Urban Trees: Barriers to Change

I have recently written about the benefits of street trees and how they can be planted without causing conflict. Street trees fit within the broader category of ‘urban trees’ which can also be located in parks, public gardens, urban woodlands, schools, church yards, and many other public spaces, not to mention privately owned trees which present rather different challenges. Collectively, all the trees in and around urban areas can also be known as the ‘urban forest’. The benefits of urban trees are well documented – the Arboricultural Association provide a good summary here – so I will not bang on about it.

In this blog I would like to share my thoughts on what the barriers might be to effectively managing urban trees in the Isle of Man. As the main urban centre, I am mainly thinking of Douglas, but some of these barriers apply to other towns such as Ramsey, Peel and Port Erin.

The biggest issue, as I see it, is the highly fragmented nature of urban tree ownership and management. Let’s consider some of the organisations involved. DEFA’s estate is mostly rural but they do manage a few key urban-fringe woodlands. In Ramsey, one of these is now managed by the Manx Wildlife Trust. Being the owners of many local parks and amenity spaces, local authorities are a major stakeholder. The DoI is another major stakeholder, but the urban trees they are responsible for are split between two separate Divisions. The Highway Services Division is responsible for all the street trees and trees growing in roadside verges. The Public Estates and Housing Division is responsible for managing trees around our public buildings (e.g. schools, health centres, sports facilities).

Each of these bodies on its own is too small to be reasonably expected to have adequate skills and resources at its disposal for managing urban trees effectively.

These silos also mean there is no coordinated, strategic approach among stakeholders to manage urban trees. It’s also the reason there is no baseline data on urban tree canopy cover (see September 2022 blog post for further detail), or the species profile, age-structure and condition of our urban tree population. Without baseline data and a strategic approach, if it does occur, management will only ever be reactive, responding to issues as they emerge, rather than proactively planning and acting towards an improved urban forest. As well as making much better use of existing resources, adopted strategies and collaborative working are a way of securing new funding, as politicians (and their dreaded bean counters) start to realise that investment delivers tangible benefits. Strategic documents can also help to raise the profile of urban trees, generating public support and awareness.

The Isle of Man is not alone when it comes to having a lack of strategic oversight for urbans trees, however.  A recent research paper reported that only 41% of English Local Authorities (LAs) have a tree strategy, and this figure drops to 22% for rural areas. Interestingly, two-tier local authorities (e.g. overlapping county and district councils) were also found to be less likely to have a tree strategy. The author of the research suggests that this may be due to ambiguity over which level of local government is responsible for tree management. Is that what is happening here with our fragmented urban forest?

Perhaps not a ‘barrier’ as such, the planning system in the Isle of Man is also an issue. The Area Plan for the East failed to undertake an assessment of Green Infrastructure in and around our capital. The Strategic Plan also has very little to say about the importance of urban trees and what role development in urban areas plays in contributing to (or hindering!) the urban forest. If the Island is serious about promoting sustainable development, we need to get serious about our urban forests. Urban trees are an important tool for climate change adaptation; they help to lessen the impact of extreme weather events. Urban trees also help the local economy by attracting investment and creating favourable environments for retail and hospitality. In July 2022 I wrote about the poor results we are seeing from soft landscaping and tree planting associated with new developments, which shows, whether it’s a policy, development control or enforcement issue, something isn’t working.

The aforementioned research paper discusses the possibility of making tree strategies mandatory for LAs and setting a template through an (England and Wales) National Tree Strategy. This would be a positive step forward for the adjacent isle and, by setting an example, may make it easier to generate public and political interest in being more proactive about the management of our own urban trees. How degraded will our urban forests become though, if we wait for others to show us the way?

How to Survive on the Street (Street Trees Part II)

In my last blog post I championed a special type of tree: The Street Tree. A couple of people pointed out that if we planted trees in our streets, they are likely to get too big and cause nuisance issues and damage our infrastructure. The planting of any street tree which caused such issues could not be deemed a success. Street trees need to thrive in the urban environment without causing damage to surrounding infrastructure, and without causing conflict with neighbours or users of the highway. How can this be achieved?

To answer this question it is helpful to think about what a tree needs to thrive in the urban environment.

Firstly, all temperate trees need soil. They need sufficient soil volume relative to their size and leaf area. The soil needs to be well structured, to allow water and air to flow through it. Most roots need air to survive. The soil should be able to supply all the nutrients that the tree needs.

Most people have never thought about soil in the urban environment. Why would you?! There is soil underneath our roads and pavements isn’t there? Isn’t there?? Well….yes (perhaps), but the structure of the road (the wearing course, base course and subbase) occupies the space where the biologically active soil should be. If there is soil (‘subgrade’) beneath a road, it is likely to be compacted (lacking air) and poor quality.

Trees also need access to water. Water is essential for photosynthesis and nutrient transport. Fortunately groundwater is not often in short supply on our island, but extreme weather events are predicted to increase, so drought is something we need to think about. However, too much water is also bad because waterlogged soils are devoid of air.

When transplanting nursery trees to any location, it is important to provide the young tree with support until the roots get a chance to grow into the surrounding soil and provide sufficient anchorage. In an urban environment this can be challenging as tree stakes don’t look great, they create trip hazards and need to be maintained/removed at the appropriate time to avoid damaging the tree. Fortunately underground guying systems have been developed to provide ‘invisible’ support to newly planted trees.

It is a common misconception that tree roots grow deep into the ground. Due to the requirement for air (and gas exchange) most trees grow in the top 60cm of soil. For this reason trees naturally send their roots out close to the surface. If soil is available below a hard surface, trees often need a bit of encouragement to send their roots downwards but the roots will be quite happy there once they find it, as long as the soil remains aerated. ‘Root deflectors’ and ventilation pipes can be used for this purpose.

