I wasn't happy with the news in Part 3 of this series, which basically concluded that Mendocino County could not be food self-reliant.[i] To quote the most relevant and discouraging passage from that essay:

 

The Caltrans EIR implies that in about a ca. 20 year span, Mendocino County went from 69,000 to 35,000 acres of prime farmland, down from and original endowment of 94,000 acres. This does seem like a remarkably high rate of loss, totaling 34,000 acres or about 1700 acres per year for 20 years. In either case, whether the real figure is closer to 69,000 or 35,000, both are far from the estimated need of ca. 95,000.

 

However, I knew that this conclusion rested on certain assumptions, and that changing these might alter the conclusion. In the end we may be left having to decide which assumptions are more realistic, or whether what may be theoretically possible is probable given human nature/folly, or, if you are more inclined, human spirit/ingenuity.

 

So I went in search of better news (and the resulting dopamine reward this could potentially provide) by re-performed some calculations, starting with the diet. I will call the diet from part 1 of this series diet 1, and the one presented in this essay diet 2.[ii] Before creating diet 2, I wanted to be clearer on what the dietary needs and expectations are in North America. The USDA has a fascinating set of web pages. Included is a survey from the Agricultural Research Service of what several hundred people eat during a day, which can be extrapolated to the whole population (standard errors noted) and then broken out by demographic category.[iii] According to this data set, on average, people eat about 2200 calories per day. As expected, the very young and old eat the least, and females eat less than males. Another branch of the USDA, the Economic Research Service concludes that people consume closer to 2700 calories per day on average.[iv] Changes in American consumption patterns over time are also discussed in a report by the same sub-agency.[v] In general we are eating more calories than 30 years ago, but we are consistently wasting about 25% of the food produced.[vi]

 

New Diet Assumptions

 

For my second go at a model diet, I selected the 2200 calorie per day figure, and I assumed we could get by with half the food waste of today, which means a production system is required that produces about 2600 calories per person/day. By contrast, diet 1 used the figure about 3000 calories per day as a guide, which is still about 700 calories per day lower than what Americans have available to them from the current system. Diet 2 therefore has less calories available than diet 1, and far less than current U.S. diets, but is still enough food overall if food waste is half of current percentages.

 

Diet 2 is given below, and for comparison I give the current U.S. consumption patterns for the modeled foods. I have made a change in the fruit and vegetable category, where potatoes are segregated for analysis purposes. Significant differences between diet 2 and U.S. averages include much lower meat, sugar and egg consumption, and much higher dry bean consumption. To compare U.S. consumption of sprouting seeds (sunflower seeds in my model) I used data on nuts, which are nutritionally similar. In the U.S. this mostly means peanuts, but locally it could be walnuts and filberts/hazelnuts. I believe diet 2 is a much healthier diet than current U.S. habits.

 

Food	Pounds/year/ person	Current U.S. average	Oz/day/person (dry)	Oz/day/person (wet)	*Calories per pound	Calories/year/ person	Calories/day/ person
grains	230	200	10.08	30.25	1550	356,500	977
dry beans	50	2	2.19	6.58	1600	80,000	219
oil	40	65	1.75	1.75	4000	160,000	438
sugar	30	150	1.32	1.32	1380	41,400	113
sprouting seeds or nuts	20	17	0.88	2.63	2560	51,200	140
fruit and vegetables	650	570	28.49	28.49	150	97,500	267
potatoes	180	150	7.89	7.89	350	63,000	173
dairy (cheese)	30	37	1.32	1.32	1500	45,000	123
eggs	10	28	0.44	0.44	650	6,500	18
meat	50	180	2.19	2.19	925	46,250	127
Totals	1290		56.55	82.85		947,350	2595
			Wet lbs per day	5.18
*calorie figures from Jeavons, 7th edition and USDA (http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20a208.pdf)

 

Diet 2 also took into account the calories yielded per area for different food items. This is one reason why potatoes were given stand-alone status-they efficiently make human food. When grains are fed to animals, as in chickens and dairy cows, area efficiency is very low. Diet 2 therefore has fewer animal products than diet 1, and more veggies and potatoes. I limited potato consumption to 180 lbs per year because potatoes are typically edible for only 6-7 months at a time and eating more than one pound of potatoes per day would get tiresome. Even with the extra load from vegetables, fruits and potatoes, the total diet weight is still low, ca. 5.2 lbs, because the total calories are reduced and grains and dry beans still form the core of the plan.

 

New Inputs and Yield Assumptions

 

In addition to fiddling with the diet, I made a giant change when modeling the land-area required for the diet-I assumed no limits to irrigation, which essentially doubles the yields of grains and dry beans.[vii] Remember also that sugar is modeled as honey and, perhaps optimistically, is given no direct land area requirement.

 

So what's in going to be? Will eating lower on the food chain plus more intensive inputs change the results? Are we gonna make it? Drum roll.....

