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. MigrationB. TradeC. ConquestD. Exploration

III. The closing of the world Community

IV. Examples

A. AncientB. Islamic EmpireC. subsequent to the discovery of AmericaD. 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)

B. Islamic Empire (“The Islamic Exchange”)

carrots (Afghanistan to Spain to

Medieval Europe)

citrus fruit (India to Iberian Peninsula)

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 Plantsa. From the Eastern Hemisphere

cotton (but already known in the Western Hemisphere)

onions

C. Subsequent to the discovery of America

1 Plantsa. From the Eastern Hemisphere

rice (to South Carolina, 1685)

sugarwheat

C. Subsequent to the discovery of America

1 Plantsb. From the Western Hemisphere

avocadosmaize (corn)white potatoessweet potatoestomatoes

C. Subsequent to the discovery of America

2 Animalsa. From the Eastern Hemisphere

new varieties of dogshorses donkeys

pigs cattle goatssheepbarnyard fowl

C. Subsequent to the discovery of America

2 Animalsb. From the Western Hemisphere

nothing significant

C. Subsequent to the discovery of America

3 Diseasesa. From the Eastern Hemisphere

bubonic plaguecholeramalaria

C. Subsequent to the discovery of America

3 Diseasesa. From the Eastern Hemisphere

measlessmallpox (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 Diseasesb. 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

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 erosionfighter (“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. ArmadilloN Central America to US

P = purposeful, A = accidental, PA = import purposeful, spread accidental, N = natural, i.e., no human interaction