North American Tree Rings, Climatic Extremes, and Social Disasters - Dendroclimatology - page 305

of a flood of this magnitude would exceed the design capacity of the flood protec-
tion system for Winnipeg, force extensive evacuations, and cause extensive property
damage (St George and Neilsen 2000).
Other interesting tree-ring studies of climatic extremes and social impacts
include Jacoby et al. ( 1999 ) , who used white spruce ring density data to reconstruct
extremely cold conditions following the Laki eruption of 1783, when hundreds of
Inuit people perished of famine in northwestern Alaska. Gil Montero and Villalba
( 2005 ) used moisture-sensitive tree-ring chronologies of Juglans australis and
Polylepis tarapacana as proxies of drought and rural socioeconomic stress in north-
western Argentina. They note a relationship between severe, sustained, and spatially
extensive drought beginning in the 1860s and heavy human mortality. The effects
of prolonged drought on human mortality appear to have been leveraged by the
decreasing availability of water, which concentrated humans and livestock around
the few remnant water sources. This concentration favored the spread of epidemic
diphtheria, which in the absence of an effective response by governmental author-
ities, contributed to the mortality and depopulation of the region (Gil Montero and
Villalba 2005 ) .
Severe nineteenth-century droughts have been identified in the documentary
record for Africa (e.g., Nicholson 1994 ; Endfield and Nash 2002 ) , including a
decadal drought from 1857 to 1865. Food was very scarce and from 'the sea coast to
the Zambesi, fountains, streams, and pools have dried up cattle of all descriptions

died everywhere from sheer poverty, and the losses of draught oxen to travelers,
hunters and traders have been very severe' (London Missionary Society, quoted
by Nash and Endfield 2002 ) . A new tree-ring reconstruction of rainfall based on
African bloodwood ( Pterocarpus angolensis ) identifies the period from 1859 to
1868 as the driest decade in the past 200 years in western Zimbabwe (Therrell
et al. 2006 ) ; the reconstruction also highlights the potential for using tree-ring
chronologies from deciduous hardwoods in seasonally dry tropical woodlands to
help document the historical impacts of climate extremes.
Extreme climate has been implicated in many other important historical events,
and the developing network of climate-sensitive tree-ring chronologies worldwide
may allow new insight into these debates. For example, the decline of the Ming
Dynasty in China has been linked in part to severe drought extending from AD 1637
to 1644 (Davis 2001 ) . This drought and the associated socioeconomic impacts have
been identified with documentary sources, but the new moisture-sensitive chronolo-
gies from Asia (e.g., Buckley et al. 1995 ; Pederson et al. 2001 ; Liu et al. 2004 ) will
help researchers determine the intensity and spatial impact of this drought and of
other climatic extremes over the past several centuries.
Kiracofe and Marr ( 2002 ) suggest that the devastating epidemic of ca. 1524
among the Inca of Peru, which killed a reported 200,000 people just prior to the
Spanish conquest, was probably caused by bartonellosis ( Bartonella bacilliformis )
transmitted by infected sand flies ( Lutzomyia sp.). Climate anomalies associated
with El Niño events have been linked with a huge increase in the numbers of
infected sand flies in the areas of Peru affected by bartonellosis. The co-occurrence
of El Niño-related climate extremes during the suspected outbreak of 1524 might be

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