Essentials of Ecology

CONCEPTS 10-1A, 10-1B, AND 10-1C 225

in its vast Amazon basin, which covers an area larger

than India.
According to Brazil’s government and forest ex-

perts, the percentage of its Amazon basin that had been
deforested or degraded increased from 1% in 1970 to

16–20% in 2005 (Figure 10-13). Between 2005 and
2007, this rate increased sharply, with people cutting

forests mostly to make way for cattle ranching and large

plantations of crops such as soybeans used for cattle
feed. In 2004, researchers at the Smithsonian Tropical

Research Institute estimated that loggers, ranchers, and
farmers in Brazil were clearing and burning an area

equivalent to a loss of 11 football fields a minute! (Con-

cept 10-1C)
Because of difficulties in estimating tropical forest

loss, yearly estimates of global tropical deforestation
vary widely from 50,000 square kilometers (19,300

square miles)—roughly the size of Costa Rica or the

U.S. state of West Virginia—to 170,000 square kilo-
meters (65,600 square miles)—about the size of the

South American country of Uruguay or the U.S. state

of Florida. At such rates, half of the world’s remaining

tropical forests will be gone in 35–117 years, resulting

in a dramatic loss and degradation of biodiversity and

the ecosystem services it provides.

RESEARCH FRONTIER

Improving estimates of rates of tropical deforestation. See

academic.cengage.com/biology/miller.

Causes of Tropical Deforestation

Are Varied and Complex

Tropical deforestation results from a number of inter-

connected basic and secondary causes (Figure 10-15).

Population growth and poverty combine to drive sub-

sistence farmers and the landless poor to tropical for-

ests, where they try to grow enough food to survive.

Government subsidies can accelerate deforestation by

reducing the costs of timber harvesting, cattle grazing,

NATURAL CAPITAL

DEGRADATION

Major Causes of the Destruction and Degradation of Tropical Forests

Tree

plantations

Cattle

ranching

Settler

farming

Cash crops

Logging

Fires

Roads

• Not valuing ecological services


• Crop and timber exports


• Government policies


• Poverty


• Population growth

Basic Causes

• Roads


• Fires


• Settler farming


• Cash crops
  
  
  • Cattle ranching
  
  
  • Logging
  
  
  • Tree plantations
  
  
  
  

Secondary Causes

Figure 10-15

Major inter-

connected

causes of the

destruction and

degradation of

tropical forests.

The importance

of specific sec-

ondary causes

varies in dif-

ferent parts

of the world.

Question: If

we could

eliminate the

basic causes,

which if any of

the secondary

causes might

automatically be

eliminated?