Foresters Push Green Mends Amid Gray Concrete Of Cifies
SYRACUSE, N.Y.-Urban
foresters recognize that most
people can’t see the forest for the
skyscrapers.
And no wonder. The very con
cept of an “urban forest” seems
contradictory. Forests and cities
aren’t supposed to grow together.
Yet 60 to 80 percent of urbanized
areas in the temperate regions of
the world meet the criteria of
forests, says Rowan A. Rowntree
of the U.S. Forest Service.
Cities are more wooded than we
think. Trees cover about 30 percent
of the land in an average U.S. city.
Islands of green have survived
among the gray concrete.
Tree-Filled Bronx
Even in densely populated New
York City, there are 4,500 acres of
oak and luckory forests, most of
them in the Bronx. In the borough
of Queens, there are as many trees
as there are people, about 1.8
million. The Forest Preserve
District of Cook County en
compasses 65,000 acres of
metropolitan Chicago.
In as much as 80 percent of any
city, excluding its central business
district, there is three to four times
more vegetation surface—leaves,
shrubs, and grass—than artificial
surface—streets, sidewalks,
parking lots, and houses.
“When we say cities are made of
concrete and building materials,
that’s not really accurate,”
Rowntree says. “They are made
up mostly of vegetation.” Among
the exceptions are some cities in
the arid Southwest, such as Tuc
son, Ariz.
Only recently have foresters
paid much attention to the urban
forest ecosystem, which can in
fluence local climate and provide a
habitat for other plants and
animals.
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selected cities across the country
by studying aerial photographs
and satellite images. He is project
leader of the Forest Service’s
Northeastern Forest Experiment
Station in Syracuse.
The Forest Service began a
small urban-forestry program in
1978. That year it joined the
American Forestry Association in
sponsoring the first National
Urban Forestry Conference.
Nationally, urban forests are
estimated to number in the
millions of acres. From the air,
Rowntree says, a typical U.S. city,
except in the Southwest, appears to
be about a third trees, a third
grass, and a third artificial sur
face. About half the city is
residential; a fourth is parks and
vacant land; and the other fourth
is commercial, industrial, and
institutional.
Wooded Hillsides
Among the most-forested cities
are those built on hills, such as
Birmingham, Ala., and Cincinnati,
where much of the land is still
undeveloped hillsides.
A Forest Service study of New
Orleans trees—live oak, crape
myrtle, slash pine, loblolly pine,
and southern magnolia
concluded that they constitute “a
genuine forest.” About 21 percent
of the developed part of the city is
covered by tree canopy.
“looking down on Salt Lake
City, you see a landscape that
looks like Connecticut,” Rowntree
says. “In what was almost a desert
basin, the city over the years has
created an urban forest.” Tree
cover reduces water runoff about
20 percent.
In Carmel, Calif., trees are
revered citizens. Some 32,000
trees, mostly tall Monterey pine,
crowd the one-square-mile town,
far outnumbering its 4,700 people.
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An island forest grows in the middle of the Potomac River between downtown
Washington, D.C., and the high-rise office buildings of Arlington, Va., on the opposite
bank (not seen). The trees of Theodore Roosevelt Island constitute an "urban forest,"
found in more cities than many people realize.
“Ours is actually a village within businesses, began an urban
a forest,” says City Forester Gary reforestation program in a number
Kelly, who keeps a computerized of barren downtown areas,
inventory of every tree. “We have Dayton, Ohio, officials consulted
no sidewalks, no curbs; we have the Forest Service about reducing
trees along the streets and trees in summertime temperatures
the middle of streets that you have downtown. Rowntree says
to drive around.” recommendations included
On a much larger scale, Atlanta planting more trees on streets and
is a rapidly growing city within a parking lots and converting some
forest. More than 743,000 acres of lots from black asphalt to per
forest land and an estimated 62 forated concrete blocks to allow
million trees make Atlanta one of grass to grow through. The air
the most heavily forested urban temperature above a “green”
areas in the country. parking lot is about 10 degrees
But the Atlanta Regional cooler, he says.
Commission, concerned that urban Computers Aid Planning
sprawl might eventually create a Rowntree hopes eventually to
terribly hot city, has sought advice develop computer programs to
from the Forest Service. In 1984, help individual cities determine
Trees Atlanta Inc., founded by the the “optimum plan for urban
parks commission and city vegetation, species of trees, size,
Bt£MpCo6o2s
and location, just as they prepare
optimum plans for sewer pipes,
roads, and utility lines,” he says.
“We could program for
maximum summer shading, for
example, then feed in maximum
access to low sun in winter.”
Sunshine in winter can be critical,
particularly for people using solar
collectors for heating.
Yet even without leaves, a single
sugar maple can cause about a 40-
percent reduction in sunlight
reaching a southern exposure,
says Gordon M. Heisler, forest
meteorologist at the Northeastern
Forest Experiment Station in
University Park, Pa. “A bare tree
still has all those branches and
twigs, and a large mass up there in
its crown.”