Visualizing Environmental Science

Soil Problems and Conservation 315

00

55

100

155

200

255

SouthSouth EuropeEurope AsiAsiaa AfrAfricaica OceaniOceaniaa

America

NorthNorth

America

Percentage of total landarea with soil degradation

Soil frozen

6%

Soil too

wet

10%

Soil suitable

for agriculture

11 %

Soil too

shallow

22 %

Chemical

problems

(for example,

soil too salty)

2 3%

Soil too dry

28 %

© J Marshall-Tribaleye Images/Alamy

One Planet, Many People: Atlas of Our Changing Environment.

United Nations Environment Programme (2005).

Based on table on page 29,

World Atlas of Desertification

,

United Nations Environment Programme (2002).

Courtesy U. S. Department of Agriculture

a. Soil and Agriculture.

Only 11 percent of the

world’s total land area

has soil that is

naturally suitable

for agriculture.

Soil that is too

dry can be

irrigated, and

soil that is too

wet can be

drained.

c. Conservation Tillage. Decaying residues from the previous

year’s crop (rye) surround young soybean plants in a field in

Iowa. Conservation tillage reduces soil erosion as much as 70

percent because plant residues from the previous season’s crops

are left in the soil.

b. Soil Degradation. This graph shows the degree of soil

degradation (eroded, desertified, or salty soil) by continent.

d. Terracing. Terraces are small earthen embankments placed

across a steep hillside or mountain. Terracing hilly or mountainous

areas, such as these rice terraces on Bali, Indonesia, curbs water

flow and reduces the amount of soil erosion. However, some slopes

are so steep that they are vulnerable to extensive erosion if not left

covered by natural vegetation.

Environmental InSight

Soil conservation

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Interpreting Data

Which continent has the most degraded soils? the

least degraded soils? Offer an explanation for why

this is the case.

Soil Problems and Conservation 315

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