Catastrophic Ecosystem Collapse in Pleistocene Australia
Abstract
Extinction of the Australian megafauna (50ñ5ka) occurred shortly after human colonization (55ñ5ka). A link between the two has been suggested, including the possibility that landscape modification was influential, but pinpointing the role of humans remains elusive. To evaluate changes at the ecosystem level across the extinction event we utilize dietary information recorded by d13C preserved in eggshells of the extant emu (Dromaius novaehollandiae), a large flightless bird. Emus are opportunistic feeders; their diet reflects the range of food sources available in the weeks before nesting (June). d13C quantifies the proportion of C3 vs C4 vegetation that constitutes the emu's diet. A 150,000-year record of emu dietary intact has been reconstructed using more than 300 individuals from Lake Eyre (south-central Australia) dated by 14C, luminescence and/or racemization. Prior to 50 ka emu diet was highly variable, ranging from 100% C3 to 100% C4. However, immediately after 50 ka, emu diet shifted dramatically: the C4 contribution never exceeded 50% (n=200) after 50 ka, whereas more than half the samples older than 50 ka old contain >50% C4 dietary sources. We attribute the observed changes in emu diet to a fundamental rearrangement of the plant ecosystems in semi-arid central Australia. Such a change in plant communities may have contributed to the extinction of many dependent herbivores. The coincidence in time of megafauna extinction and ecosystem collapse shortly after human colonization suggests there may be a causal link. Development of similar records of vegetation change for other regions of Australia are currently underway to evaluate whether the Lake Eyre record reflects a continental scale reorganization of the Australian biota.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMPP61A0313M
- Keywords:
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- 0400 BIOGEOSCIENCES;
- 1851 Plant ecology;
- 3322 Land/atmosphere interactions;
- 3344 Paleoclimatology