Urban Children Need (Urban) Forests

This time we present a very special blog – a child’s perspective on urban forests! Find out what 5-year old Jan has to say about urban forests in this blog written down by Natalija Györek, initiator of the Slovenian Network of Forest Kindergartens and Schools.

I hope this contribution will not surprise you. It is not a scientific blog about urban forests, but it is true to life. It is about (urban) children – their journey into the world, their development, learning, and their view of the world around them. An urban forest should be a place they experience positively, because it is generous, encouraging, infinitely surprising and pleasing to the senses. It should be a world that invokes the memory of forests and nature, all the way from childhood to adulthood.

My name is Jan. I’m five years old. I live with my mum, dad and my younger brother in a big city called Ljubljana. Every day my mum and dad take me to a nearby kindergarten, where I play with my friends, go for many walks and have a good time. In kindergarten I like playing outside the most. I’m also very happy when teachers Marjeta and Tanja take us for a walk. I like climbing over fences, up the slide and climbing the trees, which are my favourite. But my teachers say we mustn’t climb the trees growing in playgrounds and in the city, because we could break the branches and hurt them. We’re also not allowed to tear leaves off trees, even though I sometimes want to put one in my pocket and show it to my mum. That’s probably why they’re closed in iron boxes, from which I can’t even pick the pebbles I love so much. Marjeta and Tanja also explained to us that these trees decorate our city and clean our air. But I don’t quite understand how trees can clean our air.

One day Marjeta and Tanja told us we were going for a walk to a nearby forest. That’s where the “real trees” grow, unlike the ones that are put in boxes. We took a bus to Rožnik Hill on the other side of the city. There’s a big urban forest there and children can get lost in it, but Marjeta and Tanja let us play there. Oh my, the things we did! We could climb over slippery stumps – I fell a few times, but I didn’t cry. With my friends, Tomaž and Peter, we drilled holes into the ground and hid behind bushes. You can hide so well in the forest that no one can find you. We found three snails and two spiders, which is as many as the fingers on one hand, and we just couldn’t stop looking at them. I might have been a little afraid of them, but I won’t tell that to anyone but my mum. We also built the best house out of forest sticks. Why do we find so many sticks in the forest, but there aren’t any in the city? Maybe adults pick them up at night.

I was happy to finally see real trees – the kind you can climb and no one gets angry. Marjeta and Tanja too came back from the forest in a good mood. That day we ate all the macaroni and quickly fell asleep.

When we came to the kindergarten the next day Marjeta and Tanja explained to us that from then on we would be visiting the forest on Rožnik Hill once a week and that we would become a forest kindergarten and join other kindergartens in the Network of Forest Kindergartens and Schools of Slovenia. I like that a lot. I like going to the forest because there we can get ourselves dirty and no one gets angry. I can’t wait for next week when we go to the forest again!

jan-edit 3 DSC04009

This blog was written down by Natalija Györek, founder of the Institute for Forest Pedagogics, on behalf of Jan and all the children.



Tracking Growth Conditions: Trees, Time and a Bullet

Good management of a city’s green infrastructure requires to be based on scientifically sound and statistically reliable information. As urban trees are coping with fast-changing and quite stressful conditions, it’s crucial to monitor these – find out how it’s done in the city of Ljubljana in this blog by Dr. Simon Poljanšek, Dr. Lena Marion and Dr. Saša Zavadlav.
Tree growth in urban areas is influenced by climate, nutrient and water availability, ecological conditions, air pollution and many other factors. Because different tree species have different abilities to adapt to fast changes in urban environment, we initiated a study on how trees, growing in the city of Ljubljana, cope with fast-changing environmental conditions.

Different tree species, growing in different micro-locations were sampled and their tree-ring widths and stable carbon isotope composition in leaf material and tree-rings analysed at the Dendrochronology Laboratory and Laboratory for Stable Isotopes of the Slovenian Forestry Institute. Stem disks of different trees, cut down for safety reasons, were collected by arboristic company Tisa. Also, electronic band dendrometers were used, allowing us to measure daily change with 0.01mm accuracy in girth of the selected trees.


Dendrochronological work

The first step was to build tree-ring width chronology for individual tree species and to compare these chronologies with existing ones of other or same species from surrounding non-urban regions. After each tree-ring is labelled with the year of growth, they were manually cut and further chemically treated to extract pure a-cellulose. This is a very important step when looking at stable carbon isotope composition of tree rings, because only from purified wood component a reliable climate signal can be extracted. After all, trees are exposed to various factors that might enhance or depress their growth, which eventually diminishes climate signal. The reasons can be many – insect attack followed by a viral disease, drought, air pollution, mechanical damage and so on.

