Perception of Urban Trees by Polish Tree Professionals vs. Nonprofessionals

Abstract

Sustainable urban forests require tree acceptance and support. Two groups of respondents, professionals (working in urban green areas) and individuals (with no professional connection with trees) revealed their attitudes towards trees by assessing statements in a survey questionnaire. Similar general attitude from professionals and nonprofessionals towards the examined benefits and harms related to urban trees was observed. Tree benefits were perceived as much more important than the annoyance they might cause. However, 6% of nonprofessionals found only negative aspects in trees, proving to be arboriphobes. No arboriphobes and no “Tree sceptics” were among the professionals. Around 40% of the respondents in the two groups found the number of trees in the surrounding areas too low. The nuisance caused by trees was seen as more disturbing by younger and lower-educated professionals. Women tended to assess trees as more attractive and as having a stronger influence on socioeconomic contributions than men. Men dominated the “Tree indifferent” group. The attractiveness of trees and their impact on socioeconomic contributions were related to the place of residence and the level of education among the nonprofessionals. The level of education of the nonprofessionals was also connected to being clustered into one of the four abovementioned groups of respondents. A majority of medium and big city dwellers as well as a minority of villagers were in the “Tree liking” cluster.

Full text

Sustainability 2019, 11, 211; doi:10.3390/su11010211 www.mdpi.com/journal/sustainability
Article
Perception of Urban Trees by Polish Tree
Professionals vs. Nonprofessionals
Marzena Suchocka 1,*, Paweł Jankowski 2 and Magdalena Błaszczyk 3
1 Department of Landscape Architecture, Faculty of Horticulture, Biotechnology and Landscape Architecture,
Warsaw University of Life Sciences - SGGW, Ul. Nowoursynowska 159, 02-776 Warsaw, Poland
2 Department of Econometrics and Statistics, Faculty of Applied Informatics and Mathematics, Warsaw
University of Life Sciences - SGGW, Ul. Nowoursynowska 159, 02-776 Warsaw, Poland;
pawel_jankowski@sggw.pl
3 Department of Landscape Architecture, Faculty of Horticulture, Biotechnology and Landscape
Architecture, Warsaw University of Life Sciences - SGGW, Ul. Nowoursynowska 159, 02-776 Warsaw,
Poland; magdalena_blaszczyk@sggw.pl
* Correspondence: marzena.suchocka@interia.pl; Tel.: +48-506-650-607
Received: 1 December 2018; Accepted: 26 December 2018; Published: 3 January 2019
Abstract: Sustainable urban forests require tree acceptance and support. Two groups of
respondents, professionals (working in urban green areas) and individuals (with no professional
connection with trees) revealed their attitudes towards trees by assessing statements in a survey
questionnaire. Similar general attitude from professionals and nonprofessionals towards the
examined benefits and harms related to urban trees was observed. Tree benefits were perceived as
much more important than the annoyance they might cause. However, 6% of nonprofessionals
found only negative aspects in trees, proving to be arboriphobes. No arboriphobes and no “Tree
sceptics” were among the professionals. Around 40% of the respondents in the two groups found
the number of trees in the surrounding areas too low. The nuisance caused by trees was seen as
more disturbing by younger and lower-educated professionals. Women tended to assess trees as
more attractive and as having a stronger influence on socioeconomic contributions than men. Men
dominated the “Tree indifferent” group. The attractiveness of trees and their impact on
socioeconomic contributions were related to the place of residence and the level of education
among the nonprofessionals. The level of education of the nonprofessionals was also connected to
being clustered into one of the four abovementioned groups of respondents. A majority of medium
and big city dwellers as well as a minority of villagers were in the “Tree liking” cluster.
Keywords: tree professionals; tree nonprofessionals; attitudes towards trees; perception of trees;
sustainable urban development; social survey
1. Introduction
Trees are an important part of urban ecosystem as they are environmentally sustainable and
economically productive [1]. Urban forest protection plays an important role in enhancing
ecosystem services as ‘biogenic’ or ‘green’ infrastructure in the process of making livable and
sustainable cities. Therefore, to protect urban forest means to preserve and enhance the livability of a
city. Sustainable urban forests require a healthy tree and site condition, community-wide tree
acceptance and support, but also a comprehensive approach [2]. Tree professionals should consider
how the forest can best meet people's needs [3]. There is considerable and growing literature
suggesting that air-pollution mitigation, energy savings, avoidance of runoff, and other benefits are
associated with trees [4–6]. The benefits can be estimated, and the monetary value of ecosystem
services is the most important and most effective argument supporting tree management. For

Sustainability 2019, 11, 211 2 of 22
example, a benefit–cost ratio of 2.83 indicates that the value of projected benefits is nearly three times
the value of projected costs [7]. On the other hand, it is known, also among professionals, that
different values and attitudes can cause social conflict between the need to protect urban trees or to
cut them down [1,8,9]. Kirkpatrick [1] points out that trees are not necessarily accepted by all people.
People are known to vary considerably in their appreciation of urban forests and green spaces, with
attitudes ranging from worship to fear [10,11]. This means that professionals need to deal with
public pressure to cut trees down, especially when they are in conflict with development, or block
out sunlight or the view. People also fear that trees might damage property or cars and should be cut
down for sanitary or just personal reasons [12,13]. Hence, it seems very important that professionals
take an objective look at the role of trees in the city, free of prejudice and bias.
This problem is also important in Poland, where the landscape architect or arborist profession
does not have enough formal and legal support and, therefore, tree protection often depends on
their individual decisions. Poland is developing dynamically—similarly to other former socialist
members of the EU in Central and Eastern Europe, due to high rates of overcrowded dwellings [14],
Poland is undergoing a construction boom. The removal of trees in Polish cities results to a large
extent from construction processes and regulations do not contain guidance on technical procedure.
Hence, tree protection on construction sites depends on the commitment of professionals and their
understanding of the role of trees in the city. Unfortunately, in the design process, a lack of
consistent application of tools allowing for the sustainable management of green areas can be
observed. That may lead to a decrease of sustainable indicators, such as tree canopy cover and green
space, as the percentage of city area (e.g., Siemens Green City Index) [15,16], or indirectly green
fabric quota and connectivity of green spaces [17]. More and more often, architects create urban and
historic green spaces without proper tree protection, which adversely affects their composition and
functions.
To a certain extent, tree professionals are responsible for the successful management and
protection of urban forests and must deal with different kinds of constraints. Keeping existing trees
in the construction and management process needs the concise environmental and socioeconomic
benefits of tree preservation to be successfully communicated to architects and developers [18].
Therefore, it is important to know how professionals perceive the various benefits and harms
associated with trees, which can be summarized as (increasing) attractiveness, (improving) social
relations and economic value, (causing) nuisance, (being a source of) contamination and damage,
and (causing) danger. To assess professionals’ understanding of the role of urban forests, it is
interesting to compare their attitudes towards trees with the attitudes of a representative group of
nonprofessionals.
1.2. Perceptions of Attractiveness
City residents appreciate visual and aesthetic benefits [19]. Some tree attributes, such as height,
canopy size, and leaf color, or tree characteristics, like higher branching trunks and dense canopy,
are the driving factors for a tree’s aesthetic quality [20]. City dwellers often express a positive view of
street trees, like improvements in the aesthetic environment (sights, sounds, smells) [3]. High
importance is assigned by residents to aesthetic and practical attributes, including beautification and
the provision of shade [21].
1.3. Perceptions of Socioeconomic Contrubutions
Social and economic benefits associated with trees are well known. For example, a large existing
tree adds chic and value to properties, which in the case of new projects makes them more readily
acceptable by the community, which is especially important for retailers [18]. Psychological benefits
associated with physical activity undertaken in urban forests include a sense of community and
safety, increased enjoyment of everyday life, a stronger feeling of connection between people and
their environment [22] and reduced rates of crime, relief from stress (which can lead to improved
physical health), and enhanced feelings and moods [3,23–25]. Social contact is known to have a

