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What’s the Magic Number? 31.4 Million.

To advance Tree Equity and help slow climate change, we need to plant 31.4 million trees annually in U.S. urban areas.

By Ian Leahy, American Forests’ Vice President of Urban Forestry

An urban neighborhood in Providence, Rhode Island with a tree canopy of just 9%. Photo Credit: Eben Dente / American Forests

Source: https://americanforests.medium.com/

The challenges of an urban street tree

By: Sylvia McNeill, ISA Board-Certified Master Arborist RM-7117B © 2021 McNeill’s Tree Service

Talk about a tough life.  Before I start on what could well end up being a rant, let me state:  there are no trees “native” to the built environment.

When discussing the built environment, we are referring to anything and everything created by people.  It is contrived and manipulated.  The complete antithesis to where trees naturally grow.  And yet we want, and indeed need, them in our proximity.  If you doubt that, simply go someplace where there are no trees or plants whatsoever and then transport yourself to a place with them.  If you prefer the area without, believe me, you are in the minority.

Our cities are “built environments”.  To our credit, we keep trying to incorporate trees and plants within these areas to provide some kind of respite from the harsh concrete climate.  Are we successful?  According to some studies, not so much, suggesting the typical street tree mean life expectancy is 19-28 years.  However, it is further suggested the tree population half-life is 13-20 years, meaning for every 100 trees planted, only half of those will make it to 13-20 years.  (Roman 2014)

With all our modern technology and innovations, we are having a hard time achieving longevity in our street trees within urban areas compared to cities of the past.   Here in our area of Montana, some of our cities have street trees that are over 80 years old, some even older.  But as they decline and have to be removed, their replacements are having a hard time establishing and surviving.  So, what gives?

Modern cities are far different from cities of the past.  In the past, streets tended to be wider and unpaved.  Rainfall would be absorbed by the entire street area and any tree planted near that street would likely be able to access that water.

Streets now are paved where stormwater drains may be designed to bypass roots.  One of the many ecosystem benefits touted for trees is their ability to mitigate stormwater runoff…if it is channelled away from their roots, how are they to perform this job?

There are often paved sidewalks on one side of a tree with the parking area and adjacent street on the other side, again all paved.  These areas between the sidewalk and street often referred to as boulevards, may be very narrow or very wide.  Trees fortunate enough to be planted in wide boulevards have a much better chance of survival.  The caveat here is “if the quality of soil is sufficient to their needs”.

A lovely Gleditsia triacanthos ‘Sunburst’ – Sunburst honeylocust planted in a wide boulevard

The quality of soil in boulevards can vary from not bad to really awful.  With the construction of surrounding infrastructure and housing, all manners of debris may be buried in this area.  This may include concrete, building debris, contaminants – basically, anything that needed disposed of during construction could have been tossed here.  It may be rocky, it may be silty.  It may be seriously compacted, which restricts root growth and water drainage.

Trees planted in the narrower boulevards are subject to conflicts with the sidewalk and streets as their roots grow.  As sidewalks require repair, roots are often cut to the detriment of water uptake or even stability of the tree itself.

Roots were severely cut back to enable sidewalk repair. Tree declined to a point where removal was mandated.

Sometimes trees are completely surrounded by concrete or grates may be used to distance the trunk from the concrete. Unfortunately, if the grates aren’t maintained, they can also damage the tree.

Photo on the left example of poor tree grate maintenance. Citygreen’s Duraplate tree grate (on the right) incorporates specifically designed features for easy maintenance.

Another challenge experienced by city street trees is the pruning required to keep them above vehicle and pedestrian traffic.   Merchants do not like their signage blocked and it is important to keep trees from blocking clear view triangles on street corners to ensure public safety.

Please remember, the trees did not plant themselves.  Very few are volunteers in these areas.  It is up to the people who plant them to select a species that is hardy enough to have a reasonable chance of survival in the site selected, that the site is actually suitable for a tree at all (some sites simply should not be planted), to ensure the tree has the potential structure to minimize pruning needs (which is a factor not only in the health of the tree but the expense for management), to ensure planting is done correctly and that aftercare is prearranged and committed.  These last two conditions are the most common reasons why trees do not survive the establishment period for any area, let alone for the challenges faced by street tree selections.

Additional challenges include damage by vehicles, vandalism, and extreme weather conditions enhanced by the infrastructure around them.  I often think trees survive in spite of us, not because of us.

These photos show the opposite sides of the same tree taken on the same day.

We need to work on being better stewards because we need trees.  There is no need to quantify “ecosystem benefits”.  All you have to do is remember without plants, we (humans) would not exist.

