As city populations grow, urban trees cannot be viewed as a luxury: Trees are an essential component of a livable community and a core strategy for improving public health.
The Nature Conservancy in America has just released its latest report, ‘Funding Trees for Health – An Analysis of Finance and Policy Actions to Enable Tree Planting for Public Health’ and it states that scientific case for the benefits of trees and urban nature has become more solid over the last few decades. The report focuses on the links between trees and public health stating that recent science shows that the link is robust and economically significant. The central question of this report asks: If trees are so important for health, how can cities use innovative finance and policy tools to enable tree planting for public health?
Despite the large literature on the many benefits provided by street trees and other natural features, U.S. cities are experiencing declines in urban forest cover. New tree planting isn’t keeping pace with the mortality of existing trees, either from natural causes or from clearing of trees for new development. If trees provide so many benefits, why are cities letting this natural resource dwindle away?
The report identifies four main barriers preventing cities from fully seizing the power of street trees and other natural features:
- Lack of knowledge: Decision-makers and the public may lack knowledge of the benefits trees provide. For cities willing to invest time and resources, urban forestry science and tools have advanced enough that it is possible to estimate the benefits that current (or future) street trees provide to residents. To systematically planning urban forestry activities to achieve multiple ecosystem service objectives can be found in The Sustainable Urban Forest: A Step-by-Step Approach, developed by the US Forest Service and The Davey Institute.
- Public concerns: There are public concerns about potential negative problems with trees, such as problems with fallen limbs causing power outages, or trees and untended parks providing spaces for criminal activity. Concerns can often be alleviated by better urban forestry practices or public education campaigns. The report suggests following the Arbor Day Foundation’s Right Tree, Right Place best practices.
- Silos: The responsibility to advance tree planting often falls on one municipal agency, such as a Forestry Office within a city’s Department of Parks and Recreation. As a result, it can be difficult for cities to efficiently identify and harness all tree planting opportunities that might be presented by the on-the-ground work of different municipal agencies. Cooperative planning processes are one way to overcome this barrier.
- Lack of financial resources: Trees are often considered a “nice to have” item compared to other critical municipal needs such as police and fire protection, education, roads, and other public services. This combined with the budget cycle of cities leaves tree planting programs minimally funded. Finally, there is lack of funding for urban forestry, caused by constrained urban budgets and cities prioritizing urban forestry budgets relatively low compared with other priorities. Budgets to support a healthy tree canopy are further strained by a lack of funding for maintenance.
The investment gap: How much more investment in trees is needed need to maintain current urban canopy and then significantly expand it to seize greater potential health benefits. The report estimates that an additional investment of around $8 per person annually would be enough to create this green future in US cities. A green urban future is not an impossible dream, but is quite affordable, if policymakers and others decide to make this investment.
The last section of the report describes some specific solutions that can enable tree planting for public health. The solution that will work will vary by city, but what matters is giving value—financial and moral—to the benefits that trees provide to health.
The report discusses some methods commonly used by cities to try to break silos by linking urban forestry to other municipal goals. These can include planning processes such as sustainability or comprehensive plans, heat action planning or planning related to compliance with existing policy such as the Clean Water Act. The report discusses common financial mechanisms for urban forestry, such as funding from public revenues, municipal codes and policies, and partnerships with companies and NGOs. The report suggests a possible way to overcome the funding barrier may be to more closely link the goals and funding of the health sector with the goals and funding of urban forestry agencies. If trees have significant benefits to physical and mental health then why not consider a link between health funding and urban forestry?
The concept of linking finance streams for nature and health seems simple. Those whose mission it is to plant and maintain trees and other urban vegetation spend money and resources to make urban areas greener, which delivers significant benefits for mental health. This helps those in the health sector better achieve their mission of improving people’s health and well-being. To complete the circle, therefore, the health sector (whether public or private institutions) could supply some financial resources that help partially pay for the activities of those in the urban forestry sector.
