Research paper
Physiological and psychological effects of viewing urban forest landscapes assessed by multiple measurements

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Abstract

The present study investigated the physiological and psychological effects of viewing urban forest landscapes on 48 young male urban residents. Four forested areas and four urban areas located in central and western Japan were used as the test sites. We found that in the forested areas, the subjects exhibited (i) significantly lower diastolic blood pressure, (ii) significantly higher parasympathetic nervous activity, but significantly lower sympathetic nervous activity, and (iii) significantly lower heart rate. The forest landscapes (iv) obtained better scores in subjective ratings, and (v) induced significantly less negative and more vigorous moods. Taken as whole, these findings suggest that even a short-term viewing of forests has relaxing effects. We have thus concluded that the approach taken in this study is useful in exploring the influences of urban green space on humans, as well as contributing to the planning and design of a healthy environment for urban residents.

Highlights

► A short-term viewing of forests has physiological relaxing effects such as lowered diastolic blood pressure and heart rate. ► Viewing forest landscapes caused higher parasympathetic nervous activity and lower sympathetic nervous activity than urban landscapes did. ► The forest landscapes induced a positive mood.

Introduction

The possible relationship between contact with nature and good health has long been discussed, and has been demonstrated to a considerable extent (Frumkin, 2001, Thompson, 2011). Despite abundant studies, however, the health benefits of green areas have long been inadequately acknowledged in urban planning and decision-making (Tyrväinen & Korpela, 2009). The current trend of building compact cities does not fully take into account the potential of natural settings in contributing to the quality of working and housing environments, which could enhance the health and well-being of residents.

In order to guarantee the benefits of access to nature areas and raise awareness of the issue in urban planning and green space management, it is fundamentally important to accurately assess the health benefits with validated measurements, and provide objective evidence. A recent review pointed out that although natural spaces and interaction with natural environments are recognized as health-promoting settings, there is a lack of quantitative data and controlled studies (Annerstedt & Währborg, 2011). Scientific information is therefore necessary to strengthen the position of health benefits derived from nature in various urban development and decision-making processes (e.g. Tyrväinen, Pauleit, Seeland, & de Vries, 2005).

There have been several studies that addressed this requirement. From a series of field experiments, it has been reported that visiting forests induced significantly lower blood pressure, pulse rate, salivary cortisol and sympathetic nervous activity, along with significantly higher parasympathetic nervous activity, as compared to a visit in urban areas (e.g. Lee et al., 2009, Lee et al., 2011). Mood states and subjective feelings were also improved while in a forest. These findings collectively support the conclusion that green environments have sedative and stress-reducing effects (review by Tsunetsugu, Park, & Miyazaki, 2010). These previous studies, however, dealt with a relatively small group of subjects (i.e. 12 males in each study). One study examined the incidence of positive emotions in natural settings among 168 participants (Park et al., 2011), but only targeted psychological responses. Few research studies, with certain exceptions (e.g. Park, Tsunetsugu, Kasetani, Kagawa, & Miyazaki, 2010), have been reported on human response to green environments as assessed based on multiple physiological measurements involving larger groups.

The present study therefore investigated the physiological and psychological responses to forested and urban environments in a larger group than in the previous studies. The aim of this study was to clarify the influence of two different settings and provide evidence to verify green spaces to be incorporated in urban design and planning. The research questions are (i) if there are differences in the effects of environment between forested and urban landscapes, and (ii) if a relatively short-term visit in accessible managed forests has beneficial effects, as it is not necessarily possible to visit green spaces for a long period of time in daily urban life. Our focus was on urban forests that are not primitive, wild nature, but semi- or fully managed nature where safety is secured.

Section snippets

Materials and method

The experiments were conducted in four areas located in central and western Japan (Kamiichi town, Toyama Prefecture, Yoshino town, Nara Prefecture, Akiota town, Hiroshima Prefecture, and Oita city, Oita Prefecture, respectively). In each area, participants visited two experimental sites: a forested and an urban site. The forested sites are located approximately 12–70 km from the city centers and their sizes varied from 800 to 34,225 ha. These forests are among the key recreation forests in the

Analysis

The time intervals of heartbeats were analyzed using the maximum entropy method (Mem-Calc, GMS Ltd.) to calculate the high frequency components (HF; 0.15–0.40 Hz) considered to reflect parasympathetic nervous activity (Cacioppo et al., 1994), and the low frequency components (LF; 0.04–0.15 Hz) that reflect sympathetic nervous activity (Weise & Heydenreich, 1989), in order to obtain the ratio of LF power to HF power (LF/HF).

The HF and LF power values were converted into a natural logarithm, with

Results

The main effect of the environment was significant in terms of diastolic blood pressure (p = 0.034, ηp2=0.10), which was significantly lower in the forested areas than in the urban areas. No significant main effect was observed for systolic blood pressure.

Time–series variation in the HF power was continuously significantly higher in the forested areas (Fig. 1, p < 0.01 for all time points, with Cohen's d varying from 0.31 to 0.70 depending on the time point). This suggests that parasympathetic

Discussion

Statistical analysis revealed that the different environments (forested vs. urban) had different impacts on most of the physiological parameters. The physiological and psychological outcomes were generally in good agreement, supporting the contention that the landscapes of forests have multiple positive effects on humans, especially in terms of relaxation. These outcomes were similar to those found in previous studies (Lee et al., 2009, Lee et al., 2011).

From the perspective of urban planning,

Acknowledgements

This study was partly supported by the Bilateral Joint Research Program of the Japan Society for the Promotion of Science (JSPS) and the Academy of Finland (project number 640065). The authors wish to thank Dr. Keiko Matsunaga for her useful comments.

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