How can working people improve their health

Influence of natural areas on health - evidence base and consequences for science and practice

Summary

Natural spaces and especially urban green spaces (city green) and bodies of water (city blue) have long been considered to have great potential to protect and promote health. They can have a positive effect on the mental, physical and social health and well-being of people in a variety of ways - directly or indirectly: directly by reducing and moderating possible risks from the living environment (e.g. noise, fine dust, heat) through the psychological-physiological effects of the experience of nature and the physical effects of exposure to natural substances and elements; Natural spaces have an indirect effect, for example, by stimulating behavior that is conducive to health (e.g. incentives for more exercise), by using them as an outdoor meeting point and by reducing aggression and the resulting effects on social well-being. Individual possible health-detrimental effects of natural areas have also been described (e.g. uncertainty or fear in a confusing nature, possible competition for use, allergies and skin irritations from natural elements, risk of infection from host animals). Against the background of the positive effects of natural areas, it is sometimes required to maintain, promote and, if necessary, restore them within the framework of an integrated, sustainable development of municipalities. But what specific interrelationships exist between natural spaces and health? Which requirements and perspectives arise for a health-promoting implementation practice? The overview article deals with these questions and provides some answers.

Abstract

Natural spaces and especially urban green and blue spaces have been recognized for a long time as spaces with great potential for protecting and promoting human health and well-being. They may affect human physical, mental and social health and well-being in various ways. On one hand, this comes to pass through reduction and moderation of potential environmental health risks (e.g. noise, particulate matter, heat), psycho-physiological effects of nature experience, as well as physical effects of exposure to natural compounds and elements. On the other hand, natural spaces can affect health and well-being indirectly e. G. through motivation of health promoting behavior (e. g. more physical activity) and through use as outdoor meeting spaces, by decreasing aggression, and through the resulting positive effects on social well-being. Yet, some potential adverse health effects of nature and landscapes have been reported too (e.g. insecurity or fear in confusing or unmaintained natural spaces, potential rivalry in usage, allergies or skin irritations due to natural elements, risk of communicable diseases from vectors). Against the background of positive effects of natural spaces, creating, restoring and enhancing urban green and blue spaces are often claimed in terms of sustainable and integrated urban development. But which associations and impacts exist between natural spaces and health? What are the resulting demands when integrating natural spaces for a health-promoting implementation practice? This overview article provides some answers to these questions.

introduction

The living environment influences health and well-being in a variety of ways and thus the quality of life of the people who live and work in it. Urban areas in particular are often associated with stressful and health-damaging effects via soil, water and air as well as from the structural, technical and social environment (e.g. noise, air and building pollutants, contaminated sites, heat islands, but also accidents, social isolation or experiences of violence, so-called “environmental bads”, see [1]). The “environmental bads” contrast with health-promoting, salutogenic resources from the environment (“environmental goods”) [1]. These can alleviate health burdens, maintain, but also increase the general well-being and health of the population. Health-promoting resources include, among others. Social support from family and neighborhood, neighborhood identity, health-related facilities (e.g. sports and fitness facilities, specialist medical practices, clinics), mobility-friendliness of rooms (walkability) as well as natural and landscape elements (cf. [2]). Many of these resources are particularly well developed in urban areas, where around 75% of the population in Germany live.

The various factors in the living environment can act as so-called health determinants in various ways on our physical, mental and social health (cf. inter alia [3]):

  • directly via direct interactions with individuals (e.g. inhalation of fine dust, exposure to noise or a view of the countryside),

  • indirectly by influencing other environmental factors (e.g. reducing heat extremes in urban areas through bodies of water [city blue] and green spaces [city green]),

  • indirectly by influencing the health behavior of individuals and different population groups (e.g. promoting physical activity).

Many of these determinants can be controlled and planned, but must always be considered from the individual to the global level, also in their spatial and socio-political dimension ([4], see Fig. 1).

In the past two decades, the health importance of natural areas, i. H. Such areas in urban as well as rural areas, which are mainly characterized by “green” and “blue” structures, have moved into the focus of science and research as well as politics, planning and implementation practice [1,2,3, 5]. The high socio-political relevance of the topic becomes apparent against the background of current, globally effective phenomena such as

  • climate change and the need for adequate adaptation strategies,

  • globalization and the pressure on natural spaces,

  • the demographic change and changed needs and usage patterns of an older and more colorful society with regard to natural spaces,

  • the ongoing rural-urban migration and re-urbanization of the inner cities,

  • the urban shortage of living space and the resulting pressure on open spaces and ultimately

  • the demand for a sustainable and health-promoting development of spaces and especially urban regions.

