Nature (including green spaces) – Healthy Cities Toolkit

Description

There is no universally accepted definition of green space. However, green spaces usually imply publicly accessible areas containing natural vegetation and less well-managed areas such as nature reserves and woodlands [Lachowycz 2013]. Apart from reducing air pollution [Meo 2021], the creation of green spaces is important for recreation and exercise [Lebel 2012].

Impact

Evidence suggests that green spaces positively influence well-being and trigger behavioural change towards healthier lifestyles leading to better health outcomes [Douglas 2017; Nieuwenhuijsen 2020; Szeremeta 2013].

Results of the research have shown that there are variations in social expectations of nature as well as the extent of societal acceptability of the relationship between urban planning for green spaces and public health [Manusset 2015]. Findings from published reviews showed that themes elicited from conceptual models in green space research include individual factors, physical and environmental factors, health effects, and the use of open space [Mansor 2017; Jabbar 2022].

Results

A total of 36 reviews comprising more than 1600 studies were identified. Most of the studies were conducted in high-income countries, with a handful conducted in LMICs. Sixteen reviews reported the impact of green spaces on mental health and well-being, nine on physical activity, and eight on general health.

Outcome: Mental health and wellbeing

Green ground cover, parks, bushes, trees, and flower beds were associated with improvements in mental health and well-being [Kerishnan 2021; Felappi 2020; Barnes 2019; Callaghan 2021; Gong 2016; Grilli 2020; Hunter 2019; Kondo 2018; Lee 2021; Nawrath 2021; Shuvo 2020; van den Berg 2015].
Green space engagement showed significant potential to facilitate ongoing meaningful life (engaging in meaningful activity, empowerment, and positive risk-taking) for people living with dementia in the community [Mmako 2020].
The effect of trees on mental health, anxiety, and mood are inconsistent [Wolf 2020].
Compared to no intervention/usual care, forest therapy produced significantly greater reductions in depressive symptoms and the likelihood of achieving remission. [Rosa 2021].
There were short-term improvements in psychological and social health outcomes in children and older adults with disabilities as well as improvements in disability-related impairments [Saitta 2019].

Outcome: Physical activity

Exposure to urban trees, park-based interventions and urban green spaces was positively associated with physical activity [Wolf 2020; Lee 2021; Shuvo 2020; Saitta 2019; De la Fuente 2020; Hunter 2019; Hunter 2015; Kondo 2018; Islam 2020].

Outcome: General health

Urban green spaces, forest bathing and the presence of vegetation were generally associated with improvements in perceived health [Wolf 2020; Di Nardo 2010; Dzhambov 2014; Lai 2019; Labib 2020].
The protective health effect of urban green spaces for children and the elderly is unclear [Kabisch 2017].
An urban park would be around 1°C cooler than a non-green site on average [Bowler 2010].
There is a paucity of multidisciplinary research on the relationship between urban forests and health, with a lack of research in LMICs [Arantes 2019].

Outcome: Obesity, diabetes, cardiovascular disease

Several studies found positive associations at the individual level between certain measures of tree exposure and reduced BMI/obesity [Wolf 2020; De la Fuente 2020; Islam 2020].
Higher levels of walkability and green space were associated with a lower risk of type 2 diabetes, while increased levels of noise and air pollution were associated with higher risk [De la Fuente 2020; Dendup 2018].
Forest bathing improved cardiovascular function and related health outcomes in healthy participants [Wolf 2020].

Outcome: Mortality

Trees and urban green spaces were found to help reduce the risks of heat-related or all-cause mortality [Wolf 2020; Kondo 2018; van den Berg 2015; Rojas-Rueda 2019]

Outcome: Allergy, respiratory disease

There was limited evidence for a lower risk of chronic respiratory disease with increasing natural space [Rugel 2020].
Green space exposure was negatively associated with the risk of wheezing and bronchitis in some cohorts [Islam 2020].
There is spatial variation in the distribution of tree pollen within cities [Weinberger 2015].
There is no scientific consensus that urban trees reduce asthma by improving air quality [Eisenman 2019].

