Why don’t trees grow well in cities?

In every city, around the world, you see trees that are not meeting their full potential within the urban environment. To the human eye, these trees can appear twisted or have damaged branches, making them unhealthy and deformed.

In serve cases, the trees will gradually decline and end up being removed, with just an open space in the pavement remaining.

Sadly, cutting down dying trees from city landscapes has become all too familiar, and is something we want to explore in this article.

Designing a Tree Planting Method

One of the first reasons for unsuccessful tree growth, in many cases, lies in the failure to fully design a tree planting method. The implementation of any successful method, must first ask questions surrounding the location of the site: what is the soil profile that the tree is being planted into; will there be enough air-filled porosity or oxygen at the depth of planting; does the location have the necessary space to provide for the tree’s root system?

These questions must then be answered by adopting appropriate solutions, such as: applying nutrients to amend the soil profile where necessary; choosing the best-sized tree to fit the location, avoiding having to repair tree root damage to pavements; utilising road-based material that is conducive to tree growth; installing adequate draining mechanisms, so that the tree does not become waterlogged in wet seasons.

Typically, the cities with a healthy and thriving urban forest today, have adopted a comprehensively designed tree planting method to overcome the problem of frequent tree deaths within city landscapes. However, if a tree planting method, like the one discussed above, cannot be fully funded, then tree growing failures in cities will continue to occur.

Tree Planting Budget

To allow trees to reach full maturity, and ideally become self-sufficient, a suitable budget must be allocated. Without a sufficient budget, cities will experience the premature deaths of trees, which will need replacement within 3-5 years of planting.

A well-funded tree planting program would avoid the cost of continual tree removal and replacements, and alternatively appreciate the future value of trees as an asset within any urban environment.

Human Behaviors

Another reason for trees not growing well in cities is human behavior.

This can be broken up into a number of areas, but one is vandalism. Unfortunately, it is not uncommon, to see trees vandalized, especially young trees. Once trees are beyond a certain stage of life, they tend to be less susceptible to vandalism, but while they’re young, they are very vulnerable to being damaged by vandals: debarking trunks; snapping branches; or scratching graffiti onto limbs

Traffic impact is another human behavior that negatively affects tree growth. This frequently occurs with curb plantings, whereby trees are planted close to the roadside. If crown lifting is not performed, and the trees develop a low canopy, then low-lying branches can be smashed and damaged by passing traffic. This is especially the case, where you see a camber on the road that causes tall vehicles to intersect with the tree’s canopy, causing limbs and branches to tear off, allowing infection to set in.

Low-speed vehicular impact in parking lots can similarly impact tree growth. This frequently happens in parking lots, where trees have been planted with the best intentions, but wheel stops have been either omitted or placed in the wrong positions.

For example, at home improvement centers, frequented by trade vehicles with overhanging tray bodies; reverse parking can lead to vehicles, unintentionally smashing into the young trees.  This can be overcome by studying the trees surrounding, to allow for better tree placement and tree protection.

An Altered Environment

The urban climate in which trees are planted can also lead to poor growth performance. Cities have their own microclimate, which is a very different environment to the natural forest. It is well documented that some tree species will actually grow a lot faster in a city than they will in their natural open forest environment, because of the urban heat island effect, leading to warmer temperatures and thus more growth.

However, in a lot of cases, the urban environment does not necessarily result in successful tree growth.  For example, wind velocities in city landscapes are very different to the natural forest environment.

In the forest, trees are protected by one another against environmental forces of nature, but in urban planting, trees are typically planted on their own, and therefore become more exposed.

Adding to this exposure is the fact that the trees are often planted in close proximity to tall buildings, where the street forms a canyon. Winds can then blast up this ‘canyon’ with extremely high velocity, blowing the trees around, causing damage to the root systems.

Oftentimes, the wind will cause a young tree’s root system to be weakened, which may only be noticeable when the tree becomes much larger, unfortunately resulting in limbs breakages, or a whole tree collapses, which can be catastrophic.

Solutions

Fortunately, there are solutions to all of these issues. Citygreen has decades of experience in successfully establishing urban forests to prevent premature tree death. A system that Citygreen has patented and used throughout the world with success is the Stratavault™ system.

 

Case Studies – Stratavault™ system

Downtown Ennis, located south of Dallas, in the United States, is known for its 19th-century historic architecture and iconic brick streets. With its current population of over 20,000, the city was looking to cultivate residential growth.

With this goal in mind, Citygreen’s Stratavault™ system was chosen the make the area more attractive, accessible and beneficial to downtown residents and tourists alike.

Adopting a ‘Green Streets’ approach, the areas impermeable curb and gutter section was replaced with a suspended paving system – that is, Citygreen’s Stratavault™ system, to allow trees to grow and thrive into maturity.

Capable of supporting heavy duty vehicular loading, permeable pavers were installed on top of soil cells which provided a medium for trees to grow in, whilst also capturing stormwater on-site to irrigate the trees.

Citygreen’s Stratavault™ was also utilised to enhance the redevelopment of Barangaroo South, in Sydney, Australia.

Designed to encourage both passive and active outdoor activities, the redevelopment of Barangaroo South’s landscape, initially faced significant difficulties. The density of paved areas and streets, was not able to provide a conducive environment for trees to thrive in.

