Pr Pre-Columbian Columbian def defor oresta estation as an tion as an amplifier amplifier of of dr drought in Cent ought in Central al America America Benjamin I Cook Jed O Kaplan, Kevin J Anchukaitis, Michael Puma, Maxwell Kelly
Pr Pre-Columbian Columbian Centr Central al America America • Home to over 19 million people • Sedentary agricultural societies • Major population crash after European conquest • Landscape probably looked less like this
And more like this. . .
Pre-Columbian Droughts • Impacted Maya, Toltec, Aztec… • Causes? • Solar forcing, random variability • Could deforestation have contributed?
Land Cover Reconstruction • Based on population a) 800-950 C.E. (approx.) • Varying per capita land use; arable land restriction b) 1500-1650 C.E. (approx.) • More extensive/intensive land use than previous reconstructions • New input for climate models c) 2000 C.E.
Experiments • NATVEG : Natural vegetation only; no crops or anthropogenic land cover • DEFOREST : pre-Columbian land cover • REGROWTH : post-Columbian land cover • Compared against paleorecords from the Yucatán
NATVEG minus DEFOREST a) Precipitation a) 800-950 C.E. (approx.) b) 1500-1650 C.E. (approx.) b) Surface Temperature c) 2000 C.E.
NATVEG minus DEFOREST a) Net Radiation, TOA a) 800-950 C.E. (approx.) b) 1500-1650 C.E. (approx.) b) Convection c) 2000 C.E.
Yuca ucatán: tán: 800 800-950 C 950 C.E. .E. vs vs 1500 1500-1650 C 1650 C.E. .E. • Paleo-records indicate regional water balance changes precipitation minus evaporation • Lake records, cave records • Drier Classic/Post-Classic era relative to the Colonial regrowth period • Hard to convert most to quantitative estimates • Tzanab Speleothem -14% decline in P-E
Conclusions • Warmer/Drier average conditions with pre-Columbian deforestation (higher albedo, less energy available for convection and precipitation) • DEFOREST minus REGROWTH : -18% decline in JJA P-E (-6%, annual), comparable to Tzanab (-14%) • Future deforestation in the Yucatán? Modern Pre-Columbus
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