Can Different Forest Structures Lead to Different Levels of Therapeutic Effects? A Systematic Review and Meta-Analysis

Abstract

In recent decades, forests have expanded from natural resources for conservation and production to health-promoting resources. With the growing body of evidence supporting the therapeutic effects of forests, the number of investigations on the relationship between forest characteristics and therapeutic effects have increased. However, quantitative synthesis of primary studies has rarely been conducted due to a limited number of health studies including forest description and high heterogeneity of forest variables. In this study, we conducted a systematic review and meta-analysis to evaluate the relationship between the forest structure and the therapeutic effect. We systematically searched the studies examining the therapeutic effects of forests with different stand density and canopy density and synthesized the results. As a result of subgroup analysis, we found that stand density modifies the therapeutic effects. Emotional and cognitive restoration showed greatest improvement in low-density forests with a stand density of less than 500/ha and the therapeutic effects diminish as the stand density increases. The impact of canopy density was not found due to a lack of studies reporting canopy density. Although some limitations remain, the findings in this study have great significance in providing the basis for establishing management strategies of forests for therapeutic use.

Psychological Effects of Green Experiences in a Virtual Environment: A Systematic Review

“…This review used previous systematic reviews on virtual and green-based interventions to develop keywords for searching relevant studies and obtaining reproducible search results [34,35,38,39]. This review did not use keywords for participants or comparators to collect all relevant studies on virtual green-based interventions.…”

Is altitude a determinant of the health benefits of nature exposure? A systematic review and meta-analysis

“…There have been suggestions on altitude-related elements and their physiological effects; namely, atmospheric pressure (143,144,147,149,152,195,196), air oxygen concentration (143,146,149,194), negative ions (122,143,144,147,149,152,193,194,(196)(197)(198), absence of pollutants or allergens (144,149,152), solar radiation and UVB intensity (143,144,149,199), temperature (143,144,149,196), and relative humidity (143,149,196). Several factors, which may vary with altitude, have been reported as mediators of psychological restoration; namely, visually perceivable natural components (2,43,54,55,58,59,68,71,133), forest structure and understory vegetation (2,45,…”

“…Historically, nature has empirically been used as a medium for psycho-physiological restoration. The commencement of earnest theoretical discussions in the 1980s have led to an active accumulation of scientific evidence on the restorative effects of nature (1,2). Demands of daily life and stress may deplete psycho-physiological resources and result in heightened negative emotions, cognitive fatigue, and excessive physiological arousal (3-5).…”

“…Previous studies have evaluated differences in health effects from an environmental psychological perspective using varied parameters, including the perceived amount of greenery (41)(42)(43), enclosure and openness of vegetation (44)(45)(46)(47)(48), and visual perception (49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59). Moreover, several studies have investigated the psychophysiological effects of different types of landscapes (60)(61)(62)(63)(64)(65)(66)(67)(68)(69), and compared the health impacts of natural environments with varied ecological characteristics (64,(70)(71)(72)(73) or silvicultural practices (2,(70)(71)(72)(73)(74)(75)(76)(77)(78). While recent research has predominantly focused on visual experience or ecological aspects, physical environments or nonvisual experiences remain largely unexplored.…”

An eye-tracking study on visual perception of vegetation permeability in virtual reality forest exposure

“…In recent years, to verify the potential benefits of forests in health promotion and disease prevention, an increasing number of studies address the visitors' experience of sit-down and walking behaviors in the forest, namely Shinrin-yoku ( 1 – 3 ). Most of them focus on cognitive preferences which are brought about by tourists' visual experience and investigate a wide range of forest variables, especially the physical environment features such as stand structure ( 10 , 17 ), canopy density ( 18 , 19 ), tree cover density ( 20 ), openness-enclosure ( 21 , 22 ), vegetation density ( 23 , 24 ), and species composition ( 25 ). These surveys are designed to assess the stand structure features of the forest that visitors liked and disliked through visual variables, and the results indicate that physical structural features of the forest influence visitors' visual environmental preferences ( 22 , 26 , 27 ).…”