Outcome: Birth and reproductive

An increase in residential greenness was associated with significantly higher birth weight and lower odds of small gestational age [Islam 2020; Rugel 2020; Akaraci 2020].

Outcome: Lived experiences

There was a consistent negative association between urban green space exposure and violence [Kondo 2018].
The evidence regarding the relationships between urban green space, violence, and crime is conflicting [Bogar 2015; Mancus 2018].
There was a significant race-based inequality in urban forest cover [Watkins 2018].

Strength of the evidence

Fourteen reviews provided information on the reporting quality of included studies. The quality of the reporting was moderate to high in two reviews [van den Berg 2015; Akaraci 2020], moderate in three reviews [De la Fuente 2020; Dzhambov 2014; Rojas-Rueda 2019], and low to moderate in three [Hunter 2019; Nawrath 2021; Dendup 2018]. The overall quality of reporting was low in six reviews [Lee 2021; Shuvo 2020; Mmako 2020; Rosa 2021; Saitta 2019; Rugel 2020].

The evidence base lacks rigour, and heterogeneity in study designs makes it difficult to minimise bias and confounders.

Resource implications

Resource implications were reported by three reviews, all conducted in the USA. The cost of urban green space interventions ranged from $45,000 to $3.5 million per park, to a total area-wide intervention cost of $6.1 million across two reviews [Hunter 2019; Hunter 2015]. The cost-effectiveness of three park-based interventions was reported to be $0.14 to $2.40 per metabolic equivalent of task (MET) [Hunter 2019].

A third review estimated the economic impact on the urban forests and air quality on health based on primary studies all conducted in the USA [Arantes 2019]. One study reported an annual benefit of $7 million from reduced incidence of respiratory issues. Another study reported savings of between $1.1 million and $60.1 million due to reduced mortality. A third study reported annual benefits estimated at US$38 and US$56 per tree planted, and a fourth reported decreases in cardiometabolic conditions commensurate with an annual personal income of US$ 20.000, or 1.4 years younger.

Recommendations

Longer-term and adequately powered studies are needed to robustly assess the impact of green spaces on human health.
Future studies should adequately assess the impact of the socio-economic model components on the usage of green spaces.
Specific attention should be paid to the dose-response effect when assessing the relationship between green spaces and health outcomes.
Future green space interventions should ensure that the negative consequences of gentrification and unequal access are minimised.
A better understanding of the biological aspects of contact with nature should be considered before city planners can optimize green spaces for health gains.
Research in LMICs should be a priority.
Urban forestry professionals are encouraged to consider the equity consequences of urban forestry activities, especially on public land.

Related Resources

Douglas 2017. “Green space benefits for health and well-being: A life-course approach for urban planning, design and management.” Cities Volume 66, June 2017, Pages 53-62.
Jabbar 2022. “Assessing the role of urban green spaces for human well-being: a systematic review.” GeoJournal vol. 87,5 (2022): 4405-4423.
Lachowycz 2013. “Towards a better understanding of the relationship between greenspace and health: Development of a theoretical framework.” Landscape and Urban Planning, 118 (2013), pp. 62-69.
Lebel 2012. “Lifestyles and consumption in cities and the links with health and well-being: the case of obesity.” Current Opinion in Environmental Sustainability Volume 4, Issue 4, October 2012, Pages 405-413.
Mansor 2017. “Conceptual Models of Greenspace and Health.” Journal of Computational and Theoretical Nanoscience 23(7), 2017:6326-6330.
Manusset 2015. “Green space: A new tool of public health policy?” Environnement, Risques & Santé 14(4), 2015: 313-320
Meo 2021. “Effect of Green Space Environment on Air Pollutants PM2.5, PM10, CO, O3, and Incidence and Mortality of SARS-CoV-2 in Highly Green and Less-Green Countries.” International journal of environmental research and public health vol. 18,24 13151. 13 Dec. 2021.
Nieuwenhuijsen 2020. “Urban and transport planning pathways to carbon neutral, liveable and healthy cities; A review of the current evidence.” Environment international vol. 140 (2020): 105661.
Szeremeta 2013. “The Importance of Urban Parks and Green Areas in Improving the Quality of Life in Cities.” Curitiba, v.29, 2013: p.177-193