Stable carbon isotopes

We also wanted to find out how space limitation, related to insufficient water accumulation near pavement and road surfaces, influences tree physiology. We examined bulk leaf and water soluble organic matter of maple, birch and hornbeam, growing in a non-limited location (lawn strips), 2-side limited location (between pavement and tarmac road) or 4-side limited location (on parking lots or narrow streets). The ratio between heavy and light carbon (13C/12C) is a very good tracer of drought stress. When trees experience it, they close stomata to prevent water loss, but at the same time the production of photosynthates is reduced. This results in narrower tree-rings and higher 13C/12C ratio.

Surprisingly, preliminary results on stable carbon isotope data and other eco-physiological measurements showed that trees, growing in most space-limited areas, are better coping with stress situations compared to trees growing in a non-limited space location. We assume this is related to the rate of photosynthesis of individual trees, however, further analysis will need to be taken.

The WWII, a bullet and a tree

During sample preparation of horse chestnut tree for tree-ring analysis, blade of the table saw cut straight through a bullet, hidden inside the sample. Comparing developed tree-ring chronology and tree-ring counting, we dated the shot back to spring/summer 1944. This is the time of German occupation of Ljubljana, and also the time when numerous arrests occurred at different places in Ljubljana, in one of which, this particular bullet, could be have been shot.

image description
A bullet inside a tree.

This blog post is authored by dendroclimatologist Dr. Simon Poljanšek, arborist Dr. Lena Marion and isotope biogeochemist Dr. Saša Zavadlav and is part of the #EFUF2016 blog competition.

Acknowledgements: We wish to thank STReESS COST Action: FP1106, and Ministry of Education, Science and Sport for funding the research, Ljubljana City municipality for cooperation in time of trees sampling, Ministry of Foreign Affairs for cooperation in electronic dendrometers measurements, Tisa d.o.o., arboristic company for helping collecting stem disks and National Forensic Laboratory Slovenia for inspecting and sharing the information on the bullet. Saša also acknowledges the funding of the EUFORINNO project (RegPot. No. 315982).

Does Money Grow on Trees After All?

How can a city benefit from trees? As calculated by Dan Burden, growing trees might be the best long-term investment for a city – a single street tree returns over 80,000 € of direct benefits in its lifetime. Here’s a quick look at some of the most prominent positions for hiring trees that research has thrown light upon so far.

  1. Trees increase property values

This is not surprising as trees create a tapestry of colour, fragrance and interesting form that changes throughout the year, screen unattractive views and soften the harsh contours of buildings. Trees help residential and commercial properties to rent more quickly and to have a higher occupancy rate. They can add up to 15 percent to residential property value and where the entire street is tree-lined, homes may be worth 25% more.

  1. Trees increase business and commercial activity

An abundant tree canopy can attract new residents, tourists and businesses into a neighbourhood. Studies show that people like to spend more time and money in districts with more trees. In addition, having offices with a view of nature and access to green areas during breaks translates into healthier, more productive and satisfied employees.

  1. Trees reduce energy expenditure

Strategically placed trees around a building can reduce summer cooling costs by as much as 30%, while in winter heating costs can be reduced by a similar percentage with the use of trees as windbreaks. A tree is a natural air conditioner and can produce the cooling effect of ten room-size, residential air conditioners operating 20 hours a day. Neighborhoods well-shaded with street trees can be up to 6-10 degrees cooler.

Urban trees provide many benefits for a city and its residents
  1. Trees reduce water management costs

Trees reduce stormwater management costs and produce better water quality. They act as natural water filters and prevent harmful land pollutants contained in the soil from getting into our waterways. They significantly slow the movement of stormwater, which lowers total runoff volume, soil erosion and flooding.

  1. Trees reduce costs for meeting regulatory pollution requirements

Trees contribute to meeting a city’s regulatory clean air requirements by capturing more than 60% of the particulate air pollution. They remove dust, particulates, absorb ozone, carbon monoxide, sulfur dioxide and other pollutants. Estimates show that over a 50-year lifetime, a tree provides more than 50,000 € worth of air pollution control. Trees also act as sound buffers and reduce noise pollution by absorbing and blocking more than 40% of urban noise.

  1. Trees reduce health care costs

Trees catch air pollutants that damage human lungs which enhances a community’s respiratory health and ameliorates respiratory problems, such as asthma. They provide protection against ozone-associated health issues. Studies show that hospital patients with a view of trees out their windows recover much faster and with fewer complications. Time spent in nature not only promotes greater physical activity, but also reduces stress, eye strain and lowers blood pressure.

