Extinction In Australia Research Articles

Overdone overkill – the archaeological perspective on Tasmanian megafaunal extinctions

The reasons for megafaunal extinction in Australia have been hotly debated for over 30 years without any clear resolution. The proposed causes include human overkill, climate, anthropogenic induced habitat change or a combination of these. Most protagonists of the human overkill model suggest the impact was so swift, occurring within a few thousand years of human occupation of the continent, that archaeological evidence should be rare or non-existent. In Tasmania the presence of extinct megafauna has been known since the early twentieth century ( Noetling, 1912; Scott, 1911, 1915) with earlier claims of human overlap being rejected because of poor chronology and equivocal stratigraphic associations. More recent archaeological research has not identified any megafauna from the earliest, exceptionally well-preserved late Pleistocene cultural sites. In 2008 however an argument for human induced megafaunal extinctions was proposed using the direct dates from a small sample of surface bone from two Tasmanian non-human caves and a museum sediment sample from an unknown location in a cave, since destroyed by quarrying ( Turney et al., 2008). Turney et al. (2008) supplemented their data with published dates from other Tasmanian caves and open sites to argue for the survival of at least seven megafauna species from the last interglacial to the subsequent glacial stage. To investigate the timing of extinctions in Tasmania and examine the latest claims, new excavations and systematic surveys of limestone caves in south central Tasmania were undertaken. Our project failed to show any clear archaeological overlap of humans and megafauna but demonstrated that vigilance is needed when claiming survival of megafauna species based on old or suspect chronologies. The results of our six-years of fieldwork and dating form the first part of the present paper while, in the second part we assess the data advanced by Turney et al. (2008) for the late survival of seven megafauna species. A model of human prey selection and the reasons for the demise of a range of marsupials, now extinct, are discussed in the third part of the paper.

ESR and U-series analyses of faunal material from Cuddie Springs, NSW, Australia: implications for the timing of the extinction of the Australian megafauna

The timing and cause of late Pleistocene faunal extinctions in Australia are subjects of a debate that has become polarised by two vigorously defended views. One contends that the late Pleistocene extinction was a short event caused by humans colonising the Australian continent, whereas the other promotes a gradual demise of the fauna, over a period of at least 10–20 ka, due to a combination of climatic changes and ecological pressures by humans. Cuddie Springs is central to this debate as it is the only site known in continental Australia where archaeological and megafauna remains co-occur. We have analysed more than 60 bones and teeth from the site by laser ablation ICP-MS to determine U, and Th concentrations and distributions, and those with sufficiently high U concentrations were analysed for U-series isotopes. Twenty-nine teeth were analysed by ESR. These new results, as well as previously published geochronological data, contradict the hypothesis that the clastic sediments of Stratigraphic Unit 6 (SU6) are in primary context with the faunal, archaeological and other materials found in SU6, and that all have ages consistent with the optically stimulated luminescence (OSL) estimates of 30–36 ka. These young OSL results were used to argue for a relatively recent age of the extinct fauna. Our results imply that SU6 is either significantly older than the OSL results, or that a large fraction of the faunal material and the charcoal found in SU6 was derived from older, lateral deposits. Our U and Th laser ablation ICPMS results as well as the REE profiles reported by Trueman et al. [2008. Comparing rates of recystallisation and the potential for preservation of biomolecules from the distribution of trace elements in fossil bones. C.R. Palevol. General Paleontology (Taphonomy and Fossilization) 7, 145–158] contradict the interpretation of previously reported rare earth element compositions of bones, and the argument based thereon for the primary context of faunal material and clastic sediments in SU6 layers.

Major Conservation Policy Issues for Biodiversity in Oceania

Oceania is a diverse region encompassing Australia, Melanesia, Micronesia, New Zealand, and Polynesia, and it contains six of the world's 39 hotspots of diversity. It has a poor record for extinctions, particularly for birds on islands and mammals. Major causes include habitat loss and degradation, invasive species, and overexploitation. We identified six major threatening processes (habitat loss and degradation, invasive species, climate change, overexploitation, pollution, and disease) based on a comprehensive review of the literature and for each developed a set of conservation policies. Many policies reflect the urgent need to deal with the effects of burgeoning human populations (expected to increase significantly in the region) on biodiversity. There is considerable difference in resources for conservation, including people and available scientific information, which are heavily biased toward more developed countries in Oceania. Most scientific publications analyzed for four threats (habitat loss, invasive species, overexploitation, and pollution) are from developed countries: 88.6% of Web of Science publications were from Australia (53.7%), New Zealand (24.3%), and Hawaiian Islands (10.5%). Many island states have limited resources or expertise. Even countries that do (e.g., Australia, New Zealand) have ongoing and emerging significant challenges, particularly with the interactive effects of climate change. Oceania will require the implementation of effective policies for conservation if the region's poor record on extinctions is not to continue.