References to Reviews

Akaraci 2019. “A Systematic Review and Meta-Analysis of Associations between Green and Blue Spaces and Birth Outcomes.” International journal of environmental research and public health vol. 17,8 2949. 24 Apr. 2020, doi:10.3390/ijerph17082949.

Arantes 2019. “Urban forests, air quality and health: a systematic review.” Int. For. Rev., Vol. 21, No. 2, June 2019, pp. 167-181(15).

Barnes 2019. “Characterizing Nature and Participant Experience in Studies of Nature Exposure for Positive Mental Health: An Integrative Review.” Frontiers in psychology vol. 9 2617. 4 Jan. 2019, doi:10.3389/fpsyg.2018.02617.

Bogar 2016. “Green Space, Violence, and Crime: A Systematic Review.” Trauma, violence & abuse vol. 17,2 (2016): 160-71. doi:10.1177/1524838015576412.

Bowler 2010. “Urban greening to cool towns and cities: A systematic review of the empirical evidence.” Landscape and Urban Planning Volume 97, Issue 3, 15 September 2010, Pages 147-155.

Callaghan 2021. “The impact of green spaces on mental health in urban settings: a scoping review.” Journal of mental health (Abingdon, England) vol. 30,2 (2021): 179-193. doi:10.1080/09638237.2020.1755027.

De la Fuente 2020. “Green Space Exposure Association with Type 2 Diabetes Mellitus, Physical Activity, and Obesity: A Systematic Review.” International journal of environmental research and public health vol. 18,1 97. 25 Dec. 2020, doi:10.3390/ijerph18010097.

Dendup 2018. “Environmental Risk Factors for Developing Type 2 Diabetes Mellitus: A Systematic Review.” International journal of environmental research and public health vol. 15,1 78. 5 Jan. 2018, doi:10.3390/ijerph15010078.

Di Nardo 2010. “Green areas and health outcomes: a systematic review of the scientific literature.” Italian Journal of Public Health 7(4), 2010:402-413.

Dzhambov 2014. “Urban green spaces’ effectiveness as a psychological buffer for the negative health impact of noise pollution: a systematic review.” Noise & health vol. 16,70 (2014): 157-65. doi:10.4103/1463-1741.134916.

Eisenman 2019. “Urban trees, air quality, and asthma: An interdisciplinary review.” Landscape and Urban Planning Volume 187, July 2019, Pages 47-59.

Felappi 2020. “Green infrastructure through the lens of “One Health”: A systematic review and integrative framework uncovering synergies and trade-offs between mental health and wildlife support in cities.” The Science of the total environment vol. 748 (2020): 141589. doi:10.1016/j.scitotenv.2020.141589.

Gong 2019. “A systematic review of the relationship between objective measurements of the urban environment and psychological distress.” Environment international vol. 96 (2016): 48-57. doi:10.1016/j.envint.2016.08.019.

Grilli 2020. “Health Benefits Derived from Forest: A Review.” International journal of environmental research and public health vol. 17,17 6125. 23 Aug. 2020, doi:10.3390/ijerph17176125.

Hunter 2015. “The impact of interventions to promote physical activity in urban green space: a systematic review and recommendations for future research.” Social science & medicine (1982) vol. 124 (2015): 246-56. doi:10.1016/j.socscimed.2014.11.051.

Hunter 2019. “Environmental, health, wellbeing, social and equity effects of urban green space interventions: A meta-narrative evidence synthesis.” Environment international vol. 130 (2019): 104923. doi:10.1016/j.envint.2019.104923.

