The Incas and global warming – Opportunity knocks, again, in the Andes

By Nicholas Asheshov

The last time global warming came to the Andes it produced the Inca Empire.

A team of English and U.S. scientists has analysed pollen, seeds and isotopes in core samples taken from the deep mud of a small lake not far from Machu Picchu and their report says that “the success of the Inca was underpinned by a period of warming that lasted more than four centuries”.

The four centuries coincided directly with the rise of this startling, hyper-productive culture that at its zenith was bigger than the Ming Dynasty China and the Ottoman Empire – the two most powerful contemporaries of the Inca.

“This period of increased temperatures,” the scientists say, “allowed the Inca and their predecessors to expand, from AD 1150 onwards, their agricultural zones by moving up the mountains to build a massive system of terraces fed frequently by glacial water, as well as planting trees to reduce erosion and increase soil fertility.

“They re-created the landscape and produced the huge surpluses of maize, potatoes, quinua and other crops that freed a rapidly growing population to build roads, scores of palaces like Machu Picchu and in particular the development of a large standing army.”

No World Bank, no NGOs.

The new study is called “Putting the Rise of the Inca within a Climatic and Land Management Context” and was prepared by Alex Chepstow-Lusty, an English paleo-biologist working for the French Institute of Andean Studies, in Lima. Alex led a team that includes Brian Bauer, of the University of Illinois, one of today’s top Inca-ologists. The study is being published in Climate of the Past, an online academic journal.

Alex spends a lot of time in Cuzco and he told me the other day that the report “raises the question of whether today’s global warming may be for the Andes another opportunity”.

The core samples from the sediment of the little lake, Marcacocha, in the Patakancha valley above Ollantaytambo, show that there was a major cold drought in the southern Andes beginning in 880 AD lasting for a devastating century-plus through into 1000AD. This cold snap finished off both the Wari and the Tiahuanaco cultures which had between them dominated the southern Andes for more than a millennium.

It was at this same time that the Classic Maya disappeared in Yucatan. It was also a time, on the other side of the Pacific when major migrations from East Asia took place into Polynesia, an indication of a major Niño event; a Niño sees western Pacific currents switch to flow from West to East.

Core samples from glaciers and from the mud beneath lakes in the Andes, the Amazon and elsewhere have built up a history of the world’s climate and the message is crystal clear. It is that changes have taken place in the past, during the six or seven thousand years of our agriculture-based civilizations, that are just as big as the ones we are facing from today’s CO2 warming.

The message may be, too, that climate change is especially forceful in the Andes. Here we are, sandwiched thinly between the world’s biggest ocean and the world’s biggest jungle. The peaks are so high that they have had until just a few years ago deep ice on or near the Equator.

The valleys and surrounding hills have formed the roof of the human world for at least three millennia, according to Alex Chepstow-Lusty’s core samples. Nowhere else do millions of people live at or even near 4,000ms above sea level where it is cold, but getting warmer.

Today’s warming is also following on a colder spell that started, the core samples say, not long after the arrival of the Spaniards in the 16th century.

For instance, the pollen in the cores says that there was maize being grown under the Incas around the lake at 3,300m above sea level. Until recently the upper level for maize around the Urubamba valley was 3,000-3,100ms. In the past few years the maize level has moved up and today there is maize being grown again above Marcacocha.

Alex’s records show that hundreds of terraces were being built around the lake between 1100 and 1150 AD -“lots of mud followed by the heavy pollen of maize”.

Enrique Mayer, at Yale, tells me that “the question of the expansion of maize together with the Inca state is now a proven archeological fact, notably in the Mantaro Valley (Tim Earle).

“The question of why terraces are not worked now as intensively as they could has been worked on (Bill Devevan) in the Colca Valley where the terraces are actually in franco retroceso.

“Also, you have John Treacy’s book on Coporaque which is probably the most technically accessible to the argument that terraces are, like flower pots, expensive to maintain.”

There is also, of course, the work of John Earls on the terracing at Moray.

Today there are thousands upon thousands of fine flights of Inca terraces all over the upper ends of the valleys of Central and Southern Peru but few of them are used on a regular basis.

Efforts have been made, among them by Ann Kendall, the English archaeologist, to resuscitate the old irrigation channels and the use of the terraces in the valleys above Machu Picchu. But most have been re-abandoned.

In the same vein the great forests of polylepis, the world’s highest tree, which capture and conserve moisture, have mostly been cut down for firewood.

As they say, you only have to look in the mirror to see where the problem is. FIN

Published June 25 in Caretas Magazine

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