Silent Spring

1
Silent Spring

• Chapters 7 8
• Christopher Siess, Jaclynn Chen, Catherine Flynn

2
Pests

• According to Charles Eton, the key to a healthy
  community lies in keeping the conservation of
  variety.
• This variety keeps any one species from
  dominating over the others and becoming a pest.
• We learned in the textbook that an organisms
  success in a new environment is dependent on
  predation, disease, competition, and absence of
  certain species.
• The Japanese beetle thrived in the United States
  because the U.S. lacked any species that would
  prey or compete with it.
• Once organisms such as the parasitic wasp Tiphia
  vernalis were introduced into the U.S., they
  controlled the Japanese beetle.

3
Pests

• Birds such as the woodpecker are natural
  controllers of potential pests such as the
  Engelman spruce beetle. Once these birds die as a
  result of insecticide poisoning, there is no
  natural protection left to keep the pests in
  check.
• The Tens Rule- an average of one out of ten
  introduced species become established, and one
  out of ten established become common enough to
  become pests.

4
Pesticides

• Detrimental insect poisons, pesticides, have
  wreaked needless havoc in the environment harming
  numerous species throughout the community.
• Although a single spray will temporary reduce
  numbers of pests, they will return, and a new
  spraying campaign must take place.

5
Pesticides

• Pesticides used unwisely can cause immense
  collateral damage.
• In the fall of 1959, 27,000 acres of land in
  southern Michigan was sprayed, its purpose to
  control the Japanese beetle population.
• What happened was a sharp increase in respiratory
  and nervous conditions, and scourging of the bird
  and house pet populations.

6
Pesticides

• One of the reasons birds and other species were
  eradicated was because of direct contact. The
  birds came into contact with the poison when it
  was dispersed.
• Another reason was because of the food chain.
  When infected beetles came to the surface for
  their last hours, the birds ate these easy
  pickings and became infected.

7
Pesticides

• A DDT spreading affected a flock of sheep. In a
  short time, the sheep experienced symptoms of
  intoxications almost at oncelost interest in
  food, great desire for water, displaying extreme
  restlessness, following pasture fence apparently
  searching for way out (Carson 94)

8
Abiotic Factors to Distribution Restriction
9
Chain of Infection
10
Governmental Interference

• Government officials on many levels insist that
  the plainly dangerous poisons were completely
  safe to all untargeted species.
• Budget concerns demanded the use of less-safe
  poisons for less expense.

11
Since Then

• Public attention to pesticide spraying has
  increased, as had the demand of the introduction
  of natural predators instead of poisons.
• If a natural predator is determined to not cause
  as much havoc as the pest that was introduced, it
  shall be attempted to be established.