Sustainability 2019, 11, 211 3 of 22
positive effect on mood and stress levels and an urban forest is a desirable environment in which to
undertake it [26].
1.4. Perceptions of Nuisance, Contamination, and Damage
The cost and inconvenience of urban forests can include nuisance caused by animals, insects,
and disease (i.e., Lyme disease or allergies), and displeasure with messiness and clutter [3]. These
reasons are a common excuse and cause of felling trees in Poland, especially since the beginning of
2017, when the Polish Act on Environmental Protection liberalized the regulations. Moreover, it is
relatively common to find information on trees in conflict with the underground and aboveground
infrastructure [27–32]. One of the reasons for the damage comes from the fact that tree roots grow
throughout the whole life of the tree and can exert pressure on adjacent soil and nearby
infrastructure surfaces [33,34]. This root pressure can lead to, among other things, the lifting of
sidewalks [29,30,35] and the widening of pipe cracks [36,37]. The consequent replacement of
hardscape elements can cause significant mechanical injury and loss of stability, especially in
instances where existing structural roots are severed near the trunk during construction [38].
1.5. Perceptions of Danger
Trees can also cause a sense of danger connected with falling trees or limbs [2]. Urban tree risk
assessment is a multistage process that is strongly influenced by professional (or nonprofessional)
experience, risk perception, and risk tolerance [9]. Likelihood of failure is increased by such factors
as tree defects (e.g., decay, poor branch structure) or site factors, like past construction damage in
root system or changes in hydrology [39,40]. Perceptions of risk and acceptable risk play key roles in
decisions on tree removal, often based on unsubstantiated fear [41] The darkness caused by trees can
also lead to a fear of crime [3]. Therefore, the intensity of an urban forest could be considered as a
factor in perceptions of safety [41,42,43].
1.6. Aim of the Study
Our study was performed among two groups of respondents: Professionals, i.e., specialists
working or planning to work in future on urban green areas; and nonprofessionals, i.e., respondents
having no professional connection with trees. We asked both groups about the various benefits and
harms associated with trees. The aim of the study was to compare the attitudes of professionals and
nonprofessionals towards urban trees. The comparison was performed in two ways. Firstly, we
examined the average attitudes towards the examined tree—related benefits and harms in both
groups of respondents. Next, the differences in the respondents’ attitudes were used to divide both
professionals and nonprofessionals into clusters in order to try to identify such groups as
arboriphobes or tree enthusiasts. The main goal of this clustering was to estimate and compare the
shares of professionals and nonprofessionals in the identified groups. We believe that if
professionals are to withstand public pressure to cut trees down, their group should include no
arboriphobes and rather include many tree enthusiasts, free from fears and prejudices. On the other
hand, it is the professionals who should objectively recognize both the benefits and harms associated
with urban trees.
2. Materials and Methods
2.1. Professionals
Active tree specialists working in the field of planning and construction of building projects as
well as possible future specialists were recruited in the years 2015–2016 during the project Roads for
Nature on tree diagnostic training in the LIFE project (Project LIFE 11 INF/EN/467 Roads for
Nature—a campaign promoting Poland`s trees in rural landscapes, as habitats and ecological
corridors). The training was designed for current and future design professionals, construction
employees, and tree decision-makers, such as public officials. Participants in the meeting were

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emailed an information letter asking them to fill out the questionnaire, with a link to the survey. Six
hundred emails were sent out, for which complete answers were sent back from 198 persons, giving
a 21% response rate. Twelve answers were removed from the study because the respondents had
experience neither in education concerning tree protection nor in building projects. A further two
answers were discarded because the respondents gave the same answers to all the survey questions,
leaving 184 answers to the questionnaire analyzed.
Respondents described in our study as professionals represented officials, landscape architects,
developers, on field work contractors (builders) and students of landscape architecture. They were
persons actively working or planning to work in a field of land use designing, land development,
landscaping or urban forest management.
Persons making decisions concerning urban forest management in Polish cities are mainly
landscape architects (site design), officials working in city departments of environmental protection
(public decision makers), developers, and builders (construction). The specifics of Poland are the
role of arborists as performers of care treatments commissioned by the above groups, with only an
advisory participation in the decision-making process related to urban greenery. This is mainly due
to lack of academic courses in that field in Poland. Another piece of specifics is the high feminization
of landscape architecture studies in Poland. For example, at the Warsaw University of Life Sciences
(SGGW) landscape architecture course, the highest rated nationwide (according to the Perspektywy
ranking [44]), women account for about 80% of students [45].
The overwhelming majority of the surveyed professional respondents had academic education
in landscape architecture and, to a lesser extent, in forestry or civil engineering. Less than 5% of
respondents declared academic education in architecture, spatial planning, environmental
protection, agronomy or biology. All respondents had experience regarding urban tree
management. Officials included in the survey declared mainly education in landscape architecture,
spatial planning and, partially, forestry. Work contractors and developers represented education in
landscape architecture or civil engineering. A group of students of the landscape architecture, with
completed BSc, participating in the tree diagnostic trainings and continuing MSc studies, was
additionally included to the group of tree professionals. The inclusion of students was aimed at
broadening the scope of sociodemographic research, such as comparing the attitude of respondents
to urban trees, depending on the age and experience.
The professionals were mainly women, aged under 45 years, with higher education, living in
cities with more than 200,000 residents. The professionals were divided into four categories:
Students, officials, work contractors, and designers. Their detailed sociodemographic characteristics
are presented in Table 1.
Table 1. Sociodemographic characteristics of 184 tree planning professionals who responded to a
perceptions of urban trees survey in the years 2015–2016 during the project Roads for Nature.
Sex Female 75% Place of residence Village 21%
Male 25% City below 50,000 citizens 20%
Age Below 30 47% City 50,000–200,000 citizens 9%
30–45 38% City over 200,000 citizens 51%
Over 45 15% Place of work Village 8%
City below 50,000 citizens 18%
Profession Student 31% City 50,000–200,000 citizens 10%
Official 37% City over 200,000 citizens 64%
Work contractor 15% Work experience Less than 1 year 15%
Designer 17% 1–3 years 30%
Education Secondary 29% 4–10 years 33%
Higher 71% Over 10 years 22%

