Council trees now quantifiably valued, with soil vaults delivering huge ROI

stratacell treepit

All city councils have an asset register detailing the value of assets like roads, parks, street furniture, and so on. Increasingly – and rightly so – trees are being included as quantifiable assets. In the past, it has been hard to quantify the value of trees, but today there are a number of methodologies for doing so. One such method, the Burnley Method – developed by Dr Greg Moore at the Victorian College of Agriculture and Horticulture Limited, Burnley Campus – is now being widely used and accepted. Available for download here

The City of Melbourne are pioneers in valuing their trees and looking after them accordingly. In fact, residents can even email local trees to raise concerns about their health or express their appreciation and affection for the tree. By putting a value on trees, councils are able to protect them in new and quantifiable ways. For example, if a developer is building near a valuable tree, the council may require them to pay a bond – refunded provided the tree is unharmed post construction. If a developer destroys or removes a tree without permission, the council is able to sue that developer for the value of the tree per their register. All of this is effective and much-needed motivation to keep our valuable urban trees safe.

A council’s asset register forms a key part of their balance sheet. As the assets degrade over time, there is depreciation. Spend money on their assets, and there is growth. Naturally, councils want to spend money wisely in order to generate the greatest return on investment.

Tree Planting using Stratacell

Installing the underground soil vault system beneath the parking lot.

Internationally, providing enough shade in carparks is a big issue. Not only does shade drastically improve the shopping experience, it also prolongs the life of the pavement. In the City of Belmont, Perth, Citygreen’s Stratacell system had a massive impact on the council’s bottom line. In an asphalt carpark next to an oval, five London Plane trees were planted in quite narrow islands, with adequate space and soil volume provided using the Stratacell system beneath the carpark pavement. The cost for the five trees (including the Stratacell system) was $50,000.

Four years later, as reported by Council, the trees have grown at an unprecedented rate – from a 75mm/3” trunk diameter at time of planting, to 250mm/10”. Today, according to the Burnley method, these trees are valued by Council at $17,500 each – an amazing return on investment in just four years, with so much growth (literally and financially) still to come.

As a comparison, the same council has the same species growing in a nearby carpark using the conventional method. The carpark was laid, a square cut in the pavement, some curbing placed around the edges, roadbase dug out, and a soil loaded into the hole. Planted 15 years ago (versus only four), these trees are valued at only $510 each. Of course, the initial outlay was much less ($250 per tree), but the return on investment does not compare.

tree comparison

Essentially, using the Citygreen soil vault system, this innovative Council was able to grow trees worth 34 times as much – in one quarter of the time!. As more emphasis is placed on generating ROI in relation to the value of trees, adopting innovative technology which enables trees to thrive in urban environments must be a priority. Of course, this is not just about improving councils’ bottom lines, but also improving the health and wellbeing of the communities they serve.

Is Green plus Blue viable yet? Absolutely!

urban environmental cycle

First of all, what do we mean by ‘Green’ and ‘Blue’? In this context, we’re talking about best practice for growing healthy trees (Green), and best practice for treating and managing stormwater (Blue).

For decades it has puzzled me that there is a major disconnect between the fields of urban forestry and stormwater engineering. Think about it – we plant trees into paved areas (car parks, malls, plazas, streetscapes) and partly paved areas (narrow road verges, centre medians, planter beds etc), and now we’re also paying attention to soil specifications, soil volumes for life needs of the trees, and so on. But one of the really key requirements for plant growth (H2O) is very efficiently sent away from our trees as soon as it falls on the large expanses of surrounding pavement! This doesn’t make sense whichever way you look at it.

A number of forward-thinking people around the globe have done some pioneering work in this – primarily to divert and capture water for tree health. However, how can the costs and benefits be quantified from all aspects? We need to carry the confidence of all stakeholders in the green building space, besides the developers and investors.

