Geoscience Reference
In-Depth Information
agricultural bases withered. h e scattered native peoples that were able
to persist during these prolonged dry spells in the American West were
also hard-hit by extreme l oods, so they had to develop coping strategies.
One key to their success was an intimate knowledge of their environment
and its resources. Another was the size of their population: they survived
by living in small, l exible groups, able to mobilize rapidly and relocate as
conditions dictated.
h e hardships suf ered by these early human inhabitants of the West pro-
vide important lessons. For instance, during extended periods of abundant
moisture, societies that grew rapidly were let vulnerable to collapse when the
climate inevitably turned dry again. Modern society in the West has followed
a similar path: at er a century of fairly abundant moisture, the population in
this region has exploded. Modern engineering has allowed the exploitation of
all available water sources for human use, and water policy has favored water
development for power, cities, and farms over sustainability of the environ-
ment and ecosystems. h ese policies have allowed populations to grow right
up to, and perhaps beyond, the limits that this region can support, leaving it
vulnerable should drier conditions return. In this respect, today's society in
the West resembles the Ancestral Pueblo of the twelt h century—both living
beyond their means.
Paleoclimate records also reveal that the lack of prolonged droughts
during the past 150 years is an aberration. In the past two millennia, such
droughts, some of which lasted several decades, occurred at intervals of every
i t y to ninety years. h e longest droughts experienced by the West over the
past century—lasting about six years—are meager by comparison. Certainly,
however, as discussed in chapters 1 and 3, these relatively short droughts
brought extreme hardship to the region.
Climate scientists have discovered a new complication in the West. In
addition to that region's variable climate, scientists agree that a warming
trend has been superimposed on it—a trend that began a few decades ago and
is likely caused by a rapid increase in carbon dioxide (and other greenhouse
gases) in the atmosphere. h e American West appears to be facing a potential
climatic double-whammy: a cyclical return of the drier conditions and a new
greenhouse gas-induced warming. Although we do not know exactly what
kind of weather this combination will produce, climate models indicate that
global warming will compound natural climate cycles and that a warming
world will likely make the extreme events, particularly l oods and droughts,
even larger and more frequent.
