for community forest programs
Goals are central to developing an ordinance. Goals
provide the basis for formulating and evaluating the management strategy
and any tree ordinance that results from it. Thus, selecting appropriate
and meaningful goals (step D
) is crucial
to the success of the entire process. The goals described below are consistent
with good urban forest management and are typical for municipal tree programs,
but this list is not comprehensive. (If you would like to see additional
goals treated here, please contact
The goals described here are also specific enough to allow for evaluation.
There is little point in establishing a goal if there is no practical way
of determining whether progress is being made towards realizing that goal.
To answer the management questions "Are
you getting what you want?" and "What
do you have?", you will need to evaluate tree resources, management
activities, and public attitudes. Evaluation methods
are important tools for formulating and monitoring tree management strategies
and monitoring ordinance performance.
A variety of approaches can be used to help attain any given goal. You
will need to decide which approaches are most appropriate for your own
community. If the goal is to be addressed through a tree ordinance, one
or more ordinance provisions may apply. For each goal listed below, we
have included links to specific ordinance provisions that can be used to
address that goal. We also describe and provide links to evaluation
methods that can be used to evaluate progress towards each goal.
Possible tree program goals:
Establish and maintain maximum tree cover.
The urban forest serves a wide variety of functions that promote the health,
safety, and general welfare of residents. These functions include:
conserving energy, by providing shade and evaporative cooling through transpiration;
improving local and global air quality by absorbing carbon dioxide and
ozone, adsorbing particulate matter, and producing oxygen;
reducing wind speed and directing air flow;
reducing noise pollution;
providing habitat for birds, small mammals, and other wildlife;
reducing storm runoff and the potential for soil erosion;
increasing real property values;
enhancing visual and aesthetic qualities that attract visitors and businesses
and serve as a source of community image and pride.
All these benefits increase as canopy cover increases. By establishing
and maintaining maximum tree cover, the community is able to realize the
maximum benefits the urban forest can provide. The maximum amount of tree
canopy a given community can support must be determined by analyzing limitations
posed by climate and land use.
Tree ordinance provisions covering planting, maintenance, and removal of
trees on public and private land are related to this goal. Performance
standards for the amount of tree cover the community hopes to achieve and
maintain along streets, parking lots, residential and commercial areas,
parks and open spaces should be established in these provisions. A provision
calling for development of an urban forest management plan is essential
to this goal. This plan should provide for a sustained forest canopy through
properly phased tree planting and removal.
Tree canopy cover is one of the most basic and useful descriptors of the
urban forest. Simply put, it is the percentage of land area covered by
tree canopies. By periodically measuring canopy cover, communities can
assess the effectiveness of ordinances and other management methods aimed
at maintaining or increasing tree canopy.
Canopy cover can be measured directly, through photogrammetry
from aerial photographs or digitized aerial images) or
surveys. These methods can be relatively easy to use, and do not necessarily
require expensive equipment. Tree density, the number of trees per unit
area, is indirectly related to tree canopy cover. Tree density can also
be used to estimate tree cover, if the average canopy spread per tree is
known. Tree density can be calculated for areas that have a complete tree
Maintain trees in a healthy condition through good cultural practices.
A community is not likely to realize most of the benefits that the urban
forest can provide if its trees are in poor health. Promoting tree health
helps communities protect their investment in the urban forest. Public
health and safety also depend on healthy trees. Improperly maintained and
unhealthy trees often have an increased risk of breakage or failure, which
can result in personal injury and property damage.
Cultural practices have a major impact on the health of urban trees.
Proper and timely pruning can promote good tree structure and health, whereas
topping and other improper pruning techniques can result in hazardous structure
and decay. Irrigation is necessary for tree survival in many situations,
but excess or improper irrigation practices can contribute to the decline
of established trees. By providing for proper tree care and eliminating
destructive practices, communities can go a long way toward maintaining
their urban forests in a healthy and safe condition.
Tree ordinance provisions related to this goal include those that regulate
tree maintenance practices (such as pruning) and prohibit or regulate various
activities that may harm trees. Management of specific disease or pest
problems, such as Dutch elm disease, may be facilitated by provisions that
limit species selection, require removal of diseased trees, or authorize
other pest management measures.
Progress toward this goal can be evaluated by assessing tree health over
time through ground surveys
or by record
. Community tree
that include health ratings may contain all of the data
necessary for evaluating progress toward this goal. Otherwise, sample
can be established to obtain data on tree health and/or improper
or prohibited cultural practices. For example, jurisdictions that prohibit
topping might survey specifically to determine the incidence of this particular
problem. For certain health problems affecting large areas with many trees,
(e.g., color infrared photos, multispectral satellite
imagery) may be useful.
