Big trees thrive in urban areas: “Most
of Virginia’s big trees, amazingly enough, are found
in urban areas,” says Jeff Kirwan, associate professor
in forestry at Virginia Tech and 4-H Extension specialist.
He has combined the 4-H program with the state’s Big
Tree Program to publish the official list of Virginia’s
largest trees on the College of Natural Resources website. In
recognizing the commonwealth’s rich natural heritage,
the register lists the largest of each tree species found.
The program relies on volunteers to search for, nominate,
and verify the measurements of big trees. Kirwan
is continually updating the list. In 2003, 17 newly found
big Virginia trees were added, keeping the state near the
top in the nation with the most. The easy-to-use database
provides detailed information, including directions to the
trees.
The destructive practice of "tree topping" can kill trees, lowers property values, and is costly.
Champion Honeylocust at Fincastle, Va., United Methodist Church. Photo by John McCormick.
Champion Copper Beech at Fairfax, Va., Christian Church
Reasons to plant trees: Planting 30 trees each year offsets greenhouse gases from your car and home, according to American Forests. A large front-yard tree can save $29 in summertime air-conditioning costs by shading the building (that’s about 9 percent of a typical home’s annual total AC cost). The same tree can absorb 10 pounds of air pollutants, including four pounds of ozone and three pounds of particulates. It can intercept 760 gallons of rainfall in its crown, thereby reducing stormwater runoff. And it can clean 330 pounds of CO2 from the atmosphere through direct sequestration in the tree’s wood (source: Center for Urban Forest Research, Davis, California).
Urban and forest? How can those words be yoked together?
Urban forest — not a clump of trees here, a grove there, a solitary
maple beside some bus stop, but a green aggregate, living presence interwoven
with the built world. Without trees, our cities would be a sterile landscape.
Can you imagine New York City without Central Park?
However, burgeoning growth of metropolitan areas threatens the survival
of most urban forest areas. The cost of building and maintaining infrastructure
while keeping the air, water, and energy needs safe for residents has
created a seemingly insurmountable challenge.
One promising solution is engineering cities into existing natural systems
— not a new idea but one that is not yet widely practiced. Trees
are the lungs, water filters, and air conditioners of our cities. Many
research and demonstration projects over the past decade have shown how
effectively trees clean the air, purify surface water, and cool urban
heat islands. Urban forestry offers a way that cities can build according
to nature’s laws and rise above the financial, ecological, and social
tides of urban growth.
“Don’t underestimate the value of tree cover in the nation’s
cities,” cautions Brian Kane, head of the new urban forestry program
at Virginia Tech’s College of Natural Resources. A new breed of professionals
called urban foresters is helping rebuild the urban environment, using
trees and forests.
Is
it possible to have an environmental parking lot? “The question really
is, how do we integrate our gray and green infrastructure to have the
best of both?” says Kane. “We now have some very effective GIS-based
(geographic information system) technologies that the urban forester can
use to help inventory, assess, manage, and plan the future of our urban
ecosystems. Schools, parks, parking lots, and roadways can be made nicer
with proper planning of the urban forest.”Good master plans for urban
forestry will include parks, trail systems, and green infrastructure.
Management of these valuable resources is called urban and community forestry.
An urban forest includes all of the vegetation in and around a dense human
settlement, according to R.W. Miller in his pacesetting 1997 book, Urban
Forestry: Planning and Managing Urban Greenspaces. Miller wrote, “Some
of these forested areas may have been intentionally planned and landscaped,
while other forested areas are left over from small tracts of land preserved
during development or left unattended. When buildings and other man-made
structures are included with the urban forest, a complex ecosystem exists.
The urban ecosystem and the urban forests are an indicator for the health
of the humans in that area. In short, our health can be judged by the
health of our urban forests.”
As a discipline, urban forestry brings together elements of arboriculture,
forestry, horticulture, landscape architecture, and land use planning
to manage or establish trees, forest ecosystems, or open green space in
urban and community settings.
Kane, an assistant professor of forestry, points out that there are two
components to this relatively new profession: urban forestry and arboriculture.
