mexico

food_energy.tex

@@ -88,12 +88,12 @@ height &\approx&  1000 m
 \eea
 This estimate is again surprising to students.  Five trips up the bluff to burn off $\$2$ of saturated fat, sugar, and flour!  A nice followup calculation is to imagine a car that can burn a $100kcal$ piece of toast in the engine: from rest, what speed will the toast propel it to? If (again) the engine converts $1/3$ of the energy into motion (kinetic energy), a 1300kg Honda Civic will reach a speed of about $13\frac{m}{s}\approx33mph$!  
 
-The point of these energy conversion calculations is not to give students an eating disorder.  Rather, the numbers show food's amazing power. A single slice of toast will bring a car up to the residential speed limit!  A day's food, $3000kcal$, will power you up an $8000m$ mountain peak! The body-work food allows us to do is astonishing, and increases in food production have made modern  comforts, unimaginable 150 years ago, possible to the point of being taken for granted.  
+The point of these energy calculations is not to give students an eating disorder.  Rather, the numbers show food's amazing power. A single slice of toast will bring a car up to the residential speed limit!  A day's food, $3000kcal$, will power you up an $8000m$ mountain peak! The body-work food allows us to do is astonishing, and increases in food production have made modern  comforts, unimaginable 150 years ago, possible to the point of being taken for granted.  
 
 \subsection{Where does food energy come from?}
 One feature of the aught's ``homesteading'' culture \cite{homesteading} is the idea that a person should probably be able to move to the country, eat a lot of peaches, and grow all their own food.  Learning that farming labor is \textit{skilled} labor can be a brutal and disheartening realization. Eating $3000kcals$ each day means planting, weeding, harvesting, and storing more than a million kcals each year \cite{Haspel}.  Where will those Calories come from? Is your backyard enough to homestead in the suburbs \cite{backyard_homestead}?
 
-At some point bewteen 1920 and 1950, US chemical manufacturers realized that in the post-war period, they could repurpose processes developed for manufacturing munitions and chemical warfare agents to produce chemicals that would kill insects and increase the nitrogen levels in the soil. 
+At some point bewteen 1920 and 1950, US chemical manufacturers realized that in the post-war period, they could repurpose processes developed for manufacturing munitions and chemical warfare agents, to produce chemicals that would kill insects and increase the nitrogen levels in the soil. 
 As figures \ref{corn_and_potato_yields} and \ref{ag_yields} show, the epoch of ``Better Living Through Chemistry'' produced a dramatic increase in per-acre yields across all comodity food crops, particularly corn and potatoes.  
 
 \begin{figure}[ht!]
@@ -118,7 +118,7 @@ It would be interesting to know if there are patterns of scaling among vegetable
 \label{ag_yields}
 \end{figure}
 
-However, if you're discussing backyard Calorie production it isn't reasonable to use modern yield estimates for planning.  ``Roundup Ready'' Corn, Soybean, and Sugar Beet seeds are not available to the public, nobody wants to put on a respirator to apply Atrazine ten feet from the back door,  and the edge effects from deer and insects are much smaller on a $600$ acre field than they are in an community garden allotment.  As mentioned in the introduction, in 1917 the USDA published a pamphlet \cite{USDA_1917_yields_pamphlet} giving detailed Calorie estimates of farmer might expect from a given acre of crop.  A table from this pamphlet is shown in Figure \ref{1917_yields}.  
+However, if you're discussing backyard Calorie production it isn't reasonable to use modern yield estimates for planning.  ``Roundup Ready'' Corn, Soybean, and Sugar Beet seeds are not available to the public, nobody wants to put on a respirator to apply Atrazine ten feet from the back door,  and the edge effects from deer and insects are much smaller on a $600$ acre field than they are in an community garden allotment.  As mentioned in the introduction, in 1917 the USDA published a pamphlet \cite{USDA_1917_yields_pamphlet} giving detailed Calorie estimates a farmer might expect from a given acre of a crop.  A table from this pamphlet is shown in Figure \ref{1917_yields}.  
 The pamphlet data came from pre-war, pre-chemical agriculture, and the yields cited were produced with horses, manure, lime, and large families full of children.  If you want to be self sufficient, these yield numbers are probably a good upper bound on what's realistically possible by a dedicated luddite.  
 
