Presentation on theme: "Principles of Agricultural Ecology. The Six Commandments of Theoretical Agriculture Thou shalt steal land from a natural ecosystem. Thou shalt replace."— Presentation transcript:
The Six Commandments of Theoretical Agriculture Thou shalt steal land from a natural ecosystem. Thou shalt replace the natural flora with plants that will serve thee by: –Fitting with thy nutrition-theory (see below) –Fixing lots of sunlight –Expending their fixed energy on production (as opposed to maintenance) –Concentrating their production in edible tissues (as opposed to lignin / cellulose) Thou shalt input tremendous amounts of energy to supply thy plants with: –Protection from predators (e.g., insects) and competitors (e.g., weeds) –Stuff whose lack would otherwise limit production (irrigation, fertilizer) Thou shalt develop an adequate theory of nutrition: –That supplies sufficient calories –That supplies an appropriate mix of amino acids (“protein complementarity”) Thou shalt exchange stuff of which thou hast a surplus for stuff that thou lacketh: –By developing animal husbandry –By trading with other communities Thou shalt develop ways to perpetuate (and improve?) the system: –By conserving soil resources –By improving thy captive organisms (through cultivar-substitution and artificial selection) –By stealing more land from a natural ecosystem (or from thy weaker neighbors)
Part 1: Selecting the plants that will serve you T hey do you no good unless they fix sunlight, but For photosynthetic capture, no ag system tops a rainforest. But a rainforest spends its energy in maintenance while you must produce stuff. So, first, choose plants that produce. For production of stuff, few ag systems can top a wildgrass prairie. But you can’t digest the green grass. So, choose plants that concentrate their production in edible tissue. Think (solar capture)*(production/maintenance)*(edible tissue) From hundreds of thousands of wild plants –Maybe 100 important domestications maybe 20 critical These fall into four categories: –Grasses!!!!!!!!!!!!!!!!!!!!!!!!!!!!! –Legumes –Starchy staples –Others We’ll discuss some favorite agricultural choices from among these groups.
“Flesh is Grass.” Isaiah 40:6 Grasses: –Highly efficient at solar capture. –High production-to-maintenance ratios –produce much edible reproductive tissue. The 3 critical grasses are: Rice –More calories into people than anything else –Most susceptible to global warming –Top production c. 10,000kg/ha Wheat –Most nutritious common grain –Targets: Pakistan 2,500kg/ha; US 2.5-5000kg/ha –Highest dollar-value/grain-mass Corn/maize –Relatively low nutrition, but multi-use –Worldwide targets: 0.5 – 25,000kg/ha –More calories into some poor communities
What is the anatomy of a grass seed? (We’ll use rice as our example.) The grain shown at left has already been threshed loose from the head of the rice stalk. The hull and lemma will be removed prior to shipping. The high-fiber, low-calorie bran layers are usually milled away for cooking-convenience. To increase grain’s shelf-life the nutritious embryo is removed (it may be consumed separately). The starch of the endosperm cells provides fuel for embryo development—and for human consumers. Preparation is similar for other grains (except corn/maize).
Rice: Where and how is it grown? Rice does need water, but it is usually grown in flooded fields mostly to assist with weed-control. (Domesticated rice is not a super-good competitor with other grasses.)
A great advantage of rice All agricultural crops have yield = f(input) curves of the same mathematical shape. But for rice, the slope is steeper. You input more energy; you get more rice. Schemes for energy input vary radically! How is labor invested in rice cultivation?
The labor- cycle of a rice crop (traditional version) 1. Field prep 2. Transplanting seedlings 3. Weeding 4. Irrigation 5. Harvesting 6. Threshing 7. Winnowing
Rice Infrastructure: The less visible energy input The standing irrigation system Various apparatus
Alternative modes of energy-input: Two American ways of growing rice Present-day rice culture in the USA: Input enormous amounts of energy seized from prehistoric photosynthetic systems. Weeding with an Ag-Cat
The Earlier Plan: Input labor & ideas seized from other people
Next grain: Wheat Where is it grown? Wheat is a temperate-zone crop that can thrive in moderately dry areas with plenty of sunshine. Wheat is a dollar-valuable grain. Geographically, its cultivation correlates roughly with high-income human cultures.
