Urban Forests: Natural Air Conditioners

What are urban heat islands and how do urban trees perform air conditioning services? Find out more in this blog post by Ana Simčič, a forestry engineer from Slovenia.

What do you prefer in a summer afternoon – a walk in a crowded city center or a walk in a forest? I’m sure everyone gets relieved when after a hot walk a tree shadow appears in front of them, waiting to cool them down and let them breathe a bit fresher summer breeze. Dense canopies certainly provide a much needed relief in hot summer hours.

Every city that is surrounded by forests or comprises forested fragments can be grateful for the effects they bring, especially in the summer time. Forests mitigate and moderate heat by absorbing less heat than neighborhood concrete areas and buildings. Trees lower surface and air temperatures by providing shade and through evaporation of water from the soil and leaves.

The extra heating load that comes with replacing natural vegetation with buildings, streets and sidewalks, has been recognized many decades ago. Cities are often warmer than surrounding rural areas – a phenomenon known as the “urban heat island effect”. It is caused by the absorption and storage of the sun’s thermal energy in urban infrastructure (steel, concrete or asphalt). A heat island forms over an urban area and is like a large bubble with higher temperatures than the rural surroundings. The phenomenon is common in large metropolitan cities, but it’s also noticeable in smaller cities like Ljubljana. The temperature differences between forested areas and urban environments are most pronounced during heat waves. When temperatures in urban concrete areas are near dangerous to impair human health, neighborhood green areas provide conditions that are more human friendly.

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Urban heat island effect, caused by solar energy.

Recreation in summertime is much more healthier in forested areas, where air is less polluted. A dense canopy of healthy trees can reduce the effects of air pollution associated with increasing urban temperatures. Air pollution is a serious public health threat linked to asthma, migraines, respiratory and heart diseases and most of them get especially pronounced during summer heat waves.

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A picnic in the shadow of the trees.

Trees also save energy by shading our homes and paved surfaces. Mature trees can significantly reduce summer air conditioning use by shading the sides of our homes that are exposed to overheating. In autumn, deciduous trees lose their leaves and allow us to solar heat our homes and reduce winter energy use.

Heat tires everyone – people, animals and also plants – that’s why a walk in the forest is always a good decision. In the forest, the air is more humid, temperatures are lower and the canopies protect us from harmful UV rays and sunburns. If we don’t forget a bottle of cool water, there is a pleasant walk in front of us despite the high temperatures outside of the woods.

This blog post is authored by Ana Simčič and is part of the #EFUF2016 blog competition.

Featured photos by WeatherQuestions and FHWA.

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Green Divides in Cities Are Also Health Divides

What is the cost of losing everyday contact with natural spaces in favour of more urban development? Find out more in this blog by the #EFUF2016 invited blogger, Tara Zupančič, MPH.

I was twelve years old when I first visited Slovenia. I spent my summer on the mountain where my father grew up. Among 300 acres of trees, I would love to watch the mist lift from the valley floor into the ether. My soul felt alive there, and like many people, I have grown to depend on nature to hoist my spirit, provide refuge from the heat, and restore my sense of home on this planet. So when I tell people that I study the relationship between nature and health, I’m often met with an incredulous look. Isn’t it well established that nature provides the very foundation of human health? My head bobs yes, as I explain myself.

The push for research on the health benefits of nature is related to our increasingly urban existence. Competing needs for roads, houses, and industry can easily overtake greener pastures. Nature is typically viewed as something beyond urban borders and not part of our daily city life. As cities expand their borders to house the majority of the world’s population, we need to ask, what is the cost of losing everyday contact with natural spaces in favour of more urban development? In the face of competing land use needs, is a stand of trees that important?

Despite advances in health care, our lifelong health is largely determined by our social and economic position and the settings where we live, work, and play. A strong and growing body of evidence shows that everyday contact with urban nature is critical to our well-being and is significantly associated with healthier births, as well as reduced mortality, obesity, chronic disease, depression and anxiety. Access to nature is especially important for children and is significantly associated with increased play, physical activity, and cognitive and motor development.

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Unfortunately, the ability to enjoy the benefits of nature often falls along social and economic divides, deepening health inequalities in cities. This means that poor health, disproportionately borne by those who are socioeconomically disadvantaged, is compounded by greater environmental burdens where they live. For example, a European systematic review showed that socially disadvantaged children commonly suffer from multiple and cumulative health burdens related to poor quality housing, greater exposure to traffic and industrial pollution, and a lack of healthy, natural spaces where they live. These children are more susceptible to harm from adverse environmental conditions because they often lack protective factors such as adequate nutrition, opportunity for play and essential health care.

