Preserving Trees in Construction Projects: Identifying Incentives and Barriers

David Despot; Henry Gerhold

doi:10.48044/jauf.2003.031

Article Figures & Data

Figures

Tables

Download figure
Open in new tab
Download powerpoint
Figure 1.
Comparison of knowledge (combined scale scores as percentage of maximum score) with use of tree preservation practices (total scale score as percentage of maximum score), by group and survey.
Download figure
Open in new tab
Download powerpoint
Figure 2.
Bivariate relationships between total use and total knowledge scales for arborists, builders, and designers.

Tables

Figures

View popup

Table 1

Mean scores for Use Factor 1 (use of tree preservation practices that provide enough space for trees to grow), Use Factor 2 (use of construction techniques for preserving trees), and Use Factor 3 (communication of the tree preservation message to workers). A score of 5 represented the highest level of use, and a score of 1 represented the lowest for each statement.

Group	Use factor 1^{^z} mean score		Use factor 2^{^y} mean score		Use factor 3^{^x} mean score
Group	PA	NADF	PA	NADF	PA	NADF
Arborist	16.00	15.89	13.78	14.16	7.82^*	8.59^*
Builder	18.26	18.39	13.92	14.67	6.10^*	8.80^*
Designer	17.58	18.12	12.38^*	14.35^*	6.78^*	7.98^*
Total	17.02	17.07	13.23^*	14.30^*	7.12^*	8.39^*

↵^zMaximum score = 25.
↵^yMaximum score = 30.
↵^xMaximum score = 15.
↵* Indicates significance at the .05 level of difference between Pennsylvania (PA) and NADF surveys.

View popup

Table 2

Knowledge versus use of tree preservation practices by arborists, builders, and designers. Percentage who answered “very helpful” or “helpful” for knowledge statements, “strongly agree” or “agree” for self-knowledge statements, and “always” or “frequently” for use statements.

Code	Statement	Arborist		Builder		Designer
Code	Statement	Knowledge %	Use %	Knowledge %	Use %	Knowledge %	Use %
KU	Conduct tree inventory^{^z}	99.6	37.0	81.3	61.3	97.7	53.2
KU	Erect protective fencing^{^z}	100.0	43.2	78.5	28.8	97.3	51.4
KU	Store soil out of root zone^{^z^y}	96.9	40.3	82.3	59.5	95.9	64.8
KU	Geotextile + wood chips^{^z^y}	90.4	19.7	55.7	0.1	69.1	11.2
KU	Enforce tree protection zone^{^z^y}	96.5	31.9	57.9	27.5	88.3	29.6
K	Avoid traffic on wet soil^{^z}	94.1		60.0		82.3
K	Avoid bulldozer takedowns^{^z}	86.3		32.0		67.3
K	Preserve topsoil in root zone^{^z}	96.9		68.0		95.4
K	Preserve leaf litter^{^z}	93.0		40.8		73.3
K	Pave to minimize compaction	83.8		84.6		86.9
SK	Knowledge of soils^{^z}	96.2		58.2		78.0
SK	Knowledge of preservation^{^z}	93.1		34.2		65.8
SK	Knowledge of tree biology^{^z}	97.7		48.1		66.2
U	Avoid trenches in root zone^{^y}		53.3		63.8		58.5
U	Cluster utility trenches		32.5		61.5		48.6
U	Design space for trees^{^y}		31.3		61.3		53.2
U	Avoid cuts/fills in root zone^{^y}		35.4		57.5		63.9
U	Restrict traffic on the site^{^y}		47.5		56.3		58.6
U	Cement washout site^{^y}		24.0		46.8		31.8
U	Off-site parking		30.6		32.9		31.0
U	Equipment with tracks^{^y}		15.4		30.7		0.1
U	Inform workers^{^y}		27.2		26.8		20.4
U	Retaining wall^{^y}		19.4		26.6		34.1
U	Use boring under trees^{^y}		12.6		12.7		12.1
U	Post construction care^{^y}		28.2		12.5		21.7
U	Install signs		14.4		11.3		12.0
U	Raised foundations^{^y}		0.1		0.1		0.1
Mean percentage		93.8	34.4	64.1	35.4	85.4	42.0

↵^zIndicates statements retained after factor analysis in the final three knowledge factors.
↵^yIndicates statements retained after factor analysis in the final three use factors.
K indicates a statement used to measure knowledge.
SK indicates a statement used for a self-evaluation of a respondent’s knowledge.
U indicates a statement used to measure use.

