The Little Ice Age and Other Unintended Consequences of the Conquest of the Americas

I recently read Charles C. Mann's 1493: Uncovering the New World Columbus Created, which I highly recommend. It's the best kind of popular history, full of amazingly interesting, perspective-altering stories, and I hope to blog more about it, if time permits. (Samurai in Mexico city in the sixteenth century to guard the silver coming from Potosi: somebody should make a movie about that). One of the points that Mann makes both in 1493 and in his earlier (and also excellent, in fact better) 1491 is that the "conquest" of the Americas by Europeans (and in particular, Spaniards) was ultimately made possible by the fact that the Europeans brought more lethal microbes with them. It wasn't metal, or guns, or horses, or political organization, that made the crucial difference, but smallpox (and to a lesser extent malaria and yellow fever); without these invisible armies, Cortes and Pizarro would never have won the kinds of astonishingly quick victories they achieved against the Mexica and the Inca. (In fact, Cortes almost lost, even with his microbial allies).

Smallpox was so lethal in the Americas that in places more than a third of the native population was quickly (very quickly!) wiped out, leaving in its wake collapsed political and social structures; and smallpox usually raced ahead of the Spanish and other Europeans, like an enormously powerful advance force. And after smallpox, malaria and yellow fever usually moved in, especially in wet and hot areas like the Amazon basin, making life difficult both for any natives that survived smallpox and for the Europeans themselves, with important political consequences. For one thing, in places where malaria became endemic, Europeans were often unable to settle in any great numbers, but they were able to create "extractive" institutions using malaria-resistant slave labor forces imported from West Africa; and the consequences of such extractive institutions have been enormously far-reaching and long-lasting.

There is something inhuman about this idea: the conquest of the Americas, with all its enormous injustices, is ultimately reduced to a biological event, driven by forces none of its human protagonists could understand, let alone control. But it gets worse (or more interesting, depending on your perspective). Most native peoples in the Americas, lacking iron tools, practised forms of agriculture that made much use of fire. These were not "primitive" forms of agriculture, but complex land-management practices that made possible great population densities, even in places that are today only lightly inhabited (like the Amazon). Low-level burning kept grasslands from turning into forests, helped create forests that looked to Europeans like great parks, and produced charcoal that was used to make thin soils fertile through terra preta. And these practices effectively kept enormous amounts of carbon dioxide constantly in the atmosphere rather than locked into trees and other vegetation. When  native populations collapsed, however, the burning stopped or was greatly reduced, and the carbon dioxide was quickly locked up into forests again. Now, what follows is quite controversial. Mann cites some recent research that argues that this must have made a big contribution to the so-called Little Ice Age: the sudden drop in carbon dioxide in the atmosphere, perhaps in combination with natural variations in solar radiation, generated global cooling from around 1550 to around 1660. And this global cooling in turn appears to have produced a great "general crisis" in Europe: famine, war, and pestilence. I quote from a recent piece in Ars Technica summarizing recent research by Zhang et al:

The General Crisis of the 17th Century in Europe was marked by widespread economic distress, social unrest, and population decline. A significant cause of mankind’s woes during these times was the climate-induced shrinkage of agricultural production. Bioproductivity, agricultural production, and food supply per capita all showed immediate responses to changes in temperature. In the five to 30 years following these changes, there were also responses in terms of social disturbance, war, migration, nutritional status, epidemics, and famine. 

Cooling during the Cold Phase (1560-1660 AD) reduced crop yields by shortening the growing season and shrinking the cultivated land area. Although agricultural production decreased or became stagnant in a cold climate, population size still grew, leading to an increase in grain price and an increased demand on food supplies. Inflating grain prices led to hardships for many, and triggered social problems and conflicts such as rebellions, revolutions, and political reforms. 

Many of these disturbances led to armed conflicts, and the number of wars increased 41 percent during the Cold Phase. During the latter portion of the Cold Phase, the number of wars decreased, but the wars lasted longer and were far more lethal—most notable was the Thirty Years War (1618-1648), where fatalities were more than 12 times of the conflicts between 1500-1619.

Famine became more frequent too. Nutrition deteriorated, and the average height of Europeans shrunk 2cm by the late 16th century. As temperatures began to rise again after 1650, so did the average height.

The economic chaos, famine, and war led people to emigrate, and Europe saw peak migration overlapping the time of peak social disturbance. This widespread migration, in conjunction with declining health caused by poor nutrition, facilitated the spread of epidemics, and the number of plagues peaked during 1550-1670, reaching the highest level during the study period. As a result of war fatalities and famine, the annual population growth rate dropped dramatically, eventually leading to population collapse.

I am tempted to make a bad joke about "Montezuma's revenge," except that would be in terribly bad taste.  More seriously, perhaps, I wonder about what the complexity of natural and social systems implies for political theory.Given that none of the forces that were set in motion by the arrival of European colonists in the Americas the late 15th century were understood or even controllable if they had been understood (in fact, even today we do not understand them very well), how should we think about what they did, and about  the kinds of political systems they could or should have created? And should these sorts of stories matter for thinking about the ways in which we may be unleashing similar forces today?

More on this later - Mann has another story, about the silver trade and the collapse of the Qing dinasty, that is also quite instructive for these purposes.