Here is an example of a modern ‘tree pit’, courtesy of GreenBlue Urban.

So far, we have thought about how a tree may be nurtured to prevent it becoming a troublemaker, but there is nature as well nature to consider in this noble endeavour. As well as providing a tree with a suitable rooting environment, we also need to think about the species of tree we plant. Every planting opportunity presents a different set of constraints, and every species available at the tree nursery has different characteristics. We must ensure that the right tree is planted in the right place for the right reasons.

We should think about a tree’s mature height and canopy spread, for example. Reflected heat from hard surfaces, reduced water availability due to run-off from impermeable surfaces, and contamination from de-icing salts are just some of the physiological challenges that street trees may have to deal with, and some species cope better with these challenges. Trees with prominent surface roots (e.g. Cherry) can cause problems. Nuisance issues related to honeydew or rotting fruit are an important consideration. Shade can be beneficial but can also be viewed as a nuisance, so it’s important to think about the type and extent of shade the canopy will produce when in leaf. Getting all these factors right will reduce the likelihood of conflict occurring and reduce future pressure to remove trees.

If we can nail the nature and nurture factors, a street tree should be able to thrive in the urban environment without causing conflict, but we don’t live in a perfect world. There are many existing street trees that were planted without due consideration for the factors described above. This is where management becomes essential. For example, we can prune trees regularly to maintain their height or canopy spread. Where roots begin to disturb hard surfaces, we can repair and adapt the surfaces in a sensitive way. If seasonal fruit drop is causing a nuisance issue, then we can increase the street cleaning regime during that part of the year. There are many other innovative ways that these issues can be managed, if there is a desire to do so.

By thinking about the nature and nurture issues described above we can raise a new generation of street trees which thrive in our urban environment whilst causing minimal conflict issues. By thinking creatively and being mindful of the many benefits streets bring, as well as the damage that can be caused by a lack of management or poor management, we can reduce the nuisance impact of existing trees.

A Special Type of Tree

Trees don’t only belong in forests and woodlands. They can grow and thrive among us, in our gardens, streets and public spaces, if we help them. The special type of tree I would like to champion in this blog is not of a particular species or genus, it’s of a place: The ‘street tree’.

There is no widely accepted definition of a street tree, but what I mean by the term is a tree that is growing within a public highway, including the carriageway, footpath or verge.

Good street trees can do a lot for us:

  • They help to improve air quality due to the production of oxygen and filtering of air-borne pollutants.
  • They add character and beauty to our engineered streets and create a ‘sense of place’.
  • They improve human health and well-being.
  • They encourage biodiversity by providing habitats and food sources for a variety of creatures.
  • They increase property values and promote investment and economic development.
  • They can help us adapt to a changing climate.

We shouldn’t think of roads as just for getting from A to B. They are places where we live and work. Successfully integrating trees into the built environment is, however, a challenge. It requires a cross-disciplinary approach throughout a long process, from design to delivery, to years of maintenance.

There are very few examples of good street trees on the Isle of Man. By ‘good’, I mean a mature tree that is: thriving in the urban environment without causing damage to surrounding infrastructure, resulting in conflict with neighbouring home, business owners, or users of the highway; well managed so that benefits are maximised and disbenefits are minimised; and, well suited to its setting in terms of canopy size and character.

If you know of a good street tree on the Isle of Man, we would love to see it. You can send it to us by email (info@trees.im) or share it to our Facebook page: https://www.facebook.com/manxroots.

What is ‘Arboriculture’???

If you find yourself talking to someone you don’t know at a Christmas soiree, a common ice breaker you often hear is the innocent question ‘So, what do you do?’. My answer (an Arboricultural Consultant) often comes with a standard response and follow-up question: A what?! What’s that then?

So, what is arboriculture?

Dictionary.com defines arboriculture as the cultivation of trees and shrubs. That’s nice and simple, but maybe a bit too simple.

Wiktionary.org defines it as the branch of horticulture concerned with the planting, growth and maintenance of trees. I wonder if the pun was intended.  I would disagree that arboriculture is a subdivision of horticulture. This definition tells you a bit more about what might be involved, but nothing about the purpose of the endeavour.

The Collins Dictionary (collinsdictionary.com) defines arboriculture as the cultivation of trees or shrubs, esp for the production of timber. I would say that timber (wood) is more commonly a by-product than the purpose itself.

Merriam-webster.com goes with the cultivation of trees and shrubs especially for ornamental purposes. We’re getting closer, but what about managing trees for other purposes which don’t relate to aesthetical benefits, such wildlife conservation, heritage preservation and ecosystem services?

Modern arboriculture is obviously more difficult to define than I had first realised.

The main professional body for arboriculture in the British Isles, the Arboricultural Association, has recently defined the term as

The science and practice of the cultivation, establishment and management of amenity trees for the benefit of society.

‘Amenity trees’, in this context, means the trees that deliver environmental, social, and economic benefits for society. This inevitably means that arboriculturists are concerned with trees that are near people.

There are many different roles and careers which require knowledge in the field of arboriculture, including nursery workers, grounds maintenance staff, tree surgeons, (local government) tree officers, consultants, researchers, trainers, and policymakers.

There are close connections and links between arboriculture and other tree-related and environmental professions and disciplines, such as woodland management, forestry, horticulture and wildlife conservation. However, despite some overlaps, arboriculture is a profession in its own right, distinct in many ways from these other sectors.

Perhaps its easier to tell people that I’m a professional tree geek.