In this context, a positive association between the appropriation (i.e. perception, evaluation and use) of natural spaces and the health quality of life is constantly postulated. Often there is a blanket demand to preserve, expand and, if necessary, restore natural areas that promote health in the context of integrated, future-oriented urban development planning (cf. among others [6, 7]). But what specific interrelationships exist between health, well-being and natural spaces, and what are the consequences for science, politics and planning? The following overview article provides some answers to this.

Natural spaces and health

The health protective as well as that health-promoting effect of natural areas in general and of urban greenery and urban blue in particular has been documented many times (including [8, 9]). The current evidence in this regard is presented below. Possible health-endangering effects of natural areas are also briefly discussed, but are not the focus of this article. Fig. 2 provides an overview of the aspects discussed in the following article.

Health-protecting potential of natural areas

Natural areas have a health-protective effect through numerous ecosystem services (cf. [9, 10]). Both green structures and bodies of water have considerable potential to reduce air hygiene problems by filtering pollutants from the ambient air. Deciduous trees in particular are able to absorb and convert pollutants directly or to deposit particles on their surface and discharge them into the soil with the next rainfall. However, closed canopy roofs in urban avenues can also exacerbate air hygiene problems [11].

With regard to noise, direct noise-reducing and noise-moderating effects should be emphasized (cf. [12]). Green structures reduce noise due to the greater distance between the noise source and people exposed to noise, as well as less sound reflection and greater scattering due to the comparatively rough surface. The actual level reduction can be 3–5 dB in exceptional cases, e.g. B. in the case of green railway tracks (turf tracks) with a high vegetation cover, is however often overestimated overall (inter alia [13]). For the subjectively perceived volume reduction, it is also crucial that green spaces and bodies of water create a soundscape (e.g. rustling of leaves, chirping of birds, splashing water) through the self-generated background noise. In this way, they partly overlay the disturbing ambient noise, reduce the subjectively perceived noise nuisance of the population and thus increase the quality of stay [14]. This effect is even increased by the visual shielding of the noise source [14].

From a climate-ecological point of view, green and water structures are beneficial to health in several ways. Through the transpiration performance (including an increase in the absolute humidity), the rough surface of natural, overgrown and moist soils (with less heat storage than asphalt surfaces) and the shadow effect of the canopy of trees, they can make a significant contribution to lowering the temperature on hot days, especially in heat-stressed urban areas (heat islands), to reduce [15]. Water areas have their own compensation potential with cooling effects, which at approx. 2.5 K can even be significantly higher than the reduction performance of green spaces [16]. In the colder seasons, on the other hand, open water areas act as heat stores [16]. With the increase in hot days and tropical nights as a result of the expected climate change, natural spaces in the city are becoming increasingly important as climate comfort islands, especially for particularly vulnerable population groups [17]. Furthermore, green areas, e.g. B. in the form of parks, absorb larger water masses and reduce surface runoff in urban areas (cf. [18]). Thus, they can also serve as flood protection in the event of heavy rain.

The health-promoting potential of natural spaces

Even before the turn of the millennium, some studies and reviews gave indications of an increase in the general (health) well-being of the population through the use of natural spaces (cf., among others, [19,20,21,22]), even if the quantity and quality of the " Greens “was often not systematically recorded. In the meantime, however, there are numerous studies that consider the direct and indirect positive influences of natural spaces on the well-being of individuals and population groups [3, 8, 9]. The type of natural space (near-natural or strongly anthropogenic, forest or park, cf. [23]) also plays a role here. At this point, however, it should be pointed out that the findings mostly come from epidemiological cross-sectional studies with in some cases very different natural space definitions and thus describe associations, but not reliable effects. In experimental studies, on the other hand, typically urban scenarios are often contrasted with rural, natural-looking scenarios. In the following, the evidence on connections between natural spaces and mental, physical and social well-being is presented, although a strict separation is difficult because the transitions between psyche and physique are fluid.

