Assessing evidence for human megafaunal hunting at Lynford (UK).
Global Modelling of Megafaunal Extinction Climate and Colonisation: Results from a high resolution...
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Transcript of Global Modelling of Megafaunal Extinction Climate and Colonisation: Results from a high resolution...
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
1 Environment and Sustainability Institute, University of Exeter; 2 Department of Zoology, University of Cambridge.
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
1 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, 4527–4531
Extinct Surviving
Research Premise:Assembling Global Datasets
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
100
60
20
80
40
0Early Human
ArrivalLate Human
Arrival
Per
cent
age
Var
iatio
n E
xpla
ined
(Nag
elke
rke’
s R
2 )
Unique to Humans
Unique to Climate
Shared
Explanatory Power:
Results:Overall Global Model Performance
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
don’t explain
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 America80 60 60 44 64 24 8 20 20 4 48 48 80 1680 44 44 44 48 24 8 16 16 4 44 48 72 1280 56 56 44 64 24 8 16 16 4 48 48 80 1680 56 56 44 64 24 8 16 16 4 48 48 80 1280 52 52 44 64 24 8 16 16 4 48 48 80 1680 52 52 44 64 24 8 16 16 4 48 48 80 1280 48 48 44 64 24 8 16 16 4 48 48 80 1680 48 48 44 64 24 8 16 16 4 48 48 80 12
Human Arrival Scenarios
logit(prob.extinction)= a*(1+b/LogArea)*T.Human*exp(c*(1+d/LogArea)*T.Human)
Predicting Human Effect
where ‘T.Human’ is time since human arrival
Function based on the Ricker Model for population density