 \begin{figure}[ht!]
@@ -132,29 +132,28 @@ A table from a USDA booklet giving 1917 yields for various farm products.
 \label{1917_yields}
 \end{figure}
 
-So, another question using this data.  If you want to feed your family of 4 potatoes, how much land will you need to cultivate?
+So, another question using this data.  If you want to feed your family of four people potatoes, how much land will you need to cultivate?
 Here's an estimate: a family of 4 requires 3000kcal/person each day.  If we over-estimate and produce food for the entire year, the family will need about $4.4$ million kcals.
 \be
 4~people\cdot\frac{3000kcal}{person\cdot day}\cdot\frac{365~days}{year} \approx 4.4 M kcal 
 \ee
-A brief aside for those bored by the simplistic unit conversion: when I ask students to solve problems like these, one undercurrent of conversation is ``Should I divide by 365 or multiply?''  Particularly with online homework systems, checking your answer for reasonability isn't  typically graded. Asking the students to reason proportionlly with units is a skill that gives meaning to the numbers. 
+A brief aside for those bored by the simplistic unit conversion: when I ask students to solve problems like these, one undercurrent of conversation is ``Should I divide by 365 or multiply?''  Particularly with online homework systems, checking your answer for reasonability isn't  typically graded. Asking the students to reason proportionaly with units is a skill that can give meaning to numbers. 
 
-From figure \ref{1917_yields} we can estimate 1.9 million kcals per acre of production.  Again the students might ask, should I multiple 4.4 and 1.9 or should I divide them.  It can be useful in a class discussion to have the students discuss and vote which of the following two forms will give the meaningful answer.
+From figure \ref{1917_yields} we can estimate 1.9 million kcals per acre of potato production.  Again the students might ask, should I multiple 4.4 and 1.9 or should I divide them.  It can be useful in a class discussion to have the students discuss and vote which of the following two forms will give the meaningful answer.
 \bea
 \frac{4.4 M kcal}{family}\cdot\frac{1 acre}{1.9M kcal}  & \textrm{~~or~~}&
 \frac{4.4 M kcal}{family}\cdot\frac{1.9M kcal}{1 acre}
 \eea
-This choice of operation is difficult to make without seeing the units present, which is again a learning opportunity for the students.
+The choice of operation is difficult to make without seeing the units present, which is again a learning opportunity for the students.
 
-What does the answer of $2.3$ acres mean?  The university's $91m\times49m$ football field has an area of about $1.1$ acres, so you could say that a football field of potato plants will probably feed a family through the winter.  Can a person enjoy the benefits of urban living and grow all their own food?  The population density of New Jersey is $1,263~people/mile^2 \approx1.97~people/acre$ and our 4 person family needs 2.3 acres for their potatoes.  
-BAD WRITING and REASONING.
-Unless the social model is one of a country Dacha or an endless suburb with no duplexes, urban living and food self-sufficiency seem mutually exclusive.
+What does the answer of $2.3$ acres mean?  The university's $91m\times49m$ football field has an area of about $1.1$ acres, so you could say that a football field planted in potatoes will probably feed a family through the winter.  Can a person enjoy the benefits of urban living and grow all their own food?  The population density of New Jersey is $1,263~people/mile^2 \approx1.97~people/acre$ and our 4 person family needs 2.3 acres for their potatoes.  
+Unless the social model is one of a country Dacha or an endless suburb with no duplexes or apartment buildings, urban living and food self-sufficiency seem mutually exclusive.
 
