Most people agree that trees look nice, but not everyone knows that trees can also help cities save money. A few years ago, the US Forest Service studied trees in Chicago. They found that just one tree can save a city hundreds of dollars over its lifetime.
Trees can save money by helping people save energy(能源). Trees stop the sun shining on buildings. They also block(挡住) the winter wind. That helps people use less energy to make their homes or offices warm or cool. Saving energy is saving money.
Trees have another way to help a city save money. When it rains, there will be a lot of water in a city's sewers (下水道). Cities need lots of money to clean that water. But before the rainwater gets to the dirty sewers, trees can take some into themselves. With the help of trees, there is less water to clean.
