Trees and Development: harmonious co-existence

Keeping out the cold Feb 2018

I work with trees within the development design process. Where a potential development site, or a plot, has existing tree presence, that tree presence is always a material consideration in the Planning Process. There’s a point of view that argues the environmental value of every tree belongs to everyone – this concept also underpins the notion of Public Amenity – and that therefore strident efforts must be made by Public Administrations to protect existing tree cover on behalf of us all.

Of course, it’s also true to say that developers themselves, large and small, appreciate the value of the tree cover on their sites. Nothing provides a better feeling of instant establishment than the presence of mature trees. They provide screening, privacy, separation, road-noise reduction, shade and shelter, wildlife presence, ever-changing visual interest, green character and a sense of connection with the natural world. All these valuable goods are captured by a development when existing tree cover is successfully built into design at an early stage and successfully protected during construction operations.

Best practice guidelines and recommendations exist, developed by Arboriculturalists and other science-based tree experts, providing standardized calculations, effective special engineering measures and tried and tested methods for the successful establishment of root protection areas around trees. A root protection area is a calculated amount of space, specific to a particular tree, which is considered the minimum amount of undisturbed area the tree requires to meet its survival needs. Protecting this space with robust, impenetrable fencing ensures the existing root system of the tree is safe from damage and the ground designated its feeding/root-development area is protected from compaction or any other form of degradation. The parameters for protection of tree root systems are known as ‘below ground constraints’ – for obvious reasons. Looking after tree roots on live construction sites is one of my primary professional undertakings.

The root presence of a tree is not the first thing you notice about it though, is it? ‘Above ground constraints’ are far easier to pick up on – at least most of them are. Looking at tree crowns, from broad mature Beech to the thinning dark spires of Spruce, it’s clear that what the tree supports up into the air with its scaffolding of branches is going to have a big impact on how we experience the space in proximity to it, and how practical it’s going to be to locate buildings, driveways, footpaths, roads and private (sometimes public) amenity space where a tree dominates that available space to a considerable height.

Sharing space – beautifully

Clearly we can’t build up into tree crowns. And we can’t cut unsightly holes in balanced crowns to accommodate root protection fencing or parking provision. But beyond these more obvious things, we start to meander into a more complicated realm. Local Authorities dislike the idea of homes being built less than 20m away from mature trees. Now we can all think of examples where a characterful house or other building seems to sit in happy co-existence with some impressive and relatively close-growing tree presence – I lived in a lovely red brick cottage with a substantial Ash tree situated just beyond the french windows. It shivered in the wind and its branches  tapped on the slates of the roof. Being an Ash, it didn’t get any decent leaf cover until well into June; about 3.5 months before it began losing its canopy again, vast quantities of leaves piling up on the flagstones. I still loved my Ash tree.

But fears exist among those whose responsibility it is to give or withold development consents, around home-owners’ likely resentment toward trees that shed large quantities of leaves in the autumn (such as Ash or Beech), trees that reduce light levels 24 hrs a day for 365 days of the year (such as Douglas, Spruce and Fir), trees that can achieve enormous sizes and, even when assessed as ‘large’, may still have the potential to double in height over their predicted future lifespan (such as Sequoiadendron, Fir and Cedar).

The problem is, it’s difficult to set scientifically immutable guidelines for above ground tree constraints. A lot of the issues associated with tree crowns and tree characteristics have a strongly subjective element – there are a good many of us who would love a garden dominated by a majestic mature Cedar of Lebanon, and we would tolerate without a second thought a reduction in overall ambient light levels just for the priviledge of being able to admire those huge, sculptural limbs every day and call them somehow ‘ours’. But we also all know folks who call leaf drop in autumn ‘litter’, a nuisance rather than a delightful natural phenomenon indicative of the changing seasons. Our Planners do their best. But I do think sometimes the signal is sent out that a plot or development with trees on it is a highly problematic thing. Undesirable even. This is certainly not the case. It can be tricky to rationalize, and challenging to design for, but living in proximity to trees is for many of us something we’d be very happy with. I would like to see us find a way to allow development that comes a little closer to trees, whilst sending out the message to those who buy into sites with existing tree cover that it’s unacceptable to capture ground with the aim of ridding it of inconvenient trees. If you buy for yourself a beautiful garden, you’re also buying into a big, inescapable maintenance responsibility. If you develop space among trees you need to be prepared to live, wonder, and let live.