“Urban forestry deals with the management and maintenance of trees
in a development setting where trees are interspersed with buildings,”
he says. “Arboriculture is more microscale and deals with the maintenance
of individual trees, such as how you plant a tree, prune it, manage pests,
and keep it healthy. Urban forestry relates to a larger scale.”
Kane explains that because more and more people are moving to developed
settings, urban forestry has quickly become one of the hottest professions
today. “The people who manage urban settings, as well as the people
living there, need to know the benefits of having trees there and how
to care for them to maximize the benefits and minimize the costs,”
he says. “In addition, this new professional field serves the function
of trying to make urban developments more pleasant.”
The first planned communities, known as garden cities, were developed
in the early 1900s. “Planners began realizing how nice it was to
have trees in urban settings. Such was the case with F.L. Olmstead, who
wanted to connect Chicago’s existing parks,” Kane says. “The
principle of planning, however, doesn’t apply just to major metropolitan
areas but anywhere where trees and gray infrastructures interact.”
Developer Richard Foster, owner of Baymark Construction Corporation on
Virginia’s Eastern Shore, has more than 40 years’ experience
in the construction business. He says, “Old growth trees, open water,
and wetlands are precious resources that add so much to everyone’s
quality of life. My personal goal in every development has been to preserve
the natural features of the land upon which we build for residents and
future generations to enjoy.” Foster has started a scholarship at
Virginia Tech’s College of Natural Resources for urban forestry students.
Support also comes from Trees Virginia (the state’s Urban Forestry
Council) and the Mid-Atlantic Chapter of the International Society of
Arboriculture (ISA). And Davey TreeExperts and Wood Acres Tree Specialists
in Maryland have given tree climbing equipment and other tools to the
program.
“As more citizens interact with an urban forest,” Kane continues,
“we will be training professionals to help them understand and think
about the natural processes and benefits that trees provide.”
While the task of quantifying a community’s urban forest is still
in its infancy, tree cover appears to be the best indicator for measuring
the extent of a community’s urban forest. The tree cover for a community
can be measured thanks to images taken by NASA’s Earth Observing
Landsat satellites. Software programs are available to convert Landsat
images into detailed urban tree cover images, so that the percent of a
community’s tree cover can be figured. (See “Mapping forests…”
in Graduate Student Research.)
“Unfortunately, these images reveal a dramatic decline of urban
forests across the United States,” warns Joe Murray, a member of
the Trees Virginia board and biology professor at Blue Ridge Community
College, where he also heads up the arboretum. Urban sprawl, planned and
unplanned, has been steadily replacing natural areas. In Virginia, the
population grew 14 percent from 1990 to 2000 (U.S. Census Bureau, 2001).
These additional people need a place to live, work, and shop, which results
in more buildings, roads, and other components of a gray infrastructure.
“In a sense, urban sprawl is converting Virginia’s natural forests
into urban forests, howbeit scraggly or haphazardly nice,” Murray
says.
The nation’s metropolitan areas cover a quarter of the country’s
land area and contain 74.4 billion trees, according to research by Susan
Day, visiting assistant professor and adjunct researcher. This is nearly
25 percent of the total tree canopy in the United States. “Trees
in the smaller cities, towns, and villages account for another 2.8 percent
of the total tree canopy cover, or about 3.8 billion trees,” Day
says. “When you factor in that nearly eight out of every 10 Americans
live in urban areas, you see the importance that trees have for city dwellers.”
Day’s review of the literature showed that Americans spent $1.693
billion for landscaping and tree and shrub care in 1999. The South and
Mid-Atlantic regions are among the fastest-growing in terms of garden
sales. But while these figures have blossomed, they haven’t been
enough to offset the escalating deficit of canopy cover.
Day found that urban areas in Virginia, which are growing each year,
currently account for more than 8 percent of Virginia’s land area.
The state’s average urban canopy cover of 35.3 percent approximates
the national average. However, the variation among the cities and towns
is substantial:
Big Stone Gap town — 86.1 percent canopy cover
Blacksburg town — 28 percent
Charlottesville city — 13.4 percent
Harrisonburg city — 1.4 percent
Herndon town — 4.1 percent
Quantico Station census area — 72 percent
Williamsburg city — 55 percent
As for the land lost to development, the Audubon Society reported that
between 1982 and 1992, 45,360 acres in Virginia were consumed. From 1992
to 1997, that number more than doubled. Virginia ranked 12th in the amount
of land lost to development.
