Naomi Zürcher – Arbor Aegis

Urban Forester and Consulting Arborist

Urban green

Naomi Zürcher is a practicing Urban Forester and Consulting Arborist, with over 4 decades of professional experience in her native New York and now in Switzerland as well. Her work has spanned the full range of Urban Forestry planning and management, covering both practice and applied research. She’s been active as a program manager, guest lecturer, invited (co-)author and an affiliate member of the i-Tree team as well as other international networks.

1. In your words, what is Urban Forestry, what is it meant to achieve, and why is it important?

In order to discuss Urban Forestry, we need to first understand what the Urban Forest is. I have defined it as follows:

Urban Forests are ecosystems characterized by the presence of trees and related flora, funga and fauna, the soils and landscapes they populate and the air and water resource they coexist with, all in a dynamic association with people and their human settlements. (Zürcher, 2022. p. 22)

Urban Forestry is a specialized branch of forestry. It is the melding of a forest ecology foundation and an interdisciplinary expression of art, science, theory and practice with the highly knowledgeable and creatively intuitive development and implementation of a Management Plan.

Urban Forestry’s mission – the ecologically sustainable planning and management of the Urban Forest ecosystem, as defined above, for the sustained health and well-being of ALL animate and inanimate elements within the ecosystem.

Comprehensive Urban Forest Management criteria for trees in city streets as well as open landscapes must include:

  • a GPS / GIS ground-based complete tree inventory combined with an Ecosystem Services valuation assessment ((Ed. Note: GIS stands for Geographical Information System, a type of software where data is linked to maps and exact geographic coordinates; GPS stands for Global Positioning System, a network of satellites in orbit around Earth that enables accurate positions markings)
  • planning and design, including a focus on reducing the extent of impervious surfaces and sealed soil and improving the soil food web. The food web is comprised of microbial and invertebrate communities that perform cycling and recycling of organic matter and create the living soil organism as well as a functioning soil environment that supports the wood wide web – a mycorrhizal fungal network;
  • site selection and preparation, based on forest ecosystem criteria – trees’ forest genetic-driven essential needs;
  • tree selection based on planting site analysis combined with Best Management Practices (BMPs) criteria, ensuring that selected trees are healthy, true to species-specific architecture and nursery cultural practices that impact well-being have been addressed, e.g. soil piled up against the tree’s trunk;
  • planting and establishment procedures based on current BMPs;
  • arboricultural BMP-based tree care including pruning, risk assessment and removals;
  • protection, preservation and retention of the urban ecosystem resource, especially trees and the soils and landscapes they populate; 
  • the development, adoption and implementation of “Building WITH Trees“ protocols, procedures and specifications, especially as they relate to infrastructure conflicts: construction projects, sidewalk repair, street reconstruction…;
  • culturally-inspired citizen science participatory programs and informed stewardship opportunities that connect citizens with professionals and incorporate informed actionable participation in all appropriate aspects of management.
2. In your book Connecting Trees with people (p38) you wrote “You can take the tree out of the forest, but you can never take the forest out of the tree”, to highlight how we need to understand the biology of trees, if we want them to thrive in the urban environment. What is special – and challenging – about trees in cities?

We can never forget that our urban trees remain forest trees. Yes, they are urban tolerant but they still require accommodation of the basic needs that support the metabolic processes and resulting functions. All too often, those who plan and design our streetscapes see our trees just as the ornaments between the buildings rather than the life between the buildings.

They rarely invite those who speak tree to the planning and design table and so the essential needs are rarely addressed, resulting in early decline, premature death as well as the increased maintenance that can never resolve the issues that deficient planning, selection, planting and establishment create. In addition, by NOT adapting the planting site so it can accommodate large canopy trees, we are undermining the ecosystem services that only a large maturing tree can deliver. The greatest challenge to growing that urban tolerant forest tree well into maturity is a lack of an adequate, accessible volume of living soil which must be dealt with during planning and site design.

Photo of Urban Tree
Urban Tree Platanus x hybrida – Carouge 07.2017. Credit N. Zürcher
Photo of Urban Tree
Urban Tree Platanus x hybrida @ Ave Henri Dunant Geneva- 07.17. Credit N. Zürcher
3. You have worked as an Urban Forester and a Consulting Arborist for many decades and in different countries. Since you’ve been active in this field, how much do you think that our perspective on trees and the way we integrate them in the cityscape has changed?

