agriculture notes ppt - CarrollEnvironmentalScience

Land Use Part I: Agriculture
Food and Nutrition
• Foods humans eat are composed of
several major types of biological
molecules necessary to maintain
health :
• Carbohydrates
– Sugars and starches metabolized
by cellular respiration to produce
• Proteins
– Large, complex molecules
composed of amino acids that
perform critical roles in body
• Lipids
– Include fats and oils and are
metabolized by cellular
respiration to produce energy
• Vitamins and Minerals
Agricultural Land Use
• Agriculture now covers more of Earth’s surface
than forests.
– 38% of planet’s land surface is used for agriculture
• 26% pasture/rangeland
• 12% cropland
Using Land For Agriculture
• Humans need:
– Most women need ~2,200 kilocalories / day
– Men, ~ 2,900 kilocalories / day
• Biologists estimate that there are roughly 30,000 plant species with parts that
humans can eat
• Majority of our food supply (90%) is derived from only 15 plant and 8 animal
• Three grains, wheat, rice, and corn, provide almost half of the calories consumed
by people
– These three species are all annual plants
• 2 out of 3 people on Earth survive primarily on grains
• World food supplies have more than kept up with human population growth over
the past two centuries.
– During the past 40 years, population growth has averaged 1.7% per year, while
food production increased an average 2.2%.
Chronic Hunger and Malnutrition
• Chronic undernutrition
– Occurs when people cannot grow or buy enough food to adequately
nourish themselves
– Consequences:
• Mental retardation, stunted growth, increased susceptibility to infectious diseases
• Malnutrition
– Occurs from low-protein diets that are common in countries where
subsistence farming is the most common method of food production
• Nearly 6 million children die prematurely each year from undernutrition,
malnutrition, and their effects.
Hunger Around the World
Principle Types of Agriculture
• There are two Principle Types of
1. Traditional Agriculture –
Low Input Polyculture
• Human and animal labor used
to produce only enough food
for farming family’s survival
2. Industrialized agriculture
High Input Monocultures
– Produce huge output of
single crops
(monocultures) or
livestock (which are often
fed monoculture products)
Traditional Agriculture: Low Input Polyculture
• Many farmers in developing countries use low-input agriculture to
grow a variety of crops on each plot of land (interplanting) through:
– Polyvarietal cultivation
• Planting several genetic varieties.
– Intercropping/Polyculture
• Two or more different crops grown at the same time in a plot.
Polyculture Agriculture
• Advantages of polyculture:
– Crops mature and ready to
harvest at different times
– Provides food throughout the
– Soil constantly covered,
preventing erosion
– Less need for fertilizer and water
because roots are at different
depths, using more of soil and
increasing efficiency
– Creates habitats for natural
predators of pest species,
reducing need for pesticides and
Industrial Food Production:
High Input Monocultures
• Requires large amounts of energy, water, fertilizers,
antibiotics, and pesticides; three of which come from
fossil fuels
• Produce huge output of single crops (monocultures) or
livestock (which are often fed monoculture products)
• Accounts for roughly 25% of the world’s cropland
• Mostly in developed countries, but it is spreading into
developing nations
Industrialized Food Production in the United States
• The U.S. uses industrialized agriculture to produce about 17% of the
world’s grain.
– Relies on cheap energy to run machinery, process food, produce commercial
fertilizer and pesticides.
• About 10 units of nonrenewable fossil fuel energy are needed to put
1 unit of food energy on the table.
• Industrialized agriculture uses about 17% of all commercial energy in
the U.S. and food travels an average 2,400 kilometers from farm to
Sources of Protein -- Livestock
• One of the principal uses of animals in agriculture is to
transform plant material into high-quality protein
• In traditional agriculture, livestock graze land, taking nutrients
in and then they defecate and return some of the nutrients to
the same field
• In industrial agriculture, livestock are fed grains (corn
particularly, which they are not “designed” to do) and not
necessarily in a field, so the manure does not fertilize a field
• Per capita meat consumption has increased 29% between
1950 and 1996
• 1/5th of the world’s population consume roughly half of the
world’s grain production through livestock
Sources of Protein -- Seafood
• Seafood is an important protein
• Since 1989, 13 of the 17 major
fisheries in the world have
declined or become
commercially unsustainable.
• If current practices continue, the
world’s fisheries will be
exhausted by 2048.
• Aquaculture (growing aquatic
species in pens) is providing an
increasing share of the world’s
Green Revolution
• In 1960, 60% of the population of developing countries was
considered chronically undernourished.
– Fallen to less than 14% today
• Due to major improvements in farm production which came from
technological advances and modification of a few well-known
– Corn yields jumped from 25 bushels per acre to 130 per acre in
last century.
• Most of gain accomplished through conventional plant
• Green Revolution started by Norm Borlaug.
– Promoted the use of dwarf, high yielding wheat and rice grown
around the world.
– Do require fertilizers and protection from pests.
– Borlaug won Nobel Peace Prize.
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