Visualizing Environmental Science

Earth’s Major Biomes 139

Average monthly temperature in

°C

Average monthly precipitation in cm

14

12

10

8

6

4

2

0

28

24

20

16

12

8

4

0

–4

Months

JMMJJASONDFA

© Danita Delimont/Alamy

Based on data from http://www.worldclimate.com

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This desert landscape includes tough-leaved yuccas and spine-covered prickly
pear cacti. Desert inhabitants are strikingly adapted to the demands of their
environment. Photographed near Sedona, Arizona. Climate graph shows
monthly temperatures and precipitation for Reno, Nevada.

Interpreting Data

Would you be warm year-round in this desert? Do

you think it could snow there? Why or why not?

precipitation they receive, which is generally less than
25 cm (10 in) per year. As a result of sparse vegetation,
desert soil is low in organic material but is often high in
mineral content, particularly salts.
Plant cover is so sparse in deserts that much of the
soil is exposed. Plants in North American deserts include
cacti, yuccas, Joshua trees, and sagebrush (ˆ}ÕÀiÊÈ°£ä).
Desert plants are adapted to conserve water and as a re-
sult tend to have few, small, or no leaves. Cactus leaves are
modified into spines, which discourage herbivores. Other
desert plants shed their leaves for most of the year, grow-
ing only during the brief moist season.
Desert animals are typically small. During the heat
of the day, they remain under cover or return to shel-
ter periodically, emerging at night to forage or hunt. In
addition to desert-adapted insects and arachnids (such as
tarantulas and scorpions), there are a few desert-adapted
amphibians (frogs and toads) and many reptiles, such as

the desert tortoise, Gila monster, and Mojave rattlesnake.

Desert mammals in North America include rodents such

as kangaroo rats, as well as mule deer and jackrabbits.

Birds of prey, especially owls, live on the rodents and

jackrabbits, and even the scorpions. During the driest

months of the year, many desert animals tunnel under-

ground, where they remain inactive.

Humans have altered North American deserts in sev-

eral ways. People who drive across the desert in off-road

vehicles inflict environmental damage. When the top layer

of desert soil is disturbed, erosion occurs more readily, and

less vegetation grows to support native animals. Certain

cacti and desert tortoises are rare as a result of poaching.

Houses, factories, and farms built in desert areas require

vast quantities of water, which is imported from distant ar-

eas. Increased groundwater consumption by many desert

cities has caused groundwater levels to drop, particularly

in southern Arizona and southwestern New Mexico.