Nature and Wellbeing: The Evidence
 Nature And Wellbeing: The Evidence
Nature has a significant positive impact on mental and physical wellbeing, and individuals’ health often suffers when they are deprived of it. This pattern is observed with all types of nature exposure, from direct engagement with the natural environment, to simply living within proximity to it.
For example, studies have found that the prevalence of certain mental health disorders is higher in urban areas (Peen, Schoevers, Beekman, & Dekker, 2010; Vassos, Agerbo, Mors, & Pedersen, 2016). City living has also been associated with altered brain responses to stress (Lederbogen et al., 2011). Alternatively, when individuals move to a greener area, they have shown the opposite response, of improvements in mental wellbeing (Alcock, White, Wheeler, Fleming, & Depledge, 2014).
Hartig et al. (2014) suggests these benefits occur in four key ways: through the quality of the air, via increases in exercise, by buffering the effects of stress and from boosting socialisation. It also improves the function of the immune system, which likely plays a role in the relationship between nature and health (M. Kuo, 2015).
The Biophilia Hypothesis explains how it is the return to an environment that humans have developed to respond to in our past that fosters these enhancements in health. It explains that “the brain evolved in a biocentric world, not a machine- regulated world” (Kellert et al., 1993, p. 32) and thus maintains that engaging with nature is important as we are inclined to positively respond to it.
Despite this, unfortunately more individuals are buying or renting homes away from nature, with statistics predicting that 68% of the world’s population will be living in urban areas by 2050 (The United Nations, 2018). It demonstrates how little people are aware of the advantages of being near natural environments and has the potential to cause or contribute to an increased number of global health problems in the years to come.
According to The New Economics Foundation (2008), the five ways to wellbeing are as follows: connect, be active, take notice, keep learning and give. They describe what we need to do to feel happiest in life, and in ourselves. The following section is a literature review that summarises and discusses important findings relating to how nature can facilitate several of these steps, and so has the potential to significantly improve individual wellbeing. For more information about the aims and methods of this data collection, see Appendix C.
Several bodies of research have identified an association between living in natural environments and a longer life. For example, reductions in mortality for a large cohort were found to be correlated with living near green spaces in Ontario, Canada (Villeneuve et al., 2012). The same pattern was identified in a study of women in the United States of America. Increases in green areas were linked to higher physical activity, reduction in harmful exposures, and improvements in mental health and social engagements, which all contributed to reduced mortality (James, Hart, Banay, & Laden, 2016).
Findings from a huge sample of 40 million people living in England also showed that all-cause mortality and socio-economic-based health inequalities are reduced in areas that are considered greener (R. Mitchell & Popham, 2008). It suggests the pattern is cross-culturally valid, as the same conclusions are made with populations all over the world. However, despite the concurrence in findings, all studies are based on correlations, which cannot infer causality, due to a number of potential extraneous variables that may influence results.
One explanation for the association between green space and a longer life is the increase in physical activity with nearby nature (Ambrey, 2016a, 2016b; Bjork et al., 2008; Huang, Yang, Lu, Huang, & Yu, 2017). Exercise is important for physical and mental health, and people are more likely to adhere to their workout regime if it is outside.
Natural environments are also considered “equigenic” and extremely accessible (Braubach et al., 2017). It is much cheaper and often easier to access than indoor classes, which likely contributes to reduced health inequalities, as both those with low and high socio-economic status can take advantage of it.
Nature has also been suggested to amplify the benefits of exercise through lowering blood pressure and increasing blood flow, as well as mental advantages, such as improving creativity and reducing depression (Global Wellness Summit, 2017). A study by researchers at the University of Westminster on the “Green Gym” which specialises in outdoor nature-based exercise, showed that three hours a week of participation for eight weeks led to reduced levels of stress, anxiety and depression, as well as 20-35% increase in cortisol awakening response, indicative of good health, cognition, and balance ("Trust me I'm a Doctor", 2017).
Additionally, studies in England and Sweden have identified higher levels of subjective restoration and reduced anxiety, anger and feelings of depression for participants who jogged in a natural environment, compared to those who did the same in a gym (Pretty et al., 2005; Bodin and Hartig, 2003). It suggests that natural environments have a holistic effect on wellbeing through simultaneously encouraging physical exercise and fostering boosts in mental wellbeing.
 Positive mood and negative mood recovery
Furthermore, passive exposure to real or virtual natural scenes can also support recovery from negative mood (Alcock et al., 2014; Annerstedt & Wahrborg, 2011; Bell, Foley, Houghton, Maddrell, & Williams, 2018; Beute & de Kort, 2014; Beyer et al., 2014; Bratman, Hamilton, & Daily, 2012; Larson, Jennings, & Cloutier, 2016) and cognitive functioning (Berman et al., 2012; Bratman, Daily, Levy, & Gross, 2015). For example, studies have found that, in comparison to an urban environment, participants reported feeling more comfortable, soothed and refreshed, when viewing scenes of nature. State anxiety, as well as negative feelings of tension and fatigue were also reduced (Ikei, Song, Kagawa, & Miyazaki, 2014).
Even simply observing a natural mural and sounds of nature have been linked to better pain control in patients recovering from a bronchoscopy in hospital (Diette et al., 2003). Research has explained how these restorative effects may occur due to the positive distraction of nature, which fosters mindfulness and creates the sense of being away (Gonzalez, Hartig, Patil, Martinsen, & Kirkevold, 2010; R. Kaplan & Kaplan, 1989; Ulrich et al., 1991; University of Essex, 2015).
As well as the reductions in negative mood states, increases in general happiness have been linked to green environments when compared to urban ones (Mackerron & Mourato, 2013). A meta-analysis has even demonstrated that brief contact with nature may suffice to increase positive affect (with large effect sizes) and reduce negative feelings (McMahan & Estes, 2015).
In addition, a longitudinal study has suggested that feeling connected to nature may also encourage a future tendency for happiness, even when the individual is no longer in a natural environment (Zelenski & Nisbet, 2014). McMahan and Estes (2015) imply that this boost in positive affect may be linked to our evolution. They explain that positive emotions would have increased approach behaviours in natural environments, which heightens the chance of using the resources on offer for survival.
Passive nature engagement, such as watching pictures or views through the window (Lee, Williams, Sargent, Williams, & Johnson, 2015) also benefit individuals by supporting recovery from stress and mental fatigue, more than such rest in a non-natural environment (Greenwood & Gatersleben, 2016). For example, a study in Denmark showed that participants with a high volume of green space within 3km of their home were not as physically and mentally affected by stressful life events than those with less nearby greenery (Van den Berg et al., 2010).
This effect is even found simply with exposure to the smells of nature. A recent study linked diffusing essential oils in a hospital to the reduction in number of nursing staff experiencing high levels of work-related stress, from 41% to just 3% (Reynolds, Card, & Tomes, 2016). In addition, when participants of a study were exposed to a stressful and fearful video about industrial accidents, natural scenes significantly sped up mental recovery. Those who viewed water or parks after the video felt more positive and showed lower signs of stress (including blood pressure, muscle tension and heart rate) than those who observed urban scenes. They also returned to baseline brain measures within five minutes, in comparison to the “urban group” who were still recovering 10 minutes later (Ulrich et al., 1991). It demonstrates how natural scenery has a positive restorative influence, fostering the reduction of stressful and negative emotions.
One suggestion for why this occurs involves the default mode network in the brain, which is active while we are at rest. When listening to sounds of nature, researchers recognised an “outward-directed focus of attention” (p. 8). In comparison, when listening to other, artificial sounds, the attention was focussed more inwards, which is also observed when we are experiencing anxiety, PTSD and depression (Gould van Praag et al., 2017).
From a clinical perspective, a randomised controlled study also revealed that a prescription of a nature-based treatment in a wild forest arboretum for adults with stress-related illnesses led to similar reductions in healthcare usage as participants prescribed a stress-based CBT programme for the same duration. The nature intervention incorporated therapeutic practises with mindful engagement, nature-based reflection and gardening activities, and led to reduced GP visits and reductions in sick leave (Corazon, Nyed, Sidenius, Poulsen, & Stigsdotter, 2018).
In addition, activities such as gardening have been shown to provide relief from severe stress (Van Den Berg & Custers, 2011). When discussing these benefits associated with engaging with natural environments, the concept of nature connectedness is an important consideration. Described by Shultz (2002) as “the extent to which an individual includes nature within his/her cognitive representation of the self” (p. 67), higher levels of connectedness are negatively associated with stress in adulthood and linked to subjective wellbeing (Bragg, 2014). Ways to establish a beneficial connection include green exercise and childhood nature exposure, which are both named as key moderators (Wood & Smyth, 2019).
 Increased connectedness
Another advantage of nearby nature is its ability to increase feelings of connectedness to the community and the place by providing communal, outdoor space (Baur & Tynon, 2010; Cleary, Fielding, Bell, Murray, & Roiko, 2017; Groenewegen, den Berg, de Vries, & Verheij, 2006; Kweon, Sullivan, & Wiley, 1998; Larson et al., 2016; Seaman, Jones, & Ellaway, 2010; The University of Essex, 2015; Zhang, van Dijk, Tang, & van den Berg, 2015).
Green areas are an important place for social interaction among people of all ages (Greenwood & Gatersleben, 2016) which is linked to benefits for health and wellbeing (Munoz, 2009). Neighbourhoods in which more individuals live close to parks have been identified as showing higher “social capital” (Cohen, Inagami, & Finch, 2008), suggesting more interpersonal relationships, cooperation and shared norms or understanding.
Likewise, research has concluded that the connectedness of forests is moderated through the feeling of “social inclusion” associated with these spaces (Ward Thompson et al., 2004).This finding is emphasised in a study of women living in supported housing in America, which found that nearby parks were considered one of the most important and meaningful places for improving their quality of life. When asked why this was the case, most of the women said they enjoyed the opportunity to interact with locals and the possibility of free social events that facilitated this (Plane & Klodawsky, 2013).
Similar to the boost in happiness, positive effects for mental wellbeing have been attributed to spending time in nature. For example, a study using phone data of Spanish, British, Dutch and Lithuanian participants found that contact with natural outdoor space was linked to better mental health (Triguero-Mas et al., 2017).
Natural views in hospitals or prisons have also been shown to enhance wellbeing of individuals, both in the short and long term (The University of Essex, 2015). In addition, a recent five-year study involving over 1000 individuals who moved to a new house, revealed that in comparison to before the change, those who now lived in greener urban areas showed improvements in mental health, as measured using the General Health Questionnaire. The researchers controlled for several extraneous variables and benefits were seen for the three-year remainder of the study, suggesting they may be maintained over time (Alcock et al., 2014).
However, the causality of this association needs to be verified, as other studies have indicated that the boosts to wellbeing could instead be due to changing life circumstances which influence the decision to move (Weimann et al., 2015). In addition, further research into the long-term implications (beyond three years) is required to determine the extent of the sustained benefits.
Despite this, research has also found that individuals with lower mental wellbeing benefit even more from increases in local green space than others (Weimann et al., 2015). For example, a twin study found that individuals with greater access to green areas had lower levels of depression, even when comparing within twin pairs (Cohen-Cline, Turkheimer, & Duncan, 2015).
In addition, participants with Major Depressive Disorder (MDD) showed enhancements in cognitive processes (working memory), as well as increases in positive affect after interacting with nature for 50 minutes. These benefits were even suggested to be almost five times as large as in previous research employing healthy participants (Berman et al., 2008; Berman et al., 2012).
It is therefore unsurprising that nature-based interventions for disadvantaged populations have often proven successful in enhancing wellbeing. Active nature engagement is especially beneficial, as the combination of spending time outside, alongside activities such as wilderness experiences, learning outdoor skills and green care, provide further support for the boost to health and wellbeing by allowing participants to feel a sense of confidence, purpose and meaning (Annerstedt & Wahrborg, 2011; Chiang, Li, & Jane, 2017; Cole & Hall, 2010; O'Brien, Burls, Townsend, & Ebden, 2011; Soulsbury & White, 2015).
In addition, any endeavours designed to help the greater community (such as conservation) boosts social pride and helps individuals feel like they are more connected to nearby environments, and the local community (The University of Essex, 2015). The ”Gateway to Nature” project is a key example, which provided free outdoor activities two or three times a week (such as gardening, walking, conservation and healthy cooking) for homeless or vulnerable people.
A report measuring its impact revealed that 93% participants showed significant improvements to mental and physical health, and 85% said they had improved their life chances with the skills and opportunities for work. Also, 98% users said they enjoyed the activities and 91% felt they had increased their confidence, often from overcoming fear and isolation, or learning new skills, of which 98% reported doing. One participant commented “This was the first time I had been on a proper walk after 18 months of depression. It was great for my confidence and I enjoyed talking to people and learnt something about nature” (p. 6). Additionally, one referrer noted how there were “definite psychological improvements regarding mood and recognising own abilities” and that it was a “positive social experience for some who find social situations difficult at times” (Framework Housing Association, 2014, p. 7).
There are a number of cognitive benefits that have been linked to spending time in nature. Being outdoors helps individuals learn more about the nearby ecology and learn skills within this environment, which is good for both cognition and self-esteem (The University of Essex, 2015). Additionally, learning outside is associated with enhanced creativity, an improved respect for nature, and an opportunity to meet the needs of a larger range of learning styles (Council for Learning Outside the Classroom, 2009). For example, participants focussed much better on a Stroop task when they walked in a natural environment, compared to a built up one (Bailey, Allen, Herndon, & Demastus, 2018).
The attention restoration theory suggests that the improvements in concentration are due to nature stimulating the mind in a gentle, bottom-up way. It contrasts to the dramatic and draining form of attention that urban environments often demand, so allows our brain to relax (Berman, Jonides, & Kaplan, 2008). The differences have also been observed in work environments, as LL Bean reported that exposing workers to a pop-up outdoor office improved 74% individuals’ mood, lowered stress for 71% and made tasks like brainstorming easier (Global Wellness Summit, 2019).
Additionally, a study at the University of Exeter showed that simply adding plants into an office caused a 15% increase in productivity as well as improving attention and wellbeing and reducing stress (University of Exeter, 2014). It demonstrates how nature can be utilised in a variety of different settings, to boost cognitive performance.
 Nature and young people
Regarding children and young people, increasing volumes of research support the concept that the outdoors is advantageous for them (Ashbullby, Pahl, Webley, & White, 2013; Brockman, Jago, & Fox, 2011; Christian et al., 2015; Greenwood & Gatersleben, 2016; Richardson, Pearce, Shortt, & Mitchell, 2017; Sugiyama et al., 2016; van den Berg & van den Berg, 2011; Wells & Evans, 2003). However, evidence is limited and there have been calls for more focus on the health benefits of nature engagement for youth (King & Church, 2013). Nevertheless, the following summarises research on how nature can influence young people’s wellbeing. An effort is made to compare different types of environment and exposure, as well as discuss how individual differences may affect how someone responds in a natural setting.
 Type of environment
Research discussing the benefits of green space varies in its description of nature, from the deep wilderness, to urban greenery and city parks. Different types of natural environment have different restorative effects on individuals (Han, 2010), so it is important to consider the definition of nature that is used in each publication so we can compare and contrast, and potentially identify which is most effective.
It is of particular importance within the context of children and young people who learn through interacting with their environment, so the setting has a significant impact on what kind of benefit they derive from it (Wilson, 1997). For example, wilder, more natural settings provide an opportunity for exploration and discovery, which has been shown to increase curiosity, imaginative play and sustained attention (Dowdell, Gray, & Malone, 2011).
In addition, Munoz argues that children and young people need an environment with a considerable number of natural elements in order for them to gain motor benefits, such as improvements in strength and coordination (Munoz, 2009). Features like “slopes and rocks” present children with “natural obstacles” that they need to learn to overcome (Fjørtoft, 2001, p.111). Research has also importantly discovered that these wild environments are, in fact, favoured by young people aged 10-14 (Elsley, 2004), which makes them more inclined to want to utilise them.
However, beyond this, there is limited research that directly compares the quality of natural environments and their effects, especially in children. Some studies suggest that feelings of restoration in adults are not influenced by the type of nature, but instead on whether it is present (Van den Berg, Jorgensen, & Wilson, 2014). Others, however, argue that subjective restoration is always higher in wilder environments that are considered “social”, “serene” and “natural” (referring to the quality of nature, and the appearance of being “wild” and “untouched”; Peschardt & Stigsdotter, 2013). In addition, settings that are richer in biodiversity and plant species have been linked with greater psychological benefits (Fuller, Irvine, Devine-Wright, Warren, & Gaston, 2007), as well as exposure to wildlife, which produces a sense of awe and beneficial distraction (Curtin, 2009).
A significant influence on the advantages derived from nature, that is generally agreed upon throughout existing literature, is the accessibility of natural space. For example, a systematic review revealed that children and young people under 18 years old are shown to have higher levels of confidence, cognitive development, academic achievement and emotional wellbeing, as well as improvements in social interactions, if they can easily access nature (McCormick, 2017).
In addition, another review references that 17 of the studies evaluated that measured how accessible nature was, displayed a significantly positive link to mental health, with 13 displaying non-significant results (Tillmann, Tobin, Avison, & Gilliland, 2018). It is probably linked to the fact that nearby greenery is more likely to be utilised than any that is hard to reach, which would then allow the plethora of benefits that natural environments generate to be realised.
Statistics also illustrate that most natural environments are reached on foot (64%), in comparison to by car (30%) or (3%) bike (Natural England, 2019). It shows how accessibility is a large factor in the decision to use a natural environment, and likely explains why 72% children under 16 access urban greenspace, compared to 35% who went into the countryside (Natural England, 2019).
Therefore, although there is research that does suggest wilder environments may foster larger benefits, this is not always easy for young people to access. Any natural environment is better than none, so often the focus is on getting youth out into nature, no matter it’s type.
 Type of engagement
Another large consideration are the types of engagement – that is, how the benefits differ depending on what an individual does in/with it. The following explains in greater detail the different effects of passive nature engagement (i.e. just being in nature) and active nature engagement (i.e. engaging with nature in an active way, such as through walking, playing or gardening).
 Passive engagement
Regarding learning, nature has been shown to improve cognitive functioning (Driessnack, 2009) as well as providing a number of alternative educational benefits such as higher levels of creativity and language development (O'Brien & Murray, 2007). Allowing children to learn outside also “gives them direct experience of the subject” and allows connections to be made between the classroom and the real world. In addition, children who have greater exposure to the natural environment are better at “reading, writing, maths, science and social studies” no matter their usual level of achievement, as well as displaying better cooperativeness and self-discipline (Moss, 2012, p. 9).
Another benefit of increased attention has been linked to the opportunity for “reflection” and “escape” provided by natural environments. High levels of concentration can lead to a phenomenon called “mental fatigue” which often results in irritability and distraction. The exposure to nature allows focus, without effort, away from their stressors (Kaplan, 1995). These effects have been shown as especially significant in children with ADHD, with increases in tree cover linked to reduced symptom severity (Taylor, Kuo, & Sullivan, 2001). Activities based outdoors were also shown to increase ability to concentrate in children aged 5 – 18 years old with the disorder, regardless of age, gender or income (Kuo & Taylor, 2004).
Research is beginning to recognise the importance of direct nature exposure for the health (physical and emotional) of young people, particularly in terms of helping buffer the effects of stress and depression (Driessnack, 2009). A recent systematic review found that 16 exposure-based publications concluded a significantly positive effect on participants’ mental health, suggesting that merely being in nature is likely to boost wellbeing (Tillmann et al., 2018). It may potentially be due to increased nature connectedness, as a study by Piccininni, Michaelson, Janssen, and Pickett (2018) found that the children who placed importance on connecting with nature reported lower negative psychological symptoms than those who didn’t feel as connected. An increase in feelings of connection can be obtained with as little as 15 minutes of walking in a natural setting, or even watching a video of one (Mayer, Frantz, Bruehlman-Senecal, & Dolliver, 2009). Additionally, a study in 2005 found that children aged 6-12 years old living in low-income inner-city areas of New York City, who spent the summer in a rural camp, showed increases in self-esteem and wellbeing, which was attributed to contact with nature and others (Readdick & Schaller, 2005). Louv (2005) emphasises the importance of the “constructive boredom” of being in nature, explaining how it enables children to increase awareness and comfort within themselves and their surroundings, which helps build confidence. The strong association between levels of self-esteem and psychiatric problems (Henriksen, Ranoyen, Indredavik, & Stenseng, 2017) indicate the importance of these results in the context of youth mental health. Furthermore, those who live within 1km of a green space have been found to have a lower prevalence of 15 diseases, with the strongest effect on anxiety and depression. The pattern was also found to be amplified in children and those with lower socio-economic status (Maas et al., 2009). These effects are likely to continue to influence health in the future, as a retrospective questionnaire conducted by Tristan et al. (2016) found that contact with nature in childhood is associated with reductions in depression scores in adulthood (mediated by continued contact with nature as the individual matures). The results were replicated in another, recent study, which showed that lower residential green space in childhood is associated with up to 55% higher chance of developing psychiatric disorders later in life, especially during adolescence (Engemann et al., 2019).
The protective buffering effect of nearby nature has also been linked to reduced stress, and its negative effects, in children. Wells and Evans (2003) suggested that this may be due to increases in sociability, as well as improved attention allowing them to better think through their problems. it is especially poignant considering the increases in subjective stress and stress-related illnesses reported by young people nowadays, with almost one in seven individuals aged 17-19 years old in the UK diagnosed with an anxiety disorder (NHS, 2018b). Reasons for these increases include pressures brought about by social media, with 48% respondents of a Prince’s Trust survey (2018) agreeing that they “feel more anxious about my future when seeing the lives of friends online”. In addition, according a survey by the Mental Health foundation and YouGov (2018), 60% individuals aged 17-24 felt stress related to the pressure to succeed compared to 41% for those aged 25-34 and 17% aged 45-54. Spending time in nature represents a break from these extreme pressures, allowing an escape. One study, using university students, found that places with nature were associated with relaxation and an absence of worry, making them “over-represented among favourite places” (Korpela et al., 2001).
 Physiological effects
Time spent in outdoor settings has been associated with improvements in several domains of physical health. For example, it is beneficial for sleep- and gastro- related childhood problems (Frost, 2006), and German 10-year olds living in green areas showed reductions in blood pressure compared
to those living in more urban settings (Markevych et al., 2014). In addition, being in the presence of nature has been linked to boosted immune response to disease (The University of Essex, 2015), which is potentially due to the phytoncides released by trees, that increase the body’s natural killer cell count (Qing Li, 2010). Finnish teenagers who live in areas that contain more biodiversity were also shown to possess more diverse bacteria on their skin, reducing the likelihood of immune dysfunction. It was suggested to be due to microbes that are transmitted over a sustained period of time, by air, dust and pollen, and help boost immunity (Hanski et al., 2012). Furthermore, improvements in air quality, which occurs with more greenery and trees (Frist, 2017) lead to improved lung function and development in children (Gauderman et al., 2015) as well as reductions in prevalence of asthma, although this relationship is only correlational, so causation cannot be implied (Lovasi, Quinn, Neckerman, Perzanowski, & Rundle, 2008).
 Active engagement
Psychological benefits can be observed from simply strolling through nature for fifteen minutes, as shown in a recent study on young, female individuals. The participants reported feeling subjectively more comfortable and relaxed, with reductions in anxiety and depression after the walk (Song, Ikei, Kagawa, & Miyazaki, 2019). In addition, a study of Canadian girls aged 11-15 years old, demonstrated how increasing outdoor play by half an hour a week was shown to reduce negative psychosomatic symptoms by around 24%, particularly along the psychological dimension. The same was not observed in boys (Piccininni et al., 2018), potentially due to differences in expression of mental wellbeing (Eaton et al., 2012). The researchers suggested the improvements are likely to be attributable, in part, to nature’s role in encouraging exercise, which provides several mental and physical benefits. However, they also found that the subjective experience of being connected to nature boosted the psychological effects through reducing sadness, irritability, nervousness and sleep problems, especially amongst boys (Piccininni et al., 2018).
For children, Ginsberg (2007) suggests mental health benefits are augmented through allowing unstructured “child-directed play”, which encourages them to engage in their passions, make their own decisions and build resiliency. The boost in independence and durability is also observed in the therapeutic context of adventure programmes for “at-risk” young people. After a 2-week course for 13-18 year olds, which involved nature-based activities such as camping, hiking and survival skills, both participants and their parents reported large changes in their ability to cope with conflict. This is important, as conflict difficulties can underlie a number of problems such as anxiety, depression and anger management. In addition, the parents reported their children seemed happier, showed fewer signs of depression, and were more motivated, empowered and capable (Dobud, 2018).
However, despite this abundance of supporting literature describing the benefits of nature for psychological wellbeing, a systematic review of publications measuring direct engagement with nature had conflicting findings. Twenty of the studies showed significant positive influences on mental health, which reinforces the conclusions discussed previously. Although, 24 studies also had non-significant results, which reduces the confidence in this association. It may be that these conflicting findings are caused by small differences in study design, as well as participant selection, with some focussing on at-risk or low health populations (Tillmann et al., 2018). Nonetheless, it remains important to acknowledge these insignificant results, and accept that not all studies do show large benefits to mental health.
Outdoor environments have the potential to amplify the positive effects of exercise. For example, (Thompson Coon et al., 2011) found higher levels of energy, mental wellbeing and intent of repeating the activity for individuals who did physical activity in natural environments (“green exercise”), compared to those who exercised indoors. This is especially prevalent considering the increasing rates of obesity in children and young people. In 2016, the NHS estimated that 28% of young people aged 5-15 were considered obese (Reland, 2018). Alongside this increase comes a rise in incidences of high blood pressure in young people (Charles, Louv, Bodner & Guns, 2008). According to an article by Louv (2009) although there is no evidence that this is tied in with the reductions in outside play seen in young people of this generation, the positive correlation often observed between time spent outside and levels of physical activity highlight how exposure to the outdoors can aid in reducing this health crisis. The claim is supported by a study conducted by researchers from Indiana University, who found that more neighbourhood greenness was linked to fewer increases in the body mass index of children aged 3-16 over two years (Bell, Wilson & Liu, 2008).
 Learning and development
Traditional classroom-based learning has been shown to benefit from taking children outside. A study conducted on American 9-10 year olds measured the behaviours in class following an outdoor- based lesson, and found improvements in engagement and reductions in the number of times the teacher was interrupted by a student (Kuo, Browning, & Penner, 2018). Additionally, nature helps develop understanding of risk, allowing children to make their own judgements in an unknown environment (Frost, 2006). According to Hart (1979), as children interacted with nature, “They were developing environmental competence in the sense of knowledge, skill, and confidence in their ability to use the environment to carry out their goals and enrich their experience” (Chawla, 2015, p. 437).
 Type of individual
The final consideration regarding the benefits of nature is how different people respond to it. Generally, it is found that we all evaluate nature in a similar way (Twedt, Rainey, & Proffitt, 2019), likely due to its role in enabling human survival in our past (Kellert et al., 1993). However, research has identified slight differences in response, based on individual characteristics such as introversion, area of residence and education. In addition, our personal level of “energetic, mental and emotional resources” (p. 10) has been negatively associated with the degree to which nature is favoured over urban environments. In short, the more we need mental restoration, the more we are likely to prefer a natural setting (Twedt et al., 2019). Other factors, such as age, income, or the presence of a disorder have also all been shown to have an influence, which are discussed in greater detail below.
Piccininni, et al. (2018) has suggested that the psychological improvements brought about by nature may be more beneficial for young people suffering from milder or earlier symptoms of stress, preventing them developing and manifesting as somatic symptoms later on. It is concordant with results from another, adult-based study, which highlighted the role of nature in reducing the number of individuals suffering from mental distress and improving psychological wellbeing, thus acting as a buffer for mental health difficulties (Barton & Rogerson, 2017). Researchers have therefore suggested that nature should be used as a preventative intervention (Maller, Townsend, Pryor, Brown, & St Leger, 2005), to moderate the effects of life stressors and prevent illness developing. Additionally, research on green exercise has revealed that light physical activity improved mood and increased self-esteem in all participants, regardless of demographic information. This emphasises the idea that nature can be used as a means of improving wellbeing in the general population. However, when the data was split into those who are mentally ill and healthy participants, the self- esteem of those with a mental illness improved significantly more than their healthy counterparts (Barton & Pretty, 2010). This may be due to these participants having a greater change potential (if their self-esteem was lower to begin with), but it does highlight the large impact for those suffering from mental health problems, suggesting it could be used to help treat clinical populations. Organisations like Mind also encourage the use of nature in recovery of mental health problems, endorsing “ecotherapies” – regular, structured activities that take place outside to help boost wellbeing ("About ecotherapy programmes", n.d.).
 Deprived individuals
Generally, regardless of age, there seem to be larger physical and psychological health benefits of exposure to green space in individuals with low socio-economic status or with less than ten years of education (Twohig-Bennett & Jones, 2018). Income deprivation can lead to a number of health problems, so is a growing concern in modern society. However, increases in neighbourhood greenness were shown to lessen the effect of income deprivation on general and cardiovascular mortality (Mitchell and Popham, 2008). It is also noted that low income areas tend to access natural or green environments much less frequently than those with a higher socioeconomic status (Roe, Aspinall, & Ward Thompson, 2016). The same is observed for minority groups. For example, a recent government publication revealed that whereas 69% of the white population accessed nature at least once a week , only 42% of black, Asian or minority ethnic individuals did so (Natural England, 2019). This could be due to poorer neighbourhoods containing less green space like parks or trees, which reduce accessibility. Statistics show the 20% most affluent wards in England have five times as much green area than the most deprived 10% (CABE, 2010). Also, underprivileged individuals often have a lack of knowledge about what is accessible, and how nature provides these benefits, so are unlikely to seek it out (Shanahan et al., 2019).
 Neurodevelopmental disorders
The role of nature in helping reduce the symptoms associated with certain disorders, such as ADHD, is well-known. The attention restoration theory explains how nature allows our brains to escape the tiring demands of attention that we experience when focussing on tasks, and recover by becoming occupied with softly fascinating natural objects (S. Kaplan, 1995) and open spaces (Ohly et al., 2016). A recent systematic review found some evidence that supports the existence of this theory, emphasising that nature can, in fact, provide these restorative benefits (Ohly et al., 2016). For those with ADHD, who often have difficulties maintaining attention, natural environments have been shown to help minimise these symptoms. For example, a study of 12 Dutch children aged 9-17 found that concentration was more effective when they were taken to the woods, as opposed to the town. In addition, significant behavioural improvements, including reductions in impulsivity and aggression were observed in the natural setting, in comparison to the built-up one (van den Berg & van den Berg, 2011). Likewise, regular exposure to green space through children’s play areas has been associated with milder symptoms of ADHD, independent of gender or income. Although, for those who showed hyperactivity, the improvements were only observed in more open natural settings (Faber Taylor & Kuo, 2011). By a similar token, children with ASD respond positively to natural environments, experiencing reductions in stress and anxiety (Larson et al., 2018). Lower levels of green space around where someone lives has even been associated with a higher prevalence of ASD in the population (Dadvand, Gascon, & Markevych, 2019). It highlights how nature can be used to help individuals diagnosed with neurodevelopmental disorders, to minimise symptoms and reduce stress.
According to Konijnendijk van den Bosch, Baines, and Nilsson (2007), children are an important focus within the context of the advantages of natural environments. In terms of physical activity, the benefits are pronounced to a greater extent, as access to nature during school for more than 20 minutes per day results in children engaging in five times more moderate/vigorous physical activity (Almanza, Jerrett, Dunton, Seto, & Pentz, 2012). It is significant because adolescence is known as a time in which exercise levels often drop considerably. A six-year study by Nader, Bradley, Houts, McRitchie and O’Brien (2008) on 1,032 young people found that the average nine-year-old spent 4 hours a day engaged in moderate or vigorous exercise. This value dropped to 49 minutes per weekday and 70 minutes per weekend when the child turns 15. The considerable decrease results in only 31% of 15 year olds meeting recommended daily exercise guidelines on weekdays, dropping to 17% at weekends (compared to almost all 9 year olds; Nader, Bradley, Houts, McRitchie, & O'Brien, 2008). Thus, utilising nature and green spaces to encourage more physical activity is likely to have a significant impact on this age range. In addition, researchers have proposed that the psychological benefits of nature may be amplified in young people, especially those from deprived backgrounds, alongside home workers, and the elderly (Munoz, 2009; Thompson, Travlou, Roe, Openspace, & Natural, 2006). A study by Barton and Pretty (2010) provides evidence to support these claims, demonstrating that participants aged 16-30 experienced the greatest self-esteem improvements after taking part in green exercise, compared to older participants. It demonstrates how the psychological benefits of nature can be larger in younger people. In terms of self-confidence in the transition from adolescence to adulthood, nature has also been quoted as especially important as it helps youth explore their place in the world (McMahan, 2015; Arnett 2006, 2007). It provides a means for them to fulfil their urge to explore, and “gain some perspective on their place within the broader environment” (McMahan, 2015), creating a more positive outlet through which to do this, rather than in antisocial ways (Natural England, 2014). However, due to the decreases in outdoor play, there are concerns that these developmental benefits are not being realised in children of the past few generations (Gaster, 1991), and calls have been made to advertise the advantages of nature to a greater degree to halt this decline. Furthermore, Piccininni explains how good contact with nature during the critical periods of development in young people has a strong, positive, long-term impact (Piccininni et al., 2018). Evidence has also shown that it often results in greater engagement in adulthood as well (Ward Thompson et al., 2008). Unfortunately, government data indicates that scores on the nature connectedness index (NCI) drop considerably in UK children after the age of 12 (Natural England, 2017), which is likely due, in part, to less time spent outdoors (Pensini, Horn, & Caltabiano, 2016). The paper by Piccininni et al. (2018) warns how this lack of exposure during development has a “detrimental effect on future health and well-being” (p. 173). It therefore makes sense to target youth in spreading a greater appreciation of the environment, to create a longer-term, sustainable impact on their lives and future wellbeing. In addition, there are a number of long-term health benefits of youth engaging with the outdoors. For example, a study found that public park availability during teenage years were associated with better cognitive aging later in life (especially in safer areas with low road-traffic accident density). This could be due to increased independence and mobility, or behavioural variation in teens (Cherrie, Shortt, Ward Thompson, Deary, & Pearce, 2019), and adds to the argument for focussing on youth in the context of promoting nature.
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