The third reason, which seems to be a cause for every environmental problem, is global warming. Global warming increases the temperature which decreases the relative humidity. A decrease in humidity means there is a higher possibility in living in a city that is undergoing urban desertification.

         Urban desertification is different with the ordinary desertification because of various happenings that come along with it. The most famous one is ?Heat Island.? Heat Island is a phenomenon when a cities temperature is unnaturally higher than the surrounding region. In most cases, the difference in temperature is around 1~4 degrees Celsius. It is called Heat Island because if the isothermal lines are connected, it draws a picture that resembles an island. This phenomenon has a grave impact on the city because it heightens the energy usage of the city, causes smog, and causes many health problems.

According to a research in Hong Kong, every 1 degree of increase in temperature uses 2~4% more electricity. This research also applies to LA which is located in the opposite side of the Earth. At summer, the daily energy used in LA rises 400MW for every 1 degree. This is about 2.9% of the total daily energy supply.

         The rise in temperature is also a key factor in causing smog. For every 1 degree, 4~10% smog increases. Due to the temperature difference, the poisonous gases are not able to escape the city, being trapped. While it stays, it chemically reacts with other gases with heat as the reactor making more poisonous gases until the night. Smog will later on cause pains in the nervous system, make breathing hard, and make you see hallucinations.

         As mentioned, many of the causes of urban desertification are related to city infrastructure. However, this does not mean that we need to destroy the city in order to prevent this. After many struggles, researchers have found a few ways to mitigate the damage by planting appropriate plants in the city and by placing them in various places such as the roof or the wall of buildings. In addition, many buildings are now planned as green-buildings by being a highly reflective ?mirror?to sunray.