Lecture 21 By Theme

Concept of an agricultural “system”

  • May be have begun with the domestication of animals or of crops
  • Population pressures, wild game extinctions or cultural, technological and genetic diffusion may have also led to the initiation and spread of agriculture
  • Crops, rotations, seasons
  • Inputs, intensity, labor
  • Different types of systems
    • Hunting and gathering from wild stocks
    • Cultivation of domesticated plant crops
    • Pastoralism
    • Animal feeding (including fish farming)

Developments over time
Agricultural revolutions, improvements

  • The Neolithic revolution (start/spread of domestication)
    • Agriculture as supplement to hunting, gathering and nomadic behavior
    • Increasing reliance upon cereals in vegetables in diet
    • Subsistence agriculture
    • Higher yields → caching and incentives to stay in place
    • First signs of forest clearing for agriculture
    • Shifting cultivation (swidden agriculture)
      • Agricultural system in which plots of land are cleared and farmed until soils lose fertility
      • Natural succession then permitted for several seasons of regrowth while crops are grown nearby
      • Land may then be recleared for cropping
      • Most of land constantly under shifting cultivations
  • The industrial revolution in agriculture – 19th century
    • Major shift in technological, socioeconomic and cultural conditions in the late 18th and 19th centuries
    • Economy based on manual labor replaced by one dominated by industry and the manufacture of machinery
  • Gasoline powered tractors – early 20th century
  • “Green Revolution” in US – 1940-1970
    • Driven by growing population and hunger concerns
    • Average yields are 2.6 times greater today per acre of land than in 1950
    • Three main elements:
      • Mechanical
        • Mechanized equipment was key
        • Fertilizer essential, but takes energy to produce
        • Cheap gasoline prices and rise of petrochemical industry drivers of mechanization
      • Biological
        • Crop breeders produced high yield varieties of cereal crops
        • Drought and disease resistant strains of crops were developed
        • Hybrids that increased grain yield per stalk without stem breakage
          • Selective breeding
          • Antibiotics such as Penicillin and Streptomycin were developed and given to farm animals to treat and prevent disease
            • Protested due to allowing for unhealthy practices and concerns over “superbugs”
      • Chemical
        • Fertilizers, pesticides, and herbicides
        • Pesticides and herbicides products of petrochemical industry
        • Used to combat weeds, pathogens and insects
        • Pesticide application has plateaued in the US but is still growing worldwide
    • Left legacy of high yielding crops, high input-output systems, reliance on energy, fertilizers, and pesticides
    • Food production has largely kept pace with population growth
    • Some downsides of the Green Revolution include the leakage of inputs, negative impacts of fertilizers and pesticides
  • “Second Green Revolution” as exports increased

Agricultural intensity/intensification

  • Extensive growth: more land, more people, but not more productivity per unit land or per capita of participant
  • Intensive growth or intensification: more productivity per unit land or per capita of participant
  • Inputs from outside the unit of land that raise its productivity include:
    • Irrigation
    • Fertilizer, manure, dung
    • Labor
    • Energy
    • Capital
    • Technology: plow, thresher, harvester

Population Growth ← → Agricultural Growth

  • The green revolution allowed food production to keep up with (or potentially drive) rapid population growth
  • It was built upon resources (oil, ground water) that are non-renewable
  • In the long term, we can’t rely on non-renewable resources

Major issues that confront us today

  • Hunger and equity
    • Enough food is now being produced, but it is not being distributed equitably
    • Hundreds of millions are still hungry, and tens of millions die every year from malnutrition
  • Continued deforestation
    • Essential habitats and forested areas are being cut down at alarming rates to clear for pastures and fields
  • Continued intensification
    • More inputs required to maintain such high yields
      • Alternatives in ecological farming (“de-intensification”)
      • Less artificial fertilizer, less pesticide and herbicide use, decreased use of antibiotics and hormones
  • Corporate farming, corporate control
    • Family farms are being replaced with corporate-owned megafarms
    • Reducing available varieties to a few high-yielding crops that require their products to grow
    • Decline in genetic resources due to decreased genetic diversity in crops
  • Biofuels
    • Increasing agricultural pressures to produce non-food crops, including crops that could potentially be used for fuel
      • Likely inefficient
  • Genetic engineering
    • Farmers have been manipulating crops for millennia by artificial selection, but today’s genetic engineering does it much faster and specifically
    • Genetic engineering can combine traits from different species that would never come together by other means

Concerns include:

  • Loss of water due to increased irrigation over increasing distances
  • Genetic engineering has many unknown effects
    • Pest resistance, spread of transgenes, increased herbicides, health concerns
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