Wildlife Crossings

This book is both an academic and popular science book about the many engineered wildlife road crossing structures (‘wildlife crossings’) in eastern Australia. It explains the global and Australian evolution of these iconic structures in an easy-to-read style and is supported by vivid photographs of the structures and the wildlife that use them. It brings together much of the latest research and includes photo contributions from many of Australia’s foremost researchers on the topic. The book is an ideal introduction to the topic for university applied ecology, engineering and environmental management subjects. It is also an ideal compendium on the topic for citizen scientists, lifestyle travellers and those with an interest in wildlife ecology.

Impact of Roads and Vehicles on Wildlife Populations

The book begins by providing a background to why and how roads and cars threaten wildlife populations on a global scale, beginning with the most obvious impact – wildlife road mortality, or roadkill. With over one billion cars on the planet (OICA 2016), the global scale of wildlife roadkill is enormous. Estimates include anywhere between 89-340 million birds killed each year by cars in the US (Loss et al. 2014) and 29 million mammals per year in Europe (Grilo et al. 2020). Estimates for Australia are limited but published studies have reported such figures as: over nine million kangaroos and wallabies struck on Australian roads each year (Burgin and Brainwood 2008); over 300 koalas killed annually on roads in southeast Queensland (QDES 2022); and over 40,000 frogs run over annually on one road in northern NSW (Goldingay and Taylor 2006).

Hidden within these roadkill statistics is the story that different species are impacted very differently. For some relatively common species, roadkill, generally, does not threaten the viability of local populations. But for others, such as koalas in Australia, roadkill can be the thing that pushes an already vulnerable species closer to the extinction precipice. This is largely because roadkill is additive. It adds to an already long list of threatening processes or pressures on many of our threatened species.

Landscape Transformation

Roads are also a key driver of global landscape transformation and habitat fragmentation. Roads convert enormous amounts of our natural landscape into bitumen corridors. In fact, the global road network is regarded as the largest human artifact on the planet (Forman et al. 2003). The International Road Federation reported that in 2019, globally, there were over 33 million km of roads (International Road Federation 2022). The process of removing and chopping up forest landscapes through building roads effectively separates wildlife populations into a series of smaller, isolated populations referred to as metapopulations. While many wildlife populations already existed as a series of patchy, loosely connected populations, the level of road building and landscape transformation globally is dramatically scaling up these processes. This is translating into smaller, more isolated populations becoming increasingly vulnerable to being wiped out by wildfire, disease, or changes in living conditions driven by climate change.

Re-connecting Populations

Within this context has arisen wildlife crossings – an engineering approach to reconnecting wildlife populations across road corridors. The approach recognises that ecological connectivity is critical to functioning wildlife populations and to functioning ecosystems. Indeed, for many animals, wildlife crossings provide vital links to food resources, mates, or an escape from a bushfire. In some places, like along Australia’s Great Alpine Road in Victoria’s high country, wildlife crossings are critical for enabling up and down-slope movement and maintaining gene flow amongst endangered mountain pygmy possum populations.

Wildlife crossings have been around in various forms for decades. In fact, they’ve existed since the early stages of road building in the form of drainage pipes, box culverts and bridges over waterways. In more recent times, as our understanding of the impact of roads on wildlife has grown, road authorities started installing purpose-built structures such as culverts with timber railings through them for both terrestrial and arboreal species and rope bridges over the road for canopy dwelling species.

And it is this emergence of wildlife crossing types in eastern Australia that this book documents. It also provides a snapshot of the biodiversity within each of Australia’s three eastern states and then presents 57 of the most historic, iconic and significant crossings. The sites are arranged in eight regional clusters, beginning in tropical northeast Queensland and ending in central Victoria. There is a map for each regional cluster as well as notes about access, structure details and the wildlife that use it. Detailed facts (ANIMAL INFO boxes) about charismatic users of the structures are also included throughout the site chapters. This ‘Travel Guide’ section enables readers to explore the different crossing types and the wildlife that use them and even plot their own trip to view sites of interest.

The Road Ahead

The book concludes with the acknowledgement that wildlife crossings are not a panacea to the problems of habitat loss and landscape fragmentation and the countless wildlife road mortalities. It reminds us that we need to conserve, protect, and enhance what’s left of our natural landscapes. That we need to create corridors and link the isolated and fragmented parts of our natural landscapes and continue these linkages across large road corridors by installing wildlife crossings. And we need to do this so our wildlife can move and adapt to a rapidly changing landscape and a rapidly changing climate.

Brendan Taylor is a wildlife ecologist and adjunct Research Fellow at Southern Cross University. He completed one of Australia’s first PhD’s on the efficacy of wildlife crossings and how they affect the population viability of threatened gliding possums in fragmented landscapes. He has authored/co-authored 28 scientific papers on various aspects of wildlife ecology.

The Evolution of Wildlife Crossings in Eastern Australia and a Guide to 57 Iconic Sites is available now in hardback at a 25% discount. Enter code PROMO25 to redeem.

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