As population growth and the concentration of work in urban areas put more pressure on those areas to provide housing, infrastructure, entertainment and services to the inhabitants, so green elements of the landscape are threatened. In many urban centers, more and more green space is being taken over by construction, and a reduction in the number of trees in towns and cities is common.
However, this is a development that should be resisted whenever possible. Trees are important to urban areas, for many reasons, and can actually help tackle some of the problems that are inherently a part of towns and cities, as well as global concerns.
Prevent Climate Change
Trees are a crucial component in preventing climate change. Climate change is due to the greenhouse effect – gases caused primarily by human activity such as the burning of fossil fuels enters the atmosphere and prevents sunlight radiating back out, causing the heat to buildup around the Earth. One of the primary motors of this effect is rising levels of CO2 in the atmosphere. Trees take in CO2 as part of the process of photosynthesis, storing the carbon as cellulose in their trunks to provide themselves with energy. An average mature tree can ‘fix’ an average of 13 pounds of carbon annually. Trees can also help prevent climate change by helping us reduce our energy use.
Trees placed besides building can save significant amounts of energy use within those buildings. This is particularly true of deciduous trees, as they help modify building temperatures all year round. A deciduous tree located next to a building will, in summer provide shade, lowering the temperature inside the building and reducing the need for energy-hungry air conditioning. In winter, when the tree loses its leaves, it allows more sunlight to reach the building as so reduces heating costs. Evergreen trees can also contribute to energy saving, providing shade in the summer and serving as a windbreak in the winter, when winds can draw heat from a building (however, evergreens should not be planted on the south or west side of a building, as they will block winter sun).
Trees are one of the most aesthetically appealing ways to block and muffle noise, certainly when compared to a solid fence. They have long been used to block the noise from freeways as they pass settlements. In urban areas, noise is a significant problem, nit only because of the greater concentration of people and traffic, but also because the hard surfaces of urban architecture, from the buildings to the pavements – refract noise. Trees help absorb both the original and refracted noise, which can have a significant impact on the stress levels of urban inhabitants. Broad-leaf evergreens can be useful as they block noise all year round, but that benefit must be weighed against others such as blocking winter sunlight.
Trees are significant additions to the biodiversity of an area, even an urban one, because they support a lot of different life forms. These range from the birds who perch and roost in their branches, to insects that feed on its flowers, fruit and leaves (and themselves become food for the birds), through microorganisms and bacteria which live on the rootstock. Trees can also be important ‘links’ between urban areas and the wilderness outside them, allowing species to move between the two environments. Being relatively large organisms, trees can also influence the growing conditions around them – from bringing up soil and moisture from further down in the soil profile with their deep roots, to offering shade and protection from wind on the ground – making more environmental niches for other, diverse species of plant to inhabit.
Trees are a necessary part of the urban landscape to modify and balance local climate conditions. The concrete and other hard surfaces in urban locations absorbs heat and reflect it back into the urban environment, significantly raising temperatures. Without anything to modify this effect, urban areas can become ‘heat islands’ which typically have an average temperature of between three and ten degrees higher than surrounding wilderness areas. As trees transpire moisture through their leaves during the process of photosynthesis, this added water vapor serves to lower air temperatures, offsetting the heat increases from the hard urban surfaces. Trees also modify climate by providing shade, increasing humidity, and reducing wind speed.
As we know, trees are essential to life on Earth, as they provide, as a by-product of the photosynthesis process, oxygen to the atmosphere. Having more trees in an environment increases the amount of oxygen and so makes the air quality better. But trees also improve urban air quality in other ways. For instance, their foliage serves to filter dust, ash, smoke and pollen which can be harmful to humans. Besides carbon dioxide, trees also absorb other harmful gases, such as carbon monoxide, chlorofluorocarbons and nitrous oxide, through the pores in their leaves. Absorption of such gases by trees is one effective way of reducing smog and fumes from vehicle exhausts.
All the hard surfaces and asphalt in urban areas makes flooding much more likely. The non-porous nature of urban building materials means that water runs off them into the municipal drainage system. If excessive levels of rain fall, the drains can become overwhelmed and flood the streets. Trees help prevent this by capturing and storing large amounts of water, both in their roots and in their canopy.
Having trees in our environment also improves our lives. They provide a point of difference from the harsh lines and sharp edges of modern construction. They can provide oases of calm in the midst of the bustle and noise of a city. Trees also add character to a location, with different species suited to different urban locales. And trees provide a link to nature, to parts of life that are not necessarily defined by commerce, speed and competition. And, last but not least, trees are beautiful, and having beautiful natural things around us makes us happier.