Diffusion

							                      Diffusion:

              Plants, Animals,
               and Diseases
Ronald Wiltse September 2006
I. Types of diffusion
      A. Natural (“biodiversification”—Alfred Crosby)
         1 Spread of plants by wind and
           bird
         2 Spread of diseases from one
           species to another
I. Types of diffusion
      B. Human caused
      (“diffusion”—Alfred Crosby)

          1 purposeful
          2 accidental
II. Contacts between closed areas
      A. Migration
      B. Trade
      C. Conquest
      D. Exploration
III. The closing of the world Community
IV. Examples
         A. Ancient
         B. Islamic Empire
         C. subsequent to the
             discovery of America
         D. Recent examples
A. Ancient
     rice (Pakistan, to China and Japan; to
           medieval Europe)
     wheat (SE Turkey, to S Asia, Nile, Greece by
           6000, to China by 2000 BC; known in
           the Western Hemisphere at this time)
      carrots (Afghanistan to Spain to
            Medieval Europe)
      citrus fruit (India to Iberian Peninsula)
B. Islamic Empire (“The Islamic Exchange”)
      cotton (brought to Europe ca AD 800)
      okra (Africa to India)
      sugar cane (Polynesia to China and India,
            ca. 1000 BC; to Egypt, Iberian
            Peninsula)
B. Islamic Empire (“The Islamic Exchange”)

   1 land use in Spain at the time of
        the Islamic conquest
        a. Roman “natives” grew
        wheat, grapes, barley, olive
        oil, and a few vegetables.
B. Islamic Empire (“The Islamic Exchange”)

   1 land use in Spain at the time of
        the Islamic conquest
        b. The Visigothic rulers
        preferred herding.
B. Islamic Empire (“The Islamic Exchange”)

   1 land use in Spain at the time of
        the Islamic conquest
        c. The new overlords wanted
        to introduce new plants which
        required more water;
B. Islamic Empire (“The Islamic Exchange”)

   1 land use in Spain at the time of
        the Islamic conquest
        c. thus, they built irrigation
        systems. Central to these
        systems were . . .
B. Islamic Empire (“The Islamic Exchange”)

   1 land use in Spain at the time of
        the Islamic conquest
        c. . . . norias, waterwheels
        which used the power of
        flowing water to raise some of
        the water to a higher level.
C. Subsequent to the discovery of America
      1 Plants
      a. From the Eastern Hemisphere
           cotton (but already known in the
                 Western Hemisphere)
           onions
C. Subsequent to the discovery of America
      1 Plants
      a. From the Eastern Hemisphere
           rice (to South Carolina, 1685)
           sugar
           wheat
C. Subsequent to the discovery of America
      1 Plants
      b. From the Western Hemisphere
           avocados
           maize (corn)
           white potatoes
           sweet potatoes
           tomatoes
C. Subsequent to the discovery of America
      2 Animals
      a. From the Eastern Hemisphere
           new varieties of dogs
           horses    donkeys pigs
           cattle    goats     sheep
           barnyard fowl
C. Subsequent to the discovery of America
      2 Animals
      b. From the Western Hemisphere
           nothing significant
C. Subsequent to the discovery of America
      3 Diseases
      a. From the Eastern Hemisphere
           bubonic plague
           cholera
           malaria
C. Subsequent to the discovery of America
      3 Diseases
      a. From the Eastern Hemisphere
           measles
           smallpox (note spread in North America,
      culminating in 1779-1780 among Plains Indians, due to
      the rise of mobility caused by the introduction of
      horses, over the preceding century)
C. Subsequent to the discovery of America
      3 Diseases
      b. From the Western Hemisphere
           perhaps none (why so few in the
      Western Hemisphere? Perhaps it is because of
      the lack of propinquity to barnyard animals).
D. Recent examples
      P = purposeful,
      A = accidental,
      PA = import purposeful, spread
           accidental,
      N = natural, i.e., no human
           interaction
 P =    purposeful,
 A =    accidental,
 PA =   import purposeful, spread accidental,
 N =    natural, i.e., no human interaction




D. Recent examples
        1. Russian thistle (tumbleweed)
               A from Russia to US
 P =    purposeful,
 A =    accidental,
 PA =   import purposeful, spread accidental,
 N =    natural, i.e., no human interaction




D. Recent examples
        2. Kudzu
               PA from Japan to US 1876 Centennial
               Exposition, Japanese exhibit
               ►1920s Florida nursery sells it as a
               source of animal feed
 P =    purposeful,
 A =    accidental,
 PA =   import purposeful, spread accidental,
 N =    natural, i.e., no human interaction




D. Recent examples
        2. Kudzu
               ►1930s Soil Conservation Service
               promotes kudzu as an erosion
               fighter (“the miracle vine”)
               ►1972 USDA declares kudzu a weed
               ►2050s government of the US
               collapses as kudzu covers 90% of US
 P =    purposeful,
 A =    accidental,
 PA =   import purposeful, spread accidental,
 N =    natural, i.e., no human interaction




D. Recent examples
        2. Kudzu
               PA from Japan to US 1876 Centennial
               Exposition, Japanese exhibit
               ►1920s Florida nursery sells it as a
               source of animal feed
 P =    purposeful,
 A =    accidental,
 PA =   import purposeful, spread accidental,
 N =    natural, i.e., no human interaction




D. Recent examples
        3. Killer bees
               P from Africa to Brazil, N to the US
        4. Armadillo
               N Central America to US