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Review the indicators
at a glance
- How intensively managed are U.S. forest lands? In 2002,
18% of western forests and 3% of eastern forests were in federal
wilderness areas and national parks (reserved forest), while
11% of eastern forests and 4% of western forests resulted from
replanting with seedlings in anticipation of future timber harvest.
Nationwide, planted timberlands increased
more than tenfold since 1953 to about 46 million acres. In the
U.S. outside of Alaska, reserved lands have nearly doubled since 1953
to about 44 million acres. Data for Alaska are difficult to interpret
because of changes in classification methods. Most forest lands
in the United States—including
those used for timber production—are neither national parks
or wilderness areas nor planted forests.
- How fragmented are U.S. forests? One way to report on
forest fragmentation pattern is to describe the degree to which
any forested point is surrounded by land that is mostly forested
(at least 90% forest cover). About two-thirds of all points in
both eastern and western forests are surrounded by mostly forest
cover within a radius of about 250 feet. About a quarter of all
forest points have mostly forest cover within about a 21/2-mile
radius. Tracking this indicator over time will make it possible
to distinguish between natural forest patterns and changes caused
by human activity. In addition, methods available in the future
may allow identification of smaller features (for example, forest
roads and small clearings with houses) than can readily be mapped
using the current satellite data that this indicator relies upon.
Chemical and Physical Conditions
Two indicators describe the chemical and physical condition of
forests. We track nitrate in forest streams because elevated concentrations
of this nutrient can be a sign of plants under stress or of increased
inputs from sources such as atmospheric deposition and conversion
of forest to other land use. We track carbon storage because carbon
is the major building block of forest systems and because increased
carbon storage in forests can offset emissions of carbon dioxide
from burning fossil fuels.
- How much nitrate is there in forest streams? Almost all
forest streams had nitrate concentrations below 1 part per million;
more than half had concentrations below 0.1 part per million.
The federal drinking water standard is 10 parts per million. No
trend data are available, but streams in forested regions have
the lowest nitrogen concentrations, farmland streams the highest.
- How much carbon is stored in U.S. forests? Increased
carbon storage by forests and other ecosystems can offset emissions
of carbon dioxide from the burning of fossil fuels, of concern
because of climate change. The amount of carbon stored in trees
on timberlands (a USDA Forest Service designation for areas with
trees that grow fast enough to support timber harvests and on
which harvest is not prohibited by law) has gone up steadily in
the East and remained stable in the West. Data are not adequate
for national reporting on carbon stored in roots, forest floor
litter, and soil.
Biological Components
Six indicators describe the biological condition of the forests.
One tracks the fraction of native forest species according to their
relative risk of extinction. A related measure tracks changes in
forest plant communities—specific plant groupings—whose
area has declined by at least 70% since presettlement times. Because
forests of different age structures provide different goods, services,
and values, a third measure tallies the age distribution of forest
trees. The remaining three indicators focus on several key forest
disturbances. The first focuses on non-native plants, which can
be ecologically disruptive; the second tracks acres of forest affected
by fire, insects, and disease; and the third indicator will focus
on fire frequency, a key determinant of forest composition, once
adequate data become available.
- What are the percentages of forest-dwelling species that
are at different levels of risk of extinction? About 9% of
1,700 native animal species that depend on forests are considered
critically imperiled or imperiled, and about 1.5% of forest species
may already be extinct. When “vulnerable” species are
counted, a total of 20% of forest species are considered to be
at risk. Interpretation of these data will be greatly enhanced
when it is possible to present information on population trends
for these species.
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