Disappearing Urban Tree Cover

16 Feb 2013

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President,  Nigerian Institute of Building, Mr. Chucks Omeife

The skyline of cities and of other urban areas are being stripped of tree cover for various reasons that do not add economic or health value to the livelihoods of their inhabitants, writes Bennett Oghifo

Growing up on streets lined with trees was an unprecedented experience for most adults, particularly when these are fruit-trees. These urban neighbourhoods are being left without cover of trees, fruit or ornamental,

Trees act as buffer when high velocity winds hit residential areas. They break the wind, bending or splitting to keep buildings and other structures safe. They hold the soil when storm-water rushes through residential neighbourhoods. They take in all the carbon dioxide in the air and release oxygen for mankind to breathe.

These are some of the benefits of keeping the trees in any landscape when people decide to build their homes. Horticulturists believe that the use of trees and vegetation in the urban environment brings benefits beyond mitigating urban heat.
Trees and other plants help cool the environment, making vegetation a simple and effective way to reduce urban heat.

The use of trees and vegetation in the urban environment brings benefits beyond mitigating urban heat islands including:
Trees and vegetation that directly shade buildings decrease demand for air conditioning; Improved air quality and lower greenhouse gas emissions. By reducing energy demand, trees and vegetation decrease the production of associated air pollution and greenhouse gas emissions. They also remove air pollutants and store and sequester carbon dioxide; Enhanced stormwater management and water quality.

Vegetation reduces runoff and improves water quality by absorbing and filtering rainwater; Reduced pavement maintenance. Tree shade can slow deterioration of street pavement, decreasing the amount of maintenance needed.
Trees and vegetation lower surface and air temperatures by providing shade and through evapotranspiration. Shaded surfaces, for example, may be 20–45°F (11–25°C) cooler than the peak temperatures of unshaded materials. Evapotranspiration, alone or in combination with shading, can help reduce peak summer temperatures by 2–9°F (1–5°C).

Trees and vegetation are most useful as a mitigation strategy when planted in strategic locations around buildings or to shade pavement in parking lots and on streets. Researchers have found that planting deciduous trees or vines to the west is typically most effective for cooling a building, especially if they shade windows and part of the building’s roof.

Lack of policy…
There may be laws in the country to prohibit indiscriminate felling of trees but these laws are hardly enforced. “Wherever they exist, enforcement is usually left at the discretion of officials of the Department of Forestry, who believe their mandate does not cover urban trees,” said Okpala Sam, a horticulturist in Ikoyi.

Okpala said lack of enforcement was the reason the lush green tree cover of Ikoyi was rapidly giving way to skyscrapers. “Ikoyi is looking bare these days. What attracted most people to Ikoyi was the sense of serenity that envelopes the place because of the trees that line the streets and surround the homes. The first thing the developers do is to cut down the trees before they begin construction of their buildings. They promise to replace these trees but hardly do so. Besides, it takes several years for these trees to grow to maturity.”

It is necessary to enforce laws that prevent indiscriminate felling of urban trees and those that compel people to plant, said the President of the Nigerian Institute of Building (NIoB), Mr. Chucks Omeife. “There must be a deliberate policy in place for people to have green in their neighbourhoods to a particular percentage. They must have greens of between 20 per cent and 30 per cent of the land space. They should be encouraged and if possible fined to make them do it, because Nigerians will not do it if they have their way.”
He said globally the talk was on regeneration and urban renewal. “Green areas are being encouraged in residences. The trees provide certain things for the environment. They are very  important for health purposes.”

Excuses to cut trees…
People have given several reasons to cut down trees in their communities and, these range from nuisance birds that nest on their branches cause to unimaginable fetish reasons that have not been proven.
A cleric of the Methodist Church Nigeria, Lagos Central Diocese, Rt. Rev. Jacob Kehinde Adeyemi, said he does not believe trees exude negative aura but that they are beneficial to mankind.

According to Bishop Adeyemi, “most of these trees were not even planted by men. For example when a hunter goes hunting and discovers a big tree, mountains, big rivers, etc and since he has not seen such before, he tends to ascribe certain powers to it, a sense of awe, basically because of fear.”

Fear, he said makes people to create a god out of trees or other creatures. “Once sacrifices and incantations are made at such trees, these spirits tend to inhabit the trees. So this can be ascribed to human making; that is, when humans pour libation, offer sacrifices and make incantations at these trees, then the trees get possessed.”

He said the African Traditional Religion’s point of view confirms that once sacrifices and incantations are made at certain trees, they tend to inhabit spirits. “The belief that banana and plantain shoots are place for occult meetings is not acceptable at all. We buy these plantains and bananas for consumption and that is all l care to know. The only complaints about trees as far as l can recall when growing up is that the leaves litter the environment and we had to sweep endlessly. Also, the roots could extend to the wall and damage it. The branches, if not pruned, can extend into the house.”

Benefits and costs…
The primary costs associated with planting and maintaining trees or other vegetation include purchasing materials, initial planting, and ongoing maintenance activities such as pruning, pest and disease control, and irrigation.
Although the benefits of urban forestry can vary considerably by community and tree species, they are almost always higher than the costs.

Benefits of the roadside tree…
While roadside trees can, under certain circumstances, pose a hazard to errant motorists, it is imperative to assess the benefits of these trees must be assessed before making a decision. This is an important part of a total assessment that an agency should perform. Completing and documenting a benefit assessment may prevent some conflicts with the agencies and citizen groups that may be focusing upon saving particular trees.

Environmental impacts…
Trees in forests, parks, commercial, residential areas, and in general, provide environmental benefits. However, the direct environmental benefits (not including aesthetics and historical benefits) of roadside trees to drivers and the roadway setting are minimal. Less hazardous shrubs and plants can provide many of the benefits provided by roadside trees.
These trees may also produce environmental hazards to consider in the assessment. If trees are too close to the road, for instance, it may create conditions, such as micro climates that influence road-surface conditions, hampering snow removal, blocking sight distance, and shielding pedestrians from the driver’s view.

While the aesthetic value of trees is not directly related to driving and the operation of traffic, one should consider that drivers live, work, and recreate in communities that contain the roadways. The aesthetic value of trees is a complex issue that an engineer must consider when assessing the benefits of roadside trees. The aesthetic value of trees, while difficult to measure directly, is easier to work with when using economic benefits as a surrogate measure. Economic benefits, such as higher commercial land values, increased patronage of business and spending, and higher residential property values are examples of economic benefits that serve as surrogate measures of the aesthetic value.

Many communities developed around tree-lined roads long before the prominence of the automobile. These tree-lined streets are a part of the communities’ identity as much as other historical features. Taking this perspective, congested streets are seen as invading the very core of the community. Removing trees, to allow wider roads, is not an option with which many citizens will agree. Using guardrail to shield motorists from the trees is generally not an aesthetically acceptable approach, given the currently available types of guardrails. In some cases, the mere mention of cutting down trees can cause a controversy. If historical tree-lined streets develop into hazardous routes, engineers and the communities need to consider other strategies to service traffic in the region. 

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