SUPPLEMENT 5 S31

SUPPLEMENT

5

replenished very slowly and were highly suscep-

tible to water and wind erosion when protective

vegetation was removed for growing crops and

grazing livestock. Within a few decades, the set-

tlers degraded much of this natural capital that

had taken thousands of years to build up.

When the settlers realized what was hap-

pening, they took corrective action to save the

remaining trees, and they stopped raising eco-

logically destructive pigs and goats. The farmers

joined together to slow soil erosion and preserve

their grasslands. They estimated how many

sheep the communal highland grasslands could

sustain and divided the allotted quotas among

themselves.

Icelanders also learned how to fi sh, how to

tap into an abundance of hot springs and heated

rock formations for geothermal power, and

how to use hydroelectric power from the many

rivers. Renewable hydropower and geothermal

energy provide about 95% of the country’s

electricity, and geothermal energy is used to

heat 80% of its buildings and to grow most of its

fruits and vegetables in greenhouses.

In terms of per capita income, Iceland is one

of the world’s ten richest countries, and in 2006

it had the world’s fi fth highest Environmental

Sustainability Index. By 2050, Iceland plans to

become the world’s fi rst country to run its entire

economy on renewable hydropower, geothermal

energy, and wind, and to use these resources to

produce hydrogen for running all of its motor

vehicles and ships (see Chapter 16 Core Case

Study, p. 399).

THINKING ABOUT

Past Civilizations

What are two ecological lessons that we could

learn from these three stories?

S5-2 An Overview of

U.S. Environmental

History

There Have Been Four Major Eras

of U.S. Environmental History

The environmental history of the United States

can be divided into four eras. During the tribal

era, 5–10 million tribal people (now called

Native Americans) occupied North America for

at least 10,000 years before European settlers

began arriving in the early 1600s. These hunter–

gatherers generally had sustainable, low-impact

ways of life because of their low numbers and

low resource use per person.

The Sumerian Civilization

Collapsed Because

of Unsustainable Farming

By around 4000 B.C., a highly advanced urban

and literate Sumerian civilization had begun

emerging on the fl ood plains of the lower

reaches of the Tigris and Euphrates Rivers in

parts of what is now Iraq. This civilization devel-

oped science and mathematics and built a well-

engineered crop irrigation system, which used

dams to divert water from the Euphrates River

through a network of gravity-fed canals.

The irrigated cropland produced a food

surplus and allowed Sumerians to develop the

world’s fi rst cities and written language (the

cunneiform script). But the Sumerians also

learned the painful lesson that long-term irriga-

tion can lead to salt buildup in soils and sharp

declines in food production.

Poor underground drainage slowly raised the

water table to the surface, and evaporation of

the water left behind salts that sharply reduced

crop productivity—a form of environmental

degradation we now call soil salinization (Fig-

ure 12-14, p. 289). As wheat yields declined, the

Sumerians slowed the salinization by shifting

to more salt-tolerant barley. But as salt con-

centrations continued to increase, barley yields

declined and food production was undermined.

Around 2000 B.C., this once-great civilization

disappeared as a result of such environmental

degradation, along with economic decline and

invasion by Semitic peoples.

Iceland Has Had Environmental

Struggles and Triumphs

Iceland is a Northern European island country

slightly smaller than the U.S. state of Kentucky.

This volcanic island is located in the North

Atlantic Ocean just south of the Arctic Circle

between Greenland and Norway, Ireland, and

Scotland. Glaciers cover about 10% of the coun-

try, and it is subject to earthquakes and volcanic

activity.

Immigrants from Scandinavia, Ireland, and

Scotland began settling the country during the

late 9th and 10th centuries A.D. Since these set-

tlements began, most of the country’s trees and

other vegetation have been destroyed and about

half of its original soils have eroded into the sea.

As a result, Iceland suffers more ecological deg-

radation than any other European country.

The early settlers saw what appeared to be a

country with deep and fertile soils, dense forests,

and highland grasslands similar to those in their

native countries. They did not realize that the

soils built up by ash from volcanic eruptions were

S5-1 A Look at Some Past

Civilizations

The Norse Greenland
Civilization Destroyed Its
Resource Base

Greenland is a vast and mostly ice-covered
island about three times the size of the U.S. state
of Texas. During the 10th century, Viking ex-
plorers settled a small, fl at portion of this island
that was covered with vegetation and located
near the water.
In his 2005 book, Collapse: How Societies Choose
to Fail or Succeed, biogeographer Jared Diamond
describes how this 450-year-old Norse settle-
ment in Greenland collapsed in the 1400s from a
combination of colder weather in the 1300s and
abuse of its soil resources.
Diamond suggests the Norse made three ma-
jor errors. First, they cut most of the trees and
shrubs to clear fi elds, make lumber, and gather
fi rewood. Without that vegetation, cold winds
dried and eroded the already thin soil. The
second error was overgrazing, which meant the
depletion of remaining vegetation and trampling
of the fragile soil.
Finally, when wood used for lumber was
depleted, the Norse removed chunks of their
turf and used it to build thick walls in their hous-
es to keep out cold winds. Because they removed
the turf faster than it could be regenerated, there
was less land for grazing so livestock numbers
fell. As a result, their food supply and civilization
collapsed. Archeological evidence suggests the
last residents starved or froze to death.
After about 500 years, nature healed the
ecological wounds that the Norse had caused,
and Greenland’s meadows recovered. In the
20th century, Danes who settled in Greenland
reintroduced livestock. Today, more than 56,000
people make their living there by mining, fi sh-
ing, growing crops, and grazing livestock.
But there is evidence that Greenland’s green
areas—about 1% of its total land area—are
again being overused and strained to their limits.
Now Greenlanders have the scientifi c knowl-
edge to avoid the tragedy of the commons by
reducing livestock numbers to a sustainable
level, cutting trees no faster than they can be
replenished, and practicing soil conservation.
Because of global warming, some of the ice
that covers most of Greenland is melting (Fig-
ure 19-C, p. 508). This may increase agricultural
activity and extraction of mineral and energy
resources. Time will tell what benefi cial and
harmful environmental effects such changes
will bring.

Environmental History

(Chapters 1, 2, 5, 7, 8)