A dose of nature: Tree cover, stress reduction, and gender differences

• Published in: Landscape and urban planning Vol. 132; pp. 26 - 36
• Main Authors: Jiang, Bin, Chang, Chun-Yen, Sullivan, William C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2014; Elsevier
• Subjects: 3-D visual media; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; cortisol; Density; dose response; Dose–response curve; Fundamental and applied biological sciences. Psychology; gender differences; General aspects; landscaping; Men; planning; Psychological stress; psychosocial factors; Recovery; Regression; Salivary cortisol; Skin conductance; Stress reduction; Stresses; Three dimensional; Tree cover density; Trees; women; Germany, Rheinland-Pfalz, Trier; Skin conductance; Stress reduction; Salivary cortisol; Tree cover density; 3-D visual media; Dose–response curve; Dose-response curve; Sex; Hydrocortisone; Density; Environmental management; Stress; Dose activity relation; Tree; Skin; Dose
• ISSN: 0169-2046; 1872-6062
• DOI: 10.1016/j.landurbplan.2014.08.005

•We describe the dose–response curve for the impact of tree cover density on stress reduction.•We employed 6-min, 3-D videos of community street scenes as the nature treatment.•We measured skin conductance and salivary cortisol levels as measures of participants’ stress.•For men, the dose–response curve was an inverted-U shape.•For women, we found no relationship between tree cover density and stress reduction. Although it is well established that exposure to nearby nature can help reduce stress in individuals, the shape of the dose–response curve is entirely unclear. To establish this dose–response curve, we recruited 160 individuals for a laboratory experiment. Participants engaged in the Trier Social Stress Test (TSST) to induce psychological stress, and were then randomly assigned to view one of ten, 6-min, 3-D videos of neighborhood streets. The density of tree cover in the videos varied from 1.7% to 62.0%. We measured their stress reactions by assessing salivary cortisol and skin conductance levels. Results show a clear disparity between women and men. For women, we found no relationship between varying densities of tree cover and stress recovery. For men, the dose–response curve was an inverted-U shape: as tree cover density increased from 1.7% to 24%, stress recovery increased. Tree density between 24% to 34% resulted in no change in stress recovery. Tree densities above 34% were associated with slower recovery times. A quadratic regression using tree cover density as the independent variable and a summary stress index as the dependent variable substantiated these results [R2=.22, F (2, 68)=9.70, p<.001]. The implications for our understanding of the impacts of nearby nature, and for the practice of planning and landscape architecture are discussed.