For this essay I think it would help to step outside of ourselves as humans, and consider us as another species of animal that depends upon a daily supply of resources in the forms of food, water, and air for survival. Strip the emotions from the implications as best we can. Calling us by our scientific name, Homo sapiens Linneaus may adjust the frame of mind accordingly. Linneaus was the man who, in 1758, described and named humans in a taxonomic system. In official scientific protocol, the author of a species name must be given with that name to avoid confusion because sometimes the same name is accidentally given for different species. But from now on I will abbreviate and just use H. sapiens.

Now that we are examining the population of H. sapiens, let us bring the insights of an ecologist to bear on the question of what resources must flow from the environment to support this species? Food derives from soil mediated ecological processes. Good soil by itself doesn't guarantee biological productivity. The other chief factor on land is fresh water available in proper quantities and frequencies. The potential for soil to produce food is not evenly distributed on Earth. Some places are more richly endowed than others, and historically I suppose population density would correspond to biological productivity. With cheap fossil fuels the limits of local ecology can be temporarily overcome and millions of H. sapiens now casually occupy mega-cities in deserts.[i]

The United States Department of Agriculture has codified and mapped environmental heterogeneity in the form of soil maps.[ii] These will be used to help answer the question of whether Mendocino County's current population of nearly 90,000 H. sapiens could theoretically be fed with the local land-base available. Previous essays established a hypothetical diet and calculated the land area needed to grow that diet for the current population.[iii] A summary table from the diet and area calculations is given below.

I should remind readers that I modeled the food output per area according to practices that I considered sustainable, or nearly so. I also assumed a low availability of energy compared to today, which would impact irrigation capacity. I believe the United States produces so much food today that half could be lost and there would still be enough to feed the resident population of H. sapiens. Of course livestock population and nations dependent upon our exports would be drastically impacted. Among the chief reasons for high crop productivity in the U.S. include irrigation and artificial fertilization of wheat and corn. Absent the necessary preparations to transition to a renewable energy-based agricultural system, and considering what climate change might do, I would not be surprised if the United States produced half as much food in 50 years.

Is There Enough Land?

For Mendocino County no single reference resource exists regarding soils, but two published soil surveys roughly dividing the county in half were conducted in the mid-80's.[iv] The text from the Western Survey is on-line and reports: "About 14,105 acres, or nearly 1.4 percent of the survey area, would meet the requirements for prime farmland if an adequate and dependable supply of irrigation water were available." I have a text copy of "Soil Survey of Mendocino County, Eastern Part, and Trinity County, Southwestern Part, California," while the soil data are online for both surveys. Page 127 of the Eastern survey reports: "About 55,000 acres, or nearly 5 percent, of the survey area would meet the requirements for prime farmland if an adequate and dependable supply of irrigation water were available."

Only a very small portion of Trinity County is actually surveyed in the Eastern Part publication and can therefore be safely ignored. Therefore, Mendocino County as of the mid-1980s had (14,105 plus 55,000) 69,105 acres of potentially prime farmland.

Regarding non-prime land, the 2006 Mendocino County crop report estimates that 720,000 acres of range and pasture land were in use.[v]

Compared to what is required to feed the current population of H. sapiens in Mendocino County given the modeled diet, adequate non-prime land exists, but prime farmland falls short.

It May Be Even Worse

The main concern I had with the USDA figures is that they represent field work from the mid-1980s. Unfortunately, as far as I can tell local land-use decisions since then have not made protection of farmland a high priority. So I decided to take a look at what might have happened to prime farmland over the approximately 20 years since the soil surveys were completed.

The most recently available, area-wide environmental review documents relate to plans for local freeway construction, much of which would go right through farmland. A draft Environmental Impact Report from the California Department of Transportation (Caltrans) had this to say about farmland conversion and extent remaining.[vi]

Out of 2,246,400 acres of land in Mendocino County, 94,039 acres or 4.19 percent is considered prime agricultural soils (NRCS-USDA figures). Of that amount, much is unavailable and covered by roads, highways, cities, parks, and other land uses. While growth is very slow in Mendocino County, settlement patterns have tended to occur in areas dominated by prime soils. Only one third, or approximately 35,000 acres, of prime farmland remain available for agricultural use. Besides the unavailability of prime farmland, changes in hydrology as a result of agricultural and other human uses have affected the quality and use of prime farmland.

