Essentials of Ecology

SUPPLEMENT 8 S51

the barrier islands along the coast, allowing

huge quantities of seawater to fl ood the bays

and marshes.

This fl ushing of the bays and marshes reduced

brown tides consisting of explosive growths of

algae that had fed on excess nutrients. It also

increased growth of sea grasses, which serve as

nurseries for shrimp, crabs, and fi sh and provide

food for millions of ducks wintering in Texas

bays. Production of commercially important spe-

cies of shellfi sh and fi sh also increased.

Moist surface winds

spiral in toward the

center of the storm.

Warm

moist air

Gales circle the eye at speeds

of up to 320 kilometers

(200 miles) per hour

The calm central

eye usually is about

24 kilometers

(15 miles) wide.

Rising winds exit

from the storm at

high altitudes.

1

2

3

4

Figure 9 Formation of a tropical cyclone. Those forming in the Atlantic Ocean usually are called hurricanes; those
forming in the Pacific Ocean usually are called typhoons.

Temperature (

°C)

–0.67

1880 1900 1920 1940

Year

1960 1980 2000

–0.50

–0.33

–0.17

0

0.17

0.33

Temperature (

°F)

–1.2

–0.9

–0.6

–0.3

0

0.3

0.6

Figure 10 Change in global ocean tempera-

ture from its average baseline temperature from

1880 to 2000. (Data from National Oceanic and

Atmospheric Administration)

Data and Graph Analysis

1. In 1900, the global ocean temperature dropped
   from its baseline temperature by how many
   degrees? (Give answer in both Centigrade and
   Fahrenheit.)


2. Since about what year after 1980 have global
   ocean temperatures consistently increased (with
   all changes being positive)? What has been the
   highest temperature increase since then, and in
   about what year did it happen?

benefi ts of a tropical cyclone exceed its short-

term harmful effects.

For example, in parts of the U.S. state of

Texas along the Gulf of Mexico, coastal bays and

marshes normally are closed off from freshwater

and saltwater infl ows. In August 1999, Hurri-

cane Brett struck this coastal area. According to

marine biologists, it fl ushed out excess nutrients

from land runoff and swept dead sea grasses

and rotting vegetation from the coastal bays and

marshes. It also carved out 12 channels through

the average intensity of tropical cyclones has in-
creased since 1990. With the number of people
living along the world’s coasts increasing, the
danger to lives and property has risen dramati-
cally. The greatest risk from hurricanes in the
continental United States is along the gulf and
eastern coasts, as shown in Figure 11 (p. S52).
Hurricanes and typhoons kill and injure
people and damage property (Figure 8-18,
p. 177) and agricultural production. Sometimes,
however, the long-term ecological and economic