[Aztlan] Global warming played a role in Incas' rise, report says

[Mario Cabrejos]

Global warming played a role in Incas' rise, report says
British archaeologists say a rise in temperatures helped fuel the empire,
giving access to more cultivable, fertile land, and thus food surpluses that
freed the Incas to expand and conquer.
By Thomas H. Maugh II thomas.maugh at latimes.com
July 28, 2009
http://www.latimes.com/news/nationworld/nation/la-sci-inca28-2009jul28,0,1132640.story

Global warming is not necessarily always bad.

A 400-year warm spell in South America fueled the Incas' rise, British
archaeologists reported Monday, helping them build the largest empire that
ever ruled the continent.

A several-degree increase in temperature allowed the Incas to move higher
into the Andes mountains, opening up new farmland and providing a water
source through the gradual melting of glaciers at the top of those
mountains, paleoecologist Alex Chepstow-Lusty of the French Institute of
Andean Studies in Lima reported online Monday in the journal Climate of the
Past.

"They were highly organized and they had a sophisticated [governance], but
it wouldn't have counted a jot without being underpinned by the warming of
the climate," he said in a telephone interview.

Other experts were cautious about his interpretation. "The premise that the
Incan expansion was driven by climate change is quite revolutionary," said
archaeologist Mark Bush of the Florida Institute of Technology in Melbourne.

Confirming it will require a great deal more work for paleoecologists and
archaeologists alike.

The new research is important because "data on Andean climate during this
time period are scant," said archaeologist Warren Church of Columbus State
University in Georgia, who works in Peru. "However, it is important to
remember that climates do not make empires. People do."

Chepstow-Lusty, geographer Mick Frogley of the University of Sussex and
their colleagues have been studying a 26-foot-long core of mud drilled from
the sacred Lake Marcacocha in the Patacancha Valley of Peru, near Cuzco.
Seeds, pollen, charcoal bits and other debris from successive layers in the
core paint a picture of climate and agriculture in the region for 4,000
years.

Analysis of the core showed that a major drought began in the region around
the year 880 and lasted for at least 100 years.

That drought, Chepstow-Lusty speculated, may have been the cause of the
demise of the Wari empire, which lasted from 550 to 1000. The region was
also colder than normal for the 3,000 years before 1000.

Beginning about 1150, the climate began warming and eventually got "several
degrees centigrade" warmer, Chepstow-Lusty said. That had the net effect of
extending arable regions to an altitude about 300 yards higher in the
mountains, he suggested, vastly extending the area that could be cultivated.
It also might have caused the Peruvian glaciers to melt slowly, providing
water that the Incas captured with large irrigation systems and agricultural
terraces.

The major evidence for the warming, Chepstow-Lusty said, was the appearance
of alder-like trees that hadn't been seen in the region before, as well as
increased insect activity. The trees, which normally grow in warmer
climates, grow well in poor soil and fertilize it by converting nitrogen
from the atmosphere into a usable form.

The increased cultivation would have led to large surpluses of maize and
potatoes, the researchers speculated, freeing the Incas to undertake other
activities, including building monuments and roads and creating a large
standing army that allowed them to conquer nearby peoples.

By the time the Spanish arrived in 1533, the Incas controlled an area that
stretched from what is now the Colombian border with Ecuador to the middle
of Chile, with more than 8 million inhabitants. When the Spanish arrived,
they noted that the Incas had enough food in warehouses to last for 10
years.

The Incan empire ended after the arrival of the Spanish, who inadvertently
brought diseases that devastated the population, allowing the invaders to
conquer the survivors and push them to the highest altitudes, where they are
still marginalized economically.

The story has a powerful moral for today, Chepstow-Lusty said. Peru is one
of the countries most threatened by global warming, and the glaciers that
provide much of the water for the capital, Lima, are rapidly melting and are
expected to be gone in 20 years. The terraces that previously trapped water
for agriculture have fallen into disuse, and the predominant tree in the
region is the eucalyptus, which saps what water remains in the soil and
deposits resins that poison other plant life.

Chepstow-Lusty called for removal of the eucalyptus tree and a massive
reforestation effort with alder or similar trees to replenish the soil, as
well as repair of the derelict irrigation systems so they can once more
support agriculture.

But Church, who also works in Peru, cautioned that without more research,
such an approach could be "premature and risky."