Abstract
A technique is described for evaluating householder responses to street trees in front of their homes. Evaluations of the European elm and London plane are presented. As a complement to stimulation studies, evaluation can produce new and useful information for tree agencies and arborists in guiding planting and maintenance programs.
The benefits of street trees have been described in environmental, economic, and psychological terms (5,7,9,10). However, street trees are not without problems. Some of the annoyances that can be associated with street trees are raised sidewalks, broken curbs, plugged sewer lines, broken gas and water pipes, insect infestation, blocked views and solar access, reduced visibility in high-crime neighborhoods, obstruction of power lines, and the costs associated with planting and maintenance. Nursery operators and tree maintenance personnel represent valuable sources of information about these problems (3,8). However, it is risky to view the absence of maintenance problems as a positive evaluation of a tree. A species that draws no complaints from professionals may at the same time draw no praise from city dwellers.
According to Brush and Moore (4) the chief research question for behavioral scientists interested in the place of nature in the city is to find out what attributes of city vegetation urban residents consider to be desirable. A favorite behavioral research method for studying urban forestry has been photographic simulation, often traced to the work of Shafer and Richards (11), which has demonstrated the positive effects of the presence of street trees on viewers’ perceptions of urban scenes (1,2,12).
While the information from photograph simulation has been important in documenting the advantages of street trees in general, the approach provides little guidance as to the most suitable species for particular locations. Nor does it differentiate between spectators who view trees from a distance and people who experience a tree on a daily basis. Evaluation of a resident satisfaction using survey procedures provides an alternative model for assessing the opinions of street trees held by city residents who experience the tangible reality of street trees as a multi-sensory, changing aspect in specific settings.
The present study explores attitudes toward the particular street tree in front of each respondent’s residence. The working assumptions of the present study are that collected tabulations of the direct experience of householders with specific street trees contribute to an understanding of tree benefits and liabilities and that such evaluation can provide valuable, often new, information for city tree agencies to help guide planting and maintenance programs.
Procedure
Based on discussions with the Parks and Recreation Department in Sacramento, CA, two trees were selected for mail surveys: European elm (Ulmus procera) and London planetree (Platanus acerifolia). The elm was selected because of the controversy surrounding the elm leaf beetle. Numerous complaints had been made to the city regarding the mess generated by these beetles. The intensity of these views had led the city to begin removing elms from the downtown area. Opposition from tree lovers quickly terminated the removal program, leading to a stalemate. It was hoped that the survey, by identifying the opinions of those individuals most directly affected by the elms would help the city resolve the controversy.
The London planetree was selected as another mature tree in the downtown area that would offer comparative data for the elm evaluation, as well as guidance about the good and bad features of this second species as a street tree. The Parks and Recreation Department supplied information on neighborhoods containing the two species. The researchers visited the neighborhoods to locate residences associated with a target tree. From the pool of addresses, a random sample of households was generated for each target tree. For the elm, there were 133 addresses and for the planetree, 196 addresses. Based on the earlier research by Getz, Karow, & Kielbaso (6) and our own pilot studies, a multiple-choice questionnaire was constructed and pre-tested. This instrument was printed on both sides of an 11” x 17” sheet and folded in the center to make a four-page questionnaire. Half the sample by random selection received the material (cover letter, questionnaire, and return stamped envelope) in an envelope with a personal address, while the remainder received the material in a envelope addressed to “resident.”
Results
Of the 133 surveys sent out on the European elm, 96 were returned in time for analysis, for a return rate of 72 percent. For the 196 planetree surveys, 108 were returned in time for analysis, for a return rate of 55 percent. There was no difference in return rate for surveys addressed with a personal name and those sent to “resident.”
European elm
Table 1 shows that the major benefits of the elm were shade and visual aesthetics. The elm was at the top of the list (including several other trees used in the pilot study to develop the survey procedure) in both these characteristics. The most annoying features were insects in the tree, disease, and dropping sap. Responses to the open-end question dealt largely with the leaf beetle droppings.
Perceived benefits and annoyances of elm and planetree.
A composite score was computed for each respondent by summing the mean of the benefit scores and subtracting the mean of the annoyances. This was called the Global Evaluation which could vary from -3 (totally negative with no benefits) to +3 (totally positive without any annoyances). The actual range of the elm ratings extended from -1.7 to 2.8 with a median evaluation of .81 and a mean evaluation of .88 (Table 1). The postive features of the elm tree clearly offset negative features among these householders. For most respondents the benefits were considered major, while the annoyances were in the moderate to minor range.