Establish and maintain an optimal level of age and species diversity.
The trees that make up the urban forest have finite life spans and must
be removed as they die. Living trees may also be removed when their health,
appearance, or structural integrity decline substantially, or when they
conflict excessively with utilities and structures. The likelihood that
a tree will need to be removed for one reason or another increases as the
tree grows older and larger. If areas are planted to a single species at
one time, a large percentage of the trees will need to be removed over
a short time period when they reach the end of their useful life. This
results in a rapid reduction in canopy cover, and the loss of many of the
benefits provided by the urban forest. This undesirable situation is less
likely to occur if the urban forest is composed of a variety of tree age
classes and species.
Serious pest outbreaks and epidemics can arise in communities in which
large areas are planted to a single susceptible species or variety. These
outbreaks can seriously impair the overall health, appearance, and longevity
of the urban forest. Species diversity and genetic diversity within species
helps stabilize the urban forest by buffering it from pest and disease
epidemics. Many insect pests and plant pathogens can only attack one or
a few tree species. The reproduction and spread of many tree pests and
diseases will be slowed if the community forest contains a diverse mix
of tree species. Furthermore, if an especially virulent disease or pest
problem does develop on a given species, species diversity ensures that
the condition of the entire community forest is not jeopardized.
The ordinance provisions that most directly address this goal require the
development of and adherence to a complete urban forest or street tree
master plan. To address this goal, the plan should provide for species
diversity in new tree plantings, a significant change from single species
blocks that are common in many communities. The master plan should also
describe how removal and replanting throughout the community can be phased
to attain a good mix of tree maturities.
In order to evaluate progress toward this goal, information is needed on
the distribution of tree species and age classes within the urban forest.
For public trees, this information can typically be extracted from a good
quality tree inventory
For community trees that are not listed in a tree inventory, this information
can most readily be obtained through a ground survey
Accurately determining tree age may not be possible, but for the purposes
of evaluation, it will usually suffice to group trees into broad age classes.
Promote conservation of tree resources.
The benefits derived from the urban forest generally increase as tree size
and canopy cover increase. Therefore, it is in the best interest of the
community to protect its existing tree resources from loss or depletion.
It is not possible to indefinitely preserve individual trees, since each
tree will eventually die. However, it is possible to preserve both the
urban forest and natural woodlands by restricting the indiscriminate removal
of trees in all age classes, and by making provisions for natural or human-assisted
regeneration. This embodies the concept of conservation.
Many jurisdictions have attempted to address this goal with provisions
that require approval to remove certain classes of trees under certain
conditions. Unfortunately, in focusing solely on the "preservation" of
individual trees, conservation of tree and forest resources is often overlooked.
For instance, some ordinances have focused on protection during new construction,
but make no provisions to ensure that trees will receive proper care or
be retained after construction is completed.
In areas with native tree resources, ordinance provisions that address
this goal should conserve stands of trees rather than only individual tree
specimens. They should prevent depletion of the tree canopy over both short-term
and long-term time horizons. Finally, they should set basic performance
standards for the amount of tree canopy to be retained or achieved. Provisions
related to the development of a master plan, and those regulating tree
planting, protection, and removal are most directly related to this goal.
Conservation of tree resources alone may not be sufficient to address
situations that require a more comprehensive resource management perspective.
When jurisdictions seek to conserve functional forest and woodland ecosystems,
such as in wildland parks or open spaces, the scope of management may need
to be expanded. Other components of the plant community, wildlife, natural
processes such as fire and flooding, and human land uses may also need
to be considered.
If the approach used to attain this goal involves tree protection or "preservation",
it will be necessary to have information on the long-term survival and
condition of individual trees. If woodland or forest conservation techniques
are applied, the extent, composition, and condition of stands of trees
should be documented. Both aerial and ground level photography
a simple means for documenting the presence and condition of individual
trees and stands of trees over time. Ground survey
methods and inventory data
can also be used
to provide more detailed base line data against which change can be measured.
Select, situate, and maintain street trees appropriately to maximize benefits
and minimize hazard, nuisance, hardscape damage, and maintenance costs.
Trees and structures, such as pavement, sidewalks, and curbs (collectively
referred to as hardscape), are closely associated in street tree plantings,
and this is frequently a source of problems for both. Many tree maintenance
and hardscape damage problems that occur in street tree plantings result
from incompatibility between the planting site and the tree species. Street
trees are often placed in woefully small planting spaces, resulting in
premature tree decline and/or hardscape damage. Conflicts with overhead
or underground utilities and damage to hardscape arise where:
tree species are not selected with proper attention to site limitations,
planting sites are not designed to provide a hospitable environment for
hardscape, utilities, and structures are not properly engineered to withstand
impacts associated with nearby trees.
