Tree pruning in Durham, North Carolina
James Kinder, an ISA Certified Municipal Arborist examining a Japanese Hemlock at Hoyt Arboretum
Urban forestry is the care and management of single trees and tree populations in urban settings for the purpose of improving the urban environment. Urban forestry advocates the role of trees as a critical part of the urban infrastructure. Urban foresters plant and maintain trees, support appropriate tree and forest
preservation, conduct research and promote the many benefits trees
provide. Urban forestry is practiced by municipal and commercial arborists, municipal and utility foresters, environmental policymakers, city planners, consultants, educators, researchers and community activists.
Benefits
Professional Tree Climber (arborist: Zack Weiler) climbing a willow tree in Port Elgin, ON. Canada
Urban forests provide environmental, health, and economic benefits to cities. Urban forests mitigate the effects of urban heat island through evapotranspiration and the shading of streets and buildings. This improves human comfort, reduces the risk of heat stroke and decreases costs to cool buildings. Urban forests improve air quality by absorbing pollutants such as ozone, nitrogen dioxide, ammonia, and particulate matter as well as performing carbon sequestration. Urban forests are important to stormwater management. Trees absorb and store rainwater through the canopy, and slow down and filter runoff with their roots.
Urban forests also encourage more active lifestyles by providing space
for exercise and are associated with reduced stress and overall
emotional well-being. Urban forests may also provide products such as
timber or food, and deliver economic benefits such as increased property
values and the attraction of tourism, businesses and investment.
The City of Denver Department of Parks and Recreation website
hosts interactive online tools that allow residents to view the
financial impact to their neighborhoods directly related to healthy tree
planting. In the Washington-Virginia Vale neighborhood the city website
cites 2,002 individual trees as having been planted and maintained by
the City Forester. These trees are believed to bring in an annual
ecosystem benefit of $159,521. This is mostly wrapped up in property
benefits, which cite a contribution to this total of $143,331. The
majorities of these trees are between 0 and 12 feet tall and are a mix
of mostly Elm, Maple, Pine, and Locust species.
Mental health impacts
A 2018 study asked low income residents of Philadelphia "how often they felt nervous, hopeless, restless, depressed and worthless."
As an experimental mental health intervention, trash was removed from
vacant lots. Some of the vacant lots were "greened", with plantings of
trees, grass, and small fences. Residents near the "greened" lots who
had incomes below the poverty line reported a decrease in feelings of
depression of 68%, while residents with incomes above the poverty line
reported a decrease of 41%. Removing trash from vacant lots without
installing landscaping did not have an observable mental health impact.
Practice
Urban forestry is a practical discipline, which includes tree planting,
care, and protection, and the overall management of trees as a
collective resource. The urban environment can present many
arboricultural challenges such as limited root and canopy space, poor soil quality,
deficiency or excess of water and light, heat, pollution, mechanical
and chemical damage to trees, and mitigation of tree-related hazards.
Among those hazards are mostly non-immediate risks like the probability
that individual trees will not withstand strong winds (as during a
thunderstorm) and damage parking cars or injure passing pedestrians.
Although quite striking in an urban environment, large trees in
particular present a continuing dilemma for the field of urban forestry
due to the stresses that urban trees undergo from automobile exhaust,
constraining hardscape and building foundations, and physical damage
(Pickett et al. 2008). Urban forestry also challenges the arborists that
tend the trees. The lack of space requires greater use of rigging
skills and traffic and pedestrian control. The many constraints that
the typical urban environment places on trees limits the average
lifespan of a city tree to only 32 years – 13 years if planted in a
downtown area – which is far short of the 150-year average life span of
trees in rural settings (Herwitz 2001).
Management challenges for urban forestry include maintaining a
tree and planting site inventory, quantifying and maximizing the
benefits of trees, minimizing costs, obtaining and maintaining public
support and funding, and establishing laws and policies for trees on
public and on private land. Urban forestry presents many social issues
that require addressing to allow urban forestry to be seen by the many
as an advantage rather than a curse on their environment. Social issues
include under funding which leads to inadequate maintenance of urban
trees. In the UK the National Urban Forestry Unit produced a series of case studies around best practice in urban forestry which is archived here.
By country
United States
History
Tree warden laws in the New England states are important examples of some of the earliest and most far-sighted state urban forestry and forest conservation
legislation. In 1896, the Massachusetts legislature passed the first
tree warden law, and the other five New England states soon followed
suit: Connecticut, Rhode Island, and New Hampshire in 1901, Vermont in
1904, and Maine in 1919. (Kinney 1972, Favretti 1982, Campanella 2003).
As villages and towns grew in population and wealth, ornamentation of public, or common, spaces with shade trees also increased. However, the ornamentation of public areas did not evolve into a social movement
until the late 18th century, when private individuals seriously
promoted and sponsored public beautification with shade and ornamental
trees (Favretti 1982, Lawrence 1995). Almost a century later, around
1850, institutions and organization were founded to promote
ornamentation through private means (Egleston 1878, Favretti 1982). In
the 1890s, New England's "Nail" laws enabled towns to take definitive
steps to distinguish which shade trees were public. Chapter 196 of the
1890 Massachusetts Acts and Resolves stated that a public shade tree was
to be designated by driving a nail or spike, with the letter M plainly
impressed on its head, into the relevant trunk. Connecticut passed a
similar law in 1893, except its certified nails and spikes bore the
letter C. (Northrup 1887).
The rapid urbanization
of American cities in the late 19th century was a concern to many as
encouraging intellectual separation of humanity and nature (Rees 1997).
