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Australia: The Land Where Time Began |
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The
Katapiri Fauna Collapse According to Smith when rivers, lakes and swamps
failed as the climate shifted to the drier conditions of the MIS 4 the
dryland megafauna populations also collapsed along with the regional
ecosystem. The last known evidence of significant megafauna populations
in this region is the remains of
Diprotodon from
Punkrakadarinna on the Warburton River that have been dated by
thermoluminescence to 64.9 ± 5 ka (Webb, 2009). Smith suggests there are
a couple of factors that are likely to underlie local megafauna
extinctions, such as the marked dependence of many macropods on shelter
to avoid heat stress, therefore problems for larger species were created
by the increasingly open vegetation. At the present medium to large
species of kangaroos are not common in the heart of the Lake Eyre basin.
Another problem for larger species is the need for free water, late
maturity and slower reproductive rates. Therefore, most species of the
megafauna would not be capable of tolerating the increasing
stochasticity of the environment and fragmentation of riparian habitats
(Main & Bakker, 1981; Horton, 1984).
One of the clearest examples of extinction at a
regional level driven by climate change is the demise of this dryland
megafauna. The critical importance of biogeographic factors is
demonstrated by the collapse of the Katapiri fauna, though it has been
shown by other studies that megafauna communities demonstrate resilience
in the face of climatic fluctuations in the Quaternary (Prideaux, 2007).
In the Cooper Creek-Lake Eyre region the interglacial palaeohydrology
effectively made this area part of the desert margin. Migration
corridors between the main body of megafauna in southeastern Australia
(a source) and animal populations in the Lake Eyre basin (a sink)
appears to have been disrupted by the switch to conditions that were
drier and more variable (Webb, 2009). The dryland megafauna were not
able to recover from these environmental crashes once the connection
with the southeastern source was cut. It is shown that some species survived into the
period 50-45 ka, as the find of an isolated
Diprotodon cranium near
Lake Eyre, which was associated with an OSL date of 46.6 ± 3 ka (ANU-OD
1251) suggests that in the upper reaches of these drainage systems that
were better watered these animals persisted, dispersing downstream
following exceptionally heavy rain (Webb, 2009) and personal
communication to Smith). Similarly the megafauna persisted into the
period 66-51 ka at Lake Menindee (Cupper & Duncan, 2006). Smith suggests
that the only megafauna species that is likely to have been encountered
by the first people moving into the desert was
Genyornis newtoni, a
large flightless dromornithid bird.
Genyornis Until 50 ± 5 ka
G. newtoni was
distributed widely across arid and semi-arid parts of southeastern
Australia (Miller et
al.,
1999). This bird is believed to have been able to tolerate saline waters
as it had nasal salt glands (Murray & Vickers-Rich, 2004). It appears
G. newtoni may have been
tethered to riparian corridors for nesting, based on the distribution of
its distinctive eggshell, possibly moving up and down the channel
systems and floodplains according to the seasons. In those parts of the
arid interior that are interlaced with river channels, such as in
western New South Wales, the Lake Eyre basin, the Murray-Darling basin
and southwestern Queensland,
Genyornis had a wide
range. The bones of
Genyornis are not known
among fossil assemblages from the Nullarbor, despite several field
surveys, its eggshells have not been found in the Great Victoria Desert
or around Lake Gregory or Lake Mackey. According to Smith isolated
Genyornis populations
appear to have been present on the arid west coast at Lake McLeod and in
Central Australia at Lake Lewis, the Lake Lewis population being
believed to almost certainly being a limited extension of range along
the corridor of the Finke River in good years. The eventual extinction
of
Genyornis in the Lake
Eyre basin coincided with a significant decline of the rainfall of the
summer monsoon (Johnson et
al.,
1999; Murphy, Williamson & Bowman, 2012), which is suggested to have
potentially disrupted its breeding pattern in the summer and the C4
plants, which was its preferred diet. Smith suggests it may have also
coincided with the first arrival of humans in these landscapes,
especially as any predation on eggs or young birds would have put extra
pressure on this species. Smith, Mike, 2013,
The Archaeology of Australia’s
Deserts, Cambridge University Press
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |