A Modern Fail of Beauty
“No town can fail of beauty, though its walks were gutters and its houses hovels, if venerable trees make magnificent colonnades along its streets.” (Henry Ward Beecher, Proverbs, 1887).
Trees have always been an essential part of our lives, we pass them every day yet we rarely stop to consider how important they are or the pressures they endure from the modern urban environment.
Trees provide us with many benefits, they soften the urban landscape, filter and provide us with clean air, they improve our feeling of wellbeing, they mitigate the excessive hot temperatures that can occur in our cities, they provide shelter and shade from wet weather conditions and absorb the water runoff reducing the burden on our civic drainage systems, they provide essential habitats for thousands of other creatures and they even increase the value of our property. (Sjöman and Busse Nielsen et al., 2014)
So as you can see, urban trees do a lot more for us than what many people might be aware of. There is a problem however, our town and city environments are highly engineered, making conditions hard for trees to survive in, this article aims to provide you with some insight into the challenge’s that of our urban trees face on a daily basis.
In Ireland the average annual temperature is around 9°C, the annual number of days with more than 1mm of rain varies between 150 in the drier parts and over 200 days in the wetter parts of the country (Met.ie, 2014).
Under the right conditions this should allow trees to flourish and have a natural life cycle of 50 plus years, however, according to Cornell University, the average life cycle of an urban tree is estimated to be in or around ten years.
Some of the reasons for this drastic change of life span is due to the environmental factors that the tree is situated within, urban trees have to contend with many different issues that threaten to shorten its life cycle, the following are just a few these examples.
“Highly exposed to heat, low air humidity, periods of critical water stress, high soil lime content and soil pH, limited soil volume, pollutants, and de-icing salts. Combined with the challenges of climate change and the threat of disease and pest infestations” (Sjöman and Busse Nielsen et al., 2010)
So why are our trees finding it so difficult to survive in our modern towns and cities when it is widely known that trees do not require high quality soils to flourish?
Cornell University has shown that trees can survive and grow in our cities if the right conditions are met. Trees need access to water, oxygen, nutrients and space for their root system, modern civic engineering practices do not account for this requirement and continuously install impervious surfaces such as concrete or asphalt on most surfaces to meet load bearing requirements.This in turn reduces the quantities of water, oxygen, nutrients and space that a tree requires for normal development.
“The best time to plant a tree was 20 years ago. The next best time is now.” ~ Chinese Proverb.
Another problem with the modern urban tree planting methods is, when a tree is planted, they are planted within a closed environment. A closed environment is where a tree is planted into a cell of concrete, plastic, compressed soil or some other impenetrable material. This eliminates the trees ability to expand their roots thus stunting their growth and as a result, this reduces their stability, life expectancy and the quantity of carbon that they can absorb. It also reduces a trees ability to mitigate storm water runoff which adds extra burden on storm water drainage systems.
Cornell University has been working on a number of solutions to this problem for more than a decade. Their research and development has resulted in a structured soil which they have named CU-Structural Tree Soil™.
CU-Soil is a root zone material that is made up of an angular stone with a loamy soil (or suitable soil) that is bound by a bio-gel. This material can be used in conjunction with a porous paving asphalt or resin bound stone paving system to create a water reservoir to help mitigate storm water and CU-Soil is fully compatible with SuDS requirements.
CU-Soil provides trees with the required quantities of water, oxygen, nutrients and space for the trees root system, this is accomplished by design. Spaces between the angular stone allow the tree roots to penetrate into the ground. This effectively eliminates the common heave effect while providing the engineers with the required load bearing requirements for urban planning.
The results and the benefits from using CU-Soil in the urban environment can be seen in the short term. Pavements are less likely to become cracked by tree roots, water can penetrate into the ground when used with a porous paving system and in cases of heavy flooding, storm water can be temporary stored in a low cost but effective water reservoir.
Trees can enjoy a full lifecycle, help absorb larger quantities of carbon dioxide, filter the air and provide shade which will mitigate the urban heat island effect. Trees planted with CU-Soil will increase house prices and provide peace of mind and vital habitats for the other life that enjoy living in the urban environment.
It is important that we provide the best urban greening solutions when building our towns and cities. As a species we need to reduce our footprint by utilising green walls, green roofs and technologies like CU-Soil™. Together we can create a truly green urban environment that fulfils us, and all life equally where we can be happy,healthy and productive in our lives.
“Trees outstrip most people in the extent and depth of their work for the public good.” (Sara Ebenreck, American Forests)