View popup

Table 3

Relative utility of selected methods for promoting the use of tree preservation in construction projects (mean scores, 5-point scale) by survey and group.

Method	Survey			Group				Total n = 647
Method	PA n = 275	NADF n = 372	F value	Arborist n = 268	Builder n = 75	Designer n = 204	F value	Total n = 647
Education	4.66	4.72	1.42	4.75 a	4.65 a	4.66 a	1.49	4.69
Technical help	4.37	4.47	2.40	4.57 a	4.20 b	4.38 b	7.80	4.43
Local ordinances	3.71*	4.16*	20.87	4.08 a	2.89 b	4.16 a	34.46	3.97
Govt. incentives	3.78	3.94	2.43	3.94 a	3.67 a	3.83 a	1.50	3.87
State laws	3.36	3.49	1.35	3.57 a	2.49 b	3.55 a	19.64	3.44

Between surveys, an asterisk indicates means are significantly different at p < .05; d.f. = 1, 645.
Among groups, means within a row followed by the same letter are not significantly different at p < .05; d.f, 2, 544.

View popup

Table 4

The most important reasons for preserving trees, by survey and group (mean scores representing the percentage of projects in which respondents selected a single reason why trees were preserved).

Reason why trees were preserved	Survey			Group				Total n = 585
Reason why trees were preserved	PA n = 226	NADF n = 358	F value	Arborist n = 246	Builder n = 69	Designer n = 202	F value	Total n = 585
Professional’s awareness	3.82	3.75	0.40	3.63 a	4.17 b	3.89 ab	5.31	3.76
Owner awareness	3.15	3.24	0.58	3.17 a	3.84 b	3.02 a	11.28	3.20
Unusually valuable trees	2.59	2.73	1.88	2.56 a	2.91 a	2.74 a	2.65	2.68
Laws or ordinances	2.21*	2.94*	32.13	2.62 a	1.91 b	2.91 a	10.93	2.66

Between surveys, an asterisk indicates means are significantly different at p < .05; d.f. = 1, 582.
Among groups, means within a row followed by the same letter are not significantly different at p < .05; d.f, 2, 514.
A score of 5 indicated that the item was the most important reason for preserving trees in 76% to 100% of projects, 4 indicated most important in 51% to 75% of projects, 3 indicated most important in 26% to 50% of projects, 2 indicated most important in 1% to 25% of projects, and 1 indicated not important in any projects.

View popup

Table 5

Perceived costs and benefits of preserving trees in construction projects, by survey and group (mean percentages of respondents who indicated that statements represented their perceptions accurately or very accurately).

Statement	Survey			Group				Total n = 621
Statement	PA n = 255	NADF n = 366	F value	Arborist n = 252	Builder n = 78	Designer n = 215	F value	Total n = 621
Customers willing to pay a premium	78.04*	86.07*	6.84	86.11 a	74.36 a	81.40 a	3.05	82.77
Primary cost is the extra time needed	51.37	49.18	0.29	59.13 a	50.00 ab	40.00 b	8.72	50.08
Cost is passed on to property owner	78.82	74.32	1.68	76.19 a	79.49 a	75.35 a	0.27	76.17
Unnecessarily slows down construction	16.08*	6.01*	17.12	7.54 a	24.36 b	9.30 a	9.46	10.14
Contributes little to energy conservation	5.49*	2.19*	4.82	0.10 a	10.26 b	4.65 b	8.23	3.54
Wooded lot is not important to buyers	5.49	3.83	0.97	3.97 a	1.28 a	6.51 a	1.20	4.51

Between surveys, an asterisk indicates means are significantly different at p < .05; d.f. = 1, 619.
Among groups, means within a row followed by the same letter are not significantly different at p < .05; d.f, 2, 542.

View popup

Table 6

The most important reasons for not preserving trees, by survey and group (mean scores represent the percentage of projects in which respondents selected a single reason why trees were not preserved).