Mental wellbeing

With regard to mental (psychological) well-being, which is strongly influenced by the individual perception, evaluation and construction of space, natural spaces are particularly effective through the component of experience (inter alia [22]). It could be shown that the experience of nature and landscape can have a stress-reducing, blood pressure lowering, attention-increasing, concentration-increasing and restorative effect (see following sections, cf. inter alia [9]). In particular, the results on increasing attention and concentration conform to the attention restoration theory [19], according to which cognitive recovery occurs in nature. In addition, there is now evidence from research that suggests a positive relationship between long-term exposure to green spaces and the cognitive development of children and the cognitive function of adults [24].

In addition to their importance for attention and cognitive functions, natural spaces have, among other things, an influence on emotions, psychological stress and perception of stress. Hartig et al. [25] found that a walk in nature increased positive affect while anger decreased, compared to walking along an urban street. Roe and Aspinall [26] were also able to show in a quasi-experimental study with two groups (one with a good mental condition, one with a clinically diagnosed mental disorder) that walking in rural areas had a positive effect on mood and stress for both groups . In addition, the walk in rural areas led to a higher restorative effect in the group of those with mental disorders [26]. This indicates the potential of natural spaces as a coping resource for existing psychological disorders, on the one hand due to the restorative effect, on the other hand through the promotion of physical activity and social contacts during communal activities (see below).

Further studies have shown that a higher level of green in the living environment is associated with a lower incidence of anxiety disorders, lower levels of stress and fewer depressive symptoms [9, 27, 28]. Longitudinal section evidence comes from Alcock et al. [29], in whose study the self-rated mental health of study participants improved over the long term after moving to a greener area.

Isolated studies also indicate that a perceived high level of biodiversity compared with areas of less biodiversity is positively associated with increased mental well-being (cf. inter alia [30]).

In individual studies, the experience of water structures is associated with a relaxing, stress-relieving effect that goes beyond the effects of pure green spaces, regardless of the type and size of water [31, 32]. However, it is also important to consider the type of green spaces: Forest areas in particular are said to have a positive influence on stress relief and mood, as well as reduced activity of the sympathetic nervous system (cf. [33, 34]). Kühn et al. [35] found in a study of older people in Berlin a significantly better structural integrity of the amygdala in test persons who live close to the (urban) forest compared to those who live close to water or other green spaces. This could indicate greater stress resilience in people who live near a wooded area. Since the stress response and the functioning of the amygdala play a role in the development of certain mental disorders such as depression, the results could indicate a reduced risk of the occurrence of mental disorders triggered by neuronal processes. The study results listed also show the close amalgamation of mental and physical health via physiological processes.

Physical wellbeing

In studies of the direct effects of nature and urban greenery on physical health, possible effects on mortality, morbidity and short-term physical reactions such as reduced expression of stress hormones were described.

The first statistically verified indications of the direct effects of natural areas on physical health can be found in the 1980s. In a small but much-noticed study, Ulrich [36] retrospectively examined the healing process of inpatients after gall bladder removal in a quasi-experimental design. With otherwise comparable conditions, the view out of the window made the difference. One group looked at a group of trees, while the other group looked at a brick wall opposite. The results showed that those people facing the grove of trees, among others. were discharged earlier and took significantly less pain medication [36].

Hartig et al. [25] showed the effect of the experience of nature on the blood pressure, which they use as an indicator for the stress level of the test subjects. The diastolic blood pressure decreased in one group of test persons during a walk through a rural natural area, while in the group with a walk along the street it rose significantly after a brief decrease [25].In the meantime, numerous studies have been carried out based on the results of Hartig et al. [25] support. Exposure to natural environments is always associated with a drop in blood pressure, as well as in the cortisol level and other stress hormones as an indicator of a reduced level of stress (see, among others, [9]).

Li et al. [37] confirmed the breakdown of the stress hormones adrenaline and noradrenaline in various studies in which the effects of longer stays in the forest (so-called forest bathing or Shinrin-Yoku) were analyzed. In addition, they also demonstrated a cancer preventive effect through the development of so-called cancer killer cells (“human natural killer activity”) and the release of intracellular cancer defense proteins ([37], see also [38]). The explanation discussed is the increased concentration of phytoncides (plant biocides) in the forest air.

Maas et al. [28] were able to show in a Dutch study that people who live in an urban environment with a higher proportion of greenery in the immediate vicinity (1 km radius) are significantly less likely to suffer from cardiovascular, musculoskeletal, psychological, respiratory, neurological and intestinal diseases and other diseases such as People who have less green space in their living area or who live further away from green spaces suffer from diabetes. In this study, however, green spaces were defined very broadly and also included agricultural areas.