Trees covered 37 percent of neighboring Washington, D.C., in 1973. By
1997, that had dwindled to a mere 13 percent.
Murray declares, “If the health of a community is reflected by the
health of a community’s urban forests, then all indicators point
to a serious problem for many communities across Virginia.”
American Forests, the organization leading the way in urban forestry,
points out that the problem of tree loss due to urban sprawl is compounded
by the additional problem that in an urban environment trees are exposed
to a great many more stresses than trees in a natural setting. The average
city tree lives only 32 years and dies just before it reaches its ultimate
potential to benefit an urban area. Because of this high tree mortality,
communities are experiencing a “tree deficit” in their urban
forests. Trees have been disappearing from urban areas at a rate of four
removals for each new tree planted. Researcher Gary Moll, vice president
of American Forests’ Urban Forest Center, estimated in 2001 that
the urban forests across the United States experienced a tree deficit
of more than 634 million trees during the past 30 years.
Trees
Virginia, which College of Natural Resources dean Greg Brown helped form
more than a decade ago, has been focusing on educating citizens against
the destructive practice of “tree topping.” The drastic removal
of large branches in mature trees leaves large, open wounds that subject
the tree to disease and decay. As one strategy to extend the lives of
urban trees, the organization trains tree care professionals and advises
the public on how to care for urban trees. Tree topping can kill trees,
lowers property values, and is costly. Research shows that pruning a tree
to retain its natural shape saves a homeowner $1,150 over a five-year
period in maintenance costs.
In addition to tree topping, there are other issues involved in growing
city trees, such as safety. Kane is researching tree failure to refine
tree risk assessment so that urban foresters can tell if a tree will fall.
The stakes are high because a big tree can be a great hazard if it is
not safe.
Just as he was finishing his Ph.D. at the University of Massachusetts
at Amherst, Kane learned of a group of large shade trees near the university
that were going to be removed so the area could be redeveloped. Since
the trees were going to be destroyed anyway, “It presented a tremendous
opportunity to do controlled research to observe patterns of failure,”
he says. “These are the exact kind of trees arborists and urban foresters
want to know about.”
With support from the TREE Fund, the merged organization of the International
Society of Arboriculture Research Trust and the National Arborist Foundation,
Kane has spent two summers breaking the mature trees one by one by exerting
force on them with a cable winch skidder. “We exert force that we
can measure so that we can determine where failure occurs. We are able
to control many of the variables. The goal is to observe patterns and
be able to predict failure.”
In another project, the energetic assistant professor of forestry has
launched a tree fertilization project with Virginia Tech horticulture
associate professor Roger Harris. “There is conflicting or ambiguous
information on what is the appropriate amount of fertilizer when you first
plant a tree,” Kane explains. “There are a lot of variables
that influence how fertilizer interacts with the tree system.” The
pair planted trees from the university’s tree farm around the baseball
field and the football practice field. Some will not be fertilized and
others will be fertilized according to different regimens. The researchers
will monitor growth rates and insect and disease damage for several years
so that they can help the arboriculture industry grow trees better.
Day’s research focuses on how to protect trees during construction.
She notes, “Just putting more trees in a city is not that simple.
We need to know that those trees will grow and that they are placed well
to provide the maximum services. This is not automatic but really a science
that requires professional study. As development expands, the science
becomes more critical. Lands are turning over all the time. There is constant
change to the cityscape and the infrastructure is constantly disrupted.
Urban forestry maxes out the benefits of trees.”
“As long as populations live in close proximity with trees, we will
need to have an understanding of the natural world,” says Kane. “Trees
provide benefits to residents everywhere. Along with the tangible benefits
we can’t forget the intangible benefits, such as the fact that many
people feel more comfortable with trees around and enjoy their aesthetic
appeal.
“And we need to remember that it’s not good enough just to
have trees in urban areas. We also need to know how to care for them so
they are community assets and not a liability,” Kane says.