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2.2. Nonprofessionals
Nonprofessionals were randomly selected Polish citizens who do not take part in the
decision-making process concerning urban forest management.
A quota sample of Polish citizens (n = 514) took part in a survey conducted by the market and
public opinion research IMAS International Institute in April 2015. All the survey data collection
was done via paper-assisted personal interviewing (PAPI). Qualitative methodology was used;
answers to closed questions were listed. The closed questions were prompted (with lists to be read
by the respondent). As four respondents returned empty questionnaires, the number of surveys
analyzed was 510. The detailed sociodemographic characteristics of the nonprofessionals are
presented in Table 2.
Table 2. Sociodemographic characteristics of a quota sample of 510 Polish citizens (nonprofessionals)
who responded to a perceptions of urban trees survey conducted by IMAS International Institute in
April 2015.
2.3. Questionnaire
The questionnaires used in the study for both groups of respondents were based on the
modified version used in the research conducted by Schroeder et al. [46]. In the case of the
professionals, it consisted of 29 statements regarding the benefits and harms associated with urban
trees. The respondents expressed their opinion on each of the statements, with answers given on a
5-point Likert scale anchored by “I fully disagree” and “I fully agree”. The statements are presented
in detail in Table 3. Additionally, the professionals were asked to assess the number of trees in their
current place of residence on a 5-point scale anchored by “too few trees” and “a lot of trees”. The
survey for nonprofessionals was shortened to 24 statements. Each respondent selected those
statements with which she/he agreed the most. Additionally, nonprofessionals could choose the
statement: “There are too few trees in cities”.
2.4. Statistical Data Analysis
The agglomerative hierarchical clustering (AHC) with Kendall distance and Ward
agglomeration method was used to cluster the survey questions into sets forming the latent
variables, based on the professionals’ answers. The internal consistency within each set of questions
was measured with Cronbach’s alpha. For each professional, the values of the latent variables were
computed as her/his mean answers to the questions corresponding to each of the variables. The
importance of the latent variables for nonprofessionals was estimated by the number of statements
belonging to each of the latent variables that they selected. Further analysis of the survey was based
on the latent variables. The same clustering method with Euclidian distance was further applied to
cluster the respondents, separately professionals and nonprofessionals, based on the latent variables.
The Kruskal–Wallis one-way analysis of variance test was used to compare the median
responses to the latent variables among professionals categorized according to each of their
sociodemographic characteristics and according to the clusters. In the case of statistically significant
differences among the median responses in different categories of respondents, the homogeneous
groups of categories were established using the Tukey’s honestly significant difference (HSD)
multiple comparison procedure.
Sex Female 52% Education basic/primary 37%
secondary and post-secondary 49%
Male 48% higher 14%
Age Below 30 26% Place of residence Village 40%
30–45 27% City below 50,000 citizens 24%
Over 45 46% City 50,000–200,000 citizens 16%
City over 200,000 citizens 19%

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Contingency tables were created to investigate the relations between the numbers of selected
statements associated with the latent variables defined in the study and the sociodemographic
features of the nonprofessionals, as well as the dependence of the clusters of professionals and
nonprofessionals on their sociodemographic characteristics. The dependence was examined for each
of the characteristics with Fisher’s exact test [47]. Fisher’s exact test was chosen instead of the
frequently used chi-square independence test because of the small size of the sample in the study. In
the case of significant relations, we applied the approach adopted by Zeiles et al. [48] in order to
bring out the pattern of these relations. The cells in the contingency table responsible for the
departure from independence of the examined variables were identified as those for which the
Pearson residual exceeded 1.0, 1.5 and 2.0.
All analyses were performed in the R program version 3.2.5 [49] with the use of RStudio version
0.99.896 [50].
3. Results
3.1. Latent Variables Based on Professionals’ Answers
The 29 statements used in the survey were divided via AHC clustering into five sets based on
the professionals’ answers. Each set of statements could be associated with a latent variable, related
to a different general benefit or harm associated with trees. The resulting variables can be described
as: “Attractiveness”, “Socioeconomic contributions”, “Nuisance”, “Contamination and damage”,
and “Danger” (see Table 3). The computed Cronbach’s alpha values for the latent variables and the
median as well as mean (± standard deviation) answers of the professionals to the latent variables
are given in Table 4. Values of Cronbach’s alpha exceeding 0.7 show high reliability of the latent
variables. As can be noticed, the two first variables have a positive and a further three negative
connotations.
In order to perform a comparison of the perception of urban trees by tree professionals vs.
nonprofessionals, the same definition of the latent variables was further applied in the case of the
nonprofessionals.

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Table 3. Statements from a perceptions of urban trees survey, regarding benefits and harms
associated with urban trees, performed in the years 2015–2016 among the tree planning professionals
during the project Roads for Nature. Definitions of the latent variables obtained via agglomerative
hierarchical clustering (AHC) analysis, related to a different general benefit or harm associated with
trees. Indication of statements which appeared in a perceptions of urban trees survey conducted by
IMAS International Institute in April 2015 among the quota of Polish citizens (non-professionals).
Statement Latent
variable
Nonprofessionals
“Trees are pleasant to look at”
Attractiveness = „Trees are attractive
and improve attractiveness of their
surroundings”
No
“Trees are attractive when bloom “ No
“Trees beautifully change color in the autumn” No
“Trees bring closer the world of nature” No
“Trees improve aesthetics of the house and surroundings” Yes
“Trees provide shade” No
“Trees purify the air pollution” Yes
“Trees provide privacy” Yes
“Trees protect buildings from heat in summer” Yes
“Trees hide the unpleasant views (such as, e.g., an ugly wall with
graffiti)”
Yes
“A positive effect on the feeling of social ties (e.g., with the
neighbors)”
Socio-economic
contributions =
“Trees improve social
relations and
economical value”
No
“Trees strengthen the sense of ties with home and family” Yes
“In areas with trees drivers retain their greater caution and reduces
speed”
Yes
“Trees are a source of spiritual and emotional values” Yes
“Trees increase the value of the property on which they grow” Yes
“Trees produce resins, liquids, etc., which contaminate the area
around”
Nuisance =
„Trees
cause
nuisance”
Yes
“Trees are causing allergies” Yes
“Trees attract insects unwanted by people” Yes
“Trees are causing economic damage by the roots destructive for
pavements”
Contamination and
damage = „Trees are
source of contamination
and damage”
Yes
“Trees interfere when their branches grow low from the trunk” Yes
“Trees litter around with the seeds, dry branches” Yes **
“Trees litter the area around, by falling their flowers” Yes **
“Trees litter the area around by falling their leaves in the autumn” Yes **
“Trees litter the area around when their leaves fall down
throughout the summer”
Yes **
“Trees are a threat to the security of people because of the brittle
branches “
Danger = „Trees
cause danger”
Yes
“Trees reduce visibility and therefore sense of security” No
“Trees restrict the view from windows of apartments and houses “ Yes
“Trees restrict access of light (shade the area)” Yes
“Trees should be removed from playgrounds or along roads, as
they constitute a threat to users “
Yes
** Four statements were summarized in one statement: “Trees litter the area around”.

