1.Trees Make Effective Sound Barriers

Royal Paulownia in Central Park
Steve Nix/About Forestry
Trees muffle urban noise almost as effectively as stone walls. Trees, planted at strategic points in a neighborhood or around your house, can abate major noises from freeways and airports.
2.Trees Produce Oxygen

German Tree Plantation
Placodus/Germany
A mature leafy tree produces as much oxygen in a season as 10 people inhale in a year.
3.Trees Become Carbon Sinks

der Wald
Placodus/Germany
To produce its food, a tree absorbs and locks away carbon dioxide, a global warming suspect. An urban forest is a carbon storage area that can lock up as much carbon as it produces.
4.Trees Clean the Air

Seedling Bed
TreesRus/About Forestry
Trees help cleanse the air by intercepting airborne particles, reducing heat, and absorbing such pollutants as carbon monoxide, sulfur dioxide, and nitrogen dioxide. Trees remove this air pollution by lowering air temperature, through respiration, and by retaining particulates.
5.Trees Shade and Cool

Tree Shade
Steve Nix/About Forestry
Shade from trees reduces the need for air conditioning in summer. In winter, trees break the force of winter winds, lowering heating costs. Studies have shown that parts of cities without cooling shade from trees can literally be "heat islands," with temperatures as much as 12 degrees Fahrenheit higher than surrounding areas.
6.Trees Act as Windbreaks

Arborvitae, A Favorite Windbreak
Steve Nix/About.com
During windy and cold seasons, trees act as windbreaks. A windbreak can lower home heating bills up to 30%. A reduction in wind can also reduce the drying effect on other vegetation behind the windbreak.
7.Trees Fight Soil Erosion

Clearcuts on Mt. Bolivar
Recycle/About Forestry
Trees fight soil erosion, conserve rainwater, and reduce water runoff and sediment deposit after storms.
8.Trees Increase Property Values

Trees in Urban Spain
Art Plotkin
Real estate values increase when trees beautify a property or neighborhood. Trees can