Not as much as the body of knowledge would suggest. For example, my professions do not exist here in Switzerland and although there is a Continuing Education program, the in-depth aspects that make up the Best Management Practice (BMP) toolbox of an Urban Forest practitioner are only briefly touched upon.

Trees wear everything that they have experienced, including everything we do to them. If you speak tree, you can read the story. Within the built environment, the story is rarely a happy one. The unwillingness of Administrators, Planners, Architects, Landscape Architects and Designers to share the “control” table and include those of us who speak tree is short-sighted and undermines our ability to sustain that life between the buildings. The unprofessional and uninformed excuses that “it costs too much” or “takes too much time” ignore the avoided costs of increased maintenance that must be performed by Departments that are traditionally underfunded and understaffed, as well as the resulting waste of the tree resource.

4. Interestingly, you argue that placing trees in cities should be seen as building a new form of human-nature ecosystem. (This overlaps with the current notions of green or green-blue infrastructure, but seems to be more tree-oriented). What are the main challenges you see, and where do you think we should focus our efforts? Are there any “low-hanging fruits”, solutions that can be implemented easily, and quickly bring a positive effect?

The current thoughts on creating or improving our green and blue resources (as opposed to infrastructure, which implies a man-made construct, which trees, soil and water resources are not) is well-meaning but again, if those of us who fully understand trees or soil or water in their natural context are not part of the dialogue, the resulting initiatives can be counter-productive. We have a body of research-based knowledge, developed over 5+ decades, that offers viable strategies on how to ecologically incorporate green and blue resources into urban areas, but that requires having that informed voice at the Planning table.

5. What are the most fascinating aspects of Urban Forestry for you? Are there any lessons that you would like to highlight?

The most fascinating aspect is just how much trees have taught me about life and about living it, regardless of species, about self-management and what it means to bear witness. In observing how they function and how they respond to challenges imposed on them, not only by humans but also by the environment they find themselves in, I have learned how to adapt my observations and the support decisions those observations instigate to tree time – the patience to allow the tree’s own capacities for self-management to be realized.

Luzern has a wonderful historic Linden / Lindenbaum – a Tilia platyphyllos – that has graced one of the entries to the Vierwaldstättersee Promenade since 1880. In 2008, a large section of the 120+ year old, legally protected Linden’s structural and fine roots were severely damaged as a result of a construction project that introduced an array of underground installations – gas lines, electric lines, water lines, a sewage inlet from a docked tourist boat and an advertisement kiosk. In addition, the passing years saw the Linden’s root zone used for storing bicycles, motorbikes, dozens of Christmas trees, as well as Stadtgärtnerei service vehicles that would drive through the critical root zone, completely compacting the soil and causing further damage to the roots and thus the entire tree. Needless to say, it was in severe decline. Because the damaged roots were not able to get enough water into the upper crown, there was extensive dieback and, as a result of pruning cuts made to this section of the crown, the Linden developed a saprophytic fungal disease where those cuts were made.

ALL of the damage and its outcome were the result of a legally protected tree being unprotected during invasive construction installations combined with turning the soil into an entirely compacted impervious surface, covered with Chaussierung – a landscape fabric that loses its permeability over time, thus excluding essential oxygen and moisture exchange, topped with little stones, instead of an organic layer that would feed the soil and thus the tree. This tree was mismanaged into its decline.

My own experienced observations led me to determine what I could do to help this Linden help herself. The root invigoration / soil restoration project I designed and oversaw has given this now 143+ year old Linden a new lease on life. She has compensated for the loss of sections of the crown with adventitious growth along her trunk which was only possible because there was now a living soil environment that was supporting root zone metabolic processes and resulting tree functions. Her leaf area has increased and the leaf color is excellent. The instructions for managing any deadwood demanded that any cuts remain within deadwood so as to not create new wounds which would increase the fungal disease.

6. Your book takes us through the discussion, planning and implementation process, and carefully assesses several real-life examples in different countries for each step. Public participation seems to be a crucial aspect, as you have gathered from direct experience. What are the key elements for you? Do you think that the dynamics between public and private entities has changed in significant ways?