So, a few of us have been working with design engineers to try and clarify this issue, and bring some visibility to the discussion. Let’s break this up a little:

storm water management

  1. Passive Watering: this relates to the basic interception of rainwater, to enhance or replace manual or automatic watering of trees. Whilst there’s not a huge amount of science available publicly, there is definitely a growing interest. Based on regional climatic data, catchment areas per tree, soil type, and tree species, it is possible to optimise this and address each of these needs.
  2. Stormwater Management: this relates to flows, and is a really crucial component of many development approval mechanisms globally. We are trying to restore pre-development flows for the health of waterways and improve safety of the broader populace in presence of flooding events induced by changes in land uses and climatic events. The volume of soil within our treepits can definitely be used as part of a stormwater management plan, and incorporated into numbers of different modelling programs. Note: we also have to balance the other factors (tree health, soil volumes etc) along with the stormwater flows, using a Water Balance tool.
  3. Stormwater Treatment: this relates to pollutant removal from stormwater, and is absolutely integral to the suite of benefits that are brought to the table by combining treepits with stormwater treatment and management. The statutory targets for a given region can be achieved, and in many cases surpassed, when properly sized and specified treepits are used as part of a Green plus Blue initiative.


To wrap up: ideally, none of the above should be viewed in isolation, or else one or more of the design components will be compromised. For success, and all that this means (massive benefits to society, developers, the environment, and so on) a cross-functional approach is needed – one that combines the latest science for stormwater management and treatment with current best practice in treepit designs. When this is accomplished, there are significant savings to be achieved – and this makes sense to me. Because, after all, we are just re-connecting an environmental cycle that has been broken in our cities and urban spaces.

treating and managing stormwater

For more information on the latest in water harvesting technology, please visit this page.

Thanks for reading, and please don’t hesitate to reach out to me at

CEFC to boost energy efficient community housing in Australia

energy efficient community housing in Australia

The Clean Energy Finance Corporation has announced a $250 million Community Housing program, in partnership with the federal government. The scheme, designed to ramp the construction of cutting-edge, energy efficient community housing, will help build up to 1,000 new dwellings across Australia. In addition to new builds, finance to retrofit existing buildings will also be provided to improve energy efficiency and reduce bills for tenants.

Along with the announcement, the CEFC released a market report, which states, “Evidence indicates that low-income households tend to live in buildings with poorer energy efficiency, leading to higher energy costs. Poor building energy efficiency and high energy costs can have significant financial and health effects on households in community housing.

“There are many energy efficiency improvements with payback periods of five years or less that can be incorporated into the building fabric during construction. New-build community housing should be designed to ambitious energy efficiency standards and the existing stock should be refurbished to improve energy efficiency.

“While energy efficiency improvements involve upfront costs, more energy efficient community housing would lower energy bills and increase thermal comfort, improving households’ financial, health and carbon emissions.”

CEFC Community Housing Sector Lead, Victoria Adams, said, “Over the next year, our goal is to help finance the construction of 1,000 new dwellings, built to an average seven-star rating under the Nationwide Housing Energy Rating Scheme (NatHERS). With this standard, energy use can be reduced by an estimated 25 per cent.”

image credit . Kaz Pierce

The “Greening” of Plastic

The Greening of PlasticRecycled Thermoplastics and Green Infrastructure

By Richard J. Magill, ASLA, LEED Green Associate

As practicing “green building” professionals, we are all constantly searching for the best materials for our projects. The selection of building materials that are well-engineered, cost-effective and ecologically-sound is a process that defines our effectiveness and ultimately the success of our projects. We all know how challenging it is to stay ahead of the “technology curve”, and that our understanding of the latest innovations in materials is critical to the realization of results that meet or exceed industry standards and the needs of society in general.

Technological advances in the design and production of recycled plastic “green” building materials provide us with opportunities to “push the envelope” with respect to the three important criteria mentioned above. Up-to-date and accurate information is the key to being positioned to take advantage of advances in green building materials.

The following article first steps back slightly to examine the primary concepts behind the role of recycled plastics in green infrastructure projects, then looking at more-specific applications and the future of plastics, so that we all may be completely informed in our choices going forward.

The Greening of PlasticWhat are Thermoplastics?

Also known as “engineering plastics”, thermoplastics comprise a group of materials that exhibit superior mechanical and thermal properties in a wide range of conditions over and above more commonly used commodity plastics and other materials. The term usually refers to thermoplastic (softer) materials as opposed to “thermoset” (harder) plastics. Engineered thermoplastics are typically used for parts rather than containers and packaging. A thermoplastic is made from polymer resins that can be reheated and reshaped repeatedly. These important characteristics allow the manufacturing process to be reversible, therefore making most thermoplastics recyclable.

The Greening of PlasticWhy Recycled Thermoplastics?