  1. Trees increase security and strength of a community

Trees lower anxious and violent behaviour – the greener the neighbourhood, the lower the crime rate. In homes surronded by trees there is less domestic violence and child abuse than in barren conditions. Trees also create a physical barrier between the street and the sidewalk, keeping pedestrians, children and pets out of harm’s way. Urban nature creates popular meeting places, inviting citizens to spend time together relaxing, walking, jogging or playing. These activities encourage interaction, bring neighbours together and strengthen urban communities.

As shown, urban trees provide a wide array of solutions to a city’s welfare and resilience. A city with an abundance of trees is a rich, sociably stable, safe and healthy city.

Author: Anita Mašek, Slovenian Forestry Institute

Featured photo by star5112.

How safe are urban forests?

Urban forests and green spaces should be safe and calm places. But is this really so? Read more in this blog post by Ana Simčič, a forestry engineer from Slovenia.

Cities that are surrounded by forests and have more green areas provide more quality lifestyle for their citizens. Recreation in urban forests and other green areas is one of the most appreciated and desired forest services in urban area. Jogging, walking or just hanging out with friends in urban forests is popular spending of free time during afternoons and weekends. But where more people gather, it is more likely that there will be undesired impacts left. Unfortunately, those impacts are sometimes consequences of violence that is called vandalism. It is an action involving deliberate destruction or damaging public or private property. It is a common phenomenon in public places in cities but apparently it is also inevitable in urban forests. In most cases things that are attacked by vandals are sign boards, picnic places with benches and tables, bins and also plants. But it becomes scary when vandals decide to damage trees.

My aunt once said that she is afraid of forests, because they are dark quiet places, where you can run into strange people. I thought it was so funny and was thinking that forests are probably more afraid of us than we are afraid of them. And this is not that funny anymore. Forests can live without us, but we can’t live without them. So why should they be afraid of us?

Damaged wooden bench in urban forest of Crikvenica, Croatia (photo: Ana Simčič)

Vandalism is common in public areas during night or in places that are not so crowded during the day. The widespread popularity of outdoor team sports in green spaces offers many opportunities to improve health and fitness, build strong community links with young people, burn off excess energy, develop a sense of pride in physical skills and ability. It is a key element in the reduction of juvenile crime and vandalism. But still, urban forests are usually quiet, shaded and cover big areas so vandals have many locations to hide and do the damage. Unfortunately, trees are defenseless and can be an easy target for vandals. Whether the damage is caused by someone who is deliberately trying to kill a tree, or by lovers or taggers carving their initials into the bark, the end result is the same.

Damaged urban tree

Sensitive layers of tissue lie just under the bark of a tree. This area should be protected from wounding, since wounded tissue provide an opening for pathogens and result in tree diseases.

Vandalism leaves many consequences:

  1. Fear of crime. Crime, the fear of crime, disorder and anti-social behavior in green spaces are some of the things that worry people and discourage them from using those spaces for relaxation and recreation.
  2. Investors are discouraged from the investments in new infrastructure if there are problems with vandalism or if there are abandoned areas nearby.
  3. Urgent replacement costs of broken items.
  4. Ruined aesthetics of landscape. Damaged items will give us a feeling of abandoned and dangerous place.

Vandal behavior of just a few offenders may affect all visitors in urban forests and other green spaces. We all want to enjoy nature to release our everyday worries. When we come to forests our worries should be gone and not feeling even more stressed because of damaged surroundings and injured trees.

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




We put forest trees back into our urban landscapes, not the way they were before, not the way they have evolved to exist, but according to our needs and our designs. Find out more in this blog by Naomi Zürcher.

The topic Resilient Cities has prompted me to sit back and get analytical. Most of us know what a City is – the attributes as well as the downside. I have lived in a City for most of my entire life – 70 years mostly in New York but also Mexico City and now Luzern Switzerland. The 3 represent a good sampling of cities and diverse city life.

But, what about resilience? If one looks at the Oxford definition of resilience, one finds the following:

  1. the capacity to recover quickly from difficulties; toughness;
  2. the ability of a substance or object to spring back into shape; elasticity.

While I would never equate a city itself with resilience given all the layers of Governance, what a city does do is demand resilience from everything that resides within it. Envisioning a city’s residents, I can think of none that better represents the definition than the urban trees that reside in a city’s Urban Forest.

