Visualizing Environmental Science

Conservation of Land Resources 341

The 15 most endangered ecosystems in the United

States (in order of priority) s Table 13.2

South Florida landscape

Southern Appalachian spruce-fir forests

Longleaf pine forests and savannas

Eastern grasslands, savannas, and barrens

Northwestern grasslands and savannas

California native grasslands

Coastal communities in the lower 48 states and Hawaii

Southwestern riparian communities

Southern California coastal sage scrub

Hawaiian dry forest

Large streams and rivers in the lower 48 states and

Hawaii

Cave systems

Tallgrass prairie

California river- and stream-bank communities and

wetlands

Florida scrub

Conservation of Land Resources

LEARNING OBJECTIVES

that set aside ecosystems is the best way to preserve an

area’s biodiversity.

As you have seen in this chapter, government agen-

cies, private conservation groups, and private citizens

have begun to set aside natural areas for permanent pres-

ervation. Such activities ensure that our children and

grandchildren will inherit a world with wild places and

other natural ecosystems.

1. What are three U.S. ecosystems that need
   protection? How do you think humans
   have caused these ecosystems to become
   endangered?


2. What are three criteria used to evaluate
   whether an ecosystem is endangered?


3. Name at least three of the most endangered
   ecosystems in the United States.


4. Describe several of the criteria used to
   evaluate whether an ecosystem is endangered.

O

ur ancestors considered natural areas an
unlimited resource to exploit. They appre-
ciated prairies as valuable agricultural land
and forests as immediate sources of lumber
and eventual farmland. This outlook was practical as
long as there was more land than people needed. But
as the population increased and the amount of avail-
able land decreased, people began to view land as a
limited resource. Thus, exploitation has increasingly
shifted to preservation of the remaining natural areas
in the United States and elsewhere around the world
(Figure 13.14).
Although all types of ecosystems must be con-
served, several are in particular need of protection.
The U.S. Geological Survey and the Defenders of
Wildlife commissioned studies that ranked the most
endangered ecosystems in the United States. They
used four criteria:

1. The area lost or degraded since Europeans colonized
   North America


2. The number of present examples of a particular eco-
   system, or the total area


3. An estimate of the likelihood that a given ecosystem
   will lose a significant area or be degraded during the
   next 10 years


4. The number of threatened and endangered species
   living in that ecosystem

Table 13.2 lists the 15 most endangered U.S. ecosystems
based on these criteria. Examples include the South
Florida landscape, southern Appalachian spruce-fir for-
ests, and longleaf pine forests and savannas. As these
ecosystems are lost and degraded, the organisms that
compose them decline in number and in genetic diver-
sity. Researchers have also found that some rare types
of soils are threatened, endangering individual species
that rely on them. Implementing conservation strategies

Source: From Box 1.1 in Noss, R.F., M.A. O’Connell, and D.D. Murphy. The Science

of Conservation Planning: Habitat Conservation Under the Endangered Species

Act, Island Press: World Wildlife Fund (1997).