  • Recycled plastic provides a sustainable source of raw materials to the green manufacturing and building industry.
  • Reduction of environmental impacts, such as greenhouse gas emissions, associated with the production of new plastic-rich products.
  • Greatly reduces the amount of plastic entering the primary waste stream, thus sparing our already overcrowded landfills.
  • Reduction in consumption of the world’s limited natural resources, i.e.: oil.
  • Recycled plastic production represents far less “embodied energy” than production of new, virgin polymer products.
  • Recycling in general promotes sustainable lifestyle choices.
  • Recycled plastic parts lower the cost of product manufacturing and transportation (shipping).
  • Thermoplastic products can be recycled again and again, whereby effectively closing the “lifecycle loop” of the resource.

What is Green Infrastructure anyway?

 Depending on which particular interest group is defining it, green infrastructure has been used to refer to everything from innovative green roofs, to more ecologically-sensitive stormwater management systems, to large integrated networks of natural areas.

What these different interpretations have in common is the essential recognition that our built environment and our ecological environment are irreversibly connected and closely interrelated.

When the term is used at a smaller scale, such as an urban park or streetscape, our working definition can be: an interconnected system of man-made landscapes, natural areas and open space that preserves and enhances the sustainability of the ecosystems, promotes clean air and water, and significantly benefits people and wildlife.

It should be pointed out that green infrastructure at the smaller; “implementation-level” involves the design, manufacture and installation of the best possible components of the physical systems, such as: tree grates, structural soil cells, permeable pavement, drainage systems, etc.

Some other informative definitions of green infrastructure are:

“Green infrastructure can be considered a conceptual framework for understanding the “valuable services nature provides the human environment.” At the national or regional level, interconnected networks of park systems and wildlife corridors preserve ecological function, manage water, provide wildlife habitat, and create a balance between built and natural environments. At the urban level, parks and urban forestry are central to reducing energy usage costs and creating clean, temperate air. Lastly, green roofs, walls, and other techniques within or on buildings (and building sites) bring a range of benefits, including reduced energy consumption and dramatically decreased stormwater runoff. Regardless of scale, green infrastructure provides real ecological, economic, and social benefits.”

American Society of Landscape Architects

“As communities develop and climate patterns shift, stormwater management needs can only be expected to grow. While single-purpose gray stormwater infrastructure is largely designed to move urban stormwater away from the built environment, green infrastructure reduces and treats stormwater at its source while delivering many other environmental, social, and economic benefits. These benefits not only promote urban livability, but also add to the bottom line.”

US Environmental Protection Agency

 The Benefits of Green Infrastructure

The Greening of PlasticGreen infrastructure systems protect and restore naturally-functioning ecosystems and provide a framework for future development. These systems provide a wide range of ecological, social, and economic functions and benefits, such as: cleaner air and water, restoration and conservation of natural resource processes, enriched habitat and enhanced biodiversity, increased recreational and transportation opportunities, improved human health, and better connections to nature.

Well-designed and implemented man-made and natural green spaces have proven to increase property values and significantly decrease the costs of public infrastructure and public services.

 The Benefits of Recycled Thermoplastic Materials

  • Durability- recycled plastic building products have proven to be extremely resistant to harsh environmental conditions. Plastic does not have to be painted, resists corrosion, and can be engineered to be incredibly strong.
  • Non-toxic- recycled plastic materials/parts will not leach undesirable chemicals into the environment.
  • Lower production costs- recycled and repurposed plastics are far more cost-effective than using expensive virgin polymer resins.
  • Lower shipping costs- plastic materials typically weigh less than other materials (wood and steel for example) thus transportation costs are lower.
  • Reduced environmental impacts (reduced embodied energy)-it simply requires less overall energy to produce, transport and install recycled plastic products.

Some Specific Applications of Recycled Plastic in Green Infrastructure

  • Streetscapes
  • Green Roofs
  • Structural Soil Cells
  • Porous Pavement Systems
  • Stormwater Drainage Structures
  • Green Walls
  • Tree Pit Systems

LEED Credits for Recycled Plastic Materials

LEED (Leadership in Energy and Environmental Design) offers credits for the use of recycled products, including recycled plastics, in buildings, site development and landscaping in their highly regarded green building rating system.

Specifically, products like Citygreen® Stratacell™ Systems may qualify your project for generous contributions toward LEED certifications, with recycled content being a high contributor. Contact us for more information regarding Citygreen products and LEED credits.

See for more information and proposed changes to LEED rating systems.

