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Review the indicators
at a glance
- What percentage of the plant cover in forests is not native
to the region? Non-native plants can crowd out native plants
and may provide poorer quality habitat for wildlife. Data are
not adequate for national reporting on the amount of non-native
cover in forests.
- How much of the nation’s forests is young, middle-aged,
or old? Data are currently available only for 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. Sixty-four percent of eastern
timberlands are less than 60 years old, and about 90% are
less than 100 years old. About 35% of western timberlands
are more than 100 years old. No trend data are available.
Forest age is affected by historical and management factors,
as well as by the difference in life spans of different species.
- How many acres are affected each year by fires, insects,
and tree disease? Since 1980, between 2 million and 7
million acres were burned by wildfire per year, down from
a high of 52 million acres in 1930 (note that these figures
include some grassland and shrubland fire acreage). Insect
damage decreased overall from 1979 to2002, but there are
dramatic year-to-year variations (over these two decades,
damage ranged from 8 million acres to 46 million acres).
- Are forest fires burning much more or less frequently than
in presettlement times? The frequency with which forests burn
is an important factor in shaping the composition of the forest.
Data are not adequate for national reporting on this indicator.
- How much area is occupied by forest types that have declined
in area significantly since presettlement times? Are these
forest types increasing or decreasing in area now? Many forest
community types now occupy a small fraction of their former area.
Data are not adequate for national reporting on this indicator.
Human Use
Two of the indicators of human use of forests focus on timber:
the first tracks timber harvest and the products into which it is
made (for example, sawlogs or pulpwood). The second reports whether
each year’s harvest is greater or less than that year’s
growth. A third measure focuses on recreational use of forests.
- How much timber is harvested each year, and what is it used
for? Nationally, timber harvest grew by 35% from 1952
to 2001. There was slow, steady growth through 1976, followed
by a sharp increase from 1976 to 1986, and a subsequent decline.
Pulpwood and sawlogs account for more than half of all harvest;
other uses include fuelwood and veneer logs.
- How much timber grows each year, compared to the amount
that is cut? Growth exceeds harvest on both public and
private timberlands in the East and West; this has been true
for most of the past 50 years. In 1997, growth was higher
than it was in the 1950s on all categories of land, although
growth on eastern forest lands (both public and private) was
about the same as it was in the mid-1970s. Nationally, almost
90% of harvest occurs on private lands.
- How much recreational activity takes place in the nation’s
forests? Walking and viewing activities are the most common
forms of recreation in forests. Americans take about 6 billion
forest walks per year and view scenery and wildlife about
7 billion times per year. Hiking and climbing is next in popularity;
people undertake this activity about 3 billion times per year.
What do we mean by “forests”?
Many of the data reported here are based on the USDA Forest Service
definition of forest: any lands at least 10% covered by trees of
any size, at least one acre in extent. This includes both heavily
treed areas and areas where trees are intermingled with other cover,
such as the chaparral and pinyon–juniper areas of the Southwest.
This definition includes both naturally regenerating forests and
areas planted for future harvest (plantations or “tree farms”)—that
is, areas that may not have mature trees now, but that will in the
future, are classified as forest.
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