How is wheat grown today? Take lots of sunshine; add lots of water; grow lots of wheat. Ecological costs can be high! Center-pivot irrigation apparatus Center-pivot irrigation wheat fields
Why is wheat the high-dollar grain? It yields high nutritional value per cultivated area. –Calories… –Amino-acid balance… It ships and stores well. It is by far the best grain for making bread
Bread has enormous nutritional and cultural significance! When mixed with water and an agent that produces CO 2, wheat-flour captures tiny gas-bubbles. The resulting dough can be baked into soft, chewable, storable, multi- use bread, “the staff of life.” Different dough-recipes produce different breads. “Daily bread…” “This is my body…”: Approximate biblical word-frequency: Hell: 50 Salvation: 150 Bread: 350
Third grass: Corn/maize Corn feeds tremendous numbers of poor people. And, given sufficient input of water, fertilizer, herbicides, and pesticides, almost any sunny land can produce enormous amounts of corn. But corn is a ferocious consumer of nutrients, its own nutritional value is not high, and it is highly susceptible to drought!
Nobody else grows corn quite like the USA! But what happens to this good food? A typical small grocery store may offer about 10,000 products. About 2,500 of them will contain at least some corn. The overwhelming preponderance of American corn is used to feed animals. Increasingly, American corn is used to make gasohol.
The (other) mostly non-food grass we shouldn’t forget: Sugar Cane Sugar cane fixes a high percentage of sunlight to produce a high percentage of edible tissue. It is much better than corn as a source of gasohol. (Why?) On the other hand, the export of sugar cane rapidly depletes land. (Why?) The culture of sugar cane was (and to a degree remains) an enterprise associated with unbelievable degrees of human misery. (Why?)
(Part 1 continued) Selecting the plants that will serve you: Going beyond the grasses to think beans Beans of food/ag importance come in 1000’s of varieties! Peanuts and soy beans have 100’s of uses; the most important are nutritional. Lima beans, green beans, and black-eyed peas are important staples in many human diets.
Why are beans of such extraordinary importance? By fixing atmospheric nitrogen, legumes can actually enrich the soil in which they are grown. –Nitrogen is perhaps the most important agricultural nutrient. –Symbiotic bacteria in legume root-nodes split atmospheric N 2 and make it available to the living agrisystem... –Of course the energy-cost of this process is high…. The amino acids abundant in many beans supplement amino acids almost absent in most grains (and visa versa). –We’ll discuss this in more detail when we consider Part 3: Nutritional strategy. Legumes also have many important non- food uses. –These include medicines, insecticides, varnishes, dyes, timber, soil-maintenance….
(Part 1 continued) Selecting the plants that will serve you: Going beyond the grasses and beans to think starches This is not a meaningful botanical category, but it makes nutritional sense. –Calories are the main nutrient provided by these foods. –They make excellent meal-extenders; however, when used as dietary staples, they are poor folks’ fare. –Given diets dominated by “starchy staples,” children are at particular risk. Geographically, the “starchy staples” are most important in areas where grain-culture is difficult or impossible. Bananas are arguably the most important of the “starchy staples.” The nutritional, ethical, economic, and ecological aspects of their culture could provide sufficient material for several liberal arts courses.
Additional examples of “starchy staples” (each worth a whole bunch of lectures) Taro: Pacific islands Sweet potato: Africa, southern US White potato: Poorer Europe, high-altitude tropics Breadfruit: Lowland tropics (esp. Pacific) Manioc (cassava): Lowland tropics worldwide (few words = gross over- generalizations)
(Part 1 continued) Selecting the plants that will serve you: What’s left after the grasses and beans and starches? Various nuts add calories & fun. Coconuts are by far the most important and are actually staples in some cultures.
(Part 1 continued) Selecting the plants that will serve you: What’s left after the grasses and beans and starches? “Table vegetables” add color, variety, and vitamins to enliven diets that might otherwise be very dull. Also, for rich folks’ diets, too high in fats and animal protein, they may provide other, as yet poorly understood, nutritional benefits.
(Part 1 continued) Selecting the plants that will serve you: What’s left after the grasses and beans and starches? Fruits add calories, variety, and some vitamins. They are also among the healthiest snack foods. Rambutan Mango
(Part 1 continued) Selecting the plants that will serve you: What’s left after the grasses and beans and starches? Non-nutrition agriculture. Again we should consider economics, ethics, and ecology. How many of these four super-important cash crops can you name?
Theoretical agriculture, Part 2: Working for the plants that work for you If you select plants that are ideal for serving your needs, then they will automatically be pitifully inadequate for serving their own needs. If your plants are to make lots of stuff, you may need to supply things that they lack. –In many agrisystems, supplying water will be a critical problem. –Nutrients will probably also be (or become) an important concern. If you maintain an ecosystem suitable for high-production plants that serve you, then you automatically maintain an ecosystem suitable for their high-production competitors. –Weeds almost always become a serious problem. –This is particularly true in tropical and warm-temperate agrisystems. If you maintain a lot of identical plants in the same place, then you automatically provide a tempting target for predators. –In most systems insects and soil-nematodes become the main problems. –Pests are usually most serious in areas where winters are mild or nonexistent.