The Future of Plastics and Green Infrastructure

The Greening of PlasticThe future “Greening of Plastic” doesn’t stop with the efficient recycling a petroleum-based resource. Advances in science are forthcoming that will further revolutionize the way we manufacture and use plastic. The development of “organic plastics” or Polypropylene Carbonates (PPCs) is moving forward, and in the near future, plastics will be made from the combination of carbon dioxide and propylene oxide. This new product will perhaps eliminate the need for petroleum-based plastics altogether, while utilizing a largely unwanted and ecologically-harmful element. Whether transparent, flexible, or rigid, PPC is poised to become the revolutionary product of the plastic world, and in a few short years, can be mass-produced by the chemical giant BASF.

Take a look at a video at:

Plastic, no matter the source, will continue to be a major factor in improving the durability and energy efficiency of future green infrastructure. The continued use of recycled thermoplastic materials will undoubtedly result in significant reductions in the overall carbon footprint of infrastructure development around the world.

Urban Forestry and Psycho-Social Benefits

urban forestry and psycho social benefits

by Richard J. Magill, MLA, ASLA, LEED – Magill & Associates, Inc.

This is the fourth in a series of six articles that will explore the various interactions and outcomes that result from human contact with our urban forests. This article will investigate the impacts of our city forests on human psycho-social benefits.

“People and plants are entwined by threads that reach back to our earliest experiences, as individuals and as a species”.

Psychological Benefits
A widely accepted and influential theory by S. Kaplan (1995) called Attention Restoration Theory proposes that natural environments and vegetation can assist in the functioning of human attention. Kaplan theorizes that daily life includes tasks that require long periods of directed attention, and that the execution of these tasks can be enhanced by views of nature. Urban forests provide a restorative escape from the activities that require directed attention by allowing people to rest their minds and effortlessly contemplate their environment. Studies have shown that:

  • People with views of nature from their work environment as less frustrated, more patient, have greater enthusiasm for their job, better health, and overall have a generally higher life satisfaction than those without contact with nature.
  • Those without views of nature in the workplace complain 23 percent more often of illness than those with views of nature.
  • Urban forests have proven to help children with Attention Deficit Disorder (ADD). A study conducted in 2001 by the Human-Environment Research Laboratory (HERL) demonstrated that ADD symptoms are more manageable after activities in green settings, and that the more a child’s everyday environment includes contact with nature, the more manageable their ADD symptoms are in general.

Health Benefits
In addition to the psychological health benefits mentioned above, trees can also affect the physical health of a population. Kathleen Wolf at the Center for Urban Horticulture at the University of Washington has explored the idea that trees and parks can help urban dwellers to make better, more active choices about their routine activities. Ms. Wolf asserts that with an aesthetically pleasing urban forest, people are encouraged to walk in their neighborhoods during their daily activities or for recreation. This not only encourages physical activity which can help reduce obesity and weight-related diseases, but it also increases possibilities for healthy social interaction.

psycho social benefits of city forest

Other heat-related health problems, such as heat-stroke, dehydration and skin cancer are mitigated by the urban forest’s ability to moderate the temperatures created by the urban heat island. Trees can also help decrease respiratory ailments caused by air-borne pollutants by lowering pollution levels in urban environments.
Urban life can be extremely demanding often resulting in stress-related health issues. It is widely accepted that urban open spaces and parks can provide welcome relief from stress, allowing us to calm and cope, and ultimately recharge our ability to carry on.

Crime Reduction
The Human-Environment Research Laboratory has conducted multiple studies determining that trees can actually help reduce crime. Frances Kuo and William Sullivan, the two primary researchers at HERL, suggest that trees reduce crime in two important ways.

  • First, frequent encounters with nature can help to sooth violent temperaments. As discussed above, trees help to mitigate mental fatigue which can cause outbursts of anger and potential violence in some people. HERL studies have shown that residents living in areas with trees use more constructive methods to deal with conflict.
  • Second, trees deter crime by increasing surveillance on city streets. People tend to use spaces with trees more than they use treeless spaces. Vegetation on or adjacent to streets encourages more people to use the outdoor space, thereby defending the community from crime. There is an “implied surveillance” even if people do not frequently use the vegetated space because a well-groomed neighborhood indicates that the residents care about their home and community, signaling that an intruder could be noticed or confronted. In addition, people perceive neighborhoods with blighted streetscapes and unhealthy urban forests as threatening and dangerous. Therefore, healthy urban forests can significantly decrease feelings of fear and consequently reduce incidents of crime and violence.

