Essentials of Ecology

220 CHAPTER 10 Sustaining Terrestrial Biodiversity: The Ecosystem Approach

Biodiversity experts are alarmed at the growing

practice of illegal, uncontrolled, and unsustainable log-

ging taking place in 70 countries, especially in Africa

and Southeast Asia (Concept 10-1B). Such logging has

ravaged 37 of the 41 national parks in the African

country of Kenya and now makes up 73–80% of all

logging in Indonesia.

Complicating this issue is global trade in timber and

wood products. For example, China, which has cut

most of its own natural forests, imports more tropical

rain forest timber than any other nation. Much of this

timber is harvested illegally and unsustainably and is

used to make furniture, plywood, flooring, and other

products that are sold in the global marketplace.

Fire, Insects, and Climate Change

Can Threaten Forest Ecosystems

Two types of fires can affect forest ecosystems. Surface

fires (Figure 10-9, left) usually burn only undergrowth

and leaf litter on the forest floor. They may kill seed-

lings and small trees but spare most mature trees and

allow most wild animals to escape.

Occasional surface fires have a number of ecological

benefits. They burn away flammable ground material

and help to prevent more destructive fires. They also

free valuable mineral nutrients tied up in slowly de-

composing litter and undergrowth, release seeds from

the cones of lodgepole pines, stimulate the germina-

tion of certain tree seeds such as those of the giant se-

quoia and jack pine, and help control tree diseases and

insects. Wildlife species such as deer, moose, muskrat,

and quail depend on occasional surface fires to main-

tain their habitats and provide food in the form of veg-

etation that sprouts after fires.

Another type of fire, called a crown fire (Figure 10-9,

right), is an extremely hot fire that leaps from treetop

Reduces biodiversity

Destroys and

fragments wildlife

habitats

Increases water

pollution, flooding,

and erosion on

steep slopes

Eliminates most

recreational value

Higher timber

yields

Maximum profits

in shortest time

Can reforest with

fast-growing trees

Good for tree

species needing

full or moderate

sunlight

Advantages Disadvantages

TRADE-OFFS

Clear-Cutting Forests

Figure 10-8 Advantages and disadvantages of clear-cutting forests.

Question: Which single advantage and which single disadvantage

do you think are the most important? Why?

Figure 10-9 Surface fires (left) usually burn undergrowth and leaf litter on a forest floor. They can help to prevent
more destructive crown fires (right) by removing flammable ground material. In fact, carefully controlled surface
fires are deliberately set sometimes to prevent buildup of flammable ground material in forests. They also recycle
nutrients and thus help to maintain the productivity of a variety of forest ecosystems. Question: What is another
way in which a surface fire might benefit a forest?

David J. Moorhead/The University of Georgia © age footstock/SuperStock