To overcome this problem, Citygreen’s Stratavault™ was utilised. With its open matrix design, the system ensures that there is enough uncompacted soil space to facilitate strong root growth without damaging the surrounding paved surfaces.

Call us Today

As shown above, Citygreen is an expert in every phase of design, and implementation of streetscape upgrades, incorporating healthy, sustainable green infrastructure – reach out to Citygreen for a Design Workshop today.

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.

The Human Dimensions of Urban Forestry

By: Richard J. Magill, Magill & Associates, Inc.
The Human Dimensions of Urban Forestry

Introduction

This is the first in a series of six articles that will explore the various interactions and outcomes that result from human contact with our life-sustaining urban forests. These articles will explore the impacts of the urban forest on transportation, local economies, social interaction, health and safety, and urban planning and policy.

In order to better understand the impacts that our urban forests have on the human condition and conversely the effects that humans have on the forest, an introductory discussion about urban forests and urban forestry follows.

The Urban Forest

The Plants: Generally, urban forests are found in or adjacent to populated areas and are comprised of collective masses of trees, woody shrubs, annual and perennial flowers, and various types of grasses. Trees largely play the leading role in the urban forest ecosystem but certainly the other plant species play important supporting roles. Urban forests occur on both public and private lands and vary greatly in appearance. Some may be “remnant forests”: small groups of trees preserved during development that become important open space and greenbelts. Other sites are designed landscapes made up of a thoughtful composition of trees and other plants, typically found in urban parks, transitional areas (edges between different uses) and residential landscapes. Some forests thrive on undeveloped land and may be an unintended collection of plant volunteers and weedy vegetation. Even though each of the forests described above differ aesthetically and ecologically, it is widely known that trees and plants in all forms and settings provide critically important environmental benefits such as:

  • Sustainable Carbon Dioxide Exchange
  • Reduced Energy Use
  • Air Pollution Reduction
  • Storm Water Management
  • Water Quality Improvements

The People: The challenges that face our urban forest and its human inhabitants are vast and complex. The constraints of the forest include: limited space, soil quality, air quality, and the availability of adequate water and nutrients. These constraints significantly hinder healthy tree growth and therefore comprise the quality of life of the humans that live in urban areas.

There are many positive effects of a healthy urban forest on people, not the least of which are the psycho-social benefits. It is widely known that human interaction with nature:

  • Helps to Reduce Stress and Anxiety
  • Improves Medical Recovery and Convalescence
  • Contributes to Greater Job Satisfaction and Productivity
  • Promotes Healthy Social Interactions
  • Enhances Overall Quality of Life

Urban Forestry

The Human Dimensions of Urban Forestry
The continued health of the urban forest is largely dependent upon the contributions of urban foresters, elected officials and policy-makers, urban designers and planners, and citizen volunteers- including residential homeowners. Obviously, the people listed above are also beneficiaries of a healthy urban forest. Perhaps this is why the movement to promote and preserve our urban forest resources has gained so much momentum in recent years.

  • Urban Foresters: An exciting trend in recent years is the presence of urban foresters on the staff of city governments and local agencies. These trained professionals offer critical technical knowledge of plants and their benefit to the inhabitants of urban landscapes. Even smaller municipalities are realizing the advantages of having a qualified forester to advise them on policy and procedures. Urban foresters provide important advice to local elected officials and policy-makers so that they can make informed decisions.
  • Elected Officials and Policy-Makers: The responsibility to turn the latest technical information and the tide of public opinion into effective policy and working regulations is largely in the hands of this group. An increased awareness of the importance of a healthy forest in all types of human interactions in the urban environment needs to be supported and advanced by these trusted public servants, both in policy and action-based regulations.
  • Urban Planners: Most urban planners are well versed in the importance of a healthy urban forest on the human condition. In the modern world today, planners promote the establishment and/or conservation of public and private open space, greenbelts and conservation areas, both in public community master plans and through the review of private development proposals. These trained professionals utilize the technical knowledge provided by urban foresters, sociologists, landscape architects, biologists, soil scientists, engineers and other experts to provide a framework for sustainable growth and development.
  • Citizens: An abundance of citizen volunteers provides a sizable workforce for planting and maintaining trees and other plants in cities and towns around the world. Without these volunteers, the cost of healthy urban forests would often be prohibitive, especially for smaller municipalities. Residential homeowners are responsible for a large portion of the urban forest and every consideration should be offered to these “volunteer foresters”, including but not limited to advantages of availability and affordability of quality plants and planting supplies at local nurseries, and favorable landscaping regulations in local governments and homeowners associations. Through the continued diligence of the volunteers who plant, maintain and support the cause of trees and other plants will further promote the health of the urban forest and insure the aesthetic and functional qualities of this important ecosystem for future generations.
  • Green Industry: Last but by no means least, socially and environmentally responsible companies that produce innovative products to advance the quality and efficiency of the urban infrastructure are critical the future health of our city forests. Companies such as Citygreen® produce thoughtfully designed and manufactured landscape systems, above and below ground, that provide effective solutions to the complex demands of the urban environment.

Join us for the next article in this series The Urban Forest and Transportation.

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