Visualizing Environmental Science

PROCESS DIAGRAM

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Forests return most

of the water that falls

as precipitation to

the atmosphere by

transpiration. When

an area is deforested,

almost all precipitation

is lost as runoff.

✓✓THE PLANNER

Atmosphere condensation

Precipitation

on land

25 percent or more of

water seeps into ground

or runs off to rivers,

streams, and lakes

Water from soil

absorbed by roots

Evaporation from

soil, streams,

rivers, and lakes

Transpiration

from plants

Up to 75 percent

of water recycled

by transpiration

and evaporation

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LEARNING OBJECTIVES

products. Forests supply nuts, mushrooms, fruits, and

medicines. Forests provide employment for millions of

people worldwide and offer recreation and spiritual sus-

tenance in an increasingly crowded world.

Forests also provide a variety of beneficial ecosys-

tem services, such as influencing climate conditions.

If you walk into a forest on a hot summer day, you

will notice that the air is cooler and moister than it is

outside the forest. This is the result of a biological cool-

ing process called transpiration, in which water from the

soil is absorbed by roots, transported through plants, and

then evaporated from their leaves and stems. Transpira-

tion provides moisture for clouds, eventually resulting in

precipitation (ˆ}ÕÀiʣΰÎ). Thus, forests help maintain

local and regional precipitation.

1. Define sustainable forestry and explain
   how monocultures and wildlife corridors
   are related to it.


2. Define deforestation, including clear-
   cutting, and list the main causes of tropical
   deforestation.


3. Describe national forests and state which
   government agencies administer them and
   current issues of concern.

F

orests, important ecosystems that provide

many goods and services to support human

society, occupy about one-fourth of Earth’s

total land area. Timber harvested from for-

ests is used for fuel, construction materials, and paper

In which part of

the hydrologic

cycle do trees and

other plants play

a huge role? How

would clearing the

trees on a stretch

of land disrupt this

process? What

would happen to

water in soil there?

Think Critically

324 CHAPTER 13 Land Resources