References: Roman, Lara A.  (2014) How Many Trees Are Enough?  Tree Death and the Urban Canopy.  Scenario 04:  Building the Urban Forest

How to promote deeper root growth and drought tolerance

Best Tree Root Development

Sufficient oxygen, water and nutrients are essential for healthy root growth and therefore healthy trees. If soil gets too wet, the voids between soil particles become filled with water and the root hairs cannot absorb oxygen. Over time the roots ‘drown’ which eventually may also kill the tree, through lack of the required water and nutrients.

The water from efficient tree irrigation is required not only for all the biochemical processes involved in photosynthesis, respiration and transport but also for mechanical support to leaf and stem tissue.  Insufficient (or inefficient) tree watering will result in loss of leaf turgor and a consequent reduction in new shoot extension. Eventually, this will lead to die-back and, if not remedied, the loss of the tree.

Oxygen may also be available at depth if the soil is not compacted and the action of earthworms has created tunnels through which oxygen can flow. Tree roots will grow near the surface unless adequate water and air are available below ground.

How does it work?

One method for providing both the necessary water and air to the tree roots involves the use of a perforated flexible piping system. At the time a tree is being planted, the pipe may be looped around the rootball within the immediate rooting zone of the new tree, and also in the outer rooting zone, looped throughout the root cell matrix. The pipe is then connected to an inlet located at the tree pit surface. This method may be adapted for use beside roadside verges and open space tree planting or in heavily trafficked areas.

The water inlet

The inlet enables a water hose to be attached when water is needed. The rest of the time the pipe, being looped in a circuit, allows air to flow passively through the system and around the roots of the tree. Changes in air pressure above ground are also accommodated. This arrangement enables long deep watering over the entire root system and the opportunity for the soil to dry between watering, which is better for trees than frequent light watering.

Snorkil™ RootRain

RootRain™ Urban is a large capacity irrigation system with a fixed non-removable grid inlet. The grid allows water and air through but prevents ingress of litter and debris.

Suited for: Roadside verge and open space tree planting. 

Snorkil™ Rondo & Plaza Series

Tree Pit Irrigation and AerationThe Snorkil™ Rondo (round inlet) and Snorkil™ Plaza (square inlet) series have been specially designed to interlock with our range of integrated tree grilles or be set in the pavement to provide an attractive and durable way of maintaining aeration for tree root systems. This provides a tamper-resistant system that will also prevent the inlet from sinking as a result of any soil settlement around the tree.

Suited for: Integrated tree grilles or to be set in the pavement.

The Top 10 Greenest Countries in the World

City interchange in xian, road junction at dusk, China

From widening wealth disparity to the environmental ramifications of economic development—the growing focus on global sustainability is a clear sign of the times.

Research reveals that when a sustainable ethos is applied to policy and business, it typically bodes well for economies and people alike. By providing benchmarks for those decisions, indexes like Yale’s Environmental Performance Index (EPI) can be critical to measuring national sustainability efforts.

Who’s the Greenest of them All?

Despite the decades-long trend of globalization, national environmental policies have proved to be widely divergent. The EPI report confirms that those policies—and their positive results—are highly correlated with national wealth.

This is evidenced in the global EPI distributions, seen below:

Scandinavian countries, which tend to have a high GDP per capita, show strong and consistent results across EPI parameters. Denmark for instance—which ranks first overall—leads the world in slowing its growth in CO2 emissions. Meanwhile, neighbour Sweden leads in landfill and recycling treatment, while wastewater treatment is led by a handful of countries within and beyond Scandinavia including Denmark, Finland, the Netherlands, Singapore, and Sweden.

In North America, Canada claims the top spot in the biodiversity and habitat category, while the U.S. ranks sixth in agricultural diversity globally. In Asia, Singapore leads the world in fishery health and sustainability.

Ultimately, it appears the world’s greenest countries tend to focus on all areas of sustainability, while laggard countries show more uneven performance across categories.

What Does “Green” Mean?

Each high-level performance indicator with the EPI, like “environmental health”, is broken into subsections. Nations are scored on each subsector on a scale up to 100. As a result, multiple countries can rank first in any given category.

By evaluating national sustainability on a scale that is unrelated to other nations, we get a clearer idea of comparative national progress, beyond a basic ranking.

For instance, 30 countries tie for first in marine protection, all with scores of 100. This shows that many economies are prioritizing this area of sustainability.

The Cost of Being Green

Infrastructure costs are one reason why wealthier nations tend to fare better across sustainability measures. Everything from air pollution reduction and water treatment, to hazardous waste control and mitigation of public health crises, are especially expensive—but have a huge potential impact on citizens.

This trend can be seen in the scatterplot, which demonstrates the distribution of economies evaluated by the EPI.

Post-Pandemic Outlook

Although some rankings can seem prosaic, indexes like the EPI provide a helpful benchmark for economies to compare efforts. It also allows governments to iterate and build upon environmental strategies and investments by highlighting what is and isn’t working.