Improved Community Interaction
According to HERL, a greater number of people use common spacers with trees than those without. People are also more inclined to spend time in common spaces as the number of trees populating those spaces rises, creating increased opportunities for positive community interaction. Furthermore, residents who actively participate in caring for trees and vegetation in outdoor common spaces are more likely to have strong social ties to their neighbors. The more residents socialize with their neighbors, the stronger the sense of community pride and identity. The urban forest provides neighborhoods with a unique and stimulating location for human social interaction.

psycho social benefits of urban forest

In a series of large-scale, highly controlled field studies (Kuo and Sullivan 2003), “greener” buildings and spaces were consistently characterized by better performance on a wide range of social ecosystem indicators. Trees and grass cover were linked with greater use of residential outdoor spaces by adults and children, healthier patterns of children’s outdoor activity, more social interaction among adults, healthier patterns of adult-child interaction and supervision, stronger social ties among adult residents, greater sense of safety and adjustment, lower levels of social disorder (such as graffiti), fewer property crimes, and fewer violent crimes. In other words, successful outdoor spaces are pivotal in the healthy social ecology of a community, and trees are a key element in creating effective outdoor spaces.

Next article: The Urban Forest and Health and Safety

Citygreen designs and manufactures innovative structural soil cells which provide un-compacted soil to provide valuable nutrients for trees and other plants, as well as support for pavements and roads. These soil cells are an effective way to promote a healthy urban forest, and ultimately, beneficial psycho-social interaction.

Exhibiting at The ISA Conference and Trade Show

Exhibiting at The ISA Conference and Trade ShowWe are delighted to announce we are going to be exhibiting at the ISA Conference and Trade Show promoting systems for establishing mature trees in urban areas.

AUGUST 3-7, 2013

The Citygreen StrataCell will be featured which is designed to highly advanced engineering specifications. StrataCell brings tree-root systems closer to pavement surfaces. Engineers have calculated that, with only 300mm of granular pavement depth, a StrataCell matrix can support maximum traffic loads.

Look out for our StrataCells in action.

We are on stand 135-137, please do come and say hello.

To access details on the ISA Conference and Trade show click here or register online.

Urban Forestry and Local Economies

Urban Forestry

By: Richard J. Magill, Magill & Associates, Inc.

This is the third in a series of six articles that will explore the various interactions and outcomes that result from human contact with our urban forests. This article will investigate the impacts of our city forests on local economies.

“A healthy urban forest is one the few capital investments that municipalities can make that will actually appreciate in value over time.

As urban forests flourish, they benefit local economies by: increasing property values, reducing healthcare costs associated with poor air quality, boosting energy savings, deferring street maintenance costs, increasing the economic stability of retail/commercial space, improving water quality, reducing stormwater runoff, and providing monetary value through marketable urban forest byproducts.

Urban Forest

Increased Property Values

It has been well-documented that there is a positive economic effect on properties that contain, or are adjacent to, urban forests and parks. Property values increase 8-20 percent when they are adjacent to well-landscaped streets, parks, or forested open space.

Also important to local city governments is the fact that much higher property taxes are assessed on properties with higher values due to the quality and proximity of the urban forest. Municipalities also benefit from higher sales taxes when these properties are sold.

Depending on the species, maturity, location and overall quality; individual properties that contain trees are valued 5-15 percent higher than comparable properties without trees, according to the Urban Forest Institute.

Commercial rental rates increase when trees and landscaping are present. According to The Center for Urban Horticulture at the University of Washington, rates for commercial property are approximately 7 percent higher when they are adjacent to, or contain elements of, the urban forest.

There are municipalities in the United States that have seen a more than 200% return on their investment in growing and maintaining their urban forests. An example of this level of financial return is documented in the: “Benefit-Cost Analysis of Fort Collins’ Municipal Forest”, written by Gregory McPherson, James Simpson, Paula Peper, Scott Maco and Qingfu Xiao of the Center for Urban Forestry Research, Southwest Station in 2003.

development of urban forest

Reduced Healthcare Costs

Trees can significantly decrease air pollution-related health problems in urban environments, thus decreasing the amount of money spent on health care. Urban forests also give municipalities the ability to comply with national and state standards for air pollution, which in turn saves them from having to allocate financial resources to other more expensive forms of air pollution mitigation.