Threatened species indicate hot-spots of top-down regulation

The introduction of alien mesopredators and herbivores has been implicated as the main driver of mammalian extinction in Australia. Recent studies suggest that the devastating effects of invasive species are mitigated by top-order predators. The survival of many threatened species may therefore depend on the presence and ecological functioning of large predators. Australia’s top predator, the dingo (Canis lupus dingo), has been intensively persecuted across the continent and it is extremely rare to find dingo populations that are not being subjected to lethal control. We predicted that the presence of threatened species point out places where dingo populations are relatively intact, and that their absence may indicate that dingoes are either rare or socially fractured. A comparison of a site which harbors a threatened marsupial, the kowari (Dasyuroides byrnei), and a neighboring site where the kowari is absent, offers support for this suggested pattern.

A review of the evidence for a human role in the extinction of Australian megafauna and an alternative interpretation

Arguments that megafaunal extinctions in Australia were anthropogenically mediated have focused on establishing terminal appearance ages. This approach has been underpinned by three principle tenets: (1) if megafauna disappeared before significant climate change, but after human colonisation, then it can be inferred that extinctions were human mediated; (2) climate change within the last glacial cycle was unremarkable relative to previous cycles; and (3) all or most Pleistocene megafauna were present when people arrived on the continent. We review the evidence for human causation and note mounting evidence suggesting that the last 400–300 ka in Australia has been characterised by escalating aridity and climatic variability, culminating in the breach of a hydrological threshold within the last glacial cycle. Only 21 species (35%) of megafauna whose disappearance has been attributed to human activity are known to have persisted after the Penultimate Glacial Maximum, a time of undoubtedly severe climate change. Thus, 39 species of megafauna (65%) cannot be reliably placed within 85,000 years of firm evidence for human arrival, ca 50–43 ka. At most eight species (13%) were clearly present at this time. Four or more persisted until the onset of full glacial conditions at ca 30 ka. We argue for a falsifiable model of staggered extinction in which most megafaunal extinctions predated human arrival and with the influence of people as a minor superimposition on broader trends in train since middle Pleistocene times.

Selective hunting of juveniles as a cause of the imperceptible overkill of the Australian Pleistocene megafauna

Overkill by human hunting has been cited consistently as a likely cause of the Pleistocene megafaunal extinctions in Australia, but little archaeological evidence has been found to support the notion of prehistoric Aboriginal people engaging in specialised “big game” hunting more than 40 millennia ago. Here we develop a demographic population model that considers explicitly the potential impact of harvest of small, immature (and presumably more vulnerable) individuals of the largest known marsupial, Diprotodon opoptatum. We show that remarkably low levels of exploitation of juveniles (the equivalent of one or two kills per 10 people per year) would have been sufficient to drive these large species to extinction within centuries, as a consequence of their “slow” life-histories. This conclusion is robust to assumptions regarding the compensatory response of the prey species and declines in the relative efficiency of hunting as the megafaunal populations declined. These findings dispel the idea that, at least in Australia, evidence for a sophisticated hunting toolkit and massive kill-sites are a necessary adjunct to “blitzkrieg”. Ironically, although the extinction event was likely geochronologically instantaneous (given the coarse resolution of dating from that time), on the scale of human (and megafaunal) lifetimes, the unfolding overkill would have been all but imperceptible.

Self‐organised instability and megafaunal extinctions in Australia

OikosVolume 103, Issue 1 p. 235-239 Self-organised instability and megafaunal extinctions in Australia Michael A. Forster, Michael A. ForsterSearch for more papers by this author Michael A. Forster, Michael A. ForsterSearch for more papers by this author First published: 02 October 2003 https://doi.org/10.1034/j.1600-0706.2003.12557.xCitations: 8 Michael A. Forster, PO Box A175, Sydney South, NSW 1275, Australia (micf@rpb2.com). Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume103, Issue1October 2003Pages 235-239 RelatedInformation

Determinants of loss of mammal species during the Late Quaternary 'megafauna' extinctions: life history and ecology, but not body size.

Extinctions of megafauna species during the Late Quaternary dramatically reduced the global diversity of mammals. There is intense debate over the causes of these extinctions, especially regarding the extent to which humans were involved. Most previous analyses of this question have focused on chronologies of extinction and on the archaeological evidence for human-megafauna interaction. Here, I take an alternative approach: comparison of the biological traits of extinct species with those of survivors. I use this to demonstrate two general features of the selectivity of Late Quaternary mammal extinctions in Australia, Eurasia, the Americas and Madagascar. First, large size was not directly related to risk of extinction; rather, species with slow reproductive rates were at high risk regardless of their body size. This finding rejects the 'blitzkrieg' model of overkill, in which extinctions were completed during brief intervals of selective hunting of large-bodied prey. Second, species that survived despite having low reproductive rates typically occurred in closed habitats and many were arboreal or nocturnal. Such traits would have reduced their exposure to direct interaction with people. Therefore, although this analysis rejects blitzkrieg as a general scenario for the mammal megafauna extinctions, it is consistent with extinctions being due to interaction with human populations.

Causes of the extinction of native mammals of the Western Division of New South Wales: an ecological interpretation of the nineteenth century historical record

Twenty-four mammal species – predominantly the medium-sized, ground-dwelling mammals with a dependence on grass/herbs and seeds – disappeared forever from the landscape of the Western Division of New South Wales in a period of 60 years from first settlement in 1841. The present study examines the causes of this extinction episode by constructing a picture of the changing landscape from the historical record and interpreting the findings ecologically. The conclusions point to an extinction process that can be largely attributed to the impact of sheep, an impact that was exacerbated in the scarce and fragile refuges of the flat landscape in times of intense and frequent drought. This conclusion differs from those of many others, particularly Kerin in the Western Lands Review, who pointed to "the impact of feral animals, rather than overgrazing" as the cause of mammal extinctions, and Morton, who considered that the rabbit was "principally (although not entirely)" responsible for mammal extinctions in the rangelands. The rabbit plague in the Western Division from the early 1880s and the influx of foxes in the last years of the 19th century expedited the local demise of some species and even delivered the final blow to surviving remnant populations of a few species of native mammals but they were not the primary agent of extinction. Historical accounts give prominence to the rapidly growing wool industry in the 19th century. From its dominant position as an export commodity, wool became the chief means of the successful spread of colonial settlement. By 1853 there were about 300,000 sheep based at the southern end of the Darling on the watered frontages, which were all taken up by 1858. The west of the Darling was largely occupied by sheep farmers between 1859 and 1876. The history of settlement around Menindee from 1841 can be read as a devastating critique of the failure to realise that the west could not sustain a pattern of land use imposed on it from another world. The deterioration of the pastoral landscape was such that by the late 1880s the "walls of the pastoral fortresses... were beginning to crumble of their own accord, as the foundations on which they were built — the physical environment — altered under stresses...". The sequence of occupation and land use in the Western Division and the timing of the loss of native mammal species allows the conclusion to be drawn that it was sheep, and the way the land was managed for the export wool industry, that drove so many of the mammal species to extinction. The impact of ever-increasing millions of sheep on all frontages, through all the refuges, and across all the landscape by the mid 1880s is the primary cause of the greatest period of mammal extinction in Australia in modern times.

