Megafauna - Environmental Change Institute

Megafauna - Environmental Change Institute

Global Modelling of Megafaunal Extinction Climate and Colonisation: Results from a high resolution analysis Lewis Bartlett1,2, Andrea Manica2, Graham Prescott2, David Williams2, Andrew Balmford2 & Rhys Green2 Environment and Sustainability Institute, University of Exeter; 2 Department of Zoology, University of Cambridge. 1 Research Premise: A Global Analysis for a Global Phenomenon Need for global, integrative assessment of extinction builds on work of Prescott et al. 20121 Split globe into zones: map extinction, expansion, and climate

Compare predictive power of climate and early humans 80,000 year analysis; 4000 year time steps Prescott et al 2012, Quantitative global analysis of the role of climate and people in explaining late Quaternary megafaunal extinctions. Proc. Natl. Acad. Sci.. 109, 45274531 1 Research Premise: Assembling Global Datasets Extinct Surviving Size of circle represents taxonomic abundance

Analysis Non-linear models: climate only, human only, and combined - iterate over many re-sampled datasets Predict human impact using arrival and zone area Results: Overall Global Model Performance 80 (Nagelkerkes R2) Percentage Variation Explained 100 Explanatory Power:

60 Unique to Humans 40 Unique to Climate 20 Shared 0 Early Human Arrival

Late Human Arrival Results: Predicting in sequence Results: predicting one major effect Results: predicting in parallel Results: or indeed not at all Interpretation & Direction

Strongly implicates human colonisation More informative predictor than climate Asia: the next frontier Well studied zones resolved: look to zones we dont explain Thank You for Your Attention! Any Questions? [email protected] Human Arrival Scenarios Start of Arrival Time Step (ky BP) Africa Papua Australia Tasmania Indo-Malaya Japan Madagascar Alaska & Canada North America New Zealand Europe Siberia Central Asia South America 80 60

60 44 64 24 8 20 20 4 48 48 80 16 80 44 44 44

48 24 8 16 16 4 44 48 72 12 80 56 56 44 64 24

8 16 16 4 48 48 80 16 80 56 56 44 64 24 8 16

16 4 48 48 80 12 80 52 52 44 64 24 8 16 16 4

48 48 80 16 80 52 52 44 64 24 8 16 16 4 48 48

80 12 80 48 48 44 64 24 8 16 16 4 48 48 80 16

80 48 48 44 64 24 8 16 16 4 48 48 80 12 Predicting Human Effect

logit(prob.extinction)= a*(1+b/LogArea)*T.Human*exp(c*(1+d/LogArea)*T.Human) where T.Human is time since human arrival Function based on the Ricker Model for population density

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