Carbon isotope evidence for an abrupt reduction in grasses coincident with                 European settlement of Lake Eyre, South Australia

Johnson, Beverly J.; Miller, Gifford H.; Magee, John; Gagan, Michael K.; Fogel, Marilyn L.; Quay, Paul D.

doi:10.1191/0959683605hl861ra

Cited by 20 publications

(18 citation statements)

References 38 publications

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“…Hence, C4 plants do not contribute substantially to Dromaius' diet even though they dominate the landscape. Analyses of modern (1970-2000 AD) Dromaius eggshells from the Lake Eyre region show virtually no C4 elements in the birds' diets even though canegrass (C4) is a dominant vegetation type (Johnson et al, 2005).…”

Section: Paleodietary Reconstructionsmentioning

confidence: 99%

Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

Miller

Magee²,

Fogel³

et al. 2007

Clim. Past

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Abstract. The moisture balance across northern and central Australia is dominated by changes in the strength of the Australian Summer Monsoon. Lake-level records that record changes in monsoon strength on orbital timescales are most consistent with a Northern Hemisphere insolation control on monsoon strength, a result consistent with recent modeling studies. A weak Holocene monsoon relative to monsoon strength 65-60 ka, despite stronger forcing, suggests a changed monsoon regime after 60 ka. Shortly after 60 ka humans colonized Australia and all of Australia's largest mammals became extinct. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. More than 800 dated eggshells of the Australian emu (Dromaius novaehollandiae), an opportunistic, dominantly herbivorous feeder, provide a 140-kyr dietary reconstruction that reveals unprecedented reduction in the bird's food resources about 50 ka, coeval in three distant regions. These data suggest a tree/shrub savannah with occasionally rich grasslands was converted abruptly to the modern desert scrub. The diet of the heavier, extinct Genyornis newtoni, derived from >550 dated eggshells, was more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. We suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. We speculate that ecosystem collapse across arid and semi-arid Correspondence to: G. H. Miller (gmiller@colorado.edu) zones was a consequence of systematic burning by early humans. We also suggest that altered climate feedbacks linked to changes in vegetation may have weakened the penetration of monsoon moisture into the continental interior, explaining the failure of the Holocene monsoon. Climate modeling suggests a vegetation shift may reduce monsoon rain in the interior by as much as 50%.

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Section: Paleodietary Reconstructionsmentioning

confidence: 99%

Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

Miller

Magee²,

Fogel³

et al. 2007

Clim. Past

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“…The rainfall-dependent grasslands and arid regions of the LEB also contain rare and endangered species of plants and animals (Morton et al, 1995), in addition to supporting a large cattle (and to a lesser extent, sheep) grazing industry. The terrestrial ecosystems have shown evidence of degradation since European settlement, with changes in vegetation (Johnson et al, 2005) and significant mammalian extinctions (McKenzie et al, 2007). Management of natural ecosystems and human activities requires a well-founded knowledge of rainfall and streamflow patterns within the LEB.…”

Section: Introductionmentioning

confidence: 99%

Understanding the surface hydrology of the Lake Eyre Basin: Part 1—Rainfall

McMahon¹,

Murphy²,

Peel³

et al. 2008

Journal of Arid Environments

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“…Extensive areas of stony ("gibber") and bare surfaces mantle the slopes and plains. Changes in vegetation cover (Johnson et al, 2005) and geomorphic processes occurred with the shift from Indigenous hunter-gathering to Europeanstyle pastoralism in the 19th century (Fanning, 1994(Fanning, , 1999Noble & Tongway, 1986;Pickard, 1994). Topsoil lost from the hillslopes was deposited on valley floors as laminated and cross-bedded sandy sediments [variously termed post-settlement alluvium (PSA) or post-European material (PEM); Gore et al, 2000:117].…”

Section: The Geomorphic Contextmentioning

confidence: 99%

The surface archaeological record in arid Australia: Geomorphic controls on preservation, exposure, and visibility

et al. 2009

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The conventional approach to assessing the archaeological record in most parts of the world involves a combination of excavation of stratified deposits and extensive survey of surface deposits. Although widely applied in Australia, in both research-based and management archaeology, the method does not conform well to the nature of the surface archaeological record here. Over much of semi-arid and arid Australia, archaeological "sites" are, in fact, accretion phenomena that are not easily interpreted as the outcome of short-term behavioral events. Using results from twelve years of geoarchaeological research in western New South Wales, we demonstrate that there is considerable variability in landsurface age, and hence the "availability" of archaeological surfaces, over relatively short distances. Therefore, it cannot be assumed that stone artifact deposits, for example, that appear to be similar in character are of similar age. Data are also presented that demonstrate that the presence of artifacts on the surface, their apparent absence in sediments buried beneath the surface, and the apparent recent ubiquity of the archaeological record are all a function of geomorphic processes that, at the same time, expose some artifact deposits at the surface and erode and bury others amid large volumes of sediment. Interpreting the surface artifact record within a spatial and temporal geomorphic framework is crucial to understanding the past human behavior that the artifact deposits represent.

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Carbon isotope evidence for an abrupt reduction in grasses coincident with European settlement of Lake Eyre, South Australia

Cited by 20 publications

References 38 publications

Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

Understanding the surface hydrology of the Lake Eyre Basin: Part 1—Rainfall

The surface archaeological record in arid Australia: Geomorphic controls on preservation, exposure, and visibility

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