Extinction of Australian Megafauna 1.
0 Introduction:The Pleistocene Epoch lasted from 2 million years ago to 10,000 years ago. In Pleistocene times, giant ‘megafauna’ inhabited Australia. These animals which were a part of the environment of early man on this continent mysteriously disappeared about 15,000 years ago and were totally extinct from that time. There were several types of such megafauna including giant Kangaroos, giant marsupial wombats, large land crocodiles, pythons and flightless birds.
Throughout the Pleistocene Epoch the Australian Continent was virtually in the same geographical position that it is in today. “However the Continent was becoming increasingly cool and dry with intermittent periods of warmer, wetter climates towards the Late Pleistocene”. (Joyzine) These climatic changes, in particular the aridity had profound effects on the Australian fauna and flora. This might have causes the extinction of the megafauna.
However another school of thought claims that this period represents the time during which humans first arrived in Australia. It might also be possible that these megafauna were made to die by the human beings to sustain their existence. With this background this paper examines what happened to these giant creatures and the possible reasons for the extinction of them.2.
0 Kinds of Megafauna:According to Museum Victoria (2005) while the diversity of the megafauna species can be established with a wider research, the following are the representative list of the species found so farDiprotodon optatum was the size of a rhinoceros, and is thought to have been the largest marsupial ever to exist.Zygomaturus tasmanicus was a bullock-sized relative of Diprotodon. It and related species lived in the more forested areas of southern Australia.Palorchestes azael was the size of a bull, with long claws and a longish trunk.
Imaginative writers have suggested it as the inspiration for the Aboriginal bunyip.Procoptodon goliah was the largest kangaroo ever. It belonged to the sthenurine family, which had shortened flat faces and forward-looking eyes.Thylacoleo carnifex, the so-called ‘Marsupial Lion’, was a leopard-like animal, and was almost certainly carnivorous and a tree-dweller.
Zaglossus hacketti, a sheep-sized echidna whose remains were discovered in Mammoth Cave in Western Australia, was probably the largest monotreme ever.Mihirung Birds were giant flightless birds. They included Genyornis newtoni and Dromornis stirtoni, which was the heaviest bird known.Megalania prisca was an enormous goanna-like carnivore, at least 5.
5 metres long, and with a weight of about 600 kilograms.3.0 Reasons for Extinction:There have been several theories about how the megafauna got extinguished from Austrlian Continent. The cause of the extinction is an active and contentious field of research.
It is hypothesised that with the arrival of humans (around 48,000-60,000 years ago), hunting and the use of fire to manage their environment may have contributed to the extinction of the megafauna. (Miller 2005) Some others are of the opinion that climatic conditions would have resulted in the extinction of these animals. The general causes that might have resulted in the extinction are:Megafauna were under stress due to climatic change, causing changes in vegetaionIncreased stress by human arrivval and hunting by menHyperlethal diseases causing the extinction andA combinaion of both climatic changes and hunting by human3.1 Climatic Changes:Towards late Pleistocene Epoch there were changes in climatic conditions in Australia comprisng of dry and wet periods which correspond to the glacial and interglaical periods respectively in other continents.
These changes have resulted in:More warming of temperaturesWidespread changes would have been there in the patterns of rainfallMelting of glaciersIncrease in the inter-seasonal differences in temperaturesThere had been changes in the vegetation types and their dispersalChanges in the local climatic conditionsIt has been advocated that rapid climate changes may have caused extinction due to elimination of food cources;climate changes would have caused disrutpion in birth schdules; the animals would have been exposed to conditions that were not conducive for their existence and competition among animals for habitat would alsohave resulted in their extinction.While some scholars are of the view that megafauna were extinguished because of changes in climatic conditions, Dr. Prideaux, a vertebrate palaeontologist is of the view that Australian megafauna species were resilient to glacial and interglacial cycling, climate change is unlikely to have precipitated the demise of the remarkable fauna.3.
2 Action by Human Beings:A team of researchers posit humans are responsible for this, too. Josephine Flood (1999) does note that human agency in the extinction of such species in other part of the world. She is of the opinion that since megafauna faced extinction throughout Greater Australia and this happened before the time of the principal climate change humans were likely responsible. New evidence based on accurate optical luminescence and Uranium-thorium dating of megafaunal remains suggests that humans were the ultimate cause of the extinction of megafauna in Australia.
(Prideaux, G.J. et al. 2007)Richard G.
Roberts et al. (2001) opine that aborigines changed vegetation by burning the landscape, possibly to make hunting and traveling easier. The result: less food for big browsing animals and hunting and climate fluctuations may then have tipped them to oblivion. They further state that timing and causes of these extinctions remain uncertain.
They have reported burial ages for megafauna from 28 sites and have inferred extinction across the continent around 46,400 years ago (95% confidence interval, 51,200 to 39,800 years ago). Their results rule out extreme aridity at the Last Glacial Maximum as the cause of extinction, but not other climatic impacts; a “blitzkrieg” model of human-induced extinction; or an extended period of anthropogenic ecosystem disruption. “The bulk of the evidence is now clearly aligned with a human explanation for the [Australian] event”However, Roberts et al.’s interpretation of the dates ignited a heated debate because of the selective sampling, the effective sample size and the exclusion of any site that did not contain articulated skeletal remains (bones in anatomical order).
Counter to Robert et al.’s views were expressed by Field ; Fullagar (2001) in that they opine it is not clear as yet on the basis of the available evidence that humans were even present in Australia earlier than 40,000 years ago and hence it is wrong for Robert et al. to claim that human were responsible for the extinction of the magafauna in Australia without deepening their research in this direction..
They are of the view that the megafauna might have disappeared even before the arrivals of humans in Australia due to climatic changes or other reasons. aFlannery (1994) speculated that the megafaunal extinctions were the result of a ‘blitzkrieg’: overhunting by early human colonisers combined with fire-stick farming practises which changed the ecology of the continent so dramatically that many larger marsupial species were driven to extinction. Flannery says “the likely sequence of events is that people arrived in Australia, hunted these large animals to extinction, this caused a change in vegetation and then a climate change,”4.0 Browsers and Grazers:While there has been debate over the cause of the extinction of ‘megafauna’ species during the late Pleistocene of Australia, one view is that environmental changes caused by nature or the actions of human beings was the main factor for the extinction.
This view is being supported by the observation that, among herbivores, most of the species that went extinct were apparently browsers rather than grazers. Johnson and Prideaux (2004) are of the view that browsers would presumably have been more dependent on shrubland and woodland habitats than grazers, and it has been argued that such habitats might have contracted in response to aridity or changed fire regimes in the late Pleistocene. They argue that it is true that more browsers than grazers went extinct, but this is largely because most very large herbivores in the late Pleistocene were browsers, not because large browsers were more likely to go extinct than similarly sized grazers. They opine that this result provides evidence against some forms of environmental change as a cause of the extinctions.
5.0 Conclusion:Extinction of species is not a simple issue to conclude. There are several complicating factors like fluctuations in temperature and rainfall, habitat destruction by humans, reconfiguration of habitats, fire, introduced predators and competitors, disease, and cascading effects whereby the extinction of one or a few key species forces the extinction of others. Especially in the case of extinction of megafauna in Australia, several questions like the reasons for the disappearance of these creatures before humans even arrived and the reasons why the few survivors shrunk in size yet remain to be answered and the researches continue in the quest of finding answers for these questions.
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