Landscape architects Horace W.S. Cleveland and Frederick Law Olmsted championed the cause of planting street trees not just for cosmetic attractiveness, but to improve the health and well-being of residents, as well as to reinforce the visual order and character of the city. Tree planting is a cost-effective way for cities to improve air quality and control urban noise pollution while creating recreational opportunities for citizens. Trees provide many benefits for people and communities. They reduce energy costs by shading homes during hot summers and by reducing heat island effects in warmer climates. Trees also act as natural air filters by taking out pollutants such as sulfur dioxide and nitrogen oxides that would otherwise contribute to acid rain and ozone formation. Trees help control flooding by providing surface water with places to go when it rains heavily, and they can also reduce the risk of landsliding and preserve soil integrity. Finally, trees give people a place to go for peace and quiet, to engage in leisure activities, and to escape the hustle and bustle of city life. Cleveland and Olmsted planted hundreds of thousands of trees throughout America to enhance their cities. In Boston, for example, they planted Sycamores to replace fallen Elm trees due to Dutch elm disease. Today, these other species have grown up together, forming a beautiful forest that provides beauty and habitat for wildlife.