North American Tree Rings, Climatic Extremes, and Social Disasters - Dendroclimatology - page 303

village sites during the Great Drought of the late thirteenth century (Douglass 1935 ) .
Datable timbers from the late thirteenth and early fourteenth centuries were scarce
in the region. Douglass and his collaborators finally found charcoal samples bridg-
ing the gap between the modern and archaeological chronologies south of the classic
Anasazi heartland near Jeddito Wash and along the Mogollon Rim, in fourteenth-
and fifteenth-century archaeological sites believed to have grown in part by immi-
grants from sites abandoned in the Four Corners area (Haury and Hargrave 1931 ;
Haury 1962 ; Adams 2002 ) .
The causes of regional abandonment on the Colorado Plateau are still debated,
but experiments have shown that the tree-ring record is well correlated with dryland
crop yields in the Four Corners region (Burns 1983 ; VanWest 1994 ) , suggesting a
drought sensitivity of the Anasazi practicing dryland agriculture. Burns ( 1983 ) used
tree-ring-reconstructed crop yields to simulate food storage shortfalls and surpluses
that identified probable famine among the Mesa Verde Anasazi during droughts, and
expanded construction activity during periods of surplus crops, just as Douglass had
suggested in 1935.
A number of other provocative studies describing tree-ring evidence for climate
impacts on society in Europe and elsewhere have been published. Le Roy Ladurie
( 1971 ) , for example, linked the period of exceptional growth from 1312 to 1319 in
oak chronologies from southern Germany developed by Bruno Huber with flooding,
harvest failure, and famine across France and England during one of the most severe
periods of famine of the Middle Ages. Lamb ( 1995 ) discussed a number of climate
inferences based on tree-ring data from Europe and North America, including a shift
to colder conditions in the fifth century AD contemporaneous with Roman decline
in western Europe.
Perhaps the most unambiguous link between tree-ring data, climate effects, and
societal impacts has been demonstrated with frost-damaged rings. LaMarche and
Hirschboeck ( 1984 ) and Salzer ( 2000 ) linked bristlecone pine records of frost rings
in the western United States to large-magnitude volcanic eruptions through dust
veil effects on the global climate system. The bristlecone pine records include frost
rings in 1817 and 1884, following the eruptions of Tambora in 1815 and Krakatau
in 1883. These were two of the largest volcanic eruptions in the past 500 years, and
both had global-scale climatic and societal impacts. LaMarche and Hirschboeck
( 1984 ) tentatively linked the severe frost-ring event dated to 1626 BC in the White
Mountain region of California to archaeological and radiocarbon evidence for the
destruction of the late Bronze Age site of Akrotiri by the cataclysmic eruption of
Thera (Santorini), an assignment that still generates heated debate (Manning 1999 ) .
Baillie ( 1994 , 1999 ) compiled evidence for profoundly suppressed growth in
temperature-sensitive tree-ring chronologies from Europe, North America, and
South America during the period AD 536-545. This evidence for anomalous cold
was supported by early documentary references to severe cold, crop failure, and
dry fogs, suggesting the global climatic effects of a cataclysmic volcanic erup-
tion or the impact of an extraterrestrial object. The societal impacts of the cold
climate conditions in the mid-sixth century appear to have been severe and included
famine, pandemics (e.g., the Justinian Plague occurred in the 540s), and widespread