The advantage of city wildernesses improves the resident eco-system in countless helpful ways. Apart from trees and plants providing oxygen, they also help prevent rain water from flooding the residential areas and help purify the air. The organization American Forests conducts researches on how the damages in forests affect the cities badly. Beside researching, they also provide the people information of the 2:1 ration of trees to a person in terms of giving off and using of oxygen, and also how 20 pounds of air is purified by these trees every year. Community parks help give shade and lower heat in hot places. Those who live in locations where trees are bounty find that air-conditioning is needed less. There is a decrease of fifty degrees in the temperature of a car if it is parked in the shade compared to one that is now. Public spaces in bigger cities even build manmade parks and maintain them regularly.