Inappropriate tree selection is often the underlying cause for trees that
become hazardous, are prone to breakage, or develop recurrent pest or disease
problems. Inadequate planting sites are often responsible for poor tree
growth and survival and excessive hardscape damage. By identifying and
subsequently avoiding undesirable tree species, inadequate planting site
specifications, and inappropriate tree-site combinations, it is possible
to minimize problem situations and their high maintenance costs.
Ordinance provisions related to this goal empower the tree authority to
set and modify standards for tree selection and planting sites. This goal
is normally also addressed in the development of a comprehensive management
To evaluate progress toward this goal, we need information about the types
of tree/site combinations that result in high maintenance costs or damage.
can be conducted to determine what types of tree/site combinations
are associated with current maintenance and damage problems. Most or all
of this information may already be on hand in cities with tree
that track tree maintenance. Costs of hazardous tree removals,
tree-related sidewalk repairs, and maintenance should be tallied by the
types of tree species and planting situations where they are incurred.
In the absence of good historical records, ground surveys can be conducted
to determine what types of tree/site combinations are associated with current
maintenance and damage problems. Once these relationships are established,
they can be used as a basis to evaluate current tree selection, siting,
and maintenance practices. The evaluation should be repeated periodically
to account for changes that result as new species, planting methods, and
hardscape designs are adopted, and as trees planted at different times
Centralize tree management under a person with the necessary expertise.
Due to the wide variety of situations that can impact trees in the urban
environment, tree-related issues may arise in a number of different municipal
departments. In many jurisdictions, street trees are the responsibility
of public works, while park trees are cared for by the parks department
(Bernhardt and Swiecki 1989). In addition, projects approved by the planning
department and work performed by the public works department often impact
current or future tree resources. Utility companies, tree service firms,
and private citizens are also involved in tree maintenance and removal,
and some of these activities may be regulated by various municipal departments.
Effective implementation of tree ordinances is likely to be hampered when
responsibilities are split between different departments without overall
Unless all activities that affect trees are coordinated, departments
may unintentionally undermine each other's efforts to conserve tree resources.
For example, the planning department may require that certain trees be
protected and maintained during development. Without coordination, the
same trees might be seriously damaged by trenching for underground utility
work approved through public works.
To facilitate the coordinated management of urban forest resources,
it is desirable to have a single person responsible for all tree-related
issues. To be effective, this position should serve as a clearinghouse
for information on activities that may affect trees. The position should
also have authority to approve, deny, or condition any activities in accordance
with the jurisdiction's management plan, policies, and ordinances. Clearly,
the person in this position should have the technical background appropriate
for this complex job. Many jurisdictions do have a community arborist or
forester, but this position often lacks sufficient authority to effectively
manage the urban forest.
Although small communities may lack the funds for a full-time tree specialist,
many of the administrative functions of the community forester may be filled
by a tree board or commission. The necessary technical input may be obtained
from public or private sector tree specialists. Alternatively, several
smaller communities might band together to arrange for a shared "circuit
riding" urban forester.
Ordinance provisions that establish the responsibilities, authority, and
qualifications of the municipal tree program manager relate directly to
this goal. Other related provisions direct how coordination between municipal
departments is to be established for operations that may affect trees.
Municipal records of tree-related permits
and maintenance can provide data which show whether this goal is being
realized. If tree management is truly centralized, these records should
show that all activities that may affect community tree resources have
been reviewed and approved by the municipal arborist or forester. Ground
surveys, photogrammetry, and photo
points may also be used to document situations in which a lack of coordination
has led to unintended or unauthorized tree damage or removal.
Promote efficient and cost-effective management of the urban forest.
Financial resources are in short supply in many local governments. Even
though tree care involves less than 1% of the total operating budget of
most U.S. cities (Bernhardt
and Swiecki 1993
Tschantz and Sacamano
), economic realities dictate that all municipal programs strive
for efficiency and cost- effectiveness.