Results of a study from Japan by Takano et al. [39] point out that a good supply of and good access to urban green spaces is significantly positively associated with the quality of life and life expectancy of older people.

In an English research project, Mitchell and Popham [40] also found fewer inequalities in terms of cardiovascular disease and mortality between people with high and low socio-economic status in greener areas than in areas with little access to natural green spaces. This is also important because the distribution of high-quality and safe green spaces is usually to the disadvantage of groups with a low socio-economic status and ethnic minorities [41].

Studies by Richardson and Mitchell [42] on possible gender-specific differences showed that the higher the proportion of green, the lower the mortality rates from cardiovascular and respiratory diseases in men. However, this association could not be proven for women. The authors explained this with the gender-differentiated perception and use of green spaces.

In recent years, various cross-sectional studies in Spain and Germany have also been able to identify a connection between the proportion of green space in the residential area and the birth weight of newborns ([43]; cf. [9, 44]). After adjusting for air pollution, distance to busy streets, population density and level of education, the statistical correlation increased [43]. Attempted explanations see a higher basic satisfaction and activity of the pregnant woman as moderating factors.

Physical activity incentive

The question arises again and again to what extent natural spaces, especially in urban areas, offer incentives and motivation for increased physical activity (everyday exercise, sport) and thus can be expected to have indirect health effects in terms of strengthening the cardiovascular and immune systems as well as prevention numerous diseases of civilization (e.g. obesity, high blood pressure, type II diabetes mellitus or back pain). Frank et al. [45] were able to show for Bielefeld that 71% of those surveyed said that movement is the reason for looking for green spaces. Völker and Kistemann [32] were able to prove something similar for staying in water. However, it is questionable whether more natural spaces also require more movement. Maas et al. [46] state that the degree of physical activity is hardly related to a green environment and the proportion of physical movement in a greener environment cannot explain the connection between green spaces and self-perceived health. Likewise, Dadvand et al. [47] point out that the connection between subjective health and green spaces in Barcelona, ​​inter alia, mediated by the mental health status and the perceived social support, but only to a very limited extent by the physical activity, although no distinction was made here between indoor and outdoor activity. De Vries et al. [48], on the other hand, found in a review based on numerous studies the incentive and motivation from a green environment to additional exercise, but also describe that the evidence is mixed and there is a lack of adequate, high-quality studies.

Social wellbeing

As public and freely accessible meeting places, natural spaces have a positive effect on people's social wellbeing, especially in cities [49, 50]. Because with regard to the possibilities of establishing and maintaining social contacts, urban green spaces and waterfronts are considered important meeting places [50, 51], which can also develop a great symbolic power as places of identification [32]. One thinks here e.g. B. to Central Park in New York, the Berlin Tiergarten or the Cologne Rhine Promenade. In parks in particular, there is a mix and coexistence of different social groups (e.g. with regard to age, gender, ethnic origin). Urban natural spaces thus have a potential for social integration, inclusion and increased acceptance that should not be underestimated [50] and can strengthen the social cohesion of the local population in the residential area as an unencumbered meeting and communication space [52]. This is also reflected in current movements such as urban gardening (inter alia [53]). In addition, green spaces also have the potential to counteract the emergence of crime, for example in socially disadvantaged urban areas, provided they are designed to be open and inviting and thus encourage people to stay outside more often in the sense of an “outdoor living room” [9, 51, 52]. In the case of competing usage interests (barbecuing, skating, cycling, jogging, playing, reading, resting, etc.) of different groups in small green spaces and on green paths, conflicts can arise (cf. [54]).

Influence of the quality of natural spaces

As can be seen from the previous sections, natural spaces as a whole, but especially urban green spaces and bodies of water, can exercise a wide variety of functions with regard to health-protecting and health-promoting effects (see Fig. 2).

What the studies mentioned so far have in common is that they were primarily based on the quantity of natural spaces in the study design, but not on qualitative aspects. Van Dillen et al. [55] and de Vries et al. [56], on the other hand, were able to show in a study in 80 Dutch residential areas that both the availability and the quality of green spaces and green spaces accompanying the streets were positively associated with the self-assessed health of the study participants. An Australian study also made it clear that in urban areas, it is not just the quantity of green spaces that is decisive, but that a high quality is associated with a lower psychosocial stress level [57].