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Table 4. Statistical results for the latent variables, related to a different general benefit or harm
associated with trees, defined in the study. Left: The Cronbach’s alpha values for the latent variables
and the median and mean (± standard deviation) answers of the professionals to the latent variables.
Right: The importance of the latent variables for nonprofessionals: Overall number of statements
belonging to each of the variables chosen by nonprofessionals divided by the numbers of statements
included in each variable. Average shares of statements belonging to each of the variables chosen by
the respondents. The numbers of respondents who chose at least one statement associated with a
given latent variable.
Responses of Professionals Importance for Nonprofessionals
Cronbach’s
Alpha Median
Mean ±
Standard
Deviation
Overall Average
Shares
At Least
one
Chosen
Attractiveness 0.78 4.90 4.78 ± 0.30 227.2 0.47 460
Socioeconomic
benefits 0.80 4.00 3.98 ± 0.78 107.0 0.22 267
Nuisance 0.71 2.67 2.72 ± 0.95 91.3 0.18 189
Contamination
and damage 0.91 2.33 2.32 ± 0.95 69.7 0.14 154
Danger 0.82 2.20 2.24 ± 0.80 86.2 0.14 250
The Kendall tau correlation coefficients of the latent variables are presented in Table 5.
According to the results, two groups of variables can be distinguished. First, the “Attractiveness” of
trees is positively correlated with “Socioeconomic contributions”. Second, “Nuisance”,
“Contamination and damage”, and “Danger” are related to each other. Negative correlations among
the variables from the two groups are observed, though not all of them are statistically significant.
The factor with significant, negative correlation to both “Attractiveness” and “Socioeconomic
contributions” is “Danger”.
Table 5. Kendall correlation of latent variables, related to a different general benefit or harm
associated with trees, defined in the study. Kendall tau values and corresponding p-values given.
The statistically significant correlations, at significance level α = 0.05, highlighted in bold.
Socioeconomic
Benefits Nuisance Contamination and
Damage Danger
Attractiveness 0.47 (<0.001) −0.03
(0.64) −0.12 (0.033) −0.21
(<0.001)
Socioeconomic benefits −0.04
(0.50) −0.07 (0.19) −0.22
(<0.001)
Nuisance 0.39 (<0.001) 0.26 (<0.001)
Contamination and
damage 0.47 (<0.001)
3.2. Nonprofessionals’ Choice of Latent Variables
The importance of the latent variables for nonprofessionals was estimated by the number of
statements belonging to each of the latent variables that they chose. Because the numbers of
statements belonging to each variable were not equal (5 for “Attractiveness”, 4 for “Social relations”
and “Danger”, and 3 for “Nuisance” and “Contamination and damage”), the numbers of statements
chosen were divided by the numbers of statements in each variable. The overall results are given in
Table 4. Additionally, Table 4 presents the average shares of statements belonging to each latent
variable and numbers of respondents who chose at least one statement associated with a given latent
variable.
3.3. Assessment of the Number of Trees

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Of the professional respondents, 16% and 26% assessed that the number of trees in their place of
residence is “too low” or “rather too low”; according to 26% of the professionals, the number of trees
is “just right”; 22% and 10% assessed that there are “rather a lot of trees” and “a lot of trees”,
respectively. Finally, 38% of nonprofessionals chose the statement “there are too few trees in the
cities”.
3.4. Arboriphobes
The lowest answer to the latent variable “Attractiveness” among the examined professionals
was 3.6, indicating that there were no arboriphobes in this group of respondents. On the other hand,
29 nonprofessionals (6%) chose none of the statements associated with tree attractiveness. The
average respondent in this group chose 0% of statements related to “Attractiveness”, 0% to
“Socioeconomic contributions”, 28% (approximately 1 statement out of 3) to “Nuisance”, 34%
(approximately 1 statement out of 3) to “Contamination and damage”, and 90% (between 4 and 5
statements out of 5) to “Danger”, respectively, proving that this group contains arboriphobes.
3.5. Professionals’ Answers vs. Social Characteristics
The results of the comparison of the median answers to the latent variables defined in the study
and for the assessment of the number of trees in the place of residence for various sociodemographic
groups of professionals are presented in Table 6. Tests show a weak dependence of the answers on
the sociodemographic group membership. There was no difference between the examined
professions in their attitude towards the five benefits and harms caused by trees. Significantly
different median answers were observed between female and male respondents for “Attractiveness”
and “Socioeconomic benefits”, both of which were scored higher by women. The “Nuisance” caused
by trees was assessed differently by respondents of different age, education, and from different
places of residence. The nuisance caused by trees, such as allergies or attraction of insects, is on
average seen as more disturbing by younger and lower-educated respondents living in the largest
cities. The differences in the perception of the “Danger” associated with trees were related to work
experience. Professionals with increasing seniority rate “Danger” higher. Finally, the assessment of
the number of trees in the place of residence significantly differs only among respondents living in
different places of residence, as the residents of villages and the largest cities gave the highest and
lowest scores for the number of surrounding trees, respectively.

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Table 6. Relation of the latent variables, associated to a different general benefit or harm associated
with trees, defined in the study, with the sociodemographic characteristics of the tree planning
professionals. Results of the Kruskal–Wallis test followed by the Tukey honestly significant
difference (HSD) procedure for the differences between median answers of professionals to the latent
variables, and for the assessment of the number of trees in the place of residence in various
sociodemographic categories of professionals at significance level α = 0.05. In the case of significant
differences, the mean answers to the latent variables in each sociodemographic category are given,
and homogenous groups of categories are denoted with letters.
Sex Female Attractiveness 4.83 a Socioeconomic
contributions
4.08 a
Male 4.61 b 3.70 b
Age Below 30 Nuisance 2.93 a
30–45 2.59 ab
Over 45 2.36 b
Education Secondary Nuisance 2.93 a
Higher 2.63 b
Place of
residence
Village Nuisance 2.48 b Number of
trees
3.34 a
City below 50,000
citizens
2.63 ab 2.81 ab
City 50,000–200,000
citizens
2.35 ab 2.38 ab
City over 200,000
citizens
2.91 a 2.70 b
Work
experience
Less than 1 year Danger 2.00 b
1–3 years 2.15 ab
4–10 years 2.24 ab
Over 10 years 2.53 a
3.6. Nonprofessionals’ Answers vs. Social Characteristics
The relations between nonprofessionals’ choice of latent variables and their gender, age,
education, and place of residence were examined. To simplify the description of the results, the
numbers of chosen statements belonging to each of the latent variables were coded in the following
way: Low = 0 or 1, medium = 2 or 3, and high = 4 or 5 statements in the case of 5 statements; low = 0
or 1, medium = 2, and high = 3 or 4 statements in the case of 4 statements; low = 0 or 1, medium = 2,
and high = 3 statements in the case of 4 statements.
There was no relation between the age and gender of the nonprofessionals and their attitudes
toward various tree benefits and harms. As presented in Table 7, significant relations were observed
for some of the latent variables and place of residence or education. Education seems to influence
nonprofessionals’ opinion on both the benefits of trees: Attractiveness, improvement of social
relations, and increase of economic value. An increase of the education level increases the
percentage of respondents choosing a high number of statements related to the “Attractiveness” and
“Socioeconomic contributions” and decreases the percentage of respondents choosing a low number
of such statements. Only the opinion on “Contamination and damage” caused by trees is not
influenced by the place of residence. In comparison to others, inhabitants of the largest cities seem to
select more statements related to “Attractiveness” and a lower number of statements related to
“Socioeconomic benefits”, “Nuisance”, and “Danger”. Residents of small cities, with below 50,000
inhabitants, show the least interest in the attractiveness of trees. Finally, in the case of “Danger”, the
residents of medium size cities, with 51,000–200,000 inhabitants, more often select medium and high
numbers of statements related to danger associated with trees. Table 8 presents the significant
relations between the selection of the “there are too few trees in the cities” statement and the age and
education level of the nonprofessionals (other sociodemographic categories were not significantly
related). The results show that the assessment of the number of urban trees varies among