In 1994 alone, the urban forest of New York City mitigated an estimated 2,007 tons of air pollution with an approximate value of 9.5 million dollars. (“A Snapshot of the Northeastern Forests”, Northeastern Area State and Private Forestry, October 2005)

Enhanced Energy Savings

With proper design considerations and minimal investment, a homeowner can reduce an energy bill by up to 25% by simply planting trees or large shrubs at key areas around the home. Tall deciduous vegetation placed on the south and west sides of a residence allows for a substantial decrease in heat buildup within the structure in summer and desirable solar gain during winter months, thus reducing energy consumption.

The LEED (Leadership in Energy and Environmental Design) standards that have been developed in recent years consider the planting of trees and other vegetation around residential and commercial developments vital to their core principle of improving the energy efficiency of our built environment. The application of the LEED principles ultimately leads to considerable financial savings.

Deferred Street Maintenance Costs

Streets that are constructed with asphalt are prone to fairly rapid deterioration when the sunlight is not mitigated by shade trees or other tall vegetation. Asphalt is made of a stone aggregate and an oil binder. When asphalt is exposed to heat the oil binder volatizes and leaves the stone aggregate susceptible to degradation by weather and vehicular traffic.

The Center for Urban Forestry has found that repaving can be deferred up to 10 years on a well-shaded street and up to 25 years on a heavily-shaded street.

The findings of a study called: “Effects of Street Trees Shade on Asphalt Concrete Pavement Performance” by Gregory McPherson and Jules Muchnick published in the Journal of Arboriculture indicates that shade from large trees reduced paving costs by 58% over a 30-year period.

Stability of Retail/Commercial Economic Environments

Kathleen Wolf of the University of Washington has extensively studied the positive effects of urban forests on the economic vitality and stability of businesses. Ms. Wolf definitively states that “urban trees improve economic stability of retail environments by attracting businesses and consumers.”

It stands to reason that generously landscaped areas (canopy trees included) adjacent to retail spaces tend to set a positive mood and point to overall quality, thereby attracting consumers and increasing their rate of return.

Consumers are willing to pay up to 11% more for goods and services in business districts with trees, compared with those without trees.

In a study, “Benefits of Trees in Urban Areas” by Katherine Alexander, it was found that retail consumers give a 30% higher rating to the quality of goods, and 80% higher amenity and comfort ratings for tree-lined commercial streets.

Stormwater Benefits and Water Quality

Stormwater Benefits and Water Quality

Trees and other landscaped areas benefit cities by reducing stormwater treatment and flood control costs by reducing runoff flows. Healthy plant roots aid in improving water quality through absorption of various pollutants in surface runoff.

The city of Santa Monica, California’s street and park trees intercepted over 51 million gallons of rainfall in 2002. Approximately $111,000 in stormwater treatment and flood control costs were avoided that year due to the presence of 29,299 urban trees.

The utilization of permeable pavements and tree pit surfaces for urban tree planting allows stormwater to flow to root zones more freely for absorption. In this manner, valuable water resources are utilized more efficiently and the cost of irrigation is substantially reduced if not eliminated.

Citygreen designs and manufactures innovative structural soil cells which provide un-compacted soil able to provide nutrients for the plants, as well as support pavements and roads. Soil cells also promote efficient stormwater management and improve water quality through increased permeability and filtration.

Marketable Forest Byproducts

There are numerous ways that cities can take economic advantage of inherent urban forest materials and associated byproducts.

Cities can make a profit by selling compromised urban trees as lumber for building materials. Many urban forests contain unique hardwoods that can be made into furniture and other consumer products. Hardwood tree species such as cherry, walnut, oak and ash are quite suitable for milling.

Excess wood from compromised trees and pruned materials can be used for firewood, thus discouraging people from heating their homes with expensive fossil fuel.

The biomass of the urban forest can be chipped and mulched for recycling into the soil. In this way, cities gain long-term value through improved plant vitality.

The economic advantages of the urban forest are quite clear and speak to an important symbiotic relationship between the health of urban plants and the health of local economies. Professional planners, urban foresters, designers, and elected officials are cognizant of this relationship, holding great promise for the future of a healthy and productive urban forest.

Next article: The Urban Forest and Social Interaction

The Urban Forest and Human Health and Safety

Human Health and Safety

By: Richard J. Magill, Magill & Associates, Inc.

