As in much of the world, Australia’s birds have suffered greatly from habitat loss, feral predators and direct exploitation. Less universal have been the declines caused by post-colonial changes in fire regime after 40 000 years of Indigenous fire management. Climate change and a disengagement by Australians from nature loom as threats for the future. However, Australia is a country of climatic extremes and many birds are well-adapted to stressful conditions. Given adequate investment, all the major classes of threat have potential solutions, with particular success in recent decades in the removal of feral predators from islands and in reducing the by-catch from fishing. The biggest threat of all is possibly a failure to invest in conservation as modern lifestyles take people further and further away from the natural environment.
Australia’s birds are, like those in so much of the world, travelling poorly. Of the 1239 species and subspecies regularly occurring in Australia, 17% are Threatened or Near Threatened on the basis of the IUCN Red List Criteria (Garnett et al. 2011). This number has been increasing steadily (Szabo et al. 2012a) and, while originally it was taxa of Australia’s oceanic islands that were most likely to be threatened, taxa from the mainland are now starting to slip away (Szabo et al. 2012b). Sadly some of those most threatened are the most distinctive; birds at the end of long slender branches of the evolutionary tree whose closest relatives are long gone. Other species, however, are thriving under the conditions that have arisen over the past few centuries of intense development.
Effective conservation action and biodiversity management requires an understanding of the mechanisms that cause extinction (Caughley 1994). Theoretical treatments have suggested that these mechanisms are complex. They emphasise the interactions among factors such as the intrinsic biology of species, phylogeny, ecological relationships, environmental variation, human influences and chance catastrophes (see, for example, Diamond 1989; Pimm 1991; Lande 1998). Most conservation projects focus on protecting particular species or particular areas. This focus on the specific problems of particular species or areas can be successful in identifying the idiosyncratic extinction mechanisms operating at a local scale; however, much can also be learned by using comparative methods to synthesise information across taxa and regions. The major strength of formal comparative methods is that they allow us to test whether there are general processes that determine interspecific variation in vulnerability to extinction (Bennett & Owens 1997, 2002).
In this chapter we present a framework for investigating variation in extinction risk that emphasises the interactions between evolutionary history, ecological processes and contemporary threats. We will illustrate this framework by using our work on birds, which are arguably the best-studied vertebrate class and are therefore highly suitable for large-scale comparative analyses (Bennett & Owens 2002). We will discuss how the main extrinsic causes of extinction risk to birds, such as habitat loss and human persecution, have predictable outcomes due to differences between species in intrinsic biological attributes, such as life history and ecology.
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