Effects of Agriculture on the Environment

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Chapter 12

• Effects of Agriculture on the Environment

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Clean Water FarmsCase Study

• Intensive rotational grazing is a system of
  grazing in which ruminant (animals that chew
  their cud) and non-ruminant herds are regularly
  and systematically moved to fresh pasture with
  the intent to maximize the quality and quantity
  of forage growth.
• The herds graze one portion of pasture, or a
  paddock, while allowing the others to recover.
• The grazers obtain the majority of their
  nutritional needs without the supplemental feed
  sources that are required in continuous grazing
  systems.

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Many environmental problems result from
agriculture

• Soil erosion
• Sediment transport and deposition downstream
• On-site pollution from fertilizers and pesticides
• Deforestation

• Desertification
• Degradation of water aquifers
• Salinization
• Accumulation of toxic metals and organic
  compounds
• Loss of biodiversity

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The American Dust Bowl of the 1930s

• Farming easily damages soils
• Intensive plowing and major drought loosened the
  soil
• The soil blew away during wind storms
• Houses, cars, and farms were destroyed
• Many farmers abandoned their farms
• The Grapes of Wrath was first a novel made into a
  popular movie about the dust bowl

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Dust Bowl Video
6
Must Know This!
On
Almost
Every
Birthday
Cupcakes
Rule
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7
Where Eroded Soil Goes Sediments Also Cause
Environmental Problems

• Lots of soil is in water runoff that ends up in
  streams rivers and then deposits it at the
  mouths of the rivers.
• These deposits end of destroying some fisheries
• Coral reefs are also being destroyed by sediments
  landing on them

Click Here for Info
8
Ways to Slow Erosion

• Making Soil Sustainable
• Contour Plowing
• No-Till Agriculture
• Combination of farming practices that include not
  plowing the land and using herbicides to keep
  down weeds.

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9
Controlling Pests

• Pests in agriculture feed on the live parts of
  plants
• Include worms (nematodes), bacteria, viruses,
  weeds, vertebrates (mainly rodents birds), and
  insects
• There are about 30,000 weeds (undesirable plants)

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Pesticides

• Narrow Spectrum Pesticide has a single target,
  just one pest, and not affecting anything else.
• Nice idea, but if a chemical is toxic to one it
  is very likely that it will be toxic to
  others.duh
• Arsenic was used which was very effective in
  killing pests and all other living things like
  humans
• Use of natural plant chemicals like nicotine but
  not as effective
• Use of artificial organic chemicals like DDT

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DDT

• dichlorodiphenyltrichloroethane
• Very effective but very toxic to especially apex
  birds
• The WHO's (World Health Organization)
  anti-malaria campaign of the 1950s and 1960s
  relied heavily on DDT and initially the results
  were promising, though short lived.
• Resistance of mosquitoes to DDT was largely
  fueled by its often unrestricted use in
  agriculture.
• Once the mainstay of anti-malaria campaigns, as
  of 2008 only 12 countries were still using DDT,
  including India and some southern African states
• Rachel Carsons the Silent Spring shed light on
  the use of DDT and its affect on the environment

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Pest Control

• Biological Control the use of biological
  predators and parasites to control pests
• Bacillus thuringiensis (BT) a bacterium which
  affects caterpillars and larvae of insect pests.
  Controls gypsy moths. This bacteria is harmless
  to humans and other mammals
• Small wasps parasite on caterpillars
• Ladybugs predators of many pests
• Sex pheromones attract members of opposite sex
  to insect traps and confuses mating patterns

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Ladybugs and Praying Mantis
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The goal of IPM (Integrated Pest Management) is
to reduce the use of artificial pesticides,
reduce costs efficiently control pests.
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Integrated Pest Management

• Control of agricultural pests using several
  methods together, including biological and
  chemical agents
• Goals
• To minimize the use of artificial chemicals
• To prevent or slow the buildup of resistance by
  pests to chemical pesticides

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• Why Genetically Modified Crops?
• Faster more efficient hybrids.
• terminator gene
• Transfer a variety of traits.

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Hybrids

• Genetically engineered hybrids are created to
  increase productivity and be pest resistant
• Could allow them to require less water
• Attempts are underway to transfer the ability of
  having a symbiotic relationship with bacteria to
  fix nitrogen
• Problems
• Superhybrids can grow where they are not wanted
  and become a pest
• Could create superweeds if a hybrid
  interbreeds with nearby weeds and transfer their
  new super-powers
• May require much more fertilizers, pesticides,
  and water leading to greater pollution need for
  irrigation

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Genetically Modified (GM) Crops
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How can the genetic characteristics of a GM crop
spread?
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The Terminator Gene

• A genetically modified crop which has a gene to
  cause the plant to become sterile after the first
  year.
• Prevents GM crops from spreading.
• Problem more expensive, and developing
  countries are less likely able to obtain these
  seedsand farmers use seeds from first crop to
  plant the next cropmore expensive

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Grazing on Rangelands

• Overgrazing occurs when the carrying capacity is
  exceeded. It can cause severe damage to lands.\
• It is important to properly manage livestock,
  including using appropriate lands for gazing and
  keeping livestock at a sustainable density.

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Desertification

• Desertification is the deterioration of land in
  arid, semi- arid and dry sub humid areas due to
  changes in climate and human activities
• Can be caused by
• Poor farming practices
• Conversion of marginal grazing lands to croplands

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Symptoms of Desertification

• Lowering of the water table (wells have to be dug
  deeper and deeper)
• Increase in the salt content of the soil
• Reduced surface water (streams and ponds dry up)
• Increased soil erosion (the dry soil, losing its
  organic matter, begins to be blown and washed
  away)
• Loss of native vegetation (not having adapted to
  desert conditions, native vegetation can no
  longer survive).

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Preventing Desertification

• Monitor aquifers (underground water) soil
• Observe undesirable changes
• Use proper methods of soil conservation, forest
  management, and irrigation
• Use of windbreaks (narrow lines of trees to help
  slow the wind)
• Reforestation over all, including planting
  windbreaks

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Carrying capacity of pasture and rangeland in the
US, in average number of cows per square
kilometer.
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Fighting Desertification