Sustainability 2019, 11, 211 11 of 22
respondents of different age and education: Older respondents least often and respondents with
higher education most often were of the opinion that the number of trees in cities is not enough.
Table 7. Relation of the latent variables, associated to a different general benefit or harm associated
with trees, defined in the study, with the sociodemographic characteristics of nonprofessionals.
Results of the Fisher test for the dependence between numbers of the selected statements associated
with the latent variables and various sociodemographic categories of nonprofessionals.
Nonsignificant differences, at significance level α = 0.1, denoted by ns. All values in the table given in
percentage. The cells in the contingency table responsible for the departure from independence of the
examined variables were identified as those for which the Pearson residual exceeded 1.0 (*), 1.5 (**),
and 2.0 (***). The numbers in these cells were highlighted in bold.
Attractiveness Socioeconomic
contributions
Nuisance Danger
Low
Medium
High
Low
Medium
High
Low
Medium
High
Low
Medium
High
Place of residence
Village 37 40 23 74 15 11* 82 14* 4* 85 9 5
City: <50 K 51*** 29** 20 80 12 8 89 11 1** 89 6 5
City: 51–
200K
35 43 23 79 13 8 86 10 5 76* 13** 11***
City: >200
K
28** 46* 25 88* 11 1*** 92 8 0** 95 5* 0***
p-value 0.034 0.048 0.087 0.0048
Educatio
n
Primary 42 43 15*** 85 10* 5* ns ns
Secondary 38 38 24 77 15 8
Higher 31* 32 38*** 69 17 14**
p-value 0.0050 0.051
Table 8. Results of the Fisher test for the dependence between selecting of the “there are too few trees
in the cities” statement and age and education of nonprofessionals. The cells in the contingency table
responsible for the departure from independence of the examined variables were identified as those
for which the Pearson residual exceeded 1.0 (*), 1.5 (**) and 2.0 (***). The numbers in these cells were
highlighted in bold.
“There are too few trees in the cities”
Age Selected Education Selected
Below 30 43% basic/primary 34%
30-45 44% secondary and post-secondary 38%
Over 45 33% * Higher 50% **
p-value 0.041 p-value 0.065
The small number of arboriphobes did not allow for testing the significance of the differences
between their sociodemographic characteristics and the characteristics of the examined quota
sample. The majority of the 29 arboriphobes among the nonprofessionals lived in villages (45%) and
cities with below 50,000 citizens (48%). The division of arboriphobes by gender and age was similar
to the division in the quota sample: 48% female and 52% male, 24% below 30 years, 31% between 30
and 45 years, and 45% over 45 years of age. There was a higher share of arboriphobes with
secondary/post-secondary education than in the quota sample (59%) and a lower share of
arboriphobes with higher education (7%). Finally, only a minority (21%) of arboriphobes were of the
opinion that the number of trees in cities is too low.

Sustainability 2019, 11, 211 12 of 22
3.7. Clustering of Professionals
As no significant differences between the answers to the five latent variables were observed
according to the sociodemographic characteristics of the respondents, the answers to the latent
variables were used to divide the respondents into clusters. Four clusters of respondents containing
30 (16%), 56 (30%), 76 (41%), and 22 (12%) persons, respectively, were extracted. The results of the
Kruskal–Wallis test followed by the Tukey HSD procedure for the differences between the median
answers to the latent variables defined in the study in various clusters are presented in Table 9. The
dependence between membership in a given cluster and membership in a given sociodemographic
group for each sociodemographic characteristic was assessed with Fisher’s exact test for
independence. The results of the statistically significant dependencies: Gender, place of work, and
assessment of the number of trees in the place of residence, are presented in Table 9. To simplify the
description of the results, the answers considering the number of trees were combined, leading to
three answers: “Too low” (“rather too low” and “too low”), “just right”, and “a lot of trees” (“rather
a lot of trees” and “a lot of trees”).
Table 9. Relation of the clusters of tree planning professionals with the latent variables, associated to
a different general benefit or harm associated with trees, defined in the study and with the
sociodemographic characteristics of the professionals. Upper: Results of the Kruskal–Wallis test
followed by the Tukey HSD procedure for the differences between median answers to the latent
variables defined in the study in various clusters of respondents at significance level α = 0.5. In the
case of significant differences, the mean answers to the latent variables in each cluster are given and
homogenous groups of clusters are denoted with letters. Lower: Results of the Fisher test for the
dependence between sociodemographic characteristics and clusters of professionals. Only the
significant (p-value < 0.1) results are presented. The cells in the contingency table responsible for the
departure from independence of the examined variables were identified as those for which the
Pearson residual exceeded 1.0 (*), 1.5 (**) and 2.0 (***).
 Cluster 1: Tree accepting: The respondents recognizing “Attractiveness” and the positive effect of trees on
“Socioeconomic contributions” with high scores for all three tree-related harms.
 Cluster 2: Tree liking: The respondents recognizing “Attractiveness” and the positive effect of trees on
“Socioeconomic contributions” with medium scores for all three tree-related harms.
 Cluster 3: Tree enthusiasts: The respondents recognizing “Attractiveness” and the positive effect of trees
on “Socioeconomic contributions” with low scores for all three tree-related harms.
 Cluster 4: Tree indifferent: The respondents recognizing tree “Attractiveness” with similar, medium
scores for all other benefits and harms related to trees.
Cluster
1
Cluster
2
Cluster
3
Cluster
4
Attractiveness 4.78 a 4.89 a 4.82 a 4.35 b
Socioeconomic contributions 4.00 ab 4.40 a 4.00 b 2.85 c
Nuisance 4.06 a 2.96 b 2.04 c 2.61 b
Contamination and damage 3.52 a 2.52 b 1.55 c 2.86 ab
Danger 3.15 a 2.02 b 1.83 b 2.96 a
Sex
p-value = 0.022
Female 80% 84% * 74% 50% ***
Male 20% 16% 26% 50% *
Place of work
p-value = 0.026
Village 3% 0% *** 13% ** 14% *
City: <50,000 17% 20% 16% 23%
City: 51,000–
200,000 0% *** 14% 11% 14%
City: >200,000 80% * 66% 61% 50%
Assessment of the number of trees in
the place of residence
p-value = 0.044
Too low 30% * 50% 46% 27% *
Just right 30% 21% * 20% * 55% ***
A lot of trees 40% 29% 34% 18% *