Marsupial Megafauna, Aborigines and the Overkill Hypothesis: Application of Predator-Prey Models to the Question of Pleistocene Extinction in Australia

Marsupial Megafauna, Aborigines and the Overkill Hypothesis: Application of Predator-Prey Models to the Question of Pleistocene Extinction in Australia

Marsupial megafauna, Aborigines and the overkill hypothesis: application of predator-prey models to the question of Pleistocene extinction in Australia

The worldwide extinction of large terrestrial mammals in the late Pleistocene has been attributed to climate change, overkill by human populations colonizing new continents, or some combination of these two processes. Lack of precision in chronologies for human colonization and mega- faunal extinction suggests that the role of overkill will be difficult or impossible to resolve from the archaeological and fossil record. In this study, we used a simple two species predator-prey model to examine the population density and hunting efficiency of a colonizing Aboriginal population necessary for overkill to have led to extinction (equilibrium density=0), of a range of different sized megafauna (250–1000 kg bodyweight) inhabiting an hypothetical tract of north Australian Eucalyptus savanna. We referred our modelling to this region because estimates of contemporary Aboriginal population density arguably set an upper limit for those occurring during the Pleistocene, and data are available on harvesting rates of large introduced mammals such as buffalo. Modelling results indicated a compensatory trade-off between the effect of Aboriginal population density and hunting efficiency (measured as the rate of effective search for prey) on equilibrium megafauna densities. The modelling also demonstrated that although intrinsic rate of population increase and density at carrying-capacity for mammals increase with declining body size, smaller megafauna would have been more readily exterminated than larger megafauna because they would have been harvested at a higher rate to satisfy the demand for meat. However, while at contemporary Aboriginal densities it appears plausible that over-harvesting could have affected the fate of smaller megafauna (<250 kg), hunting efficiencies required to drive medium (500 kg) and larger (1000 kg) sized megafauna to extinction appear unrealistically high. This conclusion would be reinforced if Aborigines were able to switch prey at low megafauna density, a contingency not considered in our model. Collectively, these results suggest that for overkill to have driven medium to large marsupial megafauna extinct in the northern Eucalyptus savannas, Aboriginal densities must have been considerably higher than contemporary levels, or Aboriginal hunters astonishingly efficient. Alternatively, climate change in the late Pleistocene may have played an important role in the extinction of Australian megafauna.

The genetic diversity and distinctiveness of the Yellow-footed Rock-wallaby Petrogale xanthopus (Gray, 1854) in New South Wales

Yellow-footed Rock-wallabies (YFRW) Petrogale xanthopus have declined in numbers since European settlement from past hunting for skins, habitat disturbance and predation and competition with feral animals (Gordon et al. 1978, 1993; Copley 1983; Henzell 1990). This has led to the species being classed as potentially vulnerable to extinction in Australia (Kennedy 1992), and endangered in New South Wales (Schedule 1, Threatened Species Conservation Act, 1995).

New Zealand late Cretaceous and cenozoic plant biogeography: A contribution

Palynological data from Australia and New Zealand show marked vegetational changes throughout the Late Cretaceous and Cenozoic in response to climatic changes, fluctuations of the Antarctic ice cap, drifting of the continents and to a lesser extent tectonic activity. New Zealand and New Caledonia separated from Australia and Antarctica about 80 million years ago at which time the New Zealand vegetation had predominantly Austral affinities. Podocarps and southern beeches existed in an environment characterised by long winter nights and low temperatures. As New Zealand moved northeast a gene flow was maintained with Australia by long-distance dispersal of pollen, spores and seeds by wind, water and birds. A similar vegetational history of Nothofagus in Australia, New Zealand and South America can only be explained if the gene pool was similar in each area; this implies continual contact. During the Cenozoic, New Zealand received new taxa, some of which had previously appeared in Australia and some which survived in New Zealand after extinction in Australia. The best examples of this are Acacia which appeared in New Zealand in the Early Pliocene after its Early Miocene appearance in Australia, and Beauprea which became extinct in Australia in the Miocene but still occurred in New Zealand in the Early Pleistocene. Australian and Malayo-Pacific elements in the New Zealand flora became more prominent, as did the endemic element. The New Zealand vegetation was primarily warm-temperate, reaching subtropical in the Early to Middle Miocene and cool-temperate in the Late Miocene and Pliocene. No New Zealand palynofloras can be regarded as tropical since, although Palmae pollen dominates many Late Oligocene and Miocene assemblages, tropical genera such as Mauritia (or Nipa), Anacolosa (Indomalayan), Bombax, Cupania and some genera within the Proteaceae occur only spasmodically, and the abundance of Casuarina and Nothofagus “brassi” beech at this time suggests high humidity, but not necessarily high temperatures. The New Zealand vegetation was greatly modified by Pliocene and Pleistocene glaciations, resulting in the modern unstable disjunct distribution pattern.