 

First, we look at the acres per person for diet 2:

 

Food	Pounds/year/ person	Yields/lbs/acre/ year	Acres/crop/ person	As percentage	*Calories per pound	Calories per acre	Class of farmland required
grains	230	2,000	0.12	0.38	1550	3,100,000	I or II
dry beans	50	1,800	0.03	0.09	1600	2,880,000	I or II
oil	40	835	0.05	0.16	4000	3,340,000	I, II or III
sugar	30				1380
sprouting seeds	20	900	0.02	0.07	2560	2,304,000	I or II
fruit and vegetables	650	20,000	0.03	0.11	150	3,000,000	I or II
potatoes	180	20,000	0.01	0.03	350	7,000,000
dairy (cheese)	30	1,249	0.02	0.08	1500	1,873,500	I or II
eggs	10	440	0.02	0.08	650	286,000	I, II or III
meat	50	6	8.33		925	5,550	I, II, III or greater
		Total acres/person	8.63
		Total acres minus meat	0.30

 

Not bad! The "acres minus meat" for diet 1 was 0.76 per person. Next, multiply by population size:

 

Food	Acres/crop/ person	Acres for County Population	Irrigated?
grains	0.12	10,139	yes
dry beans	0.03	2,449	yes
oil	0.05	4,223	yes
sugar	0.00	0
sprouting seeds	0.02	1,959	yes
fruit and vegetables	0.03	2,865	yes
potatoes	0.01	793	yes
dairy (cheese)	0.02	2,118	yes
eggs	0.02	2,004	yes
meat	8.33	734,675	Acres of Non-prime farmland
Total acres/person	8.63	761,225	Acres Total
Total acres minus meat	0.30	26,550	Acres minus meat = Prime farmland

 

If you read previous essays you may recall that meat is assumed to be produced on subprime farmland plus prime farmland in a green manure rotation. This brings up the need to account for crop rotations and green manure, thus:

 

Crops needing prime farmland and rotation with green manures (fruit and vegetable area given as 2/3 toward vegetables)
Food	Acres/crop/ person	Acres for County Population	*Green manure factor	Actual Acres	**N lbs/acre/ yr	**P lbs/acre/ yr	**K lbs/acre/ yr
grains	0.12	10,139	1.50	15,208	50	8.8	24.3
sprouting seeds	0.02	1,959	1.80	3,526	80	8.8	48.6
vegetables	0.02	1,920	2.00	3,839	100	13.2	64.8
potatoes	0.01	793	1.70	1,349	70	13.2	97.2
dairy (cheese)	0.02	2,118	1.50	3,176	50	8.8	24.3
eggs	0.02	2,004	1.50	3,005	50	8.8	24.3
		18,932		30,104
*Irrigated clover can fix nitrogen at a rate of about 100 lbs/acre for a year's growth and is appropriate for Mendocino County climate
**Estimates from Appendix II of "Successful Small-Scale Farming: An Organic Approach" by Karl Schwenke, referencing the "Missouri Balanced Farming Handbook
**P and K are often reported in compound forms such as phosphoric acid and potash. I am calculating elemental mass only: P is about 44% of phosphoric acid, K is about 81% of potash.

 

And finally, adding rotation-demanding to non-rotation demanding areas gives:

 

Prime land required
Area needing rotation	30,104
Area not needing rotation	7,618
Total	37,722

 

So the number here, ca. 38,000 acres, compares favorably to the amount of prime farmland currently remaining according to the Caltrans EIR.

 

Rwanda

Before getting too pleased with the results, I want to put them into perspective. Let's assume for the moment that Mendocino County does have 38,000 acres of prime farmland left, which equates to 0.43 acres per person, or in metric terms 0.17 hectares. The arable cropland per capita in Mendocino County is currently slightly less than what Rwanda had during the genocide period (0.20 hectares).[viii] Scholars have suggested that the tensions that eventually led to the bloodshed came from the fact that the land base was barely able to provide enough for the population, and that few subsistence farmers had the cash to buy imported food.

 

I am not predicting that the same kind of events would unfold in Mendocino County under similar circumstances. The point is that when populations are up against their resource capacity it is normal for stress to build, which increases the probability of violence.

 

Fertilizer Impact

Because irrigation is now assumed, the yields of the grains and dry beans, and by extension the dairy and eggs, increase substantially. Crops remove nutrients from the land in proportion to their yield; therefore quantities of fertilizer are increased per unit area. Three factors offset increased fertilizer demand per area: (1) green manure crops are also irrigated and increase in yields at the same proportion as the crops they support, (2) increased yields means a decrease in total area required to support the population, and (3) diet 2 is smaller than diet 1, with fewer animal products.

 

My estimations are very crude right now, but the overall impact is that much less fertilizer is required for the diet 2 plus irrigation model than with diet 1 and no irrigation.

 

Fertilizer Requirements per capita
Food	Acres/crop/ person	**N lbs/acre/ yr	N lbs per capita	**P lbs/acre/yr	P lbs per capita	**K lbs/acre/yr	K lbs per capita
grains	0.12	50	5.75	8.8	1.01	24.3	2.79
sprouting seeds	0.02	80	1.78	8.8	0.20	48.6	1.08
vegetables	0.02	100	2.18	13.2	0.29	64.8	1.41
potatoes	0.01	70	0.63	13.2	0.12	97.2	0.87
dairy (cheese)	0.02	50	1.20	8.8	0.21	24.3	0.58
eggs	0.02	50	1.14	8.8	0.20	24.3	0.55
			12.67		2.03		7.30

 

The proportion of fertilizer needs that can be recovered from humanure is also higher with the diet 2 model. Here's another look at the only reference I can find for the average nutrient content of human waste.

