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Chapter 9: FOOD


Chapter 9: FOOD In simplest terms, agriculture is an effort by man to move beyond the limits set by nature. Lester R. Brown President, Worldwatch Institute – PowerPoint PPT presentation

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Title: Chapter 9: FOOD

Chapter 9 FOOD
  • In simplest terms, agriculture is an effort by
    man to move beyond the limits set by nature.

Lester R. Brown President, Worldwatch Institute
9.1 Feeding the People of the World
  • Ethiopa, 1985 people were starving (lack of
    rain, soil degradation, war) when rain came, it
    washed away millions of tons of soil into the
    rivers resulted in 6,000 sq. mi. of desert
  • Efforts by us to feed more people in this world
    are causing this environmental change, making it
    more difficult to feed all the people

What People Eat
  • We must consume organic compounds in order to
    survive (carbohydrates, proteins, lipids) we
    also need vitamins and minerals to help our
    bodies function properly
  • Food is used as a source of energy and for
    building and maintaining our bodies lack of
    enough food will result in sickness or death
    starving people die from disease that our bodies
    cannot fight off malnutrition is a result of not
    eating enough of the necessary nutrients

Why People go Hungry
  • Increasing populations requires more food food
    production is increasing but amount of food per
    person is not increasing
  • It is not equally distributed throughout the
    world wealthy people have an abundance poor
    people have much less than they need
  • Malnutrition occurs everywhere in the world
    starvation results when food cannot be
    transported to where it is needed (transportation
    lines break down, wars)
  • Droughts can contribute to starvation as well
    combined with war or a break in transportation
    can result in a famine (food shortages in a wide
    spread area)

The Green Revolution
  • In an effort to increase crop yields, new
    varieties of grain and farming methods were
    introduced between 1950 and 1970, resulting in a
    much greater yield
  • Problems need the right kind of fertilizers and
    pesticides, and irrigation water
  • Subsistence farmers only grow enough for their
    families and cant afford the proper tools
    therefore, only large scale farms grow food to be
    sold (they are at their max now) large use of
    fertilizers and pesticides are polluting the
    environment machinery uses a large amount of

Political Changes
  • Making peace in war-torn countries is essential
    toward supplying its people with enough food
  • Donated food can then be distributed more
  • Sustainable farming techniques can be learned

9.2 Agriculture and Soil
  • Earth has a limited amount of arable land
    (fertile) to grow crops decreases every year
    (1/5 from 1985 to 2000)
  • 371 million acres of farmland will be covered by
    houses and industry 334 million acres will
    become unusable for farming because soil will be
  • This shortage of fertile land threatens our
    ability to feed the human population

  • Plowing, fertilization, irrigation and pest
    control began with the earliest farmers animals
    or people pulled plows through the soil (mixes up
    the nutrients, loosens soil and uproots weeds)
  • Organic fertilizers (manure) enriched soil
    digging ditches supplied water weeds were dug up
    by hand still used today in many places
  • Large farms in industrialized countries use
    machinery (to plow and harvest) synthetic
    fertilizers are used to enrich soil overhead
    drips/ sprinkles for irrigations chemicals kill

Fertile Soil
  • Soil that can support the rapid growth of healthy
    plants is called fertile soil most root in
    topsoil (loose soil comprised of rock particles,
    water, air and organic matter)
  • Living organisms (earthworms, insects and other
    small animals) play an important role in breaking
    up the soil also the decomposers (fungi,
    bacteria, microorganisms) when they break down
  • It can take thousands of years to form a few
    centimeters of soil

Topsoil Erosion A Global Problem
  • Soil that has been formed is being lost to
  • In US, about ½ of the topsoil has been lost to
    erosion in the past 200 years worldwide, 11 of
    the soil has been eroded in the past 45 years
  • Soil erosion is ranked as one of the most serious
    ecological problems we face today
  • Some farming techniques today contribute to the
    erosion (blowing wind and rain washing it away)
  • Harvesting removes roots and other organic matter
    that holds the soil together clearing forests
    for lumber water runoff carries away the soil

  • Loss of topsoil, especially in dry areas, is
    severe if it deteriorates so much the land
    becomes desert-like (desertification) worldwide
    an area the size of Nebraska becomes desert every
  • Ex In Northern Africa, if the appropriate
    method of rotating the crops and grazing their
    animals were observed, the land would adequately
    support the people of that region however,
    today, increased overuse of the land and large
    numbers of grazing animals have left the land
    barren. Resulting in desert rather than
    productive farm/grazing land

Soil Conservation
  • There are many ways to conserve topsoil and
    reduce erosion pay attention to the slope of
    the land when planting, contour plowing (plowing
    across the slope of the hill), leaving strips of
    vegetation running across the hillside, not
    farming in an area where it is very hilly
  • Use organic material rather than inorganic
    fertilizers (restores soil) compost or manure
  • Change the way farmland is plowedrather that
    plowing under, plant new crops through the
    remains of the old plants allowing less erosion
    and natural organic matter to be added to the soil