The wimpy plants we cultivate Example question: In a southern African system, how many years of neglect will pass before a typical wheat cultivar becomes extinct? Example answer: Less than one! So we have to work to keep our plants going. –Irrigating –Fertilizing –Weeding –Fighting pests
Providing what the wimps need Given plenty of sunshine (and you can’t do anything about that), water is the greatest need. Sometimes irrigation is a backup for fickle nature. Sometimes it’s a supplement for stingy nature. Sometimes it’s imported water where nature would provide none at all. Often the addition of one (or a few) limiting nutrient(s) will greatly increase production. Nutrients most often limiting are nitrogen, phosphorus, and potassium.
Protecting the wimps from competitors For many field crops, proper tillage is fundamental. Manual weeding is effective, but it requires enormous inputs of extremely unpleasant labor. Chemical herbicides have their problems too, but they are becoming increasingly popular– and sophisticated. Still, further weeding is almost always necessary.
Protecting the wimps from potential predators Mexican beetle & larva; soy beans Most plant species in most natural ecosystems occur in mixed communities, so pest-species do not typically encounter large, unbroken patches of the specific foods for which they are best specialized. Human monocultures, by contrast, provide tremendous resource reservoirs that can support specialist-pest population explosions. Today most pest-buildups are controlled by chemical warfare. You should be able to discuss the pro’s and con’s of this practice!
And, yes, right now humanity can decide to produce foods entirely without fertilizers, pesticides, and herbicides… …but we’ll also have to decide which half of the human species should be allowed to starve to death! (Still, we must begin to consider the ecological and medical costs of our chemically intense methods of supporting those wimpy plants upon which we largely depend for survival.)
Theoretical agriculture, Part 3: Developing a nutritional strategy The vast majority of the world’s people will need to rely on some “eat plants” strategy. Rule #1 is “Get sufficient calories!” Rule #2 is “Balance your amino acids the best you can!” Rule #3 is “Eat as much variety as you can.” The media are full of complex nutritional advice, but ag-theorists can simplify to 3 short rules.
Rule 1: Calories are fundamental! The body needs energy just to stay alive, and this energy- demand will be met even at the expense of other nutritional needs. Today human famine is almost always associated with: –Ecological stress –Violence and/or oppression Before you finish this course, you should be prepared to discuss the typical dynamics of 21 st Century famine! Historically, ag societies incapable of producing sufficient calories simply do not persist. (People move or something changes in a big way.) Calorie-starvation is a social pathology that radically transcends the simple worlds of agriculture and nutrition!
No single available food-plant contains amino acids in ratios sufficient to maintain human protein-health! Although few human cultures persist in areas incapable of producing sufficient calories, severe protein deficiency (kwashiokor) is very common in some poorer countries. This disease affects mostly children. –About 12,500 children die each day from malnutrition; the majority of these deaths are probably associated with protein deficiency. –Kwashiokor also exacts a more subtle toll. Delayed development and even mental retardation can result from early protein deprivation. Enough calories? Yes. Proper balance of amino acids? No! Next slide: Mixing plants to balance amino acids
Many schemes work, but the shortest recipe is “Mix grains and beans.” Rice & peas: Caribbean Rice & beans: Latin America Lentils & Bulgur wheat: West Asia Tofu (soya) & rice: East Asia Peanut butter & wheat bread: USA Note the near universality of this nutritional strategy. (Where it’s impossible, malnutrition is a serious danger!) Can you spot the little “extras” & explain why they are important?
Theoretical agriculture, Part 4: Exchanging your surplus for things you lack OK, folks, I’ve run out of time. Here are the main points: –Historically, plant-ag systems that fail to produce a surplus of anything– well, they don’t persist. –There are two common ways to swap off your surplus. Most commonly, ag people adopt animal husbandry –One scheme is to run cellulose, which you couldn’t digest anyhow, through a fermenter (preferably a foregut fermenter) –Another scheme is to feed a non-picky potential competitor (probably pigs) on scraps, etc. I have a huge amount of stuff on animal husbandry! I also have some pictures in this PPT Ag folks also trade with other cultures
Theoretical agriculture, Part 5: Preserving the system, the Striving that Ceaseth not Still, no time. Of course sustainability is a key ag-ecological concept! Historically, people gave it very little direct thought (though they developed many practices that support sustainability; consider low-density “slash-and-burn” agriculture!). Increasingly, however, the supreme importance of agricultural sustainability is becoming a more overt concern! OK, that’s all I can do by today’s meeting.