By the end of the 19th century, social reformers
were just beginning to understand the relationship between developing
parks in urban areas and "[engendering] a better society" (Young
1995:536). At this time, parks and trees were not necessarily seen as a
way to allow urban dwellers to experience nature, but more of a means of
providing mechanisms of acculturation
and control for newly arrived immigrants and their children (e.g.,
areas to encourage "structured play" and thus serve as a deterrent for
youth crime) (Pincetl and Gearin 2005). Other prominent public
intellectuals were interested in exploring the synergy between ecological and social systems, including American landscape architect Fredrick Law Olmsted, designer of 17 major U.S. urban parks and a visionary in seeing the value of including green space and trees as a fundamental part of metropolitan infrastructure (Young 2009). To Olmsted, unity between nature and urban dwellers was not only physical, but also spiritual:
"Gradually and silently the charm comes over us; the beauty has entered
our souls; we know not exactly when or how, but going away we remember
it with a tender, subdued, filial-like joy" (Beveridge and Schuyler 1983
cited in Young 2009:320). The conscious inclusion of trees in urban
designs for American cities such as Chicago, San Francisco, and
Minneapolis was also inspired by Paris's urban forest and its broad,
tree-lined boulevards as well as by the English romantic landscape movement (Zube 1973). The belief in green cover by early park proponents as a promoter of social cohesion
has been corroborated by more recent research that links trees to the
presence of stronger ties among neighbors, more adult supervision of
children in outdoor areas, more use of the neighborhood common areas,
and fewer property and violent crime (Kuo et al. 1998, Kuo and Sullivan
2001, Kuo 2003).
Many municipalities throughout the United States employ
community-level tree ordinances to empower planning officials to
regulate the planting, maintenance, and preservation of trees. The
development of tree ordinances emerged largely as a response to the Dutch Elm Disease
that plagued cities from the 1930s to 1960s, and grew in response to
urban development, loss of urban tree canopy, and rising public concern
for the environment (Wolf 2003). The 1980s saw the beginning of the
second generation of ordinances with higher standards and specific foci,
as communities sought to create more environmentally pleasing harmony
between new development and existing infrastructure. These new
ordinances, legislated by local governments, may include specific
provisions such as the diameter of tree and percentage of trees to be
protected during construction activities (Xiao 1995). The implementation
of these tree ordinances is greatly aided by a significant effort by
community tree advocates to conduct public outreach and education aimed
at increasing environmental concern for urban trees, such as through
National Arbor Day celebrations and the USDA Urban and Community
Forestry Program (Dwyer et al. 2000, Hunter and Rinner 2004, Norton and
Hannon 1997, Wall et al. 2006). Much of the work on the ground is
performed by non-profits funded by private donations and government grants.
Policy on urban forestry is less contentious and partisan than many other forestry issues, such as resource extraction in national forests.
However, the uneven distribution of healthy urban forests across the
landscape has become a growing concern in the past 20 years. This is
because the urban forest has become an increasingly important component
of bioregional ecological health with the expanding ecological footprint
of urban areas. Based on American Forests' Urban Ecosystem Analyses
conducted over the past six years in ten cities, an estimated
634,407,719 trees have been lost from metropolitan areas across the U.S.
as the result of urban and suburban
development (American Forests 2011). This is often due to the failure
of municipalities to integrate trees and other elements of the green
infrastructure into their day-to-day planning and decision-making
processes (American Forests 2002). The inconsistent quality of urban
forestry programs on the local level ultimately impacts the regional
context in which contiguous urban forests reside, and is greatly
exacerbated by suburban sprawl
as well as other social and ecological effects (Webb et al. 2008). The
recognition of this hierarchical linkage among healthy urban forests and
the effectiveness of broader ecosystem protection goals (e.g.,
maintaining biodiversity and wildlife corridors),
highlights the need for scientists and policymakers to gain a better
understanding of the socio-spatial dynamics that are associated with
tree canopy health at different scales (Wu 2008).
United Kingdom
In the UK urban forestry was pioneered around the turn of the 19th century by the Midland reafforesting association, whose focus was in the Black Country. England's Community Forests.
programme was established in 1990 by the then Countryside Commission as
a pilot project to demonstrate the potential contribution of
environmental improvement to economic and social regeneration. Each
Community Forest was established as a partnership between local
authorities and local, regional and national partners including the
Forestry Commission and Natural England. Collectively, this work has
formed the largest environmental regeneration initiative in England. In
the mid 1990s the National Urban Forestry Unit (NUFU) grew out of a
Black Country Urban Forestry Unit and promoted urban forestry across the
UK, notably including the establishment of the Black Country Urban Forest.
As urban forestry become more mainstream in the 21st century, NUFU was
wound up, and its advocacy role now carried on by organisations such as The Wildlife Trusts and the Woodland Trust.
Constraints
Resolving
limitations will require coordinated efforts among cities, regions, and
countries (Meza, 1992; Nilsson, 2000; Valencia, 2000).
- Loss of green space is continuous as cities expand; available growing space is limited in city centres. This problem is compounded by pressure to convert green space, parks, etc. into building sites (Glickman, 1999).
- Inadequate space is allowed for the root system.
- Poor soil is used when planting specimens.
- Incorrect and neglected staking leads to bark damage.
- Larger, more mature trees are often used to provide scale and a sense of establishment to a scheme. These trees grow more slowly and do not thrive in alien soils whilst smaller specimens can adapt more readily to existing conditions.
- Lack of information on the tolerances of urban tree cultivars to environmental constraints.
- Poor tree selection which leads to problems in the future
- Poor nursery stock and failure of post-care
- Limited genetic diversity
- Too few communities have working tree inventories and very few have urban forest management plans.
- Lack of public awareness about the benefits of healthy urban forests.
- Poor tree care practices by citizens and untrained arborists.