This is the fifth in a series of six articles that will explore the various interactions and outcomes that result from human contact with our urban forests. This article will investigate the impacts of our city forests on human health and safety.

Although these subjects were touched on in a previous article (The Urban Forest and Psycho-Social Benefits), they are such important aspects of human interaction with the urban forest, further discussion of these issues is in order.

Human Health
The Urban Forest Mitigates Air Pollution

In possibly the most important study to date on the effect of urban forests on human health, recently published on-line (June 2013) by the journal Environmental Pollution, researchers with the U.S. Forest Service and the Davy Institute in Syracuse, New York estimated how much fine particulate matter is removed by trees in 10 U.S. cities; their impact on PM2.5 concentrations and associated values, and impacts on human health. Cities included in the study were Atlanta, Baltimore, Boston, Chicago, Los Angeles, Minneapolis, New York City, Philadelphia, San Francisco, and Syracuse, NY.

The entire study, “Modeled PM2.5 Removal by Trees in Ten U.S. Cities and Associated Health Effects,” is available at: This is the first effort to estimate the overall impact of a city’s urban forest on concentrations of fine particulate pollution (particulate matter less than 2.5 microns, or PM2.5). Fine particulate air pollution has serious health effects, including premature mortality, pulmonary inflammation, accelerated atherosclerosis, and altered cardiac functions.

Overall, the greatest effect of trees on reducing health impacts of PM2.5 occurred in New York due to its relatively large human population and the trees’ moderately high removal rate and reduction in pollution concentration. The greatest overall removal by trees was in Atlanta due to its relatively high percent tree cover and PM2.5 concentrations.

The study found that urban trees and forests are saving an average of one life every year per city. In New York City, trees save an average of eight lives every year.

human health in urban environtment

The Urban Forest Promotes Physical Activity

Kathleen Wolf at the Center for Urban Horticulture at the University of Washington has explored the idea that trees and parks can help urban dwellers to make better, more active choices about their routine activities. Ms. Wolf asserts that with an aesthetically pleasing urban forest, people are encouraged to walk in their neighborhoods during their daily activities or for recreation. This not only encourages physical activity which can help reduce obesity and weight-related diseases, but it also increases possibilities for healthy social interaction.
Urban life can be extremely demanding often resulting in stress-related health issues. It is widely accepted that urban open spaces and parks can provide welcome relief from stress, allowing us to calm and cope, and ultimately recharge and improve overall physical health.

The Urban Forest Mitigates Other Health Issues

Other heat-related health problems, such as heat-stroke, dehydration and skin cancer are mitigated by the urban forest’s ability to moderate the temperatures created by the urban heat island.

Urban Trees

Human Safety
The Urban Forest and Road Safety

  • Speed Reduction- It has been proven over many years of observation that tree-lined roadways provide “spatial definition” that makes the road appear to be narrower; therefore encouraging slower driving speeds.
  • Stress Reduction- the psychological effect of trees along roads tends to reduce the occurrence of road rage and also improves the attention span of drivers.
  • Physical Buffers- Vegetation can provide an effective barrier between opposing vehicular traffic, and between adjacent public spaces and pedestrian ways.
  • Unwanted Obstacles- traditional road planning and design guidelines identify “clear zones” where no large objects should be allowed. Trees and other vegetation planted in these “zones” are thought of as hazards to visibility and vehicular safety. While there are certainly situations where this is absolutely true, often these guidelines are too strictly defined and applied. There are many instances where proper landscape design and plant selection would allow for trees or shrubs in or adjacent to these areas without compromising safety.

Human Health and Safety in City

The Urban Forest Promotes Neighborhood Security

It is widely known that urban green spaces provide many opportunities for casual social interaction and are key to the development of strong social ties. Research has indicated that neighbors who have strong social ties form more effective social groups (e.g., Greenbaum 1982; Warren 1981). Further findings suggest that residents of greener buildings feel more comfortable or adjusted in their surroundings in general. If strong social ties among neighbors are key to creating more effective, safer neighborhoods, and treed spaces help promote ties among neighbors, the presence of trees in the neighborhood landscape positively affects levels of safety and security.

Next article: The Urban Forest and Urban Planning and Policy

Citygreen® designs and manufactures innovative structural soil cells which provide un-compacted soil to provide valuable nutrients for trees and other plants, as well as support for pavements and roads. These soil cells are a proven and effective way to promote a healthy urban forest, and ultimately enhance the health and safety of residents.

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