Landscapes are all about creating micro-climate, or would be, if designed for that goal. Why is this important and what do I mean?
Almost all life is contained in a thin crust of soil, a wedge of atmospheric gases, and water. Plants are the principal medium that interacts with and regulates all three. Absolutely nothing else does this as well, or at all; think about it.
The way we organise our plants in our urban landscape will determine how well this interaction occurs, how successful it is. Yet I have never heard of a single project that has been developed with this understanding and this goal in mind. With climate change, we urgently need to re-think the way we design our landscapes, and why we design them. Whilst all the human-centric design reasons will always hold true, we need to layer into our thinking this new understanding of how plants interact. To build new ecologies, new ecosystems, we have to design for plants to actually function, rather than just look nice. For when they do this, our environment literally comes alive. More importantly, they might just, if done on sufficient scale, save us from ourselves.
When I use the word treescapes, I don’t just mean trees and grass; we’ve had that for years in the form of parks, and in their traditional form, they’ve done little for us. No, our designs need to build up layers of living material – biomass, for with biomass comes moisture entrapment, shade, food for insects, etc. Think of it in terms of height and depth of microclimate. How much depth is there in a stretch of irrigated grass, maybe 50mm above ground, 200mm below? No species variation, so what we have is little more than a green desert, albeit one that can hold bit a of moisture.
Trees in paved streets are also less able to generate micro-climate, but they are a bit of an exception, as they provide shade for people to walk under. Where width allows, even here we should layer our planting.
If we replace that grass with a range of groundcover plants – not a monoculture – you begin to get a little more variation; different root structures and depth, different foliage shapes, height, form and flower. More variety, more microclimate, more food source, more ecology. Looks good too.
Next we add shrubs and suddenly we are into an new realm, that of woody plants (I’m being simplistic here, many groundcovers are of course woody). Shrubs create three-dimensional space with their frameworks, within which micro-worlds reside. Deciduous plants shed their leaves, as do evergreens, and this begins to build leaf litter – mulch. Don’t tidy it up! We need ecologies in that soil, and microbes need food. Our obsession with tidyness has a lot to answer for. Suddenly, we have height in our micro-climate, three-dimensional form. We humans (for we scale everything according to our own height and perception) can walk amongst these plants, take part, interact. Our microclimate is now two metres high, maybe more. But something is missing and it’s still too hot…
Trees! Now we have a game changer and our micro-environment just became vast, in relative terms, maybe up to 30 metres, though 10-20m may be more average. We now have true diversity of shape, height, leaf, flower and roots. We have shade! Under trees it may be 10°C cooler and we love it. Plants love it too. Moisture now gets retained within the human habitable zone, fungi and microbes thrive in soils, insects and birds abound. This is our urban jungle and we need it. The planet needs it. This tiny sliver of crust we live on can be rich, abundant, in every climate and every place, if we put our minds to it, if we have the will. And when the planet becomes searing, creating livable environments with trees of any type, may be the only thing that keeps us alive, unless we become troglodytes.
This is the next level of landscape design, the new challenge; creating future ecologies and environments that matter, that keep us cool, that give us resources and soothe our souls. We will create new (novel) ecologies that fit the changing environment, trans-migrating parts of ecologies that once lived elswhere. In that place they may be dying out, as might your local ecology. If they now fit where you live, that’s where they need to be. In turn, that place of origin may itself need to adapt and change. In all things and all places, we need microclimate, shade and soil.
Are you up for it? I am!
I have said elsewhere that the landscapes of Dubai and Abu Dhabi are growing (no pun intended) at an extraordinary rate and that the knowledge and skills needed to care for the landscapes as they mature are not keeping pace. This is especially true when it comes to trees.
Palm trees are familiar to the region as a crop tree; they are tough, easy to move without too much worry and of simple form which does not necessitate any complex pruning. Broadleaf trees however, demand more than the crude lopping they are so often subject to, especially in urban spaces where there are issues of health and safety. Bad pruning, but also lack of pruning can lead to dangerous conditions.
The following two pictures show dangers from no pruning care taken:
Often a tree’s lifespan and health are determined even before they are planted on a site. Many problems come from lack of formative pruning right at the nursery stage and roots may be damaged during lifting or potting on.
So many trees are off to a poor start before they are even planted but once they are, environmental factors will kick in. How well they are planted and irrigated will effect their health. Assuming they survive and grow (and the average life-span of a UK planted urban tree is less than 10 years) then they have to cope with the occasional pruning that they are given and the damage that this may cause.
We have to understand that trees never heal. They survive damage by a process of isolation, or compartmentalisation, whereby cells surrounding damage isolate this area from the remaining areas of the tree. Unfortunately, bad pruning tends to rip right through these natural defenses, opening up the tree to infection and decay. Key to this is understanding the correctand way to place cuts. Here’s how you DON’T do it:
All these abuses and bad practices can be seen anywhere in the world, even in the UK which has a thriving profession of arboriculture. Trees in hot climates are critical, however, to the health of people and the city overall. As the landscapes of our modern cities and mega-cities continue to grow, and the effects of climate change become more severe, we need to look after our trees – everywhere – to a much higher standard than our current levels.
Trees deserve our respect – and our thoughtful care. More, they deserve active and knowledgeable management and the correct level of arboricultural skill and care to ensure they thrive and serve us, and our built environments, as best they can. The more we give, the more we get back.