Given that I am working within the Urban Forest, I approach its management from the understanding that the Urban Forest belongs to everyone. We are all part of that urban ecosystem and we are all an essential ingredient in its planning and management from an INFORMED perspective. In addition, as I stated in my book: “…we need to establish that the Urban Forest we are discussing should not begin somewhere out there – a place somewhere distant where we can go to seek respite from our urbanity. This statement is not intended to diminish the incredible value of forests or other aspects of the natural environment or suggest that we should not enjoy these spaces passively and with respect for all the residents. The protection and preservation of naturally-occurring ecosystems is critical to the existence of Planet Earth and all her inhabitants. But, many of us do not have the capability or the financial means to access the magical green spaces and places that are out there. Since the Urban Forest belongs to everyone, it should be for everyone, beginning with the place we call home. Our streets should be places you go to, not places you go through on the way to someplace else to find that respite. The Urban Forest needs to begin at every person’s doorstep, in every person’s neighborhood, as a vibrant part of our community. And, just as we make decisions about our home’s interior, we might think of what’s just beyond the door as our home’s exterior, but our home none-the-less, for isn’t that what a neighborhood is?

Why is an informed participatory approach to management so essential? The proof is always in the pudding and, if we walk around any City with informed eyes, we can see that our urban trees are struggling and suffering and rarely thriving. Many of the Agencies and Departments that are tasked with maintaining the urban tree population are underfunded and understaffed and the voice that speaks tree and should be at the Planning and Design table is rarely invited which instigates many of the maintenance demands down the road. An informed citizen constituency can often make the essential difference. Urban tree adoption initiatives often focus their care on the open soil around the curbside tree that’s been planted in the cut out in the pavement, often referred to as a tree pit. Such informed citizen initiatives have also resulted in the expansion of that open soil area, all of which provides a healthier growing environment, resulting in a healthier tree that requires less maintenance. The key ingredients – information, knowledge and the willingness on the part of the tree experts to share in a digestible manner. That sharing results in a greatly increased set of informed eyes that can intervene in abusive construction projects, offer community-based input in the Planning phase for neighborhood projects that include spatial development within treed landscapes, tree planting locations and selection, stormwater management installations and beyond. It also instigates tree advocacy at the grassroots level that can mitigate poor political decisions that undermine the green / blue resource.

Your question as to has it changed??? Unfortunately, not enough. Many of the Agencies charged with care see citizen involvement as more of a hindrance rather than a help. They have not grasped how much they need those informed helping hands, eyes and voices.

7. You’ve worked and lived in New York and now in Switzerland. How does the practice of Urban Forestry compare between both countries, particularly regarding the engagement of citizens and the role played by private actors? Any suggestions for improvement?

Since the 5+ decades of Urban Forestry research and the resulting Standards and Best Management Practices are not taught and do not exist here, Urban Forestry as a practice does not really exist. I am somewhat of an anomaly – a fact that I have been trying to change since 2014 when I was first introduced to Forestry professionals who were interested but also curious.

In addition, Swiss citizen participation here in Switzerland has some added complications. Many Swiss people feel they are paying the Agencies and Departments to do the work, so why should a citizen do the job of the person they are paying? I see the solution from a few different perspectives. First, many Swiss citizens like to garden, either on their own property, as a renter of a Schrebergarten space, an allotment garden or a participant in a Community Garden project. That would definitely be a way of engaging and sharing knowledge about how to best garden within a treed landscape – why trees are important, what makes a tree a tree and what trees need to actually be the tree they were meant to be . This can be accomplished through the Municipal Agency’s website or even better, through a weekly how-to or FYI “timely tips” column in the local newspaper.

The minute we are willing to engage with citizens, we begin to establish connective tissue that can lead to greater involvement. What is critical is that the strategies that are used to develop any of these programs have a cultural basis combined with a genuine interest in improving the environment for one and all.

8. Looking back, what is your fondest memory from your work? Which project do you think has had a greater impact (why)?

I really treasured my interactions with the concerned Public in NY City. Many disenfranchised NYC communities had a genuine interest in improving their living conditions, not just inside their residence but throughout their neighbourhoods. They readily welcomed my experienced helping thoughts and hands to assist their inspired ideas that were always offered as a “we” could do this or that.