Respondents were asked for their overall opinnion of the tree, whether they would like to see the tree removed and replaced with another, whether they would have preferred the city to plant a different tree in the first place, and if the growth rate for the tree were satisfactory. On the overall evaluation, positive opinions outweighed negative ones by a ratio exceeding 3:1. Further support of this positive evaluation appears when respondents were asked whether they would like to see the tree removed and replaced with another. About a quarter of the respondents answered affirmatively, 17 percent were undecided, while 59 percent would not want to see the tree removed.
London planetree
Table 1 shows that the major benefits of the tree are shade, visual aesthetics, and increased property values. Several of the open-ended responses mentioned improvement to the neighborhood and the increased sense of community created by these large, stately trees. Few major or moderate problems are associated with the tree. The largest source of annoyance was fallen leaves in autumn, but this was halfway between moderate and a minor annoyance. Fallen limbs and surface roots were minor problems. The Global Evaluation (weighted sum of benefits and annoyances) of 1.04 is clearly in the positive direction.
Overall rating of the tree was also very positive with only 7 percent of the respondents rating it poor, compared to 90 percent rating it from good to excellent. Opinions were similarly weighted against removing the tree (85% against, 7% for and 8% undecided) and replacing it with another (63% against, 24% for, and 13% undecided. Growth rate was considered satisfactory.
Demographics and comments
Table 2 shows that the sample for the elm contains a preponderance of males, renters, whites, is varied in income, has a modal age in the thirties, and has lived at the present residence an average of 10.6 years. The sample for the plane tree was overwhelmingly homeowners, equally divided as to gender, mostly white, varied in income, with a modal age in the sixties, and has lived in the present residence an average of 1 7 years. Opinions for the two trees did not relate to any demographic variable except for age. Older householders had a lower opinion of both trees than did younger residents. This relationship held up when length of residence was taken into account.
Demographic attributes of respondents
A majority of respondents provided additional comments at the end of the questionnaire. These statements were overwhelmingly positive, and can be most succinctly described by quoting one of them, “A city without trees is a day without sun.” People emphasized the contribution made by the trees to the neighborhood, to community life, city character, and to property values. Several people remarked that the presence of these mature trees was an important factor in their selection of the neighborhood, e.g., “The beauty of the trees in the neighborhood was a primary consideration when purchasing our home. We would not be living here without them,” and “Trees make Sacramento special!”
Discussion
Consistent with the results of simulation studies, visual aesthetics and shade are important attributes of street trees, but they are far from the major or sole determinant of householder opinions. Each species has an individual ledger of benefits and liabilities. Numerous householders with the same tree in the front yard making similar statements provide a basis for believing the findings to have some generality. Nonetheless, it would be risky to generalize without qualification from ratings obtained in one community to other cities with different climatic or socio-cultural conditions.
Evaluation can serve as an antidote to the squeaky wheel phenomenon in householder complaints. The mature elms in the survey were the subject of intense controversy between those residents who demanded their removal because of the insect infestation and tree advocates who felt that the infestation was a minor problem relative to the attractiveness of these stately trees. The city agency was caught in the middle without clear knowledge as to the extent and intensity of complaints among the affected residents. The present results show that householders are not unanimous in demanding the removal of the elms. Most, in fact, like their stately elms and do not want to see them removed. This information has been very useful to the city tree agency in deciding what to do about these trees.
During the interviews and on the written questionnaires, several respondents spontaneously requested more information about “their tree.” They were troubled when they saw an apparent problem without any explanation or indication that the city was aware of the situation. Tree agencies might consider ways of providing additional information by working through established organizations such as garden clubs, civic improvement groups or environmental organizations. Educational materials that increase public understanding, especially in regard to potentially controversial issues such as spraying, trimming, and tree removal, should be considered as low-cost extensions of existing programs. There is a large constituency of street tree advocates among householders that can mobilized in support of adequate maintenance levels.
Major benefits that can be expected to accrue from an application of evaluation procedures to street trees are as follows:
1. Cities can assess residents’ perceptions concerning various species as a basis of continuing to keep or replace trees that have reached stagnation or declining conditions and as a basis for continuing to plant species determined from the survey to be well-liked and comparatively trouble-free to householders.
2. Nurseries which have access to the results of householder evaluations can orient their inventory and sales efforts toward the kind of trees most satisfying to householders.
3. Researchers involved in the genetic improvement of urban trees can identify traits of particular species in need of modification in the interest of providing householders with trees that will be most satisfying to them.
Acknowledgement
Research performed under contract with the North Central Forest Experiment Station. We are grateful to J. Dwyer and H. Schroeder for their assistance.
Footnotes
- © 1989, International Society of Arboriculture. All rights reserved.
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