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@ -182,7 +182,7 @@ Estimates of Tenochtitlan's population in 1500CE vary widely, from 40,000 \cite{
Few if any Native American cultures made use of draft animals for food or power before the Colombian Exchange. This means that the food that fed Tenochtitlan must have been brought to the city center by foot or canoe. How much land must have been devoted to chinampas to feed the population, or conversely, how many people could be supported by the land within walking or paddling distance from the city center?
A 1964 paper in Scientific American \cite{Chinampas_1964} gives a general outline of the chinampas in the area of Tenochtitlan in 1500CE. This map seems to be the basis for the similar figure in Wikipedia \cite{chinampas_wikipedia}. Descriptions of chinampas agriculture indicate that as many as $7$ successive crops could be grown and harvested from the same plot of soil each year, two of which could be maize (corn). This is truly amazing productivity, given that in the midwest United States corn is normally grown, at most, every other year because of it's extreme nutrient demands on the soil.
A 1964 paper in Scientific American \cite{Chinampas_1964} gives a general outline of the chinampas in the area of Tenochtitlan in 1500CE. This map seems to be the basis for the similar figure in Wikipedia \cite{chinampas_wikipedia}. Descriptions of chinampas agriculture indicate that as many as $7$ successive crops could be grown and harvested from the same plot of soil each year, two of which could be maize (corn). This is truly amazing productivity, given that in the midwest United States corn is normally grown, at most, every other year because of its extreme nutrient demands on the soil.
There are many ways to approach this estimation problem. We could assume a Tenochtitlan population of $100,000$ people has a $3000kcal/day$ diet that comes completely from corn. Assuming that corn's density and nutritional content haven't changed in the $4$ centuries preceding the 1917 data in figure \ref{1917_yields}, we could assume $1lbs$ of corn contains $\approx1594kcal$ of food energy.
Looking at the map with ImageJ \cite{imageJ}, it seems like the recorded area devoted to chinampas might be about
@ -194,7 +194,7 @@ Population~requires &=& 100,000~people\cdot \frac{3000kcal}{person\cdot day}\cdo
P \approx 38\frac{bu}{acre} &&
\eea
This crop productivity is in remarkable agreement with the 1917 USDA yields, $35bu/acre$, which seems to validate the assumed $100,000$ person population of Tenochtitlan. Some references \cite{Chinampas_1964} describe an extensive tribute system that Aztec government required of it's subjects, which certainly would have been necessary to support populations on the upper end of historical estimates \cite{400k}.
This crop productivity is in remarkable agreement with the 1917 USDA yields, $35bu/acre$, which seems to validate the assumed $100,000$ person population of Tenochtitlan. Some references \cite{Chinampas_1964} describe an extensive tribute system that Aztec government required of its subjects, which certainly would have been necessary to support populations on the upper end of historical estimates \cite{400k}.
@ -242,7 +242,7 @@ Like the Holodomor or the Great Leap Forward, the numbers suggest that large-sca
\centering
\includegraphics[width=\columnwidth]{Population_of_Ireland_since_1600.png}
\caption{
The population of Ireland over time, file from Wikipedia \cite{pop_image}, data sources \cite{pop_sources}. The humble potato, kale, and milk were part of an amazing population boom. Note that there were two weather-related ``potato'' famines in Ireland, in about 1740 and 1850. government policy response to the famines could explain the drastic difference in subsequent population following each of the two famines. The population of Ireland finally re-reached it's 1851 peak in 2021 \cite{Ireland_5M}.
The population of Ireland over time, file from Wikipedia \cite{pop_image}, data sources \cite{pop_sources}. The humble potato, kale, and milk were part of an amazing population boom. Note that there were two weather-related ``potato'' famines in Ireland, in about 1740 and 1850. government policy response to the famines could explain the drastic difference in subsequent population following each of the two famines. The population of Ireland finally re-reached its 1851 peak in 2021 \cite{Ireland_5M}.
}
\label{ireland_population}
\end{figure}
@ -251,7 +251,7 @@ The population of Ireland over time, file from Wikipedia \cite{pop_image}, data
\section{Conclusion}
A class about Energy and Social Policy and the author hasn't mentioned climate change, coal, or solar panels even once! What is he thinking?
How many tons of carbon does your car release in a year? How many shiploads of iron oxide will we have to dump into the ocean for phytoplankton to eat up the equivalent about of carbon? Every question in a class like this is, to at least some extent, informed by numerical calculation and it's pretty arrogant to assume that ``those students'' don't need to (or can't) do the math. If you're going to have success talking about numerical calculations, you might as well start with examples that everyone can relate to, and everyone eats! Along the way you might find fascinating historical questions to investigate.
How many tons of carbon does your car release in a year? How many shiploads of iron oxide will we have to dump into the ocean for phytoplankton to eat up the equivalent about of carbon? Every question in a class like this is, to at least some extent, informed by numerical calculation and it is pretty arrogant to assume that ``those students'' don't need to (or can't) do the math. If you're going to have success talking about numerical calculations, you might as well start with examples that everyone can relate to, and everyone eats! Along the way you might find fascinating historical questions to investigate.
\ack
@ -270,7 +270,7 @@ The United States Department of Agriculture (USDA) provides historical crop info
\cite{USDA_NASS} .
Data was downloaded in spreadsheet csv format and then combined and plotted via a Python Jupyter notebook.
Each crop has its own bespoke units, for example potatoes are sold by hundredweight (CWT) but sugar beets are measured by the ton.
Each crop has its own custom units, for example potatoes are sold by hundredweight (CWT) but sugar beets are measured by the ton.
Every imaginable agricultural product seems to be tracked in the NASS site, for example Maple Syrup production is tracked and given in gallons of syrup per tap!
Conversion factors used are summarized in Table \ref{conversions}.
Calorie (kcal) density for each crop was taken from the USDA's Food Data Central
@ -313,7 +313,7 @@ Raw data from the USDA NASS is plotted in figure \ref{raw_production_per_acre}.
\centering
\includegraphics[width=\columnwidth]{raw_production_per_acre.pdf}
\caption{
Average USDA per acre yields for a number of commodity crops over time. This ``raw'' data (in bespoke harvest units) was scaled to produce the data in figure \ref{ag_yields} earlier in the paper.
Average USDA per acre yields for a number of commodity crops over time. This ``raw'' data (in custom harvest units) was scaled to produce the data in figure \ref{ag_yields} earlier in the paper.
}
\label{raw_production_per_acre}
\end{figure}
@ -371,7 +371,7 @@ Encyclopedia of Food Sciences and Nutrition. 2nd ed.
% (Second Edition),
Academic Press;
2003.
p. 5762-7.
pp. 5762-7.
%ISBN 9780122270550,
%https://doi.org/10.1016/B0-12-227055-X/01188-3.
%(https://www.sciencedirect.com/science/article/pii/B012227055X011883)