To operate efficiently and ensure that resources are directed toward
the most critical activities, a tree program must have a clear set of priorities
and a long-range plan. Although short-term savings may be achieved by deferring
tree maintenance, long-term costs will be lowest when resources are spent
on preventing problems rather than dealing with them after the fact. For
example, a program of early and regular tree maintenance helps prevent
later, more costly problems and prolongs tree longevity. Investments in
time and money at the time of installation on high quality plant materials
and proper site preparation will pay off in terms of tree health and low
maintenance costs. Problems arising from poor site designs, defective or
diseased planting stock, and improper installation procedures are typically
difficult and costly to correct. Similarly, a small investment in the proper
pruning of young trees will head off many structural problems that would
otherwise develop and require more expensive pruning or tree removal.
This goal is addressed in provisions that spell out the responsibilities
of the tree program manager. These responsibilities should include short-
and long-range planning for the tree program, setting maintenance priorities
based on long-term benefits, and tracking maintenance costs. Many of these
aspects would also be addressed in provisions related to the urban forest
on costs and the types of operations
performed are used to determine the cost-effectiveness and efficiency of
the urban forest management program. An accounting of labor and materials
expenses should be maintained, preferably broken down by the types of activities
performed, such as tree planting, pruning, and removal. Time devoted to
other aspects of the tree management program should also be tracked. Activities
such as planning, ordinance enforcement, research, public outreach, and
education, are all important to urban forest management. Overhead costs
and time should also be tracked and scrutinized, because these costs can
have a major influence on the cost efficiency of the entire program.
If work records do not contain sufficient detail to track activities,
data can be collect through auditing a representative sample
of work days or other measurement units. Data on the amount of time required
to complete various tasks may be self-reported or tracked by an observer.
Foster community support for the local urban forestry program and encourage
good tree management on privately-owned properties.
To achieve urban forestry goals, the local government needs the support
of the citizens in the community. In most jurisdictions, the overwhelming
majority of the trees which make up the urban forest are on private property.
For all practical purposes, the care of these privately-owned trees is
up to the residents of the community. A local government cannot completely
control tree management on private lands, but it can take steps to promote
proper management of privately-owned trees. Educational and incentive programs
are positive ways to encourage good tree care within the community.
It is important that local citizens understand the relationship between
urban forestry goals and specific actions taken to achieve these goals.
Otherwise, support for the overall program goals may not translate to support
for the program itself. Programs to educate citizens about, and involve
them in, the local urban forestry program will help increase public support
and interest in the program. Voluntary compliance with tree ordinances
is likely to be improved if citizens understand and agree with the management
approaches implemented through the ordinance.
Provisions that address this goal include those calling for the formation
of a citizen tree commission and the establishment of educational and other
outreach programs. Conducting such programs may be the responsibility of
either the tree program manager or the tree commission. Incentive programs,
such as those providing for cost-sharing, grants, or loans for tree planting
or maintenance, are also related to this goal.
There are two distinct aspects to this goal, so evaluating progress requires
two different types of methods. The first aspect involves changing the
way that people think about the urban forest. Public
opinion polling methods
provide the best means to measure changes in
public attitudes and knowledge. The process of assessing public attitudes
can also serve an educational function in itself, by helping to keep urban
forestry issues in the public eye.
Beyond determining what people think, it is also necessary to know if
new knowledge or attitudes are translated into action. For instance, if
a city decides to use public education to discourage tree removal on private
property, it is not enough to know whether public attitudes about this
practice have changed. Success is measured by the degree to which changed
attitudes result in a decreased incidence of tree removal. This requires
the use of techniques that measure the extent of tree resources on private
lands over time, including photogrammetry and
Facilitate the resolution of tree-related conflicts between citizens.
Trees sometimes become the focus of conflict between property owners when
they obscure scenic views or keep sunlight from reaching solar energy collectors.
Such conflicts may become important where property values are related to
specific views (e.g. ocean or lake views). It can be helpful to set up
a mechanism by which such conflicts may be resolved with a minimum of impact
to the community's tree resources.
This goal is addressed through a special set of provisions establishing
a mechanism for resolving disputes over trees which obstruct light or views.
The provisions covering this goal may be included in the tree ordinance
or enacted as a separate view or solar access ordinance.
The effectiveness of the conflict resolution process is the primary issue
in evaluating progress toward this goal. The first question to be answered
is whether the process is being utilized to resolve tree-related disputes.
This information can be easily obtained from records
through the system that is established.
Assuming that the process is being used, the next question is whether
the process works. This question has to be answered by those who have used
the process. Extreme care must be taken to separate reactions to the outcome
of the process from reactions to the process itself. It is not reasonable
to expect that all parties involved in conflicts will be entirely happy
with the eventual resolution. However, if the process is serving its purpose,
participants should perceive it as useful and helpful. Carefully-designed
procedures and/or follow-up interviews with process participants can
be used to rate the effectiveness of the conflict resolution process.