Sustainability 2019, 11, 211 13 of 22
Firstly, it can be noticed that though there was a difference in the scores for tree
“Attractiveness”— in all clusters, this variable was highly rated. According to the results, the
clusters can be divided into two groups. Clusters 1 to 3, all with very high scores for
“Attractiveness”, contained professionals who additionally rated the influence of urban trees on
social relations and increased economic value highly and differed mostly in their recognition of
tree-related harms. Cluster 4 was of professionals who rated tree attractiveness highly but
significantly lower in comparison to other clusters. The clusters can be characterized in the following
way:
 Cluster 1: Tree accepting: The respondents recognizing “Attractiveness” and the positive effect
of trees on “Socioeconomic contributions” with high scores for all three tree-related harms. In
comparison to clusters 2 and 3, respondents in cluster 1 least often assessed the number of trees
in their place of residence as too low. This group could be named “Tree accepting”. This group
contains a high percentage of respondents working in the largest cities and low share of
professionals working in villages.
 Cluster 2: Tree liking: The respondents recognizing “Attractiveness” and the positive effect of
trees on “Socioeconomic contributions” with medium scores for all three tree-related harms.
This group contains a high percentage of respondents who think that there are too few trees in
their place of residence. This group could be named “Tree liking”. Cluster 2 contains the highest
percentage of women. No respondents working in villages were found in this group.
 Cluster 3: Tree enthusiasts: The respondents recognizing “Attractiveness” and the positive
effect of trees on “Socioeconomic contributions” with low scores for all three tree-related harms.
Like cluster 2, this group contains a high percentage of respondents who think that there are too
few trees in their place of residence. This group could be named “Tree enthusiasts”. In
comparison to clusters 1 and 2, a high share of respondents working in villages were found in
this group.
 Cluster 4: Tree indifferent: The respondents recognizing tree “Attractiveness” with similar,
medium scores for all other benefits and harms related to trees. This group contains
respondents who seem to have no thought-out opinion about the role of urban trees or whose
attitude towards trees is indifferent. This group could be named “Tree indifferent”. Cluster 4
consists of respondents with an excess of men in comparison to the respondents examined in
the survey. This group has a high share of respondents working in villages and smaller cities.
3.8. Clustering of Nonprofessionals
Clustering of nonprofessionals was performed after the exclusion of arboriphobes from the set
of respondents examined. The division of nonprofessionals into clusters was based on the numbers
of chosen statements concerning the five analyzed benefits and harms related to trees and the results
are presented in Table 10. Five clusters of respondents containing 64 (13%), 96 (19%), 40 (8%), 16
(3%), and 265 (52%) persons, respectively, were extracted. The relation between membership in a
given cluster and membership in a given sociodemographic group for each sociodemographic
characteristic was assessed with Fisher’s exact test for independence. The results of the statistically
significant dependencies, for education, place of residence, and assessment of the number of trees in
cities, are presented in Table 10.
The clusters can be characterized in the following way:
 Cluster 1: Tree accepting: Respondents who consider trees to be moderately attractive but
notice their positive impact on social relations and property value as well as the nuisance
related to trees. In comparison with clusters 2 and 3, the respondents in cluster 1 more often
recognize the contamination and damage caused by trees. Only 30% of them think that the
number of trees in the cities is too low. This group could be named “Tree accepting”. This group
contains a very high percentage of respondents from villages, and a low number of respondents
with higher education.

Sustainability 2019, 11, 211 14 of 22
 Cluster 2: Tree liking: Respondents who find trees highly attractive but choose very few
statements related to other tree benefits and harms. These nonprofessionals seem to “just” like
trees. About half of them think that the number of trees in the cities is too low. Hence, it seems
justified to call this group could “Tree liking”. In comparison to other clusters, cluster 2 contains
the average percentage of respondents with only primary education and a high share of persons
with higher education. This group also contains the highest percentage of respondents from the
largest cities.
 Cluster 3: Tree enthusiasts: Respondents who find trees highly attractive, with a high
assessment of their impact on socioeconomic benefits. Nearly two-thirds of them think that the
number of trees in the cities is too low. This group could be named “Tree enthusiasts”. Cluster 3
is dominated by respondents with secondary education. Half of the members of this group live
in villages.
 Cluster 4: Tree omnibus: Respondents who seem to find all the tree aspects examined in the
study important. Similarly, all except one person in this group selected the “There are too few
trees in the cities” statement. This cluster could be named “Tree omnibus”, as its members seem
to recognize all benefits and harms related to trees. There are no citizens of the largest cities in
this group and, like cluster 3, cluster 4 is dominated by respondents with secondary education.
 Cluster 5: Tree sceptics: Respondents who were not included into the group of arboriphobes
but do not find trees attractive and do not find other benefits and harms related to trees.
Similarly to cluster 1, only about 30% of them think that the number of trees in the cities is too
low. This group could be named “Tree sceptics”. Also like cluster 1, cluster 5 contains a
significantly larger percentage of respondents with only primary education. Among all the
clusters, this group contains the lowest share of nonprofessionals with higher education. The
respondents in cluster 5 do not stand out due to the place of residence.
Table 10. Relation of the clusters of nonprofessionals with the latent variables, associated to a
different general benefit or harm associated with trees, defined in the study and with the
sociodemographic characteristics of nonprofessionals. Upper: Average number of selected responses
per person in each group of statements divided by the numbers of statements in each group. Lower:
Results of the Fisher test for the dependence between sociodemographic characteristics and
assessment of the number of trees in the cities and clusters of nonprofessionals (cluster 5 excluded
from the last analysis). Only the significant (p-value < 0.1) results presented. The cells in the
contingency table responsible for the departure from independence of the examined variables were
identified as those for which the Pearson residual exceeded 1.0 (*), 1.5 (**) and 2.0 (***).
 Cluster 1: Tree accepting: Respondents who consider trees to be moderately attractive but notice their
positive impact on social relations and property value as well as the nuisance related to trees.
 Cluster 2: Tree liking: Respondents who find trees highly attractive but choose very few statements
related to other tree benefits and harms.
 Cluster 3: Tree enthusiasts: Respondents who find trees highly attractive, with a high assessment of their
impact on socioeconomic benefits.
 Cluster 4: Tree omnibus: Respondents who seem to find all the tree aspects examined in the study
important.
 Cluster 5: Tree sceptics: Respondents who were not included into the group of arboriphobes but do not
find trees attractive and do not find other benefits and harms related to trees.

Sustainability 2019, 11, 211 15 of 22
4. Discussion
The results of the study show a similar general attitude from professionals and
nonprofessionals towards the examined benefits and harms related to urban trees. For both groups
of respondents, the highest ranked is the benefit of “Attractiveness”, followed by the impact of trees
on “Socioeconomic contributions”. Harm caused by trees seems to be less important. These results
agree with the research of Schroeder et al. [46], which showed that the benefits of trees are much
more important than the annoyance they cause. Various authors have also shown that the highest
ranked benefits were related to tree attractiveness: The ability of trees to provide shade and cool
surroundings, followed by trees’ influence on helping people to feel calmer [51]; attracting and
providing a biodiversity of wildlife [52,53]. This suggests that the aspects of contamination and
inconvenience caused by trees have a lower impact on their perception of urban trees and could
support conservation of the urban forest.
The negative perception of trees due to the damage that they cause could be further minimized
by making the public aware that street trees can potentially reduce the extent of urban infrastructure
damage by reducing the need for maintenance of asphalt roadways through shading [54,21] or
reduce maintenance costs of underground infrastructure through their interception of rainfall [55].
Still, in the case of nonprofessionals, the difference between the average number of statements
selected concerning trees related to the variables “Socioeconomic contributions” versus “Nuisance”,
“Contamination and damage”, and “Danger” seem to be smaller than the analogous difference
between the average scores for these variables given by professionals. This may suggest that
professionals are more attached to trees than average citizens. As was shown by Lohr et al. [51],
respondents who strongly confirmed that trees were important to their quality of life perceived the
benefits of trees as higher than those who did not strongly confirm this.
Similar percentages of professionals and nonprofessionals found the number of trees to be too
low: 42% vs. 38%. These numbers cannot be directly compared, as professionals were asked about
the number of trees in their place of residence and nonprofessionals could select the statement
regarding too few trees in the cities. Still, as the share of questioned nonprofessionals from villages
was only 21%, the results suggest small differences between the two groups of respondents in
respect to the number of trees around them.
Cluster 1 Cluster 2 Cluster 3 Cluster 4 Cluster 5
Attractiveness 0.50 0.76 0.89 0.91 0.28
Socio-economic contributions 0.47 0.078 0.61 0.70 0.13
Nuisance 0.38 0.21 0.20 0.69 0.096
Contamination and damage 0.23 0.031 0.058 0.92 0.12
Danger 0.16 0.12 0.16 0.92 0.088
Education
p-value = 0.012
Primary 44% * 30% * 20%
**
19%
** 42% *
Secondary 41% 48% 57% 62% 48%
Higher 16% 22% * 22% * 19% 10%
**
Place of residence
p-value = 0.049
Village 56%
*** 34% 50% * 31% 37%
City: <50,000 17% 22% 15% 31% 25%
City: 51,000–
200,000 14% 19% 12% 38%
** 17%
City: >200,000 12% * 25% * 22% 0%
*** 22%
“There are too few trees
in the cities”
p-value < 0.001
Not selected 70% 49%
**
35%
*** 6% 69% *
selected 30% * 51%
***
65%
*** 94% 31%
**

