How warming earth increased Inca prosperity

Times:

Supreme military organisation and a flair for agricultural invention are traditionally credited for the rise of the Incas. However, their success may have owed more to a spell of good weather — a spell that lasted for more than 400 years.

According to new research, an increase in temperature of several degrees between AD1100 and 1533 allowed vast areas of mountain land to be used for agriculture for the first time. This fuelled the territorial expansion of the Incas, which at its peak stretched from the modern Colombian border to the middle of Chile.

“Yes, they were highly organised, and they had a sophisticated hierarchical system, but it wouldn’t have counted a jot without being underpinned by the warming of the climate,” says Dr Alex Chepstow-Lusty, a palaeo-ecologist from the French Institute for Andean Studies in Lima, Peru.

As the treeline moved higher up the mountains, the Incas re-sculpted their landscape to maximise agricultural productivity. They carved terraces into the mountainsides and developed a complex system of canals to irrigate the land.

Although the climate remained dry, the gradual melting of glacial ice meant that they had a constant supply of water to nourish their crops.

The resultant surplus of maize and potatoes freed a large part of the growing population for activities outside food production, such as constructing roads and buildings, and serving in an increasingly ambitious army.

“It was the perfect incubator for the expansion of a civilisation,” says Dr Chepstow-Lusty, who led the study.

The Incas’ Royal Road, which went through the highlands for a distance of 3,250 miles, and the Coastal Road, which stretched for 2,520 miles, were both constructed during the warm spell. So, too, was Machu Picchu, “the Lost City of the Incas”, where temples, sanctuaries and houses stand remarkably intact today, demonstrating the scale and the skill of Inca architecture.

By the time the Spanish colonials arrived in 1533, the Incas had built up food supplies to last the population more than ten years.

However, internal divisions, the Spanish invasion and the consequent introduction of new diseases led to the Inca population plummeting.

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And to think they probably attributed this prosperity to human sacrifice. In someways the current globo warmers would like to sacrifice our prosperity for their own superstitions about a warming planet.