Collaborative Research: Identifying the Footprints of Human Colonization on Australian Ecosystems and Climate

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The project seeks to address the scientific question: Did systematic burning by early human colonizers sufficiently alter Australian vegetation to produce a distinctly non-linear disruption of climate and biota? The researchers will address this question using a series of testable predictions to evaluate the hypothesis using tracers in dateable geological archives. The research team will integrate field and analytical data to provide environmental scenarios that can be tested with mesoscale climate models to evaluate the impact of hypothesized human-induced vegetation change on monsoon rainfall.Over the past 60,000 years, modern humans have branched out of their ancestral African home to colonize many lands. Australia, isolated from the rest of the world for 50 million years, provides a unique setting to evaluate the footprint of human activity. A joint US-Australian team has reconstructed ecosystem and climate change across portions of semi-arid Australia. Recent efforts by this team have centered on using biogeochemical tracers in eggshells of large, flightless birds that document the extinction of megafauna and an irreversible loss of vegetation at the time of human colonization. An emerging scenario is that prior to human colonization, arid-zone vegetation included a diverse mixture of grasses and drought-tolerant trees and shrubs, supporting large marsupial herbivores (most now extinct) and marsupial and reptilian carnivores. When global conditions favored strong monsoonal rainfall, the Australian summer monsoon regularly penetrated well into the interior of Australia. However, megafauna became extinct following human colonization when vegetation diversity was much reduced and monsoon rains failed to materialize, even when global forcing was strong and other monsoon systems were reinvigorated. The education component will be undertaken in collaboration with the Carnegie Institution's Academy of Science Education (CASE). Several undergraduate students and a postdoctoral scholar will be supported with the research. CASE will test various learning modules and the best will be made available to a wider audience through the group's website. Three activities are planned: 1) an activity using geographic information systems (GIS) software written for students teaching the principles of GIS as well as the science of ecosystem change in terms of Australia; 2) Educational sections on Australia's climate, fauna, and flora will be on the project's website to augment the GIS activities; and 3) Connecting schools in Washington DC with a sister school(s) in Australia.