Global Warming May Have Helped Make the Incas Mighty

By Allison Bond | July 28, 2009 5:28 pm

Machu Picchu 2The ancient civilization known as the Incan empire, which at its peak reached a population of 8 million people spread throughout South America, may owe its success at least in part to a warming climate, according to a study in the journal Climate of the Past. A rise in temperatures would have melted glaciers and allowed crops to grow further into the Andes mountains, fostering agricultural growth.

The study found that between 1100 and 1533 AD, temperatures increased several degrees, making it possible for the Incas to use new mountain land for agriculture. It also expanded the swath of land the empire occupied which, at its peak, spanned from the middle of Chile to the border shared by Ecuador and Colombia. This climate information came from an analysis of deeply buried sediment samples in the region the Incans once occupied. The researchers examined pollen and seeds buried in layers of mud on the floor of Lake Marcacocha in the Cuzco region of the Peruvian Andes. Similar to the rings in the trunk of a tree, each layer of sediment represents a fixed period of time. In the case of Lake Marcacocha, the researchers were able to analyze a 1,200-year-old sediment record [Discovery News].

The scientists noted the appearance for the first time of a range of trees and crops at the lake, which is 11,000 ft above sea level, over the critical period, corresponding to a tree line edging upwards [Times Online]. The alder trees that researchers found evidence of would have prevented erosion and fertilized the soil, which would have made maize and potato cultivation more efficient. Researchers think the Incas took advantage of the more temperate climate on the mountain slopes by carving terraces into the mountainsides and develop[ing] a complex system of canals to irrigate the land [Times Online], as gradually melting glaciers provided a steady source of water for the crops. The scientists’ analysis also revealed evidence of a drought around 880 AD, which may have caused the collapse of Incas’ predecessors, an empire known as the Wari.

Today, global warming has an exaggerated effect on high-altitude plants and animals, such as the now-endangered pika, and plants that have relocated to higher altitudes in pursuit of a cooler climate. There have been other changes as well: Peru’s capital continues to get much of its water from glaciers, but they are predicted to dry up within the next two decades due to climate change. Additionally, 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. [Lead author Alex] 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 [Los Angeles Times]. Other experts, however, say these measures are too drastic to take before further research is done to confirm the study’s findings.

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Image: flickr / kudumomo

CATEGORIZED UNDER: Environment, Human Origins
  • Shaithis

    Interesting how Earths climate has changed over the eons of time. I believe that man’s influence over climate is way over hyped and there are several other factors involved that the green movement fails to mention. Probably because it would hurt their political agenda. Yet you can’t escape the truth, that the last few years do not appear to mirror the predictions of global warming. In fact they are the opposite. This is very damaging to the overall environmental cause. Because it shows that to a certain degree that skeptics are correct.

  • Marcus

    Skepticism is not welcome here, Shaitis. Al Gore is god and he will carbon cap trade us to a Glorious new kingdom on Earth.

    Clearly this article was written by an agent provocateur from Exxon, because obviously a few degrees higher temperatures will destroy all life on Earth. Think of where the world would be now if the glorious conquistadors had not taken away SUVs from the Incans.

  • Pasty Muncher

    There is an opportunity to get involved and add your voice to the current Oxfam campaign to help reduce global warming by adding support to Oxfam’s climate change campaign.

  • Roberta M. Soyars

    This article helps to confirm what I have been preaching (to mostly deaf ears) for the past two decades: (Roberta’s Law)

    “The only thing in the last 12,000 years, that could have been worse for Planet Earth than ‘global warming’, would have been lack of global warming!”

    How could the “human origins” guys have missed what really happened to the Neanderthals? They simply froze and starved to death, what could they eat besides each other?

    It’s a miracle that so-called “modern man” survived!

    Sure I’m all for a clean, poison-free environment. The real problem is pollution, that’s a separate, but allied issue.

    Roberta M. Soyars

  • Shaithis

    I agree with Roberta. I would like to add that I believe all the time and energy that goes into the “Stop Global Warming” machine could be better served with focusing on how we can be better stewards of the land and maintain it.

  • Alex F

    I agree with Roberta and Shaithis. We’re focusing on something too narrow with global warming. One, its going to happen regardless of what we do, the big UN study makes that clear enough. Two, it takes us away from the real issue and that is: we can survive global warming but we can’t survive pollution. If we keep pumping our bodies and our environment full of chemicals we simply won’t be around to worry about global warming. Where do you think modern illnessess come from. Its all the man-made toxins in our environment, it all finds its way straight back into our food supply and into us. I know, it’s happenned to me. I just hope we wise up to it, so it doesn’t happen to our kids and grandkids. By the way, the Inca’s probably killed themselves by polluting their water supply with mercury thanks to the gold they dug up. Climate change probably just forced them to relocate. Remember the Romans and the lead poisoning their water. Pollution is worse than global warming. Its way more nefarious.

  • Alex F

    Oh and still, I did enjoy the article.

  • Robert

    Not saying we as people are doing wonders but if you look at the cycles of temperature and climate through-out the geological history we’re stuck on a roller coaster and we’re not doing the harm that propagated. Most physicists will attest to the last mini-ice age 400 yrs ago, we’re still warming up, who knows what will happen in another 400?


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