persistence in road environments. Chapter 2 assesses habitat use of wombats in a road environment at a local scale. Results suggest that wombats select for roadside habitat and as a result populations could be under threat. Chapter 3 is a predictive model of wombat road fatalities which demonstrates the importance of incorporating habitat use in predictive fatality modelling. Through use of a spatially explicit population viability analysis, Chapter 4 demonstrates that roads, in conjunction with other threats can affect the persistence of a common species at a local scale. Chapter 5 is a landscape extent assessment of wombat habitat use, finding that increased effort should be employed in evaluating how reserves confer resilience to species from the impacts of roads and that habitat quality can dictate road-based fatality rates. Chapter 6 summarises the research presented in the thesis and suggests direction for future work, particularly the importance of evaluating the interplay between susceptibility and abundance on species vulnerability in road environments.