Honeybees construct perfectly hexagonal combs and surmount architectural challenges by altering their building behavior.
Image credit: Michael L. Smith.
Edited by Joyce Marcus, University of Michigan, Ann Arbor, MI, and approved February 26, 2010 (received for review October 15, 2009)
Abstract
The “hydraulic city” of Angkor, the capitol of the Khmer Empire in Cambodia, experienced decades-long drought interspersed with intense monsoons in the fourteenth and fifteenth centuries that, in combination with other factors, contributed to its eventual demise. The climatic evidence comes from a seven-and-a-half century robust hydroclimate reconstruction from tropical southern Vietnamese tree rings. The Angkor droughts were of a duration and severity that would have impacted the sprawling city’s water supply and agricultural productivity, while high-magnitude monsoon years damaged its water control infrastructure. Hydroclimate variability for this region is strongly and inversely correlated with tropical Pacific sea surface temperature, indicating that a warm Pacific and El Niño events induce drought at interannual and interdecadal time scales, and that low-frequency variations of tropical Pacific climate can exert significant influence over Southeast Asian climate and society.
Footnotes
- 1To whom correspondence should be addressed. E-mail: bmb{at}ldeo.columbia.edu.
Author contributions: B.M.B. and T.M.H. designed research; B.M.B., K.J.A., D.P., R.F., E.R.C., M.S., L.C.N., A.W., T.T.M., and T.M.H. performed research; B.M.B., K.J.A., D.P., E.R.C., and M.S. analyzed data; and B.M.B., K.J.A., D.P., R.F., E.R.C., and A.W. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: Tree Ring Data have been deposited at the International Tree Ring Data Bank (ITRDB) at http://www.ncdc.noaa.gov/paleo/treering.html.
This article contains supporting information online at www.pnas.org/cgi/content/full/0910827107/DCSupplemental.
Freely available online through the PNAS open access option.
Climate as a contributing factor in the demise of Angkor, Cambodia
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- Environmental Sciences
- Physical Sciences
- Geology
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