 % This is interesting, but probably a weak argument because organic yields can be as high as ~ 140bu/acre BUT must be grown in a 3 or 4 year rotation vs corn's 2-year rotation.
 %
 % https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjswtTZo8X8AhXkjokEHW-yD74QFnoECA8QAQ&url=http%3A%2F%2Fextension.agron.iastate.edu%2Forganicag%2Fresearchreports%2Fn-kltar98.pdf&usg=AOvVaw2mLZB25pv44LX_EBAR5kXU&cshid=1673638241316994
 %
-Related, and more emotionally charged conversations can be had about converting the United States to all organic agriculture, which typicaly has yields closer to the 1917 model.  At $180bu/acre$ you need 22 million acres (half of Wisconsin, or all of Indiana) to feed 350 million people corn for a year.  The remainder of the corn belt can be devoted to animal food, ethanol and export.  If all of this area were devoted to producing organic corn at lower yield, cheap grocery store meat and ethanol vehicle fuel would likely disappear.   
+More emotionally charged conversations can be had about converting the United States to all organic agriculture, which typicaly has a yield penalty of about $20-40bu/acre$ when compared to conventional production.  The 1917 data isn't directly applicable, but it relates. At $180bu/acre$ conventional corn requires 22 million acres (half of Wisconsin, or all of Indiana) to feed the US population (350 million people) corn for a year.  The remainder of the corn belt can be devoted to animal feed, ethanol, and export.  If the corn belt was devoted to producing organic corn at lower yield \cite{organic_corn_yield}, we probably wouldn't starve, but cheap meat and ethanol vehicle fuel would likely disappear.   
 %WI 42M acres
 %IN 23M acres
 %
@@ -165,7 +164,10 @@ Related, and more emotionally charged conversations can be had about converting
 % 113M acres / 5.1 ~= 22M acres
 
 \section{Example: How big could Tenochtitlan have been?}
+The questions described thus far have largely been centered within a physics context.  The paper closes with two more examples that leverage this food energy picture to make historical claims.  The first example relates to the pre-columbian capital of the Aztec Empire, Tenochtitlan, now known as Mexico City.  Tenochtitlan was build on and around a endorheic lake, Texcoco.  Crops were grown in shallow parts of the lake via chinampas, foating patches of decaying patches of vegetation and soil.  Given proximity to water and decaying vegetation these fields were very fertile and productive.  
 
+Estimates of Tenochtitlan's population in 1500CE vary widely, from 40,000 \cite{40k} to more than 400,000 \cite{400k}inhabitants. These estimates are made from oral and written records and estimates of archeological building density and land area.  
+was    
 If Tenoch was 100k people, how much land area?
 
 \section{Example: Was the Irish Potato Famine a Natural Disaster?}
@@ -329,6 +331,27 @@ American Scientist
 vol 63
 413-419
 
+\bibitem{organic_corn_yield}
+This is an old article 
+1998
+\url{http://extension.agron.iastate.edu/organicag/researchreports/n-kltar98.pdf}
+Comparison of Organic and Conventional Corn, 
+Soybean, Alfalfa, Oats, And Rye Crops at the Neely Kinyon Long-Term Agroecological Research (LTAR) 
+Site-1998 
+Dr. Kathleen Delate, assistant professor, Depts. of Horticulture \& Agronomy 
+Dr. Cynthia Cambardella, soil scientist, USDA National Soil Tilth Lab 
+Bob Burcham, farm superintendent, Neely-Kinyon Research and Demonstration Farm
+
+\bibitem{40k}
+Susan Toby Evans. 
+2013. 
+Ancient Mexico and Central America: Archaeology and Culture History. 
+Thames \& Hudson, London and New York
+page 549
+
+\bibitem{400k}
+\url{https://www.britannica.com/place/Tenochtitlan}
+
 \bibitem{Aztec_Cannibalism} 
 Aztec Cannibalism: An Ecological Necessity?
 Bernard R. Ortiz de Montellano