Sustainable Agriculture
  • How can we feed the worlds population without
    depleting the worlds resources?
  • Low-input farming farming without using a lot
    of energy, pesticides, fertilizers and water
  • Ex organic farming farming without the use of
    synthetic materials, use manure, compost and keep
    the land planted at all times (reducing erosion),
    alternating crops
  • Aquaculture fish farming or raising fish in
    artificial environments

Preventing Salinization
  • Salinization is the accumulation of salt in the
    soil salt is in the soil naturally, but when it
    is irrigated with water from rivers or
    groundwater, it builds up and makes the land
    unusable rainwater contains less salt than
  • Ways to slow soil salinization irrigation
    canals, water soil heavily prior to planting
    seeds, plant salt tolerant crops or trees to
    reclaim the land (shade trees will reduce
    evaporation from the soil surface fallen leaves
    add organic matter to the soil)
  • Total restoration of the land takes decades

Old and New Foods
  • Researchers are investigating ancient plants and
    looking at new varieties of plants
  • Looking for plants betters adapted to different
    climates and produce high yields without large
    amounts of fertilizers, pesticides and water
  • Studying plants that have not been widely used
    for food in the past but may be useful
  • Ex Amaranth sacred food of the Aztecs and
    Glasswort can be grown in saline soil

9.3 Pest Control
  • In North America, 13 of all crops are destroyed
    by insects tropical climates enough greater
    damage Kenya lose 25 of their crops from
    insects worldwide, 1/3 of the worlds potential
    food harvest is destroyed
  • Wild plants have more protections from pests than
    do crop plants wild plants are scattered,
    therefore, harder to find, have evolved defenses
    and have pest predators living in or around them
    crops plants are all in one location, a one-stop
    food source
  • Over the last 50 years, many new chenical
    pesticides have been developed and farmers have
    begun to rely on them to protect their crops

Drawbacks of Pesticides
  • Unfortunately, the new pesticides affect a lot
    more than just the pests that they were designed
    to kill
  • They can also harm people and wildlife

Health Concerns
  • Many pesticides can cause people to get sick
  • Ex California has seen an increase in cancer
    rates among children in areas which grow fruits
    and vegetables with high pesticide use
  • Workers in pesticide factories may become ill, as
    well as the people living near these factories,
    from accidental chemical leaks

Pollution and Persistence
  • Pesticides can become problematic for humans and
    wildlife because they are persistent (dont break
    down rapidly into harmless substances when they
    enter the environment), they accumulate in the
    water and soil
  • Ex DDT used in the 1940s to kill mosquitoes
    (malaria, lice that spread typhus) DDT is very
    persistent, gradually accumulates in bodies of
    water, absorbed by fish, and then eaten by birds
    resulted in increased levels of DDT in bodies
    eggs were so thin they broke when sat on
    (penguins, pelicans, peregrine falcons, eagles)
    many became endangered
  • DDT banned in U.S. but continues to remain in
    the environment

Pesticide Resistance
  • Spraying large amounts of pesticides is NOT the
    most effective way to get rid of pests it
    usually makes it worse pests evolve resistance
    (ability to tolerate a particular pesticide)
  • How? Some of the insects have a gene that
    protects them from a pesticide they go on to
    reproduce, passing on that resistance gene to
    their offspring
  • More than 500 species of insects have developed
    resistance to pesticides since the 1940s

Biological Pest Control
  • Because resistance evolves so rapidly, farmers
    and pest-control companies are using fewer
  • Turning to biological pest control (using living
    organisms or naturally produced chemicals to
    control pests
  • Generally do no harm anything but the particular
    pest it is designed to control, resistance takes
    longer to evolve

Predators and Pathogens
  • Releasing a natural predator or parasite is one
    method of biological control
  • Pathogens (organisms causing disease) is another
  • Ex Bacillus thuringensis (bacterium) kills
    larvae (caterpillars of moths and butterflies)

Plant Defenses
  • Cross breeding some plant varieties to produce
    crops that have their own defenses
  • Ex production of chemical compounds that repel
    pests tougher skin

Chemicals from Plants
  • Make use of plants defense chemicals
  • Ex extracting chemicals from the chrysanthemum
    and sell it as a pesticide they are

Disrupting Insect Breeding
  • Pheromones (chemicals produced by an organism
    that affect the behavior of another) are also
  • Ex female moths find mates by releasing
    pheromones that attract males, farmers treat
    crops with those pheromones to confuse the males
    (interferes with mating)
  • Another example treat male insects with xrays,
    making them sterile when they mate, eggs do not
    get fertilized

Thank You!
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