Posted by: Johan Normark | September 6, 2012

The Anthropocene and Precolumbian land use

In a short paper that I sent away for review a couple of weeks ago I used a quote from McAnany and Yoffee (p 8) that in hindsight seems wrong. I wrote that “the humanability to impact environment on a global scale is newfound and cannot be pushed back beyond the Industrial Revolution of the 1800s.” This refers to what some geologists call the Anthropocene, the geological time period when human activities affect global ecological processes. There is debate on how far back in time we can push this time period. McAnany and Yoffee clearly think it is around two centuries old. Others trace it back to the “Neolithic revolution”. I have no actual opinion about when it “began” but it seems to be older than two centuries. What made me think differently about this issue was an article by Dull and others (2010) that I read last week. I was looking for climate studies that focused on the Spanish contact period and this article suits my objectives like a hand in glove.

In this article it is stated that Precolumbian land use has been neglected in global greenhouse forcing. It is argued that aggregate carbon footprint of Neotropical farmers (the area between the Tropic of Cancer and the Tropic of Capricorn) was enough to raise global temperatures via greenhouse forcing long before the European encounter. However, the epidemics that spread around the Americas in the 16th and 17th centuries led to the abrupt abandonment of agricultural clearings. Human fire ignitions therefore decreased dramatically. The Little Ice Age cooling and its decrease in atmospheric CO2 followed the native population collapse (particularly in the Amazon). This thermal anomaly (-0.1 degrees C between 1550 and 1750) has earlier been attributed to solar-volcanic forcing. Climate skeptics have used such “natural” processes to argue against the claim that global warming today is caused by anthropogenic causes. What this study indicates is that the demographic collapse in the Americas either caused or at least intensified the global cooling. The supposedly “normal” temperature before this event was upheld by slash-and-burn farmers.

The more people burn the more fire prone the forest becomes. More burning leads to “more forest openings, more forest edges, drier fuel loads, higher wind speeds, and greater susceptibility to future flammability…Conversely, the absence of anthropogenic fire in most tropical biomes leads to rapid increases in woody biomass…and a “hardening” of the forest against future fire incursions” (Dull et al 2010:758). This is important to know when we study the earlier Maya collapse. With the disappearance of these forest clearings it began increasingly difficult to re-occupy the inland during the Postclassic period. This in combination with new trade routes kept the forest in the central and southern Maya lowlands more or less free from settlements (with the exception of the Itza and Kowoj states and refugees from the later Spanish empire). In fact, there were even less interest in clearing the forest during the Colonial period as the forest was a place for hideout.

McAnany, Patricia A. and Norman Yoffee (2010). “Why We Question Collapse and Study Human Resilience, Ecological Vulnerability, and the Aftermath of Empire.” In Questioning Collapse: Human Resilience, Ecological Vulnerability, and the Aftermath of Empire, edited by Patricia A. McAnany and Norman Yoffee, 1-17. Cambridge: Cambridge University Press.

Dull, Robert A. et al. (2010). “The Columbian encounter and the Little Ice Age: Abrupt land use change, fire, and greenhouse forcing.” Annals of the Association of American Geographers 100 (4):755-771.

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Responses

  1. On subjects like this one, I’m just an ignorant brainless layman, but what you’ve said here squares with something else that I read a while back:

    http://web.ku.edu/~hoopes/nature.html

    If this hypothesis about the “Little Ice Age” is correct, it ties some things together. I don’t “like” the hypothesis much, just as I don’t “like” what’s said in the link that I cite: I´d much prefer to believe that there have been pristine old-growth forests in Maya lands since time began, and that humankind didn’t affect the environment much until comparatively recently.

    But reality has a habit of not caring much about my preferences!

  2. There are too many “garden” trees in the contemporary “pristine forest”, i.e. trees used by the ancient Maya, for there to be an actual pristine forest. People have been living in the this area for millennia and it has affected the ecology.

    • Yes, that’s what I learned while helping my friend with the math of his pollen analyses. I’d had no idea of the extent to which the Maya had shaped the environment.

  3. Here’s a convenient link to the article by Professor Dull:

    http://westinstenv.org/wp-content/Annals_2010_Dull_et_al.pdf


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