Sustainability 2019, 11, 211 16 of 22
The main difference between the professionals and nonprofessionals examined lies in their
division into groups with different relations to trees. No dependence on the represented profession
was observed. All the professionals rated tree “Attractiveness” highly. Moreover, there was only one
group, containing 12% of professionals, who did not recognize the influence of trees on
“Socioeconomic benefits”. As the average scores for each of the tree features apart from
“Attractiveness” in this group were close to 3, corresponding to “I neither agree nor disagree with
the statement”, this group was denoted as “Tree indifferent”. Additionally, most of the members of
this group believed that the number of trees in their place of residence was just right. The division of
the remaining professionals was due to a different assessment of the harms related to trees. The
three indicated groups of professionals were subjectively denoted as “Tree accepting”, “Tree liking”,
and “Tree enthusiasts”. These names result not only from the fact that members of the subsequent
groups see the harms related to trees as less and less important. The professionals contained in the
first group indicated significantly least often that the number of surrounding trees is too low.
Importantly, there were no groups of “tree sceptics” or arboriphobes among the professionals, while
such groups were observed among the nonprofessionals. This again supports the conclusion that
professionals are more attached to trees than average citizens, which, to some extent, could have
been predicted, as practicing this kind of profession is usually consistent with a “pro-nature”
approach.
The division of nonprofessionals into groups with different relations to trees is more
complicated, as nonprofessionals differ strongly in their assessment of tree “Attractiveness” and the
impact of trees on “Socioeconomic contributions”. Still, similarly to the professionals, three of the
indicated groups of nonprofessionals were subjectively denoted as “Tree accepting”, “Tree liking”,
and “Tree enthusiasts”. The main difference between the groups of professionals and
nonprofessionals in the groups denoted with the same name is that all of the former rated
“Attractiveness” and “Socioeconomic contributions” very highly and, in the case of
nonprofessionals, the number of selected statements related to tree “Attractiveness” and
“Socioeconomic benefits” increases between the groups. The exception from this scheme is the
group of nonprofessionals denoted as “Tree liking”, where very few statements related to
“Socioeconomic contributions” were selected. As members of this group also selected few
statements related to tree harms, this group could also be interpreted as “Tree indifferent”. The
correctness of the naming of these groups is suggested by the increasing number of respondents
selecting the “there are too few trees in the cities” statement. While only 30% of “Tree accepting”
nonprofessionals selected the statement, the corresponding numbers of “Tree liking” and “Tree
enthusiasts” increased to 51% and 65%, respectively. The following group of nonprofessionals,
denoted as “Tree omnibus”, consisted of nonprofessionals who found all of the statements
describing tree benefits and harms important. This may result either from the high estimation of
trees by these respondents, supported by the fact that 94% of them assessed that the number of trees
in the cities is too low, or from the fact that these respondents want to prove themselves as experts in
the field of ecology. The two remaining groups included the “Tree sceptics” and “Arboriphobes”.
“Tree sceptics” did not find trees attractive and a minority (31%) thought that there are not enough
trees in the cities. “Arboriphobes” selected none of the statements related to tree-related benefits and
only a minority (21%) were of the opinion that the number of trees in cities is too low.
A variety of attitudes of urban residents towards trees was also presented in the studies by
Kirkpatrick et al. [1,53]. In the study from 2012, respondents were divided into 7 groups ranging
from arboriphobes, through indifferent residents, tree huggers, and aesthetes to practical tree lovers
and native wildlife lovers. As the division of respondents was based on other questions than in the
current study, their results cannot be directly compared. Most interestingly, in the study by
Kirkpatrick et al. [1], 13% of respondents were identified as arboriphobes. Additionally, the study by
Kirkpatrick et al. [53] found 0.4% of respondents who could not agree with anything positive about
trees. The ratio of 6% of arboriphobes among residents identified in the current study falls within the
range indicated by the above analysis. Kirkpatrick et al. [1] found also 7% of indifferent residents.
We, on the one hand, found a comparable number of 12% of tree indifferent specialists, but on the