 

Pounds Produced Per Person Per Year
	Nitrogen	Phosphorus	Potassium	Calcium
Urine	7.5	1.6	1.6	2.3
Manure	2.8	1.9	0.8	2
Total	10.3	3.5	2.4	4.3

 

Adding the straw and other non-edible residue from farming to the humanure could potentially provide sufficient closure of the nutrient cycle loop and make the local agricultural not dependent upon large quantities of imports.

 

Nutrient Content of Straw
Acres in grain	Ton of straw (lbs)	N (lbs)	P (lbs)	K (lbs)
14,260	22,816	342,234	50,194	388,093
	Per capita	3.9	0.6	4.4

 

The Water Assumption

If about 38,000 acres of prime farmland need to be irrigated to provide high enough yields, the obvious question to ask is whether the water resources exist?

 

The Mendocino County Crop Report shows that about 19,000 acres are in production for apples, pears, and wine grapes.[ix] Another 6000 acres of pasture are irrigated. Perhaps another 1000 acres can be added for vegetable cultivation, tree farms and nurseries. Therefore, currently around 26,000 acres are irrigated.

 

The United States Geological Survey assessed ground water resources in Mendocino County in the mid-1980s.[x] In general, valley bottoms with prime farmland have shallow water tables that are recharged annually given the usually abundant rainfall regime of the county.

 

Because much of the area requiring irrigation is sown in small grain crops, the period of irrigation is limited to late spring, i.e., May and June. By mid-late June these crops will finish maturing and watering should be ceased. I don't currently see water being a limiting factor for productivity on prime farmland in Mendocino County as long as the infrastructure exists to access it.

 

Ground water pumping using shallow wells (usually less than 50 ft) is not extremely energy demanding and should be backed by renewable energy resources. Encouraging existing farms (mostly vineyards) to take advantage of any state or federal programs for renewable energy could help prepare for a more diverse local food system.[xi] Since Mendocino County likes to promote its wine industry as "organic," and one major winery is the first to go "carbon neutral" this may not be a difficult sell in the southern half of the county.[xii]

Alternative Food Sources

A quick mention of what I didn't evaluate: acorns, wild game, fish, seaweed, etc. I suspect acorns could provide for some serious calories, and the others occasional protein and mineral supplements. My main worry about wild game is that it would be extirpated if our current population tried to rely on it for long. The local ocean-going fishing industry is probably fuel intensive, but it would be interesting to evaluate the potential for low-energy input, sustainable fishing off the Mendocino coast.

Conclusion

 

Population growth and land-use changes in Mendocino County have created the surprising situation, in this largely rural area, of a very low availability of high quality, prime farmland per person. While it is theoretically possible to feed the current population of the county on likely available farmland, it would require full-scale irrigation and a restricted diet-and no margin for failure. Maintaining soil fertility over the long-term would also mean cycling human body waste and agricultural residue back to the land.

 

In this series I did not develop any scenarios about when Mendocino County might need to be more food self-reliant, nor make a strong case for the benefits of a local food system, but these arguments can be found elsewhere.[xiii] I found the exercise useful in that it highlighted the resources on which our population depends-good soil, adequate water, sufficient mineral nutrients, reliable climate-and quantified about how much of that exists within our locale. By following the references provided, similar analyses could be done just about anywhere.

 

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[i] http://www.energyfarms.net/node/1491

[ii] http://www.energyfarms.net/node/1489

[iii] http://www.ars.usda.gov/Services/docs.htm?docid=14958

[iv] See the Calories spreadsheet here: http://www.ers.usda.gov/Data/FoodConsumption/FoodGuideIndex.htm

[v] http://www.ers.usda.gov/publications/foodreview/jan2000/frjan2000b.pdf

[vi] http://www.ers.usda.gov/publications/FoodReview/Jan1997/jan97a.pdf

[vii] http://www.energyfarms.net/node/1490; diet 1 assumed about 18 bushels of wheat per acre, diet 2 about 37 bushels per acre.

[viii] http://ideas.repec.org/p/wpa/wuwpdc/0409061.html; See Table 1, divide farmland per household by adult equivalent household size.

[ix] http://www.co.mendocino.ca.us/agriculture/pdf/2006%20Crop%20Report.pdf

[x] http://www.willitseconomiclocalization.org/files/well/GroundWaterResourcesMendoCounty.pdf

[xi] http://attra.ncat.org/farm_energy/funding.html

[xii] http://www.mendowine.com/MendocinoCountyOrganicWineGuide2006rev.pdf; http://www.winebusiness.com/news/dailynewsarticle.cfm?dataId=47813

[xiii] http://www.energyfarms.net/node/1488; http://globalpublicmedia.com/relocalization_a_strategic_response_to_peak_oil_and_climate_change