That love of trees interest was profoundly evidenced during the Asian Longhorned Beetle (ALB) infestation, starting with the initial sighting of ALB by Mr. Ingram Carter, a Greenpoint Brooklyn resident. Mr. Carter was concerned that someone was vandalizing the Norway Maple street tree planted in front of his house, by drilling holes along the trunk. His decision to play sleuth resulted in the discovery, not of a who but a what and his capture of this very exotic, highly invasive wood-boring insect. Mr. Carter’s discovery of ALB “…was the opening salvo in a very long, protracted war against an insect that globalized its way from Asia to the US, Canada and Europe in untreated wooden pallets with a host list consisting of almost every urban-tolerant tree species. With thousands of infested trees being removed from NYC’s Urban Forest, it became painfully clear that this problem could not be addressed without additional informed eyes. I proposed and was awarded Federal funding to develop an ALB Public Outreach Program for NYC’s residents. The program intent: to inform all NYC residents about ALB and how they could help – the short-term, crisis-driven goal.

ALB Project in New York
Sample of materials from ALB project in New York. Credit: N. Zürcher

But also, to turn the disaster into a positive long-term benefit – to foster a real tree awareness and sense of stewardship. Rather than survey the entire City’s trees for ALB, I was hoping instead to grow the existing tree – people relationship, the one that already existed between people and the trees they were intimate with – to have them observe the tree that lived in front of the house where they lived, the trees they passed every day on their way to work, or walking the dog or going to the supermarket. Their trees!!!

The diverse, extensive program that I had developed was devised to address as broad a base as possible. It’s delivery was made possible with the help of a wonderful team of partners from Federal and State government agencies, not-for-profit institutions, local elected officials, and the private sector…” and included:

  • A train-the-trainer program using a Beetle Buster Toolbox presentation kit;
  • A Living & Working in an Asian Longhorned Beetle Quarantine Zone brochure that was distributed via Federal, State and Local Government Agencies and as a bill stuffer by Con Edison, NYC’s primary electric utility reaching millions of NYC households;
  • An all-day Battling the Beetle: How to stop your neighborhood tree terminator conference for professionals and citizens from quarantine zones, funded and hosted by Con Edison;
  • A published resource entitled Suggested Woody Substitutes for ALB for Landscape Architects and Designers to facilitate their use of replacements for ALB host species;
  • A Beetle Buster Patch Program for Brownie, Junior, Cadette and Senior Girl Scout Troops – earned with Beetle Buster training, design and assembling of 25 ALB Preferred Host Herbaria for the 25 original Toolbox recipients plus ALB awareness activities in quarantined communities;
  • The Greenpoint Counts Trees Because Trees Count tree inventory involving trained local citizens along with Arborists who donated their professional time. The purpose of the inventory was to determine what tree species still existed within the Greenpoint Community, public and private, how many of each species, their condition (professionally rated) as well as the number of available planting spaces for the replacement planting initiative.

The ALB NYC Public Outreach Program and its very modest funding trained over three thousand people and, through its varied activities, connected directly with tens of thousands of residents. The Con Edison bill stuffer mailing reached millions of NYC dwellers, all through donated services. People retained the ALB brochure for years after ALB was no longer in the headlines and would often call me with tree concerns or questions.

An important outcome of the local Community Board 1 Strategic Plan, was the development of a community-based educational endeavor including school curriculum. In addition, the partnerships and informed citizen connections that developed formed a basis for a collaboration that still exists today, realized through advocacy and taking ownership of our trees in their time of need. The Greenpoint community has exemplified that spirit of grassroots stewardship through the model Greenpoint Tree Corps program.

Disasters have the extraordinary potential to bring out the best in us. In times of crises, communities have a way of pulling together and lending a helping hand, especially in the face of natural disasters the likes of earthquakes, hurricanes and tornados. This has been no less true for disasters which have threatened our trees. It is tragic to see entire treed areas being devastated by some natural or unnatural occurrence, but it does not have to remain a tragedy. The negative can lay the groundwork for a massive stakeholder collaboration enabling partnerships and empowered communities.” (quotes from Zürcher 2022 book).

My work on the Asian Longhorned Beetle NYC Public Awareness Program exemplified the very best of us in relation to our urban trees.

Naomi’s Practice as her alter ego Arbor Aegis, named after the Roman goddess Diana’s “shield of protection” for the woodlands and forests she guarded, offers planning and management support for urban trees – rooted beings and their life partner, the soil – within the context of their association with humans and the built environment.
Examples of her Practice include: developing and implementing Urban & Community Forestry participatory management programs for youth and adults; the formulation and implementation of a “Building WITH Trees” ecological approach to spatial development, with corresponding Tree / Landscape Protection / Conservation specifications; oversight and enforcement work on the Design & Build teams of large Public Infrastructure projects.