Tackling health inequalities is a major global health priority, and ensuring equitable access to nature must be part of that strategy. While exposure to nature can benefit everyone, there is consistent evidence that the benefits are strongest among socioeconomically disadvantaged groups.

The association between green space and reduced mortality has been found to be strongest in the most socioeconomically deprived urban areas. Increased green space exposure also appears to decrease the effect of income deprivation on all-cause and cardiovascular mortality. Multiple studies on green space exposure and birth have found that the strongest positive associations are found among the most socially disadvantaged. It is not clear why these stronger associations exist but emerging evidence suggests that nature may provide a buffer from difficult life circumstances, and be protective against stress as a setting for emotional, physical, and social support.

The benefits of everyday contact with nature are vast and there is a need to ensure that this nurturing from nature is not determined by a person’s wealth, income, or ability to leave the city. Time in nature is an essential right of childhood and sets a critical foundation for lifelong health. As an increasingly urban planet, we need to configure our cities to maximize nature in every nook and cranny and guarantee everyone is free to benefit from it. Instead of planning the apportioning of trees amid sprawling cites, there is an opportunity to plan vibrant cities amid great forest canopies. Our health depends on it.

Studies referenced:

Bolte, G., Tamburlini, G., & Kohlhuber, M. (2010). Environmental inequalities among children in Europe—evaluation of scientific evidence and policy implications. The European Journal of Public Health, 20(1), 14-20.

Brown, S. C., Lombard, J., Wang, K., Byrne, M. M., Toro, M., Plater-Zyberk, E., … & Pantin, H. M. (2016). Neighborhood Greenness and Chronic Health Conditions in Medicare Beneficiaries. American Journal of Preventive Medicine.

James, P., Banay, R. F., Hart, J. E., & Laden, F. (2015). A review of the health benefits of greenness. Current epidemiology reports, 2(2), 131-142.

About the author: Tara Zupančič, MPH is the Founder and Director of Habitus Research in Canada.

Green Infrastructure: A Positive Development for Urban Forestry?

Is the term Green Infrastructure a positive development for urban foresters? Find out in this blog post by Clive Davies, research fellow at the Newcastle University and the director of MD2 Consulting Ltd, where he is an international advisor & enabler supporting clients in all aspects of green infrastructure planning, urban & peri-urban forestry.

Green Infrastructure has become a really popular planning term in the last 10 years and has come to dominate the discourse on urban green. I have been reflecting on this for some time and have concluded that it is a positive development for practitioners and researchers engaged in urban forestry. Why?

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Urban Green Infrastructure

The answer is that in urban areas where tree cover is low urban forestry has often struggled to get accepted as a term of importance. Yet some of the same urban areas where urban forest recognition is limited are now beginning to plan for green infrastructure. This creates an opportunity to promote trees and urban woodlands as functional green infrastructure (GI) and embed the concepts of urban forestry in GI plans and projects – surely this is an opportunity. Of course for this to happen urban areas need urban forest advocates to make a strong case. Could that be you?

I also see a developing role for the EFUF partnership; if EFUF can produce authoritative, persuasive and relevant information on urban forestry targeted at professionals working on green infrastructure planning then we have a powerful new tool to promote the role of urban trees and urban woodland. At the EFUF Brussels/Waterloo Forum in 2015, there was discussion about creating a digital platform called EFUF 2.0. This promotional role on urban forestry as a crucial part of green infrastructure could be one of the functions of the digital platform.

Recently attention has been focused on Nature Based Solutions and the role green infrastructure plays in this. If you haven’t read the report Towards an EU Research and Innovation policy agenda for Nature-Based Solutions & Re-Naturing Cities then I recommend it to you. Urban forestry can make a huge contribution to nature based solutions and this is recognised, take this abstract from the EU report as an example: Planting trees to reduce air pollution and improve health.

  • Objective/Theme: Air pollution is a serious problem with more people moving to towns and cities combined with increased traffic.
  • Solutions/measures: There are a range of measures including the important one of reducing the source of the pollution. It has become increasingly clear that appropriate tree planting can be effective in reducing levels of air pollution in urban areas.
  • Short description (rcommendation): Provide incentives to encourage the planning of lines of trees in areas where high densities of pollutants and people coincide.

Reports of this kind can support arguments for urban forestry investment. So even in the era of austerity gripping Europe, there are new arguments we can put forward to promote urban forestry.

Author: Clive Davies, Strategic Urban Forestry & Green Infrastructure Consultant

Featured photo by mpstudio123.