edits

food_energy.tex

@@ -121,44 +121,51 @@ It would be interesting to know if there are patterns of scaling among vegetable
 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}.  
 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.  
 
-So, another question using this data.  If you want to feed your family of 4 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
-\frac{4~people}{year}\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 I hear is ``Should I divide by 365 or multiply?''  Particularly with online homework systems, checking your answer for reasonability isn't typically graded, and asking the students to reason and convert proportionally, with units is a skill worth emphasizing. 
-
-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.
-\bea
-\frac{4.4 M kcal}{family}\cdot\frac{1 acre}{1.9M kcal}\\
-\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.
-
-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 potatoes will probably feed a family through the winter.  
-
 \begin{figure}[ht!]
 \centering
 \includegraphics[width=\columnwidth]{USDA_1917_cropped.pdf}
 \caption{
-A table from a USDA published booklet giving 1917 yields for various farm products.  The amounts listed were almost certainly produced via only animal and human power with only manure and lime available as chemical soil amendments.  Accordingly, they are probably a reasonable upper bound on what's possible in a modern ``back to the land'' backyard garden.
+A table from a USDA booklet giving 1917 yields for various farm products.  
 }
+%The amounts listed were almost certainly produced via only animal and human power with only manure and lime available as chemical soil amendments.  Accordingly, they are probably a reasonable upper bound on what's possible in a modern ``back to the land'' backyard garden. }
+
 \label{1917_yields}
 \end{figure}
 
-1917 data
+So, another question using this data.  If you want to feed your family of 4 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. 
 
-Grow your own food, possible?  
+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.
+\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.
 
-Grow your own food, how far apart (urban life?)
+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.
 
+% 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.   
+%WI 42M acres
+%IN 23M acres
+%
+%1917: 35 bu/acre
+% 350M ppl*1M kcal / (3.1Mkcal/acre) = 113M acres
+% 2022
+% 180bu/acre / 35bu/acre = 5.1x (less)
+% 113M acres / 5.1 ~= 22M acres
 
 \section{Example: How big could Tenochtitlan have been?}
 
-1917 (A\&M) USDA pamphlet
-
-Corn for US - area
-
 If Tenoch was 100k people, how much land area?
 
 \section{Example: Was the Irish Potato Famine a Natural Disaster?}
@@ -168,7 +175,7 @@ If Tenoch was 100k people, how much land area?
 
 %\begin{acknowledgments}
 \ack
-The work was prompted in part by discussions with John Deming, Carl Ferkinhoff, and Sarah Taber.
+The work was influenced by discussions with John Deming, Carl Ferkinhoff, and Sarah Taber.
 %\end{acknowledgments}
 
 %The command \appendix is used to signify the start of the appendices. Thereafter
@@ -297,6 +304,16 @@ The Backyard Homestead: Produce all the food you need on just a quarter acre!
 Carleen Madigan
 Storey Publishing, LLC; 14th Printing edition (February 11, 2009)
 
+
+\bibitem{USDA_1917_yields_pamphlet}
+Human Food from an Acre of Staple Farm Products
+Morton O. Cooper and W.J. Spillman
+Farmers' Bulletin 877
+United States Department of Agriculturey
+October 1917
+Government Printing Office
+
+
 \bibitem{math_encounters}
 https://www.mathscinotes.com/2017/01/calorie-per-acre-improvements-in-staple-crops-over-time/
 Mark Biegert 
@@ -312,9 +329,12 @@ American Scientist
 vol 63
 413-419
 
-\bibitem{Aztec_Cannibalism} for crop productivity
+\bibitem{Aztec_Cannibalism} 
-
+Aztec Cannibalism: An Ecological Necessity?
-\bibitem{USDA_1917_yields_pamphlet}
+Bernard R. Ortiz de Montellano
+Science, May 12, 1978, New Series, Vol. 200, No. 4342 (May 12, 1978), pp. 611-617
+American Association for the Advancement of Science
+https://www.jstor.org/stable/1746929
 
 \end{thebibliography}
 \end{document}