Visualizing Environmental Science

Summary 345

Seed tree cutting Clear-cutting

forage; water resources and watershed protection; mining;

hunting, fishing, and other forms of recreation; and habitat for

fishes and wildlife.

3

Rangelands 333

1. Rangelands are grasslands that aren’t intensively managed
   and are used for grazing livestock. Rangelands are also mined
   for mineral and energy resources, used for recreation, and
   preserved for biological habitat and for soil and water resources.


2. Overgrazing is the destruction of vegetation caused by too
   many grazing animals consuming the plants in a particular
   area, leaving them unable to recover. Overgrazing accelerates
   land degradation, which decreases the future ability of the
   land to support crops or livestock. Desertification is the
   degradation of once-fertile rangeland or tropical dry forest
   into nonproductive desert.


3. A conservation easement is a legal agreement that
   protects privately owned forest or other property from
   development for a specified number of years. Conservation
   groups often pay for conservation easements to preserve
   open rangeland.


4. The BLM manages more than three-fourths of U.S. public
   rangelands, excluding Alaska; the USFS manages the
   remainder. Current issues on public rangelands include
   conflicts between environmental groups and ranchers over
   the number of livestock allowed to graze and the potential
   to manage the areas for uses such as biological habitat,
   recreation, and scenic value. Conflicts also arise over whether
   grazing fees paid by livestock operators on public lands
   should be high enough to cover all costs of maintaining herds,
   removing taxpayer burden.

Summary

1

Land Use in the United States 322

1. More than one-half of U.S. land is privately owned.
   Approximately one-third—including many types of ecosystems
   and land uses—is owned by the federal government. Nine
   percent belongs to state and local governments, and more
   than 2 percent to Native American tribes.

2

Forests 324

1. Sustainable forestry is the use and management of forest
   ecosystems in an environmentally balanced and enduring
   way. Sustainable forestry maintains a mix of forest trees, by
   age and species, rather than a monoculture, in which only
   one type of plant is cultivated over a large area. Adopting
   sustainable forestry principles requires setting aside
   sanctuaries and habitat corridors, protected zones that
   connect isolated unlogged or undeveloped areas.


2. Deforestation is the temporary or permanent clearing of
   large expanses of forest for agriculture or other uses. Clear-
   cutting is a logging practice in which all the trees in a stand
   of forest are cut, leaving just the stumps; clear-cutting over
   a wide area is ecologically unsound. The major causes of
   tropical deforestation are subsistence farming, commercial
   logging, and cattle ranching, all accelerated by growing
   human populations. Increased needs for fuelwood drive
   deforestation of tropical dry forests.


3. Most U.S. national forests are managed by the U.S. Forest
   Service (USFS); the rest are overseen by the Bureau of Land
   Management (BLM). National forests face conflicts associated
   with supporting multiple uses: timber harvest; livestock

✓✓THE PLANNER