Urban green space is a necessary component for delivering healthy, sustainable and liveable cities. Green space interventions deliver positive health, social and environmental outcomes for all population groups – particularly among lower socioeconomic status groups. There are few other public health interventions that can achieve this.
The recent World Health Organisation’s report Urban green space interventions and health: A review of impacts and effectiveness. Full report (2017) notes that interventions on green space in urban settings can help address public health issues related to obesity, cardiovascular effects, mental health and well-being. However, knowledge on their effectiveness in relation to health, well-being and equity is incomplete.
The World Health Organisation (WHO), in 2016, published an evidence review on the health impacts of urban green spaces. Urban green spaces and health – a review of evidence (2016). This report summarizes the health benefits, discusses pathways to health and evaluates health-relevant indicators of urban green space. Such indicators enable local authorities and urban planners to assess in which urban areas green space accessibility should be improved, and to establish respective planning decisions.
What are the most effective ways to deliver urban interventions on green spaces, and how can we guarantee that the environmental, social and health benefits are maximized while potential side effects are prevented or reduced? WHO has compiled:
- available research evidence on urban green space interventions and their impacts;
- local green space intervention case studies and lessons learned;
- existing Impact Assessment experiences on green space planning.
Results indicate that urban green space is necessary to deliver healthy, sustainable and liveable cities. Interventions to increase or improve urban green space can deliver positive health, social and environmental outcomes for all population groups, particularly among lower socioeconomic status groups. There are very few other public health interventions that can achieve all of this, and especially the impact on active lifestyles, mental well-being and social interaction is frequently highlighted as a key benefit. Yet, there is a need for better inclusion of health and equity outcomes in studies on green space interventions, and an improved monitoring of local green space management and related health and equity impacts. It is equally important to note that there is little evidence available on the unintended side effects of urban green space interventions.
Urban green space interventions seem to be most effective when a physical improvement to the green space is coupled with a social engagement/participation element that promotes the green space and reaches out to new target groups. Evidence shows that multidisciplinary and cross-sectoral collaborations help to ensure that urban green space interventions deliver on multiple outcomes and provide a variety of functional opportunities that attract different population groups.
Urban green space interventions need to be planned and designed with the local community and the intended green space users thus ensuring benefits for the local residents and the delivery of interventions that serve the needs of the community – especially in deprived areas.
As green space interventions need to be considered as long-term investments, they need to be integrated within local development policies and frameworks (e.g. urban masterplans, housing regulations, transport policies, sustainability and biodiversity strategies). This requires continued political support within local government, and the general understanding that urban green spaces go beyond environmental or ecological objectives and also deliver social and health benefits that increase the quality of life and well-being of all urban residents.
Urban Green Space Interventions and Health: A review of impacts and effectiveness – Report Conclusions
Green space should be available to all residents as a part of their daily surroundings. This applies to both small-scale and large-scale green spaces, irrespective of categorizations into private or public spaces or functionalities. Be it the remote view of green space within the neighbourhood, the passive exposure to green space by having a walk by the river or taking a break in a park, or the active use of green spaces through e.g. play, leisure or gardening – all kinds of urban green space should be promoted through urban planning and governance across all sectors
Multidisciplinary and cross-sectoral collaborations will help to ensure that urban green space interventions deliver on multiple outcomes. Urban green space interventions are most effective when a dual approach is adopted where a physical improvement to the environment is coupled with a social engagement/participation element promoting the use of the green space.
Urban green space interventions need to be situated within the overall context of the urban area and integrated within the relevant strategies, frameworks and plans (e.g. urban masterplans, health and transport policies, sustainability and biodiversity strategies). Good design, implementation and maintenance of urban green space interventions will mitigate any potential adverse outcomes from the intervention and maximize their benefits.
Urban green space interventions need to be planned and designed with the local community and the intended green space users. This will ensure the derivation of benefits for the local community and will aid the delivery of interventions that serve the needs of the community – especially in deprived areas.
This post highlights 2 recent research papers focusing on the links between health benefits and exposure to green infrastructure.