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.

Can We Just Import Our Food?

Subpopulations of H. sapiens are unusual in their extensive exchange of non-food items for food items and the transport of food over vast distances. When food is viewed as the embodiment of land, water and nutrients, the importation of food into a subpopulation requires the export of environmental carrying capacity from other places occupied by other subpopulations. Therefore, a subpopulation dependent upon imported carrying capacity should be aware of consumption patterns in the subpopulations of exporters it relies upon.

An importing population should ask whether the following statements are true or false:

1. We can feed ourselves without these food imports.
2. Consumption of the food we are importing is decreasing among those exporting it to us.
3. Production of the food exported to us is not being undermined by unsustainable activities that degrade productivity over time, such as loss of top soil, pollution, and conversion of farmlands to other uses.
4. Production of the food exported to us does not require that the exporting populations import supporting resources, such as fuels, fertilizers and water.

To my knowledge, in the case of the population of H. sapiens occupying Mendocino County, the answer to all these statements is false, which means this population faces food insecurity.[vii] The nearest source of importation into Mendocino County would be from within the great agricultural state of California. Yet the California population is so large that the tillable cropland (usually equal to prime farmland) available per person is only 0.30 acres.[viii] Where might California turn? Of the three neighboring states, Nevada and Arizona are mostly deserts and mountains. The cropland available per capita in the U.S. overall is 1.45 acres per person, suggesting sufficient land continent-wide but highlighting a misalignment of population distribution with carrying capacity.[ix] Furthermore, how can land fertility be maintained in the Midwest if the nutrients extracted from the soils are shipped in the form of food to coastal populations who then flush them down the toilet?

What Would an Ecologist Think?

H. sapiens are omnivorous with highly flexible diets. This enables them to exploit different food resources, and to find alternatives to a preferred diet when it becomes scarce--a practice called "resource switching" in foraging theory.[x] The diet modeled in part 1 was based loosely on cultural norms for consumption of grains and animal products. It might be possible that the Mendocino County population will be able to feed itself on a diet with greater conversion rates of land area into edible food. Methods for doing this might include more extensive irrigation and a diet richer in foods with high caloric yields per area.

If food imports decline and the Mendocino County population is unable to feed itself, the population will decline. Population decline occurs through emigration, lower rates of birth and/or higher rates of death.

In part 4 of this series I will revise the diet model to be more area efficient. Can sufficient calories per day be grown using 0.4-0.8 acres per person?

[i] http://www.satellite-sightseer.com/id/1008/United_States/Nevada/Las_Vegas/Las_Vegas_Strip

[ii] http://websoilsurvey.nrcs.usda.gov/app/

[iii] http://www.energyfarms.net/node/1489; http://www.energyfarms.net/node/1490

[iv] Soil Survey of Mendocino County, California, Western Part. http://www.ca.nrcs.usda.gov/mlra02/wmendo/ and http://soildatamart.nrcs.usda.gov/Manuscripts/CA694/0/MendocinoWP_CA.pdf; search for Mendocino County at http://soildatamart.nrcs.usda.gov/

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

[vi] http://www.dot.ca.gov/dist1/d1projects/willits/chapter6_10.pdf

[vii] http://www.energyfarms.net/node/1488

[viii] http://www.ers.usda.gov/StateFacts/CA.HTM

[ix] http://www.ers.usda.gov/StateFacts/US.HTM; Note that two soil data sets are used in the U.S. The main data set used for my analyses is from surveys by soil scientists (NRCS-USDA) to reflect agriculture potential.In many other cases, including references viii and ix in this paper, the USDA agricultural census data are used. These data reflect what land owners or farm operators report. From my reading of the reporting guidelines for the 2007 census, what farmers are asked to report as “cropland” would come close to what is judged by soil scientists to be prime agricultural farmland. See section 2 of the census instructions for details: http://www.agcensus.usda.gov/Help/Report_Form_&_Instructions/2007_Report_Form/2007_RFG.pdf

[x] http://en.wikipedia.org/wiki/Optimal_foraging_theory; http://en.wikipedia.org/wiki/Foraging; http://links.jstor.org/sici?sici=0011-3204%28198312%2924%3A5%3C625%3AAAOOFT%3E2.0.CO%3B2-L&size=LARGE&origin=JSTOR-enlargePage