CO2 emissions, for instance, are a major driver of climate change. Although the global economic stall has led to a temporary dip in CO2 emissions in early 2020 (a slower growth rate than the 11% expected to rise), global emissions still continue.

However, the EPI shows that investments have an impact. High-level sustainability efforts—political commitment, media coverage, regulations—can deliver results, even at the grassroots level.

For more detailed information visit the following link: visualcapitalist.com/greenest-countries-in-the-world/

Source: https://www.visualcapitalist.com/

Did you know Melbourne has an entire map dedicated to urban trees?

Melbourne urban trees

Did you know Melbourne has an entire map dedicated to urban trees?

Melbourne’s tree population is vast – we have 70,000 council-owned trees, worth around $650 million. Trees are a defining part of Melbourne and our parks, gardens, green spaces and tree-lined streets contribute enormously to the liveability of the city. ​

But the trees are now under threat. More than a decade of drought, severe water restrictions and periods of extreme heat, combined with an ageing tree stock, have put our trees under immense stress and many are now in a state of accelerated decline. As a result, we expect to lose 27 per cent of our current tree population in the next decade and 44 per cent in the next 20 years.

Combined with this loss, Melbourne’s urban forest is facing two significant future challenges: climate change and urban growth. The City of Melbourne’s Urban Forest Strategy seeks to manage this change and protect against future vulnerability by providing a robust strategic framework for the evolution and longevity of Melbourne’s urban forest.

The Urban Forest Visual is an interactive, online map that marks every single tree in Melbourne’s key urban areas. As well as naming the genus each tree belongs to, the map also lists details about each tree’s overall health and life expectancy. For example, the map shows many healthy London plane trees located near the State Library of Victoria. However, a few blocks down at the ‘Paris end’ of Collins Street, the London plane trees aren’t fairing as well.

You can use the map to look up tree data for the whole of the Melbourne CBD, as well as surrounding suburbs including Carlton, Docklands, Kensington, Parkville, Flemington and South Yarra. You can filter the map depending on whether you want to see street trees or park trees – and you can even email individual trees if you need to report something.

If you’re keen to see what the future holds for street trees in Melbourne, you can access a detailed tree planting schedule via the website. Each Urban Forest Precinct Plan includes a map showing when urban forest planting will occur in each street over the next 10 years. The tree planting roadmap shows when each street will be planted and what the scope of planting will be. In some streets, tree planting might be limited, while other streets may include intensive planting as part of a redevelopment project. Detail about the factors considered to develop the planting schedule is included in each local Precinct Plan.

Check out the tree planting schedule and find out everything you’ve always wanted to know about your favourite Melbourne street trees by visiting the Urban Forest Visual website.

Source: https://www.timeout.com/melbourne/news/fyi-theres-a-whole-map-of-melbourne-dedicated-to-the-citys-trees-100418

The “Greening” of Plastic – Recycled Thermoplastics and Green Infrastructure

Introduction

As practising “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.

What 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.

Why 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 the 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 grey 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

Green 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 installs 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 and Stratavault Systems may qualify your project for generous contributions toward LEED certifications, with recycled content being a high contributor. Contact info@citygreen.com for more information regarding their products and LEED credits.

Visit usgbc.org for more information and proposed changes to LEED rating systems.

The Future of Plastics and Green Infrastructure

The future “Greening of Plastic” doesn’t stop with the efficient recycling of 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.

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.

Can tree canopies help to offset increases in urban heat?

Transformation of an impervious parking lot site in Lawrenceburg, Indiana to a public green space providing a desirable amenity to the community, while also reducing UHI and stormwater run-off.

What is an Urban Heat Island?

An urban heat island occurs when a city experiences much warmer temperatures than in nearby rural areas. The difference in temperature between urban and less-developed rural areas has to do with how well the surfaces in each environment absorb and hold heat.

Why does this happen?

Urban Heat Island effect (UHI) is a very real challenge in cities -it’s recorded and documented that cities are heating up, becoming far hotter in some cases than any modern recording statistics available. Urban climates are distinguished by the balance between solar gain and heat lost from walls, roofs and ground; by heat exchange via air movement between ground, buildings and atmosphere; and by the generation of heat within the city itself (Earl et al, 2016).

The nature of urban materials and surfaces (hard, paved), land cover (lacking vegetation) and metabolism (waste heat from transport, industry and air conditioning) creates a significant temperature discrepancy between city and country –the abovementioned urban heat island (UHI) effect (Akbari et al, 2008).