“Green spaces and cognitive development in primary schoolchildren.” – Dadvand, P., Nieuwenhuijsen, M., Esnaola, M., Forns, J., Basagaña, X., Alvarez- Pedrerol, M., Rivas, I., López-Vicente, M., De Castro Pascual, M., Su, J., Jerrett, M., Querol, X. & Sunyer, J.. (2015). Proceedings of the National Academy of Sciences. 112(26): 7937–7942. DOI: 10.1073/pnas.1503402112
Exposure of primary schoolchildren to outdoor green spaces is linked to an improvement in their cognitive development, finds a new study, which is the first of its kind. The association may be partly explained by reductions in traffic-related air pollution (TRAP) near green areas.
Approximately half of the global population live in cities, and it is projected that by 2030, three of every five persons (60%) will live in urban areas worldwide. Yet urban areas are characterised by increased levels of pollutants and fewer green spaces. Several studies have linked exposure to urban green spaces to improved physical and mental health and wellbeing (1.) Children may be particularly susceptible to the psychological effects of the urban environment, as key cognitive traits are developed during infancy and childhood.
Researchers have now investigated the association between exposure to green spaces and memory and attention in children. They also evaluated the role of TRAP as one of the potential mechanisms underlying this association. This new study took place in the context of the EU-funded Barcelona BREATHE project (2.) which investigates the possible effects of traffic-related air pollution TRAP on brain development in children.
In the 36 primary schools taking part in BREATHE, 58% of children aged 7–10 (2 623) agreed to participate. Children were evaluated four times every three months over a year, using computerised tests to assess their working memory and attention, both of which grow steadily during adolescence. The ‘greenness’ around each child’s home address, within and near their school and along their commute to school was measured using satellite imagery and the Normalized Difference Vegetation Index, a measure of greenness based on reflected light. The values were combined with variables such as time spent in school or at home to estimate each child’s total exposure to greenness. Models were constructed to evaluate the association between green spaces and cognitive development. The research leading to the methodology (PHENOTYPE) used in this study to assess exposure to green spaces received funding from the Commission’s Seventh Framework Programme (3.)
The researchers found that a higher level of exposure to green spaces was associated with improved cognitive development. More specifically, this consisted of a median score of 5% improvement in working memory, 6% increase in superior working memory, and a 1% reduction in inattentiveness. This was attributable specifically for greenness within and near schools. There was no association between residential surrounding greenness and cognitive measurements.
The researchers also investigated whether reduced levels of TRAP could explain the association between green spaces and cognitive development. High-quality data on exposure to the air pollutant elemental carbon (EC) — a tracer of road traffic emissions — in the schools was available through BREATHE. Previous analyses had found lower levels of EC in schools with higher greenness. Adding TRAP exposure to the models explained 20–65 % of the association between school greenness and change in cognitive development. The researchers theorise other mechanisms may include lower exposure to ambient noise and increased physical activity associated with green spaces.
The study provides evidence that targeted interventions such as improving greenness in schools could have significant effects on children’s cognitive development. Based on their study, the authors suggest that if schools with the lowest levels of greenness increased this resource to be on a par with schools with the highest greenness, the number of children with impaired superior working memory development would decrease by 8.8%. The improved cognitive development in children could lead to improved mental capabilities for the rest of their lives. Since this was the first epidemiological study to report on the impact of exposure to green space on cognitive development in schoolchildren, further research is needed to investigate the robustness of these findings. Additional research should explore if similar effects are found during other periods of cognitive development in children, such as prenatal and preschool periods.