Historically, almost all of our urban trees originate in a Forest somewhere in the world. In order to understand the underpinnings of our urban trees and the extent of their resilience, we first have to understand the where and what they came from:

  • Forests are a Process of Succession, of Evolution.
  • Forests don’t happen in a day, a week, a year. They occur over millennia, beginning with the specific soils they populate.
  • Forests are a sophisticated, highly-developed community of trees and all their associates – other flora, fauna and, most importantly, soil containing a healthy soil microbial community, providing the nutrients, macro and micro, all associates in the Forest community depend on.
  • Forests evolve in direct relationship to their environment – temperature range, the soil’s pH and the availability of light and water will all dictate what is growing and where – edge or interior.
  • Although a Forest may consist of many different species of trees, space above ground is shared in competition while space below ground is shared in community.
  • Forest soil is always covered by plants, leaf litter or other organic Forest debris – a constant renewing and recycling of organic nutrient resources.
  • Trees grow with their root crown – their buttress roots – above the soil line; all parts of the tree that are covered with bark are always above the soil.

So, here are all these trees, growing in a Forest community somewhere and along we come!!!

43. Curbside trees cartoon
We plant our public trees into hardscape coffins.

First, we built roads inside the Forest creating new edges, introducing sunlight to the Forest floor, where it never was before. Then we cleared the land and evolved through cultivating it into urbanizing it. Now that most of us are living in cities, we’ve decided we want to put these Forest trees back into our urban landscapes, not the way they were before, not the way they have evolved to exist, but according to our needs and our designs:

  • When we plant inner Forest trees out in the landscape, the above ground competition is now gone and with it the space restriction on the spread of the tree’s branches, resulting in a much larger crown which, when not thought about before buying the tree, usually results in the wrong tree being planted in the wrong place – requiring either constant, excess pruning or the unnecessary and premature removal of the tree.
  • We plant trees out in the lawn ignoring the competition turf inflicts on trees, both above and below ground; as a heavy feeder, grass deprives trees’ roots of essential moisture and nutrients, thus impacting and reducing tree root development.
  • If we don’t plant our trees in lawn, then we plant them where the soil is bare and we leave it that way, diminishing the soil food web and leaving trees without the renewable nutrient resources they must have.
  • We use construction equipment to build a project within a treed landscape, not realizing what we are doing to the soil and those important absorbing roots found within the top 30cm of soil; construction activities on unprotected soil usually compacts the entire underground landscape, making it inhospitable for trees’ roots. Healthy soil contains pores for air and water. Compaction crushes the pores that hold air and water. Roots cannot live in soil that has no air or water so existing roots begin to die and new ones will not grow.
  • We plant our public trees into hardscape coffins in an inaccessible, inadequate soil volume and we expect those large canopy trees to thrive and provide all those wonderfully beneficial Ecosystem Services.
  • Because the landscape underground is out of sight, it’s usually out of mind, leading to trees being planted in impossible growing conditions – too deep, in the wrong type of soil, in compacted soil or in an inadequate amount of soil to support the tree’s rooting needs – and then we blame the tree or the nursery we bought the tree because it didn’t survive or do what we had expected.

The fact that our urban trees, given their genetics and evolution, have found ways to deal with everything our cities and the new, very dynamic associate – us – inflict on them, one could, without any hesitation, give them the resilience award of the century. They not only embody the very spirit of the word “resilience”, they endure.

It behooves us – scientists, researches, academics and practitioners – to afford the powers that be an enhanced understanding of what City life could be if we, in the midst of all our urban UN-naturalness, recognized that when you plant a tree, you begin an entire universe so why not begin it tree -positive and really create a Forest in a then resilient city.

Naomi Zürcher is an independent Consulting Arborist and Urban Forester as Arbor Aegis and is involved with the current COST Action GreenInUrbs  project.

Photo courtesy of the New Yorker Magazine.


The Secret Life Of Trees

Do trees have a secret life that we rarely think about? Find out in this blog by Astrid Hamm, a consultant in the fields of Urban Forestry and Urban Greening currently working in Germany.

Forests are communities of trees. Most people look at trees as woody plants that provide us with timber. Many people enjoy their recreational aspects, landscape aesthetics, and their positive influences on human health and well-being. In recent years, our professional focus has moved on to numerous ecosystem services and environmental benefits trees provide to our society, such as reducing air pollution and storm water attenuation.

We are Urban Forestry professionals – but do we really know enough about trees? Are there different aspects to trees and urban forests that we haven’t explored yet?

Trees are the second-largest, but above-ground largest living beings on earth. Do we ever consider that trees may be able to communicate and interact with each other? Do trees have a ‘social life’? Do they care for other trees? Is there such a thing as ‘sympathy’, preference or dislike among trees and tree species – is it possible that a tree “can’t smell” (= dislikes) another tree? Can trees pass on their ‘knowledge’ to others? Do they communicate with each other, or even with us? Is it possible for trees to interact, even though they are fixed to their location?

