Incorporating trees into our built environment is one of the great challenges architects, urban planners and engineers face at the moment.
In the late 90s and beginning of the new Millenium, planting trees in cities was generally frowned upon. We needed to put a lot of infrastructure underground. Cables, pipes, sewers. And trees and their roots stood in the way of progress. We were not ready.
Luckily, we are more clever with every year and every project we finish. We now understand that there are many benefits that trees provide in the built environment and it is worth a bit of extra effort to plant them properly, because it pays off in the long run. So let’s take a look at the most important positive effects of trees in cities.
Reducing air pollution
There are many ways how trees protect our air and make it cleaner.
First of all, trees can form a living barrier which captures dust particles from roads, which are later washed down. This barrier can protect parks, pavement and other areas with the flow of city dwellers from roads and dust stirred up by the flow of vehicles.
Secondly, trees absorb a range of pollutants and toxins which are emitted by our everyday activities. This is crucial, as air pollution – especially in urban areas – means the air we breathe is reaching (or exceeding) toxic levels.
While all trees can achieve this, the most successful ones are ones that are suited for their location and require minimal maintenance or trees that have long lives and are disease resistant.
Ultimately, trees produce oxygen and thus improve the imbalance seen in the cities, where oxygen levels are lower than in the coutry.
While producing oxygen, trees also absord carbon dioxide, helping to fight against its raising levels and thus mitigating global climate changes.
Mitigating heat island effect
Heat island effect negatively influences city dwellers across the globe. Trees can help to reduce this temperature imbalance.
Most of the surfaces in the city are either asphalt, pavement, or dark roofs. Those surfaces absorb a large percentage of energy from sun rays. Trees, on the other hand, help to shade surfaces, therefore ground around trees has much lower temperature than open asphalted roads.
Satisfying biophilia
Trees do not help only to improve the climate or save us cost in the long run; trees also help us with our ability to cope mentally with life in an artificial urban environment.
Being around nature, trees, flowers, grass has been shown to reduce the levels of cortisol, otherwise known as stress hormone, in our brains. Lowering it can help to reduce anxiety and stress. We are also more likely to leave our homes, go outside and exercise if there is a green, welcoming environment full of trees and nature.
Trees have been part of the natural landscape since humans evolved on Earth. We have a deep, innate desire to be around them, even if you aren’t aware of it.
Reducing water runoff
All the hard, impermeable surfaces in the city increase the risk of flooding. Natural ability to use and retain water can help to reduce water run off during heavy rain and thus stop potentional flooding. This also reliefs sewer pipes and lowers maintenance cost.
The water is retained both in the canopy as well as root system. This water is than slowly released back into ground and helps to maintain levels of groundwater.
Promoting biodiversity
Trees are a great help in improving biodiversity by providing habitat, food and shelter to animals and plants. Birds can roost in their branches and insect can live there too.
Increasing real estate values
Studies have shown that properties in environment containing trees and other natural elements have higher values and can be rented for a premium in comparison to properties in barren areas.
The proximity of healthy, beautiful trees directly affects property value. Decent tree cover can increase property prices by up to 7 per cent. Quality landscapes with healthy trees can also increase retail spending by up to 12 per cent. Tree-filled office properties can expect up to 7 per cent higher rents than those without trees or quality landscaping.
Cooling the environment
As well as absorbing water, trees also release it as water vapour through evapotranspiration from their leaves. This cools the air in the surroundings. By shading and cooling air, less energy is used to maintain optimal temperature in buildings. The overall cooling effect of a single, mature tree is equivalent to 10 air conditioning units running for 20 hours a day, which greatly reduces heat island effect.
Additional benefits
But wait, there is more.
Trees are effective in absorbing noise, which can travel long distances in otherwise hard surfaces of the built environment.
Certain types of trees can produce foods, which can be harvested by local communities.
Conclusion
Vegetation is one of the most versatile tools for urban planners interested in climate-sensitive design. It plays a role in surface and air temperature modification through shading and, to a lesser degree, evaporative cooling. It has the potential to remove air pollutants, provides noise control, and plays a role in carbon sequestration.
All these positives have long term impact on the environment, people and cost. Therefore, it is worth incorporating them in our cities as much as possible and go the extra mile for the future benefits.
Can you think of any other benefits of lush greenery in cities?
Take care.