Landscape Institute’s, “Public health and landscape: creating healthy places” Position Statement (November 2013). Download A4 version
“Positive health effects of the natural outdoor environment in typical populations in different regions in Europe (PHENOTYPE): a study programme protocol.” – Mark J Nieuwenhuijsen, Hanneke Kruize, Christopher Gidlow, Sandra Andrusaityte, Josep Maria Antó, Xavier Basagaña, Marta Cirach, Payam Dadvand, Asta Danileviciute, David Donaire-Gonzalez, Judith Garcia, Michael Jerrett, Marc Jones, Jordi Julvez, Elise van Kempen, Irene van Kamp, Jolanda Maas, Edmund Seto, Graham Smith, Margarita Triguero, Wanda Wendel-Vos, John Wright, Joris Zufferey, Peter Jan van den Hazel, Roderick Lawrence and Regina Grazuleviciene. British Medical Journal, BMJ Open 2014;4:e004951 doi:10.1136/bmjopen-2014-004951.
Growing evidence suggests that close contact with nature brings benefits to human health and well-being, but the proposed mechanisms are still not well understood and the associations with health remain uncertain. The Positive Health Effects of the NaturalOutdoor environment in Typical Populations in different regions in Europe (PHENOTYPE) project investigates the interconnections between natural outdoor environments and better human health and well-being. This project is a Collaborative Project funded through the European Commission Seventh Framework Programme
Urban planners should be given guidelines to include a minimum amount of green space in cities, according to researchers who have found that exposure to parks and trees helps to prolong life, improve mental health and even increase the birthweight of babies.
Professor Mark Nieuwenhuijsen from the Center for Research in Environmental Epidemiology (CREAL) in Barcelona, Spain, says that access to nature does not merely top up your wellbeing, but it might actually be a necessary condition for good health. Prof. Nieuwenhuijsen coordinates the EU-funded PHENOTYPE project (4.), which is aiming to build up the evidence base for so-called urban greening by understanding how exactly it can influence your health and why. The idea is to feed into decisions made by landscape architects, urban planners and policymakers.
‘Lack of green space causes detrimental health effects,’ he said. ‘Green space is necessary for healthy psychophysiological functioning (and) there could be a set level for good health.’
This is important as more than half of the world’s population lives in urban areas, a figure which is set to grow more than 1 % per year between now and 2030. However, there is currently no agreement on just how much greenery cities should contain for optimal health.
‘At the moment there are no guidelines for green space. It would be nice to be able to give more information to urban planning to make sure that there’s provision of green space. How much green space do you need? There are questions still remaining.’
PHENOTYPE researchers are conducting studies of the health effects of green space in four different parts of Europe: Lithuania, the Netherlands, the UK and Spain. So far they have found that an increase in surrounding greenness leads to higher birth weight for babies, reduced blood pressure during pregnancy, and lower obesity levels in children. They have also found that an increase in surrounding greenness is associated with better mental health and self-perceived physical health. The project is also uncovering suggestions that not all greenery is equal. Prof. Nieuwenhuijsen says that being surrounded by greenery, such as living on streets lined with trees or being able to see vegetation from your office window, may have greater health benefits than having access to a park.
Initial indications are that it is more complicated than the fact that living close to a park could encourage people to take more exercise and lead an active lifestyle. In a study of coronary artery patients in Kaunas, Lithuania, researchers found that people benefitted more from walking in parks than when they did the same amount of exercise but walked on busy urban streets.
Prof. Nieuwenhuijsen says that there is some good evidence that the reason behind this effect could be a reduction in stress levels. ‘There are some studies that show a reduced blood flow in the subgenual prefrontal cortex (which controls stress) when people are exposed to green space.’ Other mechanisms could include a reduction in air pollution and an increase in social contacts. While the exact mechanisms are still under investigation, Prof. Nieuwenhuijsen believes that humans are hard-wired to appreciate the benefits of vegetation.
- The BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn (BREATHE) was supported by the European Research Council. See: http://www.cordis.europa.eu/project/rcn/99632_en.html
- Positive Health Effects of the Natural Outdoor environment in Typical Populations in different regions in Europe (PHENOTYPE) project was funded through the European Commission Seventh Framework Programme: http://www.staffs.ac.uk/research/
- PHENOTYPE – intended to provide a better understanding of the potential mechanisms, and better integration of human health needs into land use planning and green space management.