In his book “The Secret Life Of Trees” German Forester Peter Wohlleben writes about a wide variety of ‘out-of-the-ordinary’ research studies from all over the world, looking at trees from different perspectives. He describes the forest as a community where strong trees support weaker ‘community members’. Similar to human society, a natural forest seems to work along the principle ‘together we are strong’. According to various studies, trees interact and communicate with each other in several ways. They also take care of each other and look after their offspring, as well as nursing the ‘elderly’. If there are pest attacks or other dangers approaching, they will ‘warn’ other trees by releasing gaseous odors. Similar to humans, they don’t like to interact with just any other tree. So is there such a thing as “tree sympathy”? Do trees develop “feelings”, such as compassion, like and dislike?

Wohlleben wants us to acknowledge trees as living beings they are. He presents scientific findings in his own language, comprehensible for everyone. He passionately campaigns for a different – more humane – attitude towards trees as social ‘creatures’ with their own needs and requirements as members of a forest community.

So maybe Urban Foresters have to learn much more about ‘the secret life of trees’ beyond our current knowledge to effectively promote urban forests.

‘The Secret Life Of Trees’ will be translated into English in autumn 2016, after being a top ten bestseller in the category “non-fiction” in Germany 2015.

This book is an appeal to everyone that we can still learn a lot about and from trees.

Wohlleben Cover

This blog post is authored by Astrid Hamm and is a part of the #EFUF2016 blog competition. Join in to win a free conference package! Want to learn more about Astrid’s work? Visit her project Citybranching/Stadtverzwingungen!

Green Infrastructure: A Positive Development for Urban Forestry?

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

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

Urban Green Infrastructure

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

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

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

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

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

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

Featured photo by mpstudio123.

Is Urban Forestry a Risky Business?

Is urban forestry a risky business? Find out in this blog by the #EFUF2016 invited blogger, Prof. Dr. Cecil Konijnendijk van den Bosch, professor of urban forestry and editor-in-chief of the scientific journal Urban Forestry and Urban Greening.

Having been an urban forestry researcher for about two decades now, I have had the pleasure to attend many different conferences and seminars across the globe. Not all of them are as good and rewarding as the annual European Forum on Urban Forestry, obviously, but there is always something one learns and takes home.

During the last week I was at the 2nd Urban Tree Diversity congress in Melbourne, Australia. Over 300 participants discussed the many aspects of tree diversity, from selection and resistance to pests and diseases to the diversity in links between people and trees. At the conference we spoke, as always, of the many benefits of urban trees and urban woods. However, it struck me once again how we urban foresters sometimes tend to be almost ‘apologetic’ in terms of the risks associated with trees. In our research and practice we have often focused on minimising risks in terms of e.g. tree and branch failure. Many books and articles have been written about hazard trees, visual tree assessment, branch failure, storm damages, and so forth.

Is urban forestry a risky business? Photo: Brian Yap

At a seminar at the University of Sydney after the Melbourne conference, my Australian colleague Ian McKenzie raised this issue of our biases view on risk related to urban trees. Ian is somewhat of a ‘rare bird’, by the way, as he is both an arborist and a local politician. When he spoke of our problematic relation with risk, and the way other professions look at urban forestry primarily as a ‘risky business’ (or rather: a risk-minimising business), I realised that we urgently need to turn things around, in the minds of politicians, the public and other professionals, but also within our own field.

It is risky for a city NOT to have trees. When walking the streets of Sydney as well as many other cities, some streets can be scorching hot – and these are typically those streets without trees. Thus one is exposed to the risks of succumbing to heat and higher vulnerability to skin cancer in tree-less environments. City governments have the statutory obligation to provide us with basic infrastructure, clean water, safe roads, etc. They are also responsible for enhancing public health. So why should it not be seen as a duty for them to provide us with canopy-covered walkways and cycle routes, where threats to our health because of radiation, pollution, stress etc. are minimised?

Time for a paradigm shift, perhaps? Something to discuss at the upcoming European Forum on Urban Forestry, in Europe’s Green Capital of Ljubljana. The overall theme of the Forum fits well, as we will discuss the contributions of urban forests to resilient cities. To me, resilient cities are also vibrant and healthy cities, offering safe and attractive places for people of all ages to live, work and play. Resilient cities are also cities where the small risks of trees or branches falling and hitting someone are far outweighed by the crucial benefits of trees. Urban forestry is not a risky business, it’s a pure necessity.

Author: Cecil Konijnendijk van den Bosch, PhD

Featured photo by Brian Yap.