Introduction

The positive benefits of nature connection have been extensively documented; however, empirical evidence on which programs are most effective, and which instruments best measure the effectiveness of these programs, are limited (Shanahan et al., 2016). This paucity of evidence means nature-based health interventions (NBHIs) are not yet fully accepted and implemented in mainstream health care settings. Despite this, in recent years, nature connection and engagement with nature in various formats is being increasingly used across various health disciplines.

Meaningful connection and engagement with nature is associated with positive outcomes for human, social and environmental health (Brymer et al., 2019; Gray, 2018; Kahn & Kellert 2002; Mygind et al., 2019). Positive individual health outcomes reported from nature connection branch across physical, emotional, cognitive, social, and spiritual health domains. For instance, nature connection and exposure has been shown to reduce stress and anxiety as well as restore attention (Buckley et al., 2018; Maller et al., 2006; McEwan et al., 2019); to improve emotional regulation and increase positive affect and happiness (McEwan et al. 2019; Richardson and McEwan, 2018; Stevenson et al., 2018; Zhang et al., 2014), to lead to increased quality of life, self-reported growth, vitality, psychological development as well as enhance one’s outlook on life (Buckley et al., 2018; Maller et al., 2006; Pritchard et al., 2019; Zhang et al., 2014). Moreover, exposure to green spaces in children is shown to positively influence social play, concentration as well as motor ability (Pretty et al., 2007). Finally, physical health may be improved via protection and quicker recovery from disease, reduce incidence of type 2 diabetes, lower salivary cortisol, and improved cardiovascular health and brain growth (Allan et al., 2020; Maller et al., 2006; Twohig-Bennett & Jones, 2018).

The potential positive environmental outcomes from nature connection also are critical to harness considering the current climate and biodiversity crisis the world is now facing (Brymer et al., 2019). Meaningful nature connection is shown to enhance pro-environmental behaviours and conservation behaviours such as conservation volunteering (Richardson et al., 2020). These behaviours are imperative to address the climate crisis and restore natural ecosystems. Moreover, NBHIs can enhance our understanding of how healthy people require a healthy ecosystem. Considering the need to increase connection with nature for both environmental and individual health reasons, research needs to address the gaps in the current literature so NBHIs may be promoted and accepted in mainstream healthcare settings and facilitated according to evidence-based standards.

Although research demonstrates the benefits to human and environmental health of nature-based activities, more empirical evidence is required to include NBHIs in the mainstream health sector, particularly through standardised measurement and delivery of programs (Annerstedt & Wahrborg, 2011; Buckley et al., 2018; Shanahan et al., 2019). Current challenges in the NBHI field include lack of quantitative and controlled studies (Annerstedt & Wahrborg, 2011; Shanahan et al., 2016), the absence of research that has a practical application for practitioners (Brymer et al., 2019), little understanding of what components of health nature impacts (Russell et al., 2015; Zhang & Chen, 2019) as well as broad and differing definitions of what NBHIs entail across various disciplines (Annerstedt & Wahrborg, 2011; Shanahan et al., 2019). Research must overcome these current challenges for NBHIs to be accepted into mainstream healthcare and made accessible to a greater population.

The use of, and scientific interest in, nature-based programs for health has been increasing across various disciplines such as psychology, education, health and more (Brymer et al., 2019; Frumkin et al., 2017). This is beneficial in that more practitioners are offering and harnessing the healing properties of connecting with nature; however, it also poses a challenge to the unification of the field and program delivery (Annerstedt & Wahrborg, 2011; Shanahan et al., 2019). For instance, Annerstedt & Wahrborg (2011) note that program structures, settings, modalities, population targeted, health outcomes achieved, as well as outcome measures used vary considerably across interventions and disciplines. This variation leads to a lack of consensus in the field, limited information dissemination and ambiguity regarding what outcomes are actually being target by NBHIs. Additionally, a dearth of research investigates the mechanisms of improved wellbeing through NBHIs (Annerstedt & Wahrborg, 2011; Shanahan et al., 2016, 2019).

To the best of our knowledge, no review exists for wellbeing and health outcome measures used specifically in NBHIs, despite some reviews of tools and measures being conducted in related areas, such as wellbeing measures and wellbeing tools used in physical activity interventions (Linton et al., 2016). This means that understanding of how nature impacts health as well as best practice for delivering and measuring effectiveness of NBHIs are largely unknown. Our review aims to address this gap by identifying, classifying, and collating data about tools and instruments used across the numerous disciplines to assess the effectiveness of NBHIs. By identifying the instruments used, this research will support reproducibility of results and standards of evidence-based practice across all types of NBHIs (Annerstedt & Wahrborg, 2011; Brymer et al., 2019; Shanahan et al., 2019). In addition, this rapid review aims to contribute to research in the field by analysing and outlining specific health outcomes and components targeted by each tool or instrument. This will be beneficial in reducing the ambiguity in the field of what outcomes are targeted by NBHIs (Russell et al., 2015) as well as provide insight on specific dimensions of health that are being targeted by programs that involve interaction and engagement with nature (Linton et al., 2016). Moreover, breaking down tools into the specific health dimensions they target will help practitioners choose the right tool for their purposes (Linton et al., 2016).

Methods

This rapid review utilised the methodological framework provided by JBI International for conducting scoping reviews (Peters et al., 2020), but adapted some of its procedures in order to produce information in a timelier manner within resource allocation constraints. As explained by Booth (2015, p.32), a rapid review is often characterised by “explicitly sidestepping, or performing more superficially, one or more of the accepted processes used in a systematic review to allow a review team to deliver a product within a shortened timescale.” In the current case, we chose to limit the number of databases/sources searched as well as avoided a formal quality assessment of studies and used a descriptive approach to data synthesis and presentation, as opposed to the more thorough processes used in systematic reviews. We nonetheless used a multi-step approach as suggested by JBI, including: identifying the research questions, developing inclusion criteria aligned with the study objectives, performing a systematic search, selecting, and extracting the evidence, synthesising, and analysing the evidence and, lastly, summarizing and presenting the findings (Arksey & O'Malley, 2005; Peters et al., 2020).

Research questions

The following questions provided the focus for this rapid review:

  1. 1.

    What instruments and assessment tools are used to measure the effect of nature-based activities on health?

  2. 2.

    What are the settings and major population groups being addressed by NBHIs?

  3. 3.

    What are the health domains and outcomes measured by individual assessment tools and instruments?

Eligibility criteria

Considering the varied use of nature-based programs across disciplines, it is important to establish a definition for what this rapid review considers a NBHI. For the purpose of this review, a NBHI is any program, treatment or intervention that includes some element of nature and intends to achieve a health benefit to participants as an outcome (Annerstedt & Wahrborg, 2011). This may be through interaction with a certain natural setting (e.g., the ocean) or through immersion in a natural setting (e.g., forest bathing). Common modalities that use nature include adventure therapy, outdoor behavioural healthcare, horticulture therapy, green prescriptions, and sailing therapy (Annerstedt & Wahrborg, 2011). This rapid review focuses on programs that interact with natural environments but does not include animal-assisted therapy or other programs that include living creatures as main aspects of the intervention. This exclusion is due to literature arguing that animals are commonly not included in nature-assisted therapy (Annerstedt & Wahrborg, 2011), as well as animal-assisted therapies being a defined and extensive field separate to other nature-based therapies (Frumkin et al., 2017).

This rapid review considered all intervention design studies that addressed the research questions. Given the focus on assessment tools, only empirical peer-reviewed studies that included a nature-based intervention where one or more domains of health were assessed using a standardised instrument were considered, therefore excluding non-primary research such as reviews, protocols, policy documents and opinion articles.

Studies published in English from 2010–2020 were included. The index year of 2010 was chosen as this yields the most recent evidence surrounding current practice in nature-based therapies. All population groups participating in a nature-based therapeutic intervention were included.

Search strategy

Articles were identified for review via a search of the following databases: Cumulative Index to Nursing and Allied Health Literature (CINAHL) Plus, Embase Classic, and OVID Emcare. These databases were selected for their size and reach, covering the vast majority of peer-reviewed publications in the fields of health and medical sciences and of education. Additional literature was identified throughout the review process by manually searching reference lists. Three categories of search terms were identified: nature-based activities, health and wellbeing, and intervention types. The complete list of search terms is outlined in Table 1.

Table 1 Search terms by category
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As a result of this process, the initial search identified 14,412 articles (see Fig. 1 for PRISMA flow chart). All retrieved articles were screened, and 5,380 duplicates were removed. Titles and abstracts were then reviewed for eligibility, with 8,813 articles excluded in this process. Of the 219 full text articles reviewed, 167 met the inclusion criteria and were included in the final review.

Fig. 1
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Prisma flow chart of the search strategy and study selection

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Data extraction and analysis

The full-text articles of the final papers selected were retrieved and analysed using an adaptation of the JBI data extraction instrument (Peters et al., 2020). The data extracted from each of the articles included the following study information: author(s), year of publication, country, target population/study participants, and outcomes. In addition, the following relevant data pertaining to the research questions were included: setting, nature-based therapy modality, program content, health condition(s), health domain, name of tool, description of tool, tool validity and reliability, and whether the tool included a nature-specific component (i.e., item/s assessing aspects/outcomes related to engagement with nature).

Given the large number of studies included in the full review, articles were categorised according to the nature setting, as follows: Garden/Horticulture, Blue Spaces, Urban Green Spaces, Wild Nature, and Camp/Residential settings. Garden/horticulture settings encompass both gardens and farm settings; Blue Spaces include those spaces that involve large bodies of natural water, such as seas/oceans, rivers, creeks and lakes; Urban Green Spaces include outdoor settings that are managed or altered by humans and typically used for outdoor recreation, such as urban parks, nature reserves and other unspecified outdoor areas; Wild Nature encompasses natural settings that have minimal management by humans and often include an element of risk or unpredictability due to the less controlled nature of the setting; Camp/Residential settings include interventions that may engage with any of the above natural settings but as day activities from a base camp or residential facility. In addition to those, a few studies were classified as ‘Other’ as they were not focused on a particular setting but on developing assessment tools for NBHIs.

Results

The final dataset of 167 records (Appendix 1) was classified into the five nature setting categories plus ‘Other’ (n = 4) (see Table 2). The majority of research was conducted in Urban Green Spaces (n = 50), followed by Garden/Horticultural (n = 49) and Camp/Residential programs (n = 32), with only a small proportion of research conducted in Wild Nature (n = 19) and Blue Spaces (n = 13).

Table 2 Articles by nature setting category
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Table 3 presents the characteristics of included studies. Of note, research into NBHIs was conducted across thirty countries, with the majority of research occurring in the United States of America (n = 59). The next most common countries were the United Kingdom (n = 16), Australia (n = 10), Hong Kong (n = 9) and Canada (n = 7). Figure 2 includes a summary of main characteristics by nature-based setting by number of studies, to provide an overall sense of the most common population groups, countries of origin and health domains assessed.

Table 3 Summary characteristics of included studies
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Fig. 2
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Most Common Tools by Setting

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Table 4 presents a summary of the instruments used across studies, including what they were used to measure. A total of 336 distinct instruments were used across the dataset. Within this extremely broad range of tools, only a small number were used in five or more studies, including: the Perceived Stress Scale (n = 10), the Positive Affect & Negative Affect Scale (n = 8), the Profile of Mood State (n = 8) the Youth Outcomes Questionnaire Self-Report (n = 8), the Self Efficacy Scale (n = 6), the Rosenberg Self-Esteem Scale (n = 6), The Depression Anxiety Stress Scale (n = 5), the Borg Rating of Perceived Exertion (n = 5), the UCLA-3-item Loneliness Scale (n = 5), and the Geriatric Depression Scale (n = 5). An additional seven tools were used across four studies, and nine instruments were used across three studies. Figure 3 presents a summary of most common assessment instruments used by nature-based setting by number of studies.

Table 4 Instruments and outcome measures used in included studies
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Fig. 3
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Main Study Characteristics by Setting

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In the following section, we present a descriptive summary of the studies included in each category setting, providing a brief overview of the population groups targeted, health domains and outcomes assessed, general tools utilised, and information on tools, if any, designed to specifically assess NBHIs.

Urban green spaces

Fifty Urban Green Spaces NBHIs were identified in the rapid review. The interventions incorporated a range of modalities including guided nature activities, forest therapy, group and individual walking, cycling, exposure to nature, outdoor therapy and mindfulness, and various aerobic exercises. Several studies were multimodal, investigating the effects of a combination of interventions.

Population groups

The majority of urban nature research included adult participants (n = 33), with a further seven studies investigating seniors. The interventions for older adults tended to be passive (e.g., guided relaxation) or exercise-based (e.g., brisk walking) activities in a natural setting. Ten studies focused on children (up to 14 years of age) in urban nature settings, with one study including also youth (up to 18 years of age); only one study had an exclusive focus on adolescents. Interventions targeted at younger children were typically centred around outdoor schooling, including free play and education about nature. Studies including older children typically involved adventure therapy or prescribed outings to local natural spaces. The majority of studies recruited mixed gender participant cohorts (n = 43), with a similar small number of male-only (n = 4) and female-only (n = 3) groups.

Health domains and outcomes

The health conditions targeted by Urban Green Space interventions were varied; however, almost half (n = 21) of the studies had a focus on psychological health. Eleven interventions specifically targeted stress, and other psychological conditions included schizophrenia, negative affect, depression, eating disorders, and anxiety. The second most common health domain investigated in Urban Green Space studies was a physical attribute of the participants (n = 16), including the management of a physical pathologies such as cancer or a spinal cord injury, and a lack of physical exercise. Several studies included a focus on multiple health conditions, and other outcomes of interest included: gut microbiome, academic performance, eating habits, and quality of life.

Overview of tools

A total of 180 measurement tools were used across the Urban Green Space studies, with 119 unique tools. Of the unique tools, the majority were questionnaires (n = 99), many of which were measured with a Likert-type scale (n = 59). Other questionnaires used frequency, percentile scales, ordinal scales, pictorial scales, or yes/no responses. Except for seven questionnaires which were completed by a child’s carer, all questionnaires were self-reported. Of the 28 tools that were not questionnaires, most were physical assessments of health or fitness (n = 19), and the rest were psychological assessments of wellbeing or capacity (n = 9). Physical tools were predominantly used to assess middle-aged and older adults, and included blood pressure, heart rate, and capacity for specific exercises, though accelerometers were used to assess the activity of young children. Several tools were recurrently used in the studies: Profile of Mood State (n = 8), Connectedness to Nature Scale (n = 5), Perceived Stress Scale (n = 5), and the Positive and Negative Affect Schedule (n = 5). Of the 180 tools used across various studies, only 29 were not considered to be both valid and reliable for the context of the study (i.e., either no evidence or very low levels of validity and reliability presented or were found to be unvalidated).

Nature-based tools

Thirteen unique nature-based tools were identified in the Urban Green Space studies. The Connectedness to Nature Scale and the Connection to Nature Index are two similar, valid, and reliable tools included in the Urban Green Space group of studies. The most notable difference is that the Connection to Nature Index was initially designed for use with children, and the Connectedness to Nature Scale was initially designed for use with adults.

Four of these tools were developed in conjunction with specific programs. The Semantic Differential and the List of Threatening Experiences (LTE) were adapted for a specific nature setting. The Connectedness to Nature Scale, Connection to Nature Index, Nature Related Scale, Love and Care for Nature Scale, Engagement with Beauty Scale, and Perceived Restorativeness Scale are all tools that were developed for use in multiple nature-based studies.

Common threads can be found in many of these nature-based tools, including care for the natural environment, empathy for creatures, appreciation for natural beauty, and regard for ecological sustainability. Many studies used a combination of nature-related tools with instruments that were relevant to other aspects of health, such as the Play & Grow study by (Sobko et al., 2020). This study used two nature-based tools, the Connectedness to Nature Index and Nature Related Scale, in combination with three tools related to a child’s willingness to try foods in order to identify a link between engagement with nature and diet.

Garden/horticulture

Forty-nine Garden/Horticulture NBHIs were found in the included studies. A wide range of modalities were utilized in the interventions, including care farming programs, horticultural therapy, community gardening, occupational therapy, and unspecified nature-based therapy. A small number of studies incorporated the combination of two or three modalities; for instance, exercise and horticulture (Makizako et al., 2020), socialisation and therapeutic horticulture (Chiumento et al., 2018), gardening, nutrition, and cooking (Gatto et al., 2017), and occupational and horticultural therapy (Im et al., 2018).

Population groups

Across the Garden/Horticulture NBHIs, a variety of age-groups was noted. Ten studies focused on older adults exclusively, while thirteen focused on children. Most studies (n = 27), however, were focused on adults over 18 years of age including older adults in most cases. Research with adolescents was notably absent in Garden/Horticulture NBHIs. Most studies included a mixed cohort (n = 44), with a small number of male-only (n = 2) or female-only (n = 1) studies across different age groups.

Health domains and outcomes

The majority (n = 21) of the Garden/Horticulture NBHIs evaluated the efficacy of horticultural therapy in reducing the level of mental health conditions such as schizophrenia, dementia, depression, loneliness, and stress. Seven of the thirteen studies with children focused on food behaviour and attitudes (e.g., vegetable consumption), and one study investigated gardening as an intervention to deal with children’s obesity (Gatto et al., 2017; Johnson-Jennings et al., 2020).

Overview of tools

A total of 126 distinctive assessment tools were used across the Garden/Horticulture NBHIs to assess various health domains, including depression, stress, anxiety, mood, satisfaction, memory, emotional level, social connectedness, quality of life, perceived wellbeing, nature-connectedness, food behaviours, daily activities, physical activity, physical assessments, and community empowerment. The largest category of instruments were self-reported measures, typically using a Likert-type scale. A small proportion of the instruments were modified versions of pre-existing tools tailored for the study and targeted population. The Depression Anxiety Stress Scale 21 (DASS21) and Mini Mental State Examination (MMSE) were both utilised four times; however, most studies used unique measurement tools. While no individual instrument was used extensively, categorisation of tools revealed that most focused on mental health conditions, and only five studies directly measured perceived connectedness to nature.

In terms of psychometric properties, a large proportion of tools were found to be psychometrically sound; however, sixteen tools reported no evidence of validity and reliability, and eight tools were found to be unvalidated or demonstrated very low levels of validity and reliability.

Nature-based tools

Two studies utilised tools specifically designed for nature settings to evaluate the effect of Garden/Horticulture NBHIs on health conditions of the participating individuals. For example, Christian et al. (2014) utilised two different instruments: the Gardening Questionnaire was used to identify the level of implementation and involvement of schools in gardening programs, and the Gardening Process Measures Questionnaire identified the different types of gardening activities happening at schools to establish their level of involvement with gardening. Hutchinson et al. (2015) designed a child questionnaire to evaluate the efficacy of a school-based gardening intervention on children’s knowledge and attitudes towards fruit and vegetable intake.

Camp/residential settings

A total of thirty-two studies were found and classified in the camp/residential setting category. The types of interventions included in these studies varied considerably, but adventure and wilderness therapies within a regulated camp or residential setting were the most common. Camps for particular health conditions, such as spina bifida, cancer, depression, burns or diabetes, were also popular.

Population groups

The vast majority of studies (n = 22) were focused on children, adolescents and/or youth. Ages across all studies ranged from 6 to 75 years, with eight studies focusing solely on the adult population (i.e., 18 years and over). Two studies that were focused on children and young people also included parents in the therapy camp (Hill et al., 2019; Norton et al., 2017). In terms of gender, one study focused on female participants only (Guest et al., 2017), and one on male participants only (Bird, 2015); all other studies included a mixed cohort of participants in their interventions. The number of participants in these camps and residential settings varied considerably as well, from small studies of seven participants to large cohorts of over 200 participants.

Health domains and outcomes

Five studies assessed physical health as their exclusive health domain (Huelsing et al., 2010; Nagyova et al., 2020; Neumayr et al., 2014; Rosenberg et al., 2014; Wong et al., 2013). All remaining studies focused on psychological/emotional health, either solely or in combination with other health domains, including social, spiritual, and intellectual health.

A vast range of outcomes were measured, with quality of life being the most common. Other outcomes measured through Camp/Residential setting interventions included self-efficacy, attachment, interpersonal relationships, social connectedness, mastery, social skills, enjoyment of physical activity, effective life skills, resilience, self-concept, and goal attainment. Measures of improvement of health conditions were also present, such as: improvement of depressive symptoms, stress, anxiety, subjective distress, and improvement in physical ability and performance. Health literacy around particular conditions was a less commonly measured outcome but was present in camps that were targeted to specific health conditions (Driscoll et al., 2019; O’Mahar et al., 2010). Spiritual wellbeing was measured in two studies (Warber et al., 2011, 2015) and body image in two studies also (Bakker et al., 2011; Rosenberg et al., 2014).

Overview of tools

A total of 84 different assessment tools were used across the studies, with only a handful being used in more than one study. These were: The Chinese University of Hong Kong Physical Activity Rating for Children and Youth (CUHKPARCY); the Outcome Questionnaire-45.2; the Pediatric Quality of Life Inventory (PedsQL); the Perceived Stress Scale (PSS); the Physical Activity Self-Efficacy Scale; the Physical Activity Stages of Change Questionnaire; Positive Affect & Negative Affect Schedule (PANAS); the Rosenberg Self-Esteem Scale (RSE); the Short-Form 36 Health Survey Questionnaire (SF-36) and the Spina Bifida Independence Survey. In addition to named assessment tools, most studies also included extra survey questions to address specific content of their interventions, including satisfaction with the program and general feedback forms. These were not catalogued in this review due to their ad-hoc nature and inconsistency of the measures.

Reliability scores were not provided for 31 of the 90 assessment tools. For those that reported reliability scores, only one reported a score of less than 0.60, which is usually considered unacceptable, with the remaining ranging from acceptable to good and excellent reliability.

Nature-based tools

Although several measures were developed specifically for the context of the intervention, only a small sample (n = 3) of the measures seemed to be designed more broadly to be used in other nature-based or Camp/Residential setting interventions. These included the Pediatric Camp Outcome Measure (PCOM), utilised in Bultas et al. (2016) study for a paediatric diabetes camp, which originally designed to measure children’s perception of a specialty camp experience – the original study being based on a camp for children with heart disease (Simons et al., 2007). Similarly, the Camper Learning Scale, used by Hill et al. (2019) in their study of a youth diabetes camp, was designed by the American Camp Association’s to measure positive youth development in recreation camps, specifically targeting outcomes related to friendship, family citizenship, teamwork, perceived competence, independence, interest in exploration, and responsibility.

Wild nature

Nineteen Wild Nature health interventions were identified in the search. The interventions used a range of modalities including outdoor behavioural health care, expedition hiking, wilderness experiences and adventure therapy. Fifty-two unique tools were identified across the interventions.

Population groups

The predominant population group targeted in wild nature-based health interventions were adolescents and youth (n = 11), and a small number of studies were conducted with adults (n = 6) and older adults (n = 2). Adult veterans made up the second dominant population group addressed in Wild Nature interventions. Notably, there were no studies identified which focused on children, possibly due to the significant physical and emotional demands of Wild Nature interventions. All but one study investigated outcomes with mixed gender participants.

Health domains and outcomes

Most adolescents and youth interventions targeted mental health conditions, with some studies also measuring specific behavioural conduct such as delinquent behaviour, disruptive behaviour disorder and school/academic functioning. Veterans aged between 20 to 66 years who were experiencing some form combat-related mental health disorders comprised three of the six Wild Nature studies with adults.

The Wild Nature interventions measured various specific outcomes in the cognitive, emotional, social, and physical health domains. The most common outcomes targeted in the interventions were intrapersonal outcomes, such as self-esteem and self-efficacy (n = 7), interpersonal relationships (n = 7), and behavioural conduct (n = 6). Interpersonal factors that were measured included relations with peers, friends, family, intimate partners, sense of belonging, social support and resources, sense of loneliness, sense of cohesion with a group or a greater social environment. Behavioural conduct outcomes were most prevalent in the youth population. Outcomes included aggression, behavioural dysfunction, conflict resolution, behavioural change, and anti-social behaviours such as stealing, fighting, vandalism and substance abuse. Other outcomes included stress (n = 2), depression/anxiety (n = 3), resilience (n = 3), coping (n = 2), life satisfaction (n = 4), life functioning (n = 3), emotional wellbeing (n = 4), symptomology of various conditions (n = 5), mood (n = 2) and executive functioning (n = 2).

Overview of tools

A total of 52 unique tools were used across the Wild Nature health interventions. The majority of these tools were psychological measures (n = 43), with all but two being self-report measures. A small number of studies utilised physical assessments (n = 4), social scales (n = 3), occupational therapy (n = 1) and biofeedback (n = 1).

Seven tools, all psychological measures, were utilised more than once in the Wild Nature literature: The Youth Outcome Questionnaire—Self-report, The Youth Outcome Questionnaire 2.01, the Social Connectedness Scale, the General Perceived Self-Efficacy Scale, the Satisfaction with Life Scale, the Rosenberg Self-Esteem Scale, and the Resilience Scale. All seven common tools reported adequate validity and reliability.

All articles used at least one valid and reliable tool. However, some instruments had not undergone psychometric validation or testing of reliability. Finally, two tools were adapted from previously valid and reliable scales.

Nature-based tools

Four tools were identified in the literature to either have been developed or adapted to include specific components relevant to nature-based interventions. Caldas et al. (2016) developed the Conflict Management Scale to assess reactions, behavioural responses, and intentions during conflict situations. Moreover, the authors adapted two validated psychological measures, the Emotional Self-Efficacy Scale and the Problem Solving Confidence Scale to include nature-based components. The scales were used to evaluate the effectiveness of an Outward Bound program to promote healthy adolescent development. Finally, Bowen and Neill (2016) adapted the Youth at Risk Program Evaluation Tool to measure the impact of an outdoor adventure on life effectiveness of youth at risk of low life effectiveness, mental health, and behavioural functioning.

Blue spaces

Thirteen Blue Space NBHIs were identified in the literature. The most prevalent Blue Space modality was sailing (n = 6), closely followed by surfing (n = 5). Other modalities included nature immersion in a wetland setting (n = 1) and fly-fishing (n = 1).

Population groups

Blue Space NBHIs had a high representation of adults (n = 6) and adolescents (n = 6), with only one article including children (Clapham et al., 2020). A seniors’ program was included in one of the studies that also included younger and middle-aged adults (Vella et al., 2013). Youth interventions were either sailing programmes or surfing therapy programs, and targeted adolescents’ social and emotional wellbeing. Veterans with combat-related mental health disorders were the predominant adult group in Blue Space NBHIs (n = 5), which aimed to improve their mental health and quality of life. Most studies (n = 12) had mixed gender participants, with only one male-only study (Gelkopf et al., 2013).

Health domains and outcomes

A range of health outcomes were measured across the Blue Space interventions in the social, psychological/emotional, intellectual, and physical domains. The most common outcomes measured were depression, PTSD, or anxiety symptomology (n = 8). Interpersonal outcomes were similarly represented (n = 5), including peer support and relations, family functioning, relations with friends and social networks. Other common outcomes included emotional or psychological variables such as resilience, self-esteem, emotional regulation, psychological flexibility and acceptance, mindfulness, and hope.

Overview of tools

Thirty-one unique tools were used across the thirteen Blue Space interventions. Psychological measures were the most common (n = 23) of these tools, and all were self-reported measures except five. Other tools measured physical parameters like fitness and blood pressure, or socio-emotional factors.

Validity and reliability scores were often not reported, although all but two instruments were externally validated. The Positive Affect & Negative Affect Schedule was the only tool utilised in at least three different studies (Marchand et al., 2018; Maund et al., 2019; Vella et al., 2013). Other tools used in more than one study included the Acceptance and Action Questionnaire II, the Five Facet Mindfulness Questionnaire, the Neill & Dias Social Support Scale, the Perceived Stress Scale, the PTSD checklist-military version, the Resilience Scale, the Sheldon & Bittencourt’s Inclusion Scale, and the State Trait Anxiety Inventory-short form.

Nature-based tools

Three measures were developed specifically for NBHIs and one psychological measure was adapted to include a nature component. Neill and Dias (2001) Social Support Scale assesses youth’s perceived level of social support during a developmental voyage. The Resilience Scale measures change in resilience levels and was adapted by Neill and Dias (2001) to specifically measure resilience in outdoor adventures. The Review of Personal Effectiveness tool was developed for outdoor programs and assesses change in youth self-efficacy and social effectiveness. Finally, an extended version of the Inclusion of Nature in the Self Scale was used during a surfing intervention with youth (Hignett et al., 2018). This tool is a pictorial scale that aims to assess individuals’ interconnectedness with nature, the local community, and the marine environment.

Other studies

Four studies included in this review did not fit into the nature setting categories described above but were included nonetheless due to them describing the process of development of a nature-based intervention assessment tool (Beyer et al., 2015; Im et al., 2018; Russell et al., 2015, 2017). Im et al. (2018) developed four evaluation tools to examine the specific effects of horticultural therapy on physical, cognitive, psychological/emotional, and social domains of health of participants. The measurement tools can be used with any age group and any type of participant, including those with or without a disability. The authors conclude that “these tools can serve as instruments to produce objective data, for clinical judgement, and to pave the way for the evaluation of the effectiveness of horticultural therapy in the medical field”.

Beyer et al. (2015) developed two scales as part of their study: the Attitudes toward Outdoor Play—Benefits (ATOP-Benefits) and Attitudes toward Outdoor Play—Fears (ATOP-Fears). Both tools were found to be valid and reliable methods of determining a child’s expectations and reactions toward playing in a natural environment.

The Adventure Therapy Experience Scale was designed by Russell et al. (2017) to measure “factors reasoned to be at work in an adventure therapy experience” (p. 275) and comprise of 18 items related to group adventure, reflection, nature, and challenge, as well as a couple of questions that are more general in nature, relating to the effect of the adventure experience on participant’s recovery journey.

Finally, Russell et al. (2015) developed the Response to Stress—Outdoor Adventure Version (RSQ-OAV) to assess reactions and coping mechanisms to stress before and after outdoor adventure interventions. The scale is adapted from the original Response to Stress Questionnaire developed by Connor-Smith et al. (2000). The RSQ-OAV was shown to be a valid and reliable tool which may be used in other outdoor adventure programs or recreation therapy interventions.

Discussion and recommendations

Most NBHI research identified in this review focused on Urban Green Spaces, Garden/Horticulture and Camps/Residential settings. The lower number of NBHIs in Blue Spaces and Wild Nature could be explained by ‘higher cost of entry’ factors, such as physical fitness, emotional challenge level and financial cost. Alternatively, it could be possible that research in these modalities is lower than NBHI practice; however, it is beyond the scope of this rapid review to undertake such a comparison.

The population groups who participated in NBHIs varied across the various modalities. Urban Green Space and Garden/Horticulture interventions tended to target adults and seniors, and had only one instance of research exclusively with adolescent participants. On the other hand, Camp/Residential, Blue Space and Wild Nature interventions tended to target adolescents and young adults, and rarely included those at the younger and older ends of the age spectrum. Most studies recruited mixed gender participants across all NBHI modalities; future research could investigate how NBHI outcomes could be tailored for different genders and age groups. Notably, no study reported interventions including or targeting participants from the LGBTQI + community.

Most NBHIs across every modality focused on participants with diagnosed psychological conditions and general mental health challenges. While Garden/Horticulture studies with older adults focused on mental health conditions, those with children prioritised healthy food consumption habits. A cluster of Urban Green Space studies worked with participants learning to manage a serious disease or injury (e.g., cancers), and Wild Nature studies also included adolescents with behavioural disorders, although these could also be said to fit under the umbrella of mental health.

The prevalence of adolescent participant groups in Wild Nature may be due to the high incidence of mental health disorders in adolescents (Bowen et al., 2016). Additionally, treatment options that include an element of risk, such as adventure therapies, show efficacy for positive development and increased resilience, both important protective factors for healthy adolescent growth (Bowen et al., 2016). It might also be plausible to assume that the high number of studies in this field reflects a burgeoning wilderness therapy ‘industry’ growing particularly in North America, from where most of the studies in this field are coming. Replicating some of these experiences, with the necessary cultural adjustments, in other parts of the world to assess their effectiveness more broadly in different geographical and cultural contexts would be an invaluable addition to the field.

It follows that the most common outcomes of NBHI research centred around mental health: reduction of adverse psychological symptoms, socio-emotional functioning, and behavioural outcomes as well as intrapersonal skills like self-efficacy. Mutz and Müller (2016) suggested that the focus on self-efficacy in NBHI may be due to the effectiveness of adventure therapies to target this construct, as well as the importance of self-efficacy for increased resilience leading to overall enhanced psychological wellbeing. Additionally, interpersonal relations may be targeted due to the group nature of wild nature-based interventions, as well as the requirement for individuals to work together and socialise with peers to overcome common challenges (Schell et al., 2012). The Urban Green Space studies investigating how NBHIs can help people managing a disease also measured physical outcomes, and the Garden/Horticulture research with children assessed attitudes towards foods and healthy eating behaviours.

There was an extremely broad range of measurement tools identified in the review, and no single measurement tool was used extensively across the whole dataset or even within each NBHI category. The most prevalent instrument (i.e., the Perceived Stress Scale) was only used in ten studies, and a total of only ten tools were used in five or more studies. This practice of using unique instruments in every study provides a challenge for comparing outcomes across NBHI research, except perhaps for comparing effect sizes of instruments that appear to measure similar outcomes.

Of the total of 336 tools, only 29 instruments were identified to have been designed for a nature-specific context. The Connectedness to Nature Scale was utilised in three studies, as was its variant the Connectedness to Nature in Preschool Children; however, all other nature-specific tools were only used in one study. On the one hand it is disappointing that NBHI research has not developed and used nature-based measurement instruments, but on the other the predominant outcomes of mental health factors do not necessarily require nature-specific measurement tools. Future research may explore why certain assessment measures are selected by practitioners. This may provide greater insight into why psychological measures are predominately used instead of nature-specific tools. Additionally, the development of nature-specific assessments or adaptation of validated tools to include nature components is recommended to further strengthen evidence-based practice by exploring and measuring the specific pathways that nature may influence wellbeing. In addition, most studies targeted psychosocial health domains and occurred in non-medical settings. The added practice of using unique tools and non-standardised measures does make the utility for the application of nature-based tools within mainstream healthcare more difficult. More empirical evidence is required for integration and acceptance into medical settings for greater uptake and inclusion.

The authors concede that a rapid review does accept some limitations. Only three databases were accessed, which were understood to cover most research in health and medical science; however, it is acknowledged that additional research is likely to have been published in journals not covered by these three databases. The one-decade date range could be a limiting factor in this review; however, the large number of measurement tools identified in the review suggest that a wider date range would not have revealed further commonalities. More than one third of all NBHI research was conducted in the United States, and only three countries (USA, UK, and Australia) produced half of all the studies in the dataset. This suggests a bias towards these cultural settings in choice of tools and nature of interventions, and evokes curiosity about potentially effective NBHIs in other countries that may not have been researched.

Future studies could not only address some of the limitations of the current study but also consider exploring who are the people conducting NBHI interventions (e.g., therapists, outdoor guides, camp counsellors, etc.) to determine the level of training and expertise that might be required or needed to successfully achieve health outcome goals. In addition, a deeper dive into the population groups being targeted, including their socioeconomic levels, migrant status, accessibility to urban nature spaces, education levels, and their cultural backgrounds would provide further insights into how NBHIs can contribute to the wellbeing of diverse groups.

Conclusion

A rapidly growing body of research-based evidence is amassing in mainstream healthcare that reveals that time spent in nature is beneficial physically, mentally, emotionally, socially, and spiritually (Frumkin et al., 2017; Williams, 2023). For instance, immersion in natural settings has been shown to reduce stress levels, which impacts our wellbeing in a variety of ways (Chomley, 2021). The broad benefits and outcomes seen in empirical studies to date do offer crucial justification as to why NBHIs are rising in imminence in mainstream healthcare.

This rapid review identified 167 peer-reviewed primary NBHI research articles from three databases, occurring in Garden/Horticulture, Blue Space, Urban Green Space, Wild Nature, and Camp/Residential settings. The interventions focused mainly on mental health domains, and while Urban Green Space and Garden/Horticulture studies tended to target adults and older adults, Camp/Residential, Blue Space and Wild Nature interventions tended to target adolescents and young adults. These studies utilised 336 separate measurement tools, including 29 nature-specific instruments. This rapid review sets out the scope of NBHI research and paves the way for more specific investigation into how nature-based measurement tools can be used most effectively, and a quantitative assessment of NBHI outcomes produced.