Sustainability 2019, 11, 211 17 of 22
other hand, as many as 52% of tree sceptics among the nonprofessionals, which is a much higher
rate. Finally, the study by Kirkpatrick et al. [53] found that 45% of residents could be called tree
huggers and practical tree lovers, 16% aesthetes, and 16% native wildlife lovers. This means that 77%
of the questioned residents declared a positive attitude to urban trees. In the study by Oliveira
Fernandes et al. [56], the ratio of the respondents self-reported as tree lovers reached 96%. That result
is consistent with the results presented in the current study for the professionals, only 12% of whom
were designated as tree indifferent, but is highly inconsistent with the results for the
nonprofessionals, as only 43% of them were included in one of the groups of “Tree accepting”, “Tree
liking”, “Tree enthusiasts” or “Tree omnibus”, a fact that can be explained by the too low level of
their ecological education.
From the point of view of tree protection, it seems very positive that the numbers of questioned
professionals belonging to groups from “Tree accepting” (16%), through “Tree liking” (30%) to
“Tree enthusiasts” (41%) increases, as it shows that for the majority of professionals (71% contained
within the “Tree liking” and “Tree enthusiasts”), recognition of the positive effects of trees prevails
over the perception of their negative features. Only the smallest group of about 12% of respondents
comprised professionals who seem to be indifferent towards trees. The fact that, unlike
nonprofessionals, the “Tree accepting”, “Tree liking” and “Tree enthusiasts” groups of professionals
were similar in their assessment of tree “Attractiveness” and “Socioeconomic contributions” may
result from two factors: Education and experience. The answers of a professional respondent may be
less personal but more objective than those of a nonprofessional. The consequences of decisions
made by professionals with a low level of knowledge and a high level of fear could be particularly
devastating for urban forests and, for example, result in the removal of veteran, valuable trees
deemed unjustifiably as causing risk. In general, as pointed out by Ames and Dewald [18], the most
crucial element for tree protection is strong communication between the architect/forester and the
constructor, fostered in an environment of respect and cooperation, and is based rather on progress
than perfection. Maintaining community involvement is crucial for successful urban tree protection
[2], but keeping a high level of professionals’ education seems to be even more important for
continuity in tree protection policy across generations.
Unfortunately, the number of “Arboriphobes” (6%) and “Tree sceptics” (52%) among the
nonprofessionals is disturbing, but only small groups of respondents who seem to be concerned
about the surrounding trees (8% of “Tree enthusiasts” and 3% of “Tree omnibus”) were identified.
However, this result is highly negative for urban forest protection and development, as the
important aspect of humans’ governance of trees is that it relies on the work of individual city
residents and nongovernmental groups. Nongovernmental groups are able to affect street tree
design, and self-monitoring of trees by urban residents can support the work of professionals [9]. By
contrast, a low level of urban tree tolerance can influence the decision-making process, causing more
trees to be felled than is justified.
The low number of Polish respondents who have a positive attitude towards urban trees and
the high number of “Arboriphobes” and “Tree sceptics” may result from a low level of ecological
education and result in an overestimation of tree-related risks. Kirkpatrick et al. [1] demonstrated
that poor education results in a negative attitude toward trees and leads to their felling. As
respondents with only primary education are overrepresented in the group of “Tree sceptics”, and
this group includes the lowest ratio of nonprofessionals with higher education, education regarding
the profits resulting from urban forests and the real level of tree-related risks should be emphasized
from primary school. All city residents should be made aware that all trees, and especially large
trees, contribute to ecosystem services and can benefit human well-being, and that knowledge
should be actively promoted [5,57] in the context of climate adaptation strategies, but also regarding
individual feelings and emotions bound to the urban forest [58,59].
Some studies have shown that women are more “sensitive” than men in the way they perceive
the surrounding landscape. In Kirkpatrick et al.’s study, women dominated the group of “Tree
huggers” who loved trees for everything and appreciated them for their spirituality value [52].
Another study demonstrates that women prefer wild, romantic gardens in comparison to men, who

Sustainability 2019, 11, 211 18 of 22
prefer them to be regular and well controlled [22,60–62]. In the current study, different assessments
of tree features were observed only among the professionals. On average, women found trees
slightly more attractive than men did, and women saw the role of trees more strongly as building
good social interactions. Additionally, the group of “Tree indifferent” professionals contains an
excess of men in comparison to the examined sample of respondents. Since it is women who
dominate the group of professionals (in our study they constituted 75% of the sample), their
“sensitive” attitude may have a particular influence on decisions towards tree removal or others,
which could support the development of city green areas, and eventually the provision of ecosystem
services.
In the case of nonprofessionals, “Attractiveness” and “Socioeconomic contributions” were
related to the place of residence and education. The level of education was also positively correlated
with the attitude to trees: Lower-educated respondents were in the “Tree accepting” cluster, higher
in “Tree enthusiast”, with “Tree liking” respondents in the middle. Interestingly, respondents in the
“Tree liking” cluster were dominated by residents of medium-sized and big cities. By contrast, a
minority of villagers participating in the study were assigned to this cluster.
“Nuisance” caused by trees, such as allergies or attraction of insects, is on average seen as more
disturbing by younger and lower-educated professionals (these two groups strongly overlap in the
present study). This observation can be explained if we assume that younger people are more often
victims of allergies, which are a disease of the modern world [63,64], and especially that for them,
managing allergies in the context of social relationships could be problematic [65]. In the case of
nonprofessionals, “Nuisance” was related only to the place of residence: The statements related to
this factor were slightly more often selected by residents of villages and least often by residents of
large cities. It is worth noticing, however, that for some city dwellers, the nuisance caused by trees is
not seen, since they do not live close to green areas.
In many studies, the increasing age of the respondents had a negative impact on their
opinions towards the “Danger” caused by trees [46,56,66]. In our study, work experience (to some
extent connected with age) was the only variable influencing the perception of “Danger” in the
group of professionals: More experienced respondents were more likely to agree with that. This
confirms the results of Koeser et al. [9], who found that professional risk assessment and
recommended methods of risk mitigation are strongly influenced by experience, i.e., advanced
professionals are concerned not only about the fact that a tree may fall but also about a target that the
tree may fall over, and therefore rank the risk as higher than professionals and nonprofessionals do.
However, in Kirkpatrick’s study, the more educated respondents had significantly different
opinions on this matter, perceiving a lower level of risk, which could be explained by their ability to
evaluate the risks of trees and balance them with advantages [53].
A strong need for education in urban forestry on various social levels follows conclusions
from other studies, e.g., that of Oliveira Fernandes [56], who stated that an investment in education
and information could lead to conflict mitigation in urban forest management issues. Despot and
Gerhold [67] underlined the necessity for educational and marketing efforts to consider property
owners, site designers, and construction professionals as crucial to increasing the number of healthy
and safe trees in cities. Education, starting from primary school, could be part of the nature-based
solutions (NBS) policy concept, community-based decision-making policy or community-based
governance models, thereby improving and legitimizing the delivery of ecosystem services (ES) and
support challenges associated with climate resilience, health, and well-being in urban areas [68,69].
Interestingly, in our study, the most numerous group among the nonprofessionals stating
that the danger caused by trees is low were residents of cities with more than 200,000 inhabitants. By
contrast, respondents living in cities with 51,000–200,000 residents were more likely to evaluate the
danger as medium or high, which requires further research.
5. Conclusions

Sustainability 2019, 11, 211 19 of 22
In conclusion, a similar general attitude from Polish professionals and nonprofessionals
towards the examined benefits and harms related to urban trees was observed. For both groups, tree
benefits were perceived as much more important than the annoyance they may cause. The main
difference between the professionals and nonprofessionals examined lay in their division into
groups with different relations to trees. The group of professionals contained no arboriphobes but
41% of tree enthusiasts. By contrast, the group of nonprofessionals contained 6% of arboriphobes
and, what is most alarming, more than half of them were tree sceptics, while less than 10% were
enthusiastic about trees. The above may result from a low level of ecological education and result in
an overestimation of tree-related risks. Hence, the major postulated step to increase the ratio of
nonprofessionals accepting urban trees and understanding tree-related risks is to increase the level
of ecological education, starting from primary school in Poland.
Author Contributions: Conceptualization, M.S.; methodology, P.J., M.S., and M.B.; software, P.J.; validation,
M.S., P.J., and M.B.; data curation, MS, P.J.; writing—original draft preparation, P.J.; writing—review and
editing, M.S. and M.B.; project administration, M.B.
Funding: This research was partially funded by the Warsaw University of Life Sciences (Young Researcher
Grant awarded to Magdalena Błaszczyk).
Acknowledgments: We want to thank the following for their support of this project: Roads for Nature on tree
diagnostic training in the LIFE project (Project LIFE 11 INF / EN / 467 Roads for Nature—campaign promoting
Poland`s trees in rural landscapes, as habitats and ecological corridors) for enabling us conducting the survey
among the professionals; Beata Pachnowska and IMAS International Institute for conducting the survey among
the nonprofessionals; the reviewers who took their time to shepherd this paper to the point of publication.
Conflicts of Interest: The authors declare no conflict of interest.
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