This is the VOA SpecialEnglish ENVIRONMENT REPORT.
Officials in Chicago, Illinois, are hoping to help theenvironment by planting gardens on the tops of buildings. They sayplants and trees have the ability to clean the air and decrease thetemperature. They say rooftop gardens can keep buildings cooler,save energy and extend the useful life of a roof.
Almost half of the streets,parking areas for cars, and buildings in Chicago have dark-coloredsurfaces. More than sixty percent of Chicago's rooftops are dark incolor. During the summer, dark-colored surfaces take in and trapheat from the sun. This causes the temperature to rise higher in thecity than in surrounding areas.
This is known as the urban heat island effect. It is felt most inthe summer when temperatures are already high. More energy is neededto cool buildings as a result of the temperature increase. The heatisland effect also increases air pollution.
Not all cities experience the heat island effect. It depends onthe weather and the condition of streets, buildings and otherman-made structures. It also depends on the number of natural areaswith plants and trees, such as parks and gardens. In addition toChicago, several North American cities experience the heat islandeffect. They include Atlanta, Georgia; Baton Rouge, Louisiana, andToronto, Canada.
The city of Chicago's Department of Environment wants buildingowners to do what they can to reduce the heat island effect. Cityofficials say one way to do this is by planting gardens on the roofsof buildings. One example is the rooftop garden on Chicago's CityHall. Workers planted trees and other plants on the roof. They chosenative plants that need less water. Many kinds of insects and birdshave made their homes in the rooftop garden. Workers also replacedsurfaces with light-colored materials. They say this has helpedreduce energy use inside the building to keep the building cooler.
Officials say the Chicago City Hall rooftop garden also helpsprevent rainwater from overflowing in the streets. The water istaken in by the plants, trees and soil. Officials say the overflowof rainwater would be reduced if enough buildings in the city hadrooftop gardens.
This VOA Special English ENVIRONMENT REPORT was written byCynthia Kirk.