Reasons why trees were not preserved	Survey			Group				Total n = 553
Reasons why trees were not preserved	PA n = 212	NADF n = 340	F value	Arborist n = 230	Builder n = 71	Designer n = 190	F value	Total n = 553
Site constraints	3.27	3.42	1.45	3.00 a	4.00 b	3.64 b	20.02	3.34
Insufficient knowledge	2.36	2.38	0.02	2.90 a	1.66 b	1.90 b	33.56	2.43
Costs too much	2.50*	2.25*	4.55	2.60 a	2.20 ab	2.09 b	8.27	2.37
Too much time	2.14	1.94	3.39	2.30 a	1.66 b	1.76 b	13.55	2.03
Building codes	1.67*	1.92*	6.98	1.87 a	1.72 a	1.81 a	0.51	1.85
Deadlines	1.85	1.82	0.07	1.95 a	1.51 b	1.74 ab	4.99	1.85

Between surveys, an asterisk indicates means are significantly different at p < .05; d.f. = 1, 550.
Among groups, means within a row followed by the same letter are not significantly different at p < .05; d.f, 2, 488.
A score of 5 indicated that the item was the most important reason for not preserving trees in 76% to 100% of projects, 4 indicated most important in 51% to 75% of projects, 3 indicated most important in 26% to 50% of projects, 2 indicated most important in 1% to 25% of projects, and 1 indicated not important in any projects.

View popup

Table 7

Mean scores for Knowledge Factor 1 (self-assessment of knowledge concerning tree biology, soils, and tree preservation practices), Knowledge Factor 2 (knowledge of procedures that might damage trees), and Knowledge Factor 3 (knowledge of practices that can be used to preserve trees). A score of 5 represented the highest level of knowledge, and a score of 1 represented the lowest for each statement.

Group	Knowledge factor 1^{^z} mean score		Knowledge factor 2^{^y} mean score		Knowledge factor 3^{^x} mean score
Group	PA	NADF	PA	NADF	PA	NADF
Arborist	13.28	13.58	22.47	22.56	18.86	18.70
Builder	9.63^*	10.91^*	15.41^*	18.56^*	14.53^*	16.82^*
Designer	10.72^*	11.48^*	19.92^*	21.09^*	17.21^*	18.10^*
Total	11.69^*	12.28^*	20.44^*	21.46^*	17.59^*	18.21^*

↵^zMaximum score = 15.
↵^yMaximum score = 25.
↵^xMaximum score = 20.
↵^*Indicates significance at the .05 level of difference between Pennsylvania (PA) and NADF surveys.

View popup
Table 8
Comparison of scores on self-assessment of knowledge with scores on knowledge of damaging procedures and knowledge of protective practices (Table 7) for arborists, builders, and designers, adjusted to percentages of the maximum scores of the scales.
Knowledge factor Arborists (%) Builders (%) Designers (%)
Self-assessment 90 68 75
Damaging procedures 90 68 82
Protective practices 94 78 88

View popup

Table 9

Perceived benefit of having an improved knowledge of selected subjects (mean scores, 5-point scale) by survey and professional group.

Subject	Survey			Group				Total n = 624
Subject	PA n = 256	NADF n = 367	F value	Arborist n = 261	Builder n = 76	Designer n = 212	F value	Total n = 624
Tree health	4.34*	4.49*	4.54	4.55 a	3.99 b	4.44 a	13.67	4.43
Soil conditions	4.32	4.43	2.87	4.50 a	3.84 b	4.45 a	19.31	4.38
Tree preservation	4.36	4.40	0.33	4.49 a	3.97 b	4.38 a	10.93	4.38
Cost of preservation	4.20	4.34	3.59	4.41 a	3.91 b	4.23 ab	8.92	4.28
Benefits of landscape	3.95	3.93	0.03	4.04 a	3.55 b	3.89 ab	5.90	3.94

Between surveys, an asterisk indicates means are significantly different at p < .05; d.f. = 1, 621.
Among groups, means within a row followed by the same letter are not significantly different at p < .05; d.f, 2, 546.

View popup

Table 10

Importance of selected sources for education on the topic of preserving trees in construction projects (mean scores, 5-point scale)) by survey and group.

Sources of education	Survey			Group				Total n =576
Sources of education	PA n = 237	NADF n = 337	F value	Arborist n = 243	Builder n = 71	Designer n = 194	F value	Total n =576
Professional organization	4.27	4.16	1.51	4.45 a	3.52 c	4.19 b	25.09	4.23
Trade organization	3.83	3.67	2.15	3.95 a	3.48 b	3.55 b	7.27	3.75
Cooperative Extension	3.59	3.57	0.03	3.65 a	2.94 b	3.67 a	11.73	3.59
NADF	2.89*	3.89*	10.41	3.51 a	3.49 a	3.38 a	0.61	3.51
In-house training	3.32*	3.55*	3.97	3.76 a	2.82 c	3.32 b	15.26	3.46

Between surveys, an asterisk indicates means are significantly different at p < .05; d.f. = 1, 572.
Among groups, means within a row followed by the same letter are not significantly different at p < .05; d.f, 2, 505.