Effects dangerous to health

In addition to the potential for social conflict described above, there is also evidence on various possible health-detrimental effects of natural areas. Thus, contrary to the otherwise assumed improvement in air quality through green elements, closed canopy roofs in urban avenues, for example, can aggravate air hygiene problems [11]. Furthermore, Churkina et al. [58] show that some volatile organic compounds that are increasingly emitted by vegetation at high temperatures, in combination with high concentrations of nitrogen oxides, can contribute up to 60% to the formation of ground-level ozone on very hot days.

In addition, individual studies have been able to show that the thesis of biophilia as an inherent love for all living things is not generally valid. B. finds its clear limits in disgust or even fear of spiders, mice, etc. (cf. [59]). Furthermore, negative feelings can be caused by confusing, poorly visible natural spaces, such as dense forests or winding parks with high bushes and insufficient lighting, especially at dusk. Fears associated with this are described as well as an increased risk of promoting crime (e.g. drug-related crime, assaults, violence against women, cf. [9, 51]).

Another risk is associated with allergies or skin irritations from natural elements such as pollen (e.g. from birch trees, alder trees), animal hair (e.g. oak processionary caterpillars [60]) or plant juices (e.g. Hercules perennials) (cf. [9]) ), which can affect large proportions of the population. In the Germany-wide GEDA study, 28.1% of adults stated that they are currently affected by allergies [61]. Even if it is not clear to what extent green spaces contribute to the triggering of allergies [62], when trees are replanted in public spaces, tree species that are associated with a further increase in the number of tree pollen with allergenic potential should be avoided [63 ].

Finally, there are also risks from infectious diseases associated with host animals that are bound to green and water structures (e.g. ticks, mosquitoes, rodents).

When designing natural spaces that are also intended to fulfill an essential recreational function, these aspects must be given special consideration.

Implementation in practice: requirements for “good” natural spaces

Due to their diverse health-protecting and health-promoting effects, natural areas are nowadays an important determinant of health and an essential component of public services. On the basis of the above-mentioned study results, there is increasing discussion in science and practice how natural spaces (especially in cities) should be designed in order to be able to develop their health-promoting potential in the best possible way. The following criteria and features have emerged as particularly important (cf. [54]):

  • good availability, accessibility and accessibility of natural areas, if possible without the need to use a car and especially for population groups who do not have access to a private garden,

  • uniform and socially fair distribution and networking of natural spaces,

  • Opportunities to establish and maintain contacts (e.g. for parents with small children and the elderly), but also to observe animals and other people,

  • multifunctional use with a balanced ratio of spaces for relaxation, adventure, movement, individual rest and social interaction,

  • Avoidance of fearful areas and mobility barriers (e.g. reduction of risk of injury, lighting of main routes, clarity),

  • Combination of different aspects of natural spaces in urban areas, especially where larger natural spaces are in short supply (e.g. facade and roof greening, water features),

  • aesthetically pleasing landscapes.

In addition to these criteria and characteristics, the various patterns of perception and appropriation of different socio-demographic and cultural groups with regard to natural areas as well as socio-spatial problems in the population should always be taken into account in natural area development. Because socially disadvantaged areas in particular are often burdened several times due to their location and reduced quality of living space. B. with regard to air pollution, noise or summer heat and also show a comparatively lower availability and quality of natural spaces [54].

In previous studies on the health significance of natural areas, a clear focus was placed on the conditions in urban areas. There are no known studies that explicitly compare the health effects of natural spaces in urban and rural areas. There is therefore a considerable need for research into the difference in the effects of rural and urban natural spaces on human health.

Natural spaces in the city are not a panacea, and so-called gray structures (built structures such as rows of houses and squares), which are architecturally appealing, can be excellent destinations for health and wellbeing. But in the city as well as in the suburbs and in rural areas, it is important to understand the natural and landscape area as a limited and endangered resource also for a high health quality of life of the population and to promote it accordingly. A wide variety of actors from science, politics and practice are required to implement this goal [5, 10, 64, 65]. It is therefore all the more important to network the municipal planning, health, environment and social sectors in the sense of integrated political and administrative action as well as the courage to engage in interdisciplinary and transdisciplinary research and practice cooperation on the way to a health-promoting future for everyone.

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