Horticulture and the City: Why we need trees

Initial thoughts of the modern city tend to be characterised by expanding skyscrapers, busy car clogged streets and an increasing amount of hard surfaces - concrete and glass having stamped their superiority over grass and soil, literally burying them beneath the ground. There seems to be no place for slow growing plant life within the ever-mutating modern city, though research has long suggested that trees, plants and all things green play an increasing important role as urban densities rise, on a wide range of scales, benefiting the city as whole right down to the individual.

One of the biggest challenges for the high-density city is a phenomenon known as the Urban Heat Island Effect. This is the temperature difference between urban and rural areas created by artificial means: heat generated as a result of combustion engines, air conditioning and industry becomes trapped in the maze of hard, reflective, geometric urban forms, the wind unable to penetrate between the narrow canyons created by tall buildings. This can become not only a nuisance, but also a potentially fatal danger during summer heat waves. The importance of horticulture’s role in regulating temperatures has now been recognised, evapo-transportation (the plant’s equivalent of sweating), together with the shade provided by leaves, opening up of channels for wind to remove stagnant heat from denser areas all acting to reduce the urban temperature.

Trees also provide many other regulating ecological services to the city. Amongst these is the reduction of the effects of pollution; trapping, filtering and breaking it down into smaller, less harmful elements as well as flood protection, during periods of heavy rainfall they absorb large quantities of water (which many cities’ antiquated drainage systems cannot deal with) preventing erosion, urban runoff and flooding.

Trees and parks also play a crucial social role. Space In the city is at a premium and often the first component of the home to be sacrificed is the garden. Visit any inner city park on a summer’s day and you will understand the importance of green spaces to city-dwellers. A day in the park is both affordable and enjoyable. They provide somewhere to eat lunch, go for a walk or read a book, all for free, a rare commodity in the city. Fruit and nut trees can provide increased value for money.

During autumn trees fruit and branches bow with the weight of their crop, much of this is currently wasted. Make the most of it! When compared to shopping at a supermarket you will not only be saving money but also reducing your carbon footprint (the food miles on many fruits and nuts are often international), not to mention the fact that fruit you’ve picked yourself almost always tastes better than the alternative! Collaborative websites such as Abundance London connect you directly to the source of the fruit, as well as letting you add any further fruit trees you may know about.

Organised Urban farming is also on the rise. Community gardens are starting to appear within our cities. These are a great way to get fresh, organic fruit and vegetables at a low cost, often just requiring a few hours work a week in exchange for a big box of vegetables.

Perhaps the most obvious advantage to trees and plants is the fact that they make for a more pleasant environment. Statistics represent this less visible social role; hospital patients with a window view of trees recover faster and suffer from less complications than those without whilst tree lined suburban avenues tend to result in lower levels of domestic abuse.

Urban trees, parks and allotments are clearly not just a remnant of the past. They play both an important social and environmental role, regulating a variety of processes within our cities, so what does the future hold for the humble tree? Many urban designers have incorporated horticulture and forms of agriculture into some very forward thinking urban designs. The architect Paulo Soleri integrated gardens and urban farming into his designs for giant, massively dense sustainable cities, named Arcologys. Vertical urban farming (utilising hydroponics and aeroponics to increase yields) within skyscrapers is also becoming a very real possibility with increases in land prices.

These projects are a long way off, but such designs suggest an increase in greenery will be necessary in order to make a move towards a truly sustainable city. In the mean time, prior to the realisation of such projects, it is important we take care, improve and make use of our urban parks and trees. Charities such as Trees for Cities has many projects around the UK, having planted 225, 494 trees (and counting) around the world since it’s creation in 1993. Many of their projects welcome participation from the public. Your involvement is crucial. Appreciate trees and plants, make use of them, and, most importantly of all, don’t let them disappear.

 Author Jonathan Dennis

1 American Forests, 1999. How Trees Fight Climate Change.
2 Prow, T., 1999. The Power of Trees, The Illinois Steward, 7(4).

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