URBAN HEAT ISLAND effect seems to be a longstanding problem that is getting more and more difficult to deal with. Impervious grounds or those paved areas such as roads and sidewalks are taking over city footprints. The price that smooth roadways for faster transportation is actually a higher ambient temperature and city inhabitants are left to deal with it.
Every day, when the sun rises, it gives off heat and the pavement absorbs that heat. This raises the temperature in the city during day time. During the night, the heat absorbed by these paved areas is released.
This prevents the low temperature of the night time to cool down everything that was just soaked in the sun. It has been observed that the larger cities with more infrastructure such as roads and those with more buildings made of concrete are among the cities with the highest temperatures. However, the use of concrete and asphalt is unavoidable because as for the moment, these are the building materials that are available and practical to utilize.
This dilemma has prompted urban planners to come up with different solutions over the years. One method has proven to be the most effective, most functional, and practical.
The concept is to prevent the sunlight from reaching pavements because when the sun heats up the roads upon exposure, it starts a growing chain of events that result in higher temperatures in the city. To prevent this, urban planners have proposed to use trees along pavements to serve as canopies and shades against the heat of the sun. This solution will surely mitigate the urban heat island effect.
The question now is: how many trees? For urban planners, this is a very important question. The number of trees required for a given area is quite dependent on the cooling effect that the vegetation could offer in an urban setting. Researchers from the University of Wisconsin in Madison have equipped sensors to a bicycle that were driven around the city. Their goal was to test temperatures at regular intervals along blocks with various kinds and number of trees.
According to their findings, an area of asphalt needs about 40% of canopy coverage. This will negate the heat given off by the asphalt.
Of course, the problem is in the planning of the city. Commonly, block areas in a city are mostly paved and do not have space for much trees.
Putting in trees as an afterthought when development was already done could mean that fewer trees would be added to the cityscape. This only gives the block 0.5 to 1.0 degrees Celsius less than the current temperature. However, if trees would have been incorporated in the design resulting in less impervious areas, the temperature of the area could be lower by up to 2.5 degrees Celsius.