Islam 2020. “Green space and early childhood development: a systematic review.” Reviews on environmental health vol. 35,2 (2020): 189-200. doi:10.1515/reveh-2019-0046.

Kabisch 2017. “The health benefits of nature-based solutions to urbanization challenges for children and the elderly – A systematic review.” Environmental research vol. 159 (2017): 362-373. doi:10.1016/j.envres.2017.08.004.

Kerishnan 2021. “Factors contributing to the usage of pocket parks―A review of the evidence.” Urban Forestry & Urban Greening Volume 58, March 2021, 126985.

Kondo 2018. “Urban Green Space and Its Impact on Human Health.” International journal of environmental research and public health vol. 15,3 445. 3 Mar. 2018, doi:10.3390/ijerph15030445.

Labib 2020. “Spatial dimensions of the influence of urban green-blue spaces on human health: A systematic review.” Environmental research vol. 180 (2020): 108869. doi:10.1016/j.envres.2019.108869.

Lai 2019. “The impact of green space and biodiversity on health.” Front. Ecol. Environ. 17; 2019: 383–390.

Lee 2011. “The health benefits of urban green spaces: a review of the evidence.” Journal of public health (Oxford, England) vol. 33,2 (2011): 212-22. doi:10.1093/pubmed/fdq068.

Mancus 2018. “Integrative Review of the Intersection of Green Space and Neighborhood Violence.” Journal of nursing scholarship : an official publication of Sigma Theta Tau International Honor Society of Nursing vol. 50,2 (2018): 117-125. doi:10.1111/jnu.12365.

Mmako 2020. “Green spaces, dementia and a meaningful life in the community: A mixed studies review.” Health & place vol. 63 (2020): 102344. doi:10.1016/j.healthplace.2020.102344.

Nawrath 2021. “Exploring uncharted territory: Do urban greenspaces support mental health in low- and middle-income countries?.” Environmental research vol. 194 (2021): 110625. doi:10.1016/j.envres.2020.110625.

Parker 2018. “Public Green Infrastructure Contributes to City Livability: A Systematic Quantitative Rev.” Land 7(4), 2018: 161; https://doi.org/10.3390/land7040161.

Rojas-Rueda 2019. “Green spaces and mortality: a systematic review and meta-analysis of cohort studies.” The Lancet. Planetary health vol. 3,11 (2019): e469-e477. doi:10.1016/S2542-5196(19)30215-3.

Rosa 2021. “Forest therapy can prevent and treat depression: Evidence from meta-analyses.” Urban Forestry & Urban Greening Volume 57, January 2021, 126943.

Rugel 2020. “Quiet, clean, green, and active: A Navigation Guide systematic review of the impacts of spatially correlated urban exposures on a range of physical health outcomes.” Environmental research vol. 185 (2020): 109388. doi:10.1016/j.envres.2020.109388.

Saitta 2019. “Park-based physical activity interventions for persons with disabilities: A mixed-methods systematic review.” Disability and health journal vol. 12,1 (2019): 11-23. doi:10.1016/j.dhjo.2018.07.006.

Shuvo 2020. “Urban green space and health in low and middle-income countries: A critical review.” Urban Forestry & Urban Greening Volume 52, June 2020, 126662.

van den Berg 2015. “Health benefits of green spaces in the living environment: A systematic review of epidemiological studies.” Urban Forestry & Urban Greening Volume 14, Issue 4, 2015, Pages 806-816.

Watkins 2018. “The relationship between urban forests and race: A meta-analysis.” Journal of environmental management vol. 209 (2018): 152-168. doi:10.1016/j.jenvman.2017.12.021.

Weinberger 2015. “A review of spatial variation in allergenic tree pollen within cities.” Arboriculture & Urban Forestry 41(2), 2015 : 57–68.

Wolf 2020. “Urban Trees and Human Health: A Scoping Review.” International journal of environmental research and public health vol. 17,12 4371. 18 Jun. 2020, doi:10.3390/ijerph17124371.