No matter how close or far trees are situated from your home – they will impact the energy consumption of it. The amount of shade provided by trees will equal to cooler temperatures. The urban canopy keeps the surfaces of homes cool and forms a microclimate where paved exteriors reduce the build-up of heat. This interception will reduce the demand for air-conditioning which is powered in many global cities by fossil fuels like natural gas and coal, decreasing the amount of emittance of greenhouse gases. The air is instead pre-cooled before it enters a building. Even in colder climates and seasons where trees naturally defoliate, there is a positive influence. The wind that blows towards homes is disrupted and slowed before eventually coming into contact with walls. 25% of heat in modern homes is lost due to wind, thus the number of trees within your area will aid the energy saved. As urban trees shed their lives, more heat reaches modern structures near them and helps to warm them up. Energy is saved.
The social effects of urban trees include making roads a safer place as trees provide a ‘traffic-calming’ result – while privacy is heightened, providing a buffer between buildings erected in close proximity to one another. Absorbing sound and noise pollution as well as cushioning glare and reflection, a more comfortable urban environment is created. However, in order to reap these benefits from green architecture, the trees have to first survive, grow, and thrive within the urban landscape, despite its harsh conditions. The conversation of urban forestry slowly evolves from the importance of tree planting to the significance of tree survival.
In an article written by Lara Roman, a Research Ecologist with the USDA Forest Service for Scenario Journal, it is imperative to discuss tree growing. The average street tree has the half-life of thirteen to twenty years and for every one hundred street trees to be planted, only fifty of them will reach thirteen to twenty years in age. In the Los Angeles’ Million Trees program, it was predicted that seventeen percent of planted urban trees would die after thirty-five years in a low-mortality scenario. The observations also included that in New York City, twenty-six percent of trees were dead after eight to nine years of planting. Urban trees live fast and die young, compared to their rural counterparts.
Research finds that trees grow twenty-five percent faster in rural areas, suggesting that the ‘heat island’ effect is greater in urban areas. The ‘heat island’ effect constructs a hostile environment for tree growth because the climate becomes too warm and the heat does not escape. The salt cultivated from winter is detrimental and the root systems become traumatised. In warmer temperatures, urban trees undergo an extended growing period and photosynthesis increases, resulting in greater growth year after year. In the rural forest, the soil that lives there is filled with nutrients and moisture. The first six inches of forest soil is concluded to be fifty-percent oxygen while urban soil experiences drought and lacks nutrients necessary, containing only ten percent of oxygen.
Another factor of low urban tree survival is the air pollution that exists in modern cities. Air pollution causes visible damage to trees, leading to gradual tree decline. The symptoms of tree injury can be seen in the foliage: discolored leaves, burnt spots between the tips and veins. It was clear in the past that trees were usually affected if they have been situated nearby an industrial area. However, trees all over are now impacted on a large scale. Whole urban areas, as well as rural spots, are witnessing the ill effects of air pollution. The air pollutants to be largely blamed are ozone, sulfur dioxides, and nitrogen oxides. Large concentrations of ozone, the chemical reaction of sunlight to compounds found in paints, gasoline, adhesives, do not kill trees directly although it is possible. The pollutants, however, majorly impact the health of trees by disrupting the transportation of carbo-hydrate to the leaves. The number of sugars in the leaves increases and the foliage becomes vulnerable to attacks from insects. Acid rain, for example, damages the leaves by restricting the uptake of nutrients. More acid in the soil, macronutrients become depleted for tree growth. Trees planted nearby to traffic and become exposed to concentrated levels of polluting compounds found in automotive parts like tires and brake linings will display less growth over time. Urban trees often do not stand a chance against the already ailing environment so what needs to be done next? How will we ensure that we are reaping the benefits from the trees that our communities are planting?
Trees are no longer ornaments similar to the common lamppost nor a fire hydrant. The regard for trees cannot stop after simply installing them into a city in order to simply make it greener. What urban communities must consider is the diversity of urban trees. Native trees are the simplest to plant because of their strong abilities to survive as they are special to that particular area. However, as environmental stressors can only get more aggressive, there needs to be room for more trees to grow and their different species. It is already difficult for trees to thrive in the little soil they are planted, cocooned by paved surfaces that limit water absorption. In Europe, lindens are very popular trees to plant and they construct the largest percentage of the urban tree population. However, the issue with growing the same kind of trees is that they eventually become vulnerable to diseases or insects that can harm their health. The loss of such a high percentage of trees can be horrific to the urban green landscape.
Aside from choosing the right species of tree, other methods to ensure that urban trees grow and thrive in urban environments is to practice strategic site planning. Asking the following questions could prolong the life of the greenery: does it have adequate space for soil? Will the site pose a potential disruption to urban canopies? Considering the actual space will decide whether the tree will grow efficiently. Otherwise, it is important to improve the conditions in which the urban trees are planted. After analyzing the site, apply the best changes to improve soil conditions. What comes afterward is simply the proper maintenance of these trees. From mulching to watering, keeping the moisture and a close eye on urban trees will prevent diseases and insects.