Poor historical data drive conservation complacency: The case of mammal decline in south-eastern Australian forests

Abstract

Forested ecosystems of south-eastern Australia now differ physically, compositionally and functionally from their condition prior to European settlement. Understanding these changes, and how native species and entire ecosystems have responded, is crucial for biodiversity conservation and ecosystem management.Here I argue that a combination of limited historical information and a knowledge base biased towards modern ecological studies has resulted in a distorted perception of ecosystem condition, hindering the instigation of effective biodiversity conservation measures. This argument is based on recently obtained information about changes to the non-volant mammal community, which reveals relatively recent but underreported ecological changes, including major declines in species distribution and abundance, shifts in niche utilization and associated disruption of ecosystem functions. Ultimately, many mammal species are being denied the capacity to function to the extent they did historically. Following this re-assessment, it is evident that current forest management does not adequately address contemporary conservation dilemmas posed by detrimental ecosystem changes. This is especially salient when most of the factors responsible for causing changes to the mammal community are still active and include forest management and utilization activities. Therefore, additional conservation measures are essential to meet forest stewardship and biodiversity conservation obligations.For the health, functionality and sustainability of forested ecosystems, native mammal species must be capable of functioning to their ecological potential and occupy their original niche. This will be facilitated by the suppression of threatening processes (primarily exotic species), ensuring ecologically sensitive fire regimes and the reintroduction/translocation of missing species. The recovery or restoration of forest functionality based on mammal conservation should have wide-scale benefits for biodiversity conservation.

Ongoing unraveling of a continental fauna: Decline and extinction of Australian mammals since European settlement

“…This size pattern for extinction risk in Australian mammals is notably different to the global trend, whereby larger mammals have been and are most likely to become extinct (68). The characteristics of increased extinction risk for Australian terrestrial mammals are consistent with an explanation for decline based on predation by feral cats and foxes: the lost species are meal-sized for, and accessible to, these introduced predators (43,66,67,69).…”

“…Australia's isolation has resulted in its remarkable biodiversity distinctiveness but also the extraordinary vulnerability of its biota to novel threats. With the dwindling abundance, range, and diversity of so many species, we see now only a faint shadow of the richness and abundance of the Australian mammal fauna that existed at the time of European settlement (43).…”

“…4) (43,52): by most measures, these were remarkably successful and ecologically flexible species. Examples among the now extinct and threatened species include the brush-tailed rock-wallaby, Petrogale penicillata, for which almost 100,000 skins were marketed by a single company in 1 y (1908) (53); the koala, Phascolarctos cinereus, for which more than 500,000 skins were collected in just 31 d in the last open season, in Queensland in 1927 (54); the now extinct subspecies of brush-tailed bettong, Bettongia penicillata penicillata, for which in about 1900 "the dealers in Adelaide did a great trade in selling them by the dozen at about ninepence a head for coursing on Sunday afternoons" (55).…”

“…The subfossil record, mostly of scattered bones in caves and in caches of regurgitated owl pellets, has revealed-in pinpricks in the landscape-a rich trove of mammal evidence, typically characterized by the former abundance of now rare or extinct species and the formerly broad geographical and habitat distribution of species that are now highly localized or restricted to a narrow habitat range (41)(42)(43). A notable recent example, of analysis of owl pellets in forests in southeastern Australia, demonstrated that the loss since European settlement of native mammals in that region had been "under-estimated and severe" (42,43).…”

“…A notable recent example, of analysis of owl pellets in forests in southeastern Australia, demonstrated that the loss since European settlement of native mammals in that region had been "under-estimated and severe" (42,43). However, it is not only bones that now lost mammals have left behind.…”