Quality of urban life at risk

The combination of a warming climate, Urban Heat Island effect (UHI) and longer, hotter and more frequent heatwaves is having a growing impact on the quality of urban life, from simple low-grade misery to increased risk of death. Lack of vegetation cover is a defining feature of built-up urban areas. It is also a major contributor to the Urban Heat Island effect (UHI) effect through decreased evapotranspiration in cities. Vegetation facilitates Urban Heat Island effect (UHI) mitigation via evapotranspiration, shading and providing cooler surfaces to reduce mean radiant temperature (the ‘averaged’ effect of heat radiating from surrounding surfaces). Suitable species selection and planting design with taller vegetation – shrubs and trees – can also help channel cooling breezes to where they are needed. In addition, urban vegetation supports the combat of climate change by more effective stormwater management, improved air quality, biodiversity, urban ambience and energy-saving, often referred to as ‘co-benefits’.

How to reduce the urban heat island effect

  • Build green infrastructure improvements into regular street upgrades and capital improvement projects to ensure continued investment in heat-reducing practices throughout your community.
  • Planting trees and other vegetation—Space in urban areas might be limited, but integrating small green infrastructure practices into grassy or barren areas, vacant lots, and street rights-of-way can be easily done
  • City officials like the city of Cockburn in Western Australia, are starting to implement Urban Forest Plans to increase the tree canopy and help the city use trees to address urban heat, stormwater management, and other concerns. Read the article ‘The city of Cockburn is aiming to to increase streetscape shade with urban forest plan’ here.
    • Making traditional water quality practices serve double duty by adding trees in or around roadside planters and other green infiltration-based practices to boost roadside cooling and shading.
    • Transforming communities by planting native, drought-tolerant shade trees and smaller plants such as shrubs, grasses, and groundcover wherever possible.
  • Building green roofs—Green roofs are an ideal heat island reduction strategy, providing both direct and ambient cooling effects.  In addition, green roofs improve air quality by reducing the heat island effect and absorbing pollutants.

How to grow trees successfully on the street

Street trees have an incredibly tough life

The average life span of a tree is very short in many of the big cities. Some cities have an average replacement cycle of 10 to 11 years. Some cities it’s 14 years, but it’s very, very short considering that the natural lifespan of some of those tree species is close to a hundred years in the natural environment. This continuing replacement cycle constitutes a massive cost, as well as a huge lost opportunity cost.

Trees growing in typical urban ‘tree boxes’ are usually surrounded by compacted soil. This often leads to the roots seeking out the space between the compacted soil and the overlying pavement, where air and water are present, which then causes footpath heaving.

If the tree roots cannot expand into the surrounding soil, they continue to grow until they have filled up the available space.

When the tree’s needs for nutrients, air and water can no longer be met, the health of the tree will begin to decline and it will eventually die. Trees grown in these conditions rarely reach their full growth potential and cannot provide a wide range of benefits that mature, healthy trees have to offer.

Let’s get to the root of this problem

There are many parts to a tree. They’re a complex and finely balanced living organism, which all needs to be taken into consideration as part of the design process. So we cannot ignore the below-ground part of a tree when designing for its long-term requirements In its natural environment, a tree has a large horizontal root structure supporting the canopy.

The analogy of a wine glass on a large flat plate has been used, with the large flat base beneath the stem, with the structure above. Via the roots, trees obtain nutrients from the soil, but the roots also need the oxygen and water that occupy voids between soil particles. In uncompacted soil, voids are abundant.

The availability of space for tree roots to develop is crucial to the tree’s ability to grow and stay healthy. In the natural environment, the roots of a growing tree will extend far into the surrounding soil to more than twice the width of the mature tree’s canopy. Everybody has some experience of a neighbour’s tree roots impacting service or foundation, a long way from the tree itself

The conflict between tree growth, and built structures

However, typically, the engineering demands of paved structures make it impossible to grow trees in cities. Pavements require structural support, which historically is concrete, or crushed stone, or road base compacted efficiently, and the small opening in the pavement for the tree is not sufficient to support that large root plate (similar to wine glass on a flat plate)

For trees in hard-surfaced areas, a fundamental conflict exists between maximising the soil volume available for tree rooting while also providing a stable base for roads and pavements. If soil is treated as a structural material and required to bear the load of pedestrians, building and roadways, it will be consolidated to the point that air and water are excluded and insufficient space is available for roots to grow.

Trees planted using best practise, growing successfully in Melbourne Lonsdale Street, Dandenong, 2018

Trees planted using best practise, growing successfully in Melbourne Lonsdale Street, Dandenong, 2018

 Trees planted correctly 7 years ago, growing healthily in New South Wales | Laman Street, Newcastle, 2020.

Trees planted correctly 7 years ago, growing healthily in New South Wales | Laman Street, Newcastle, 2020.

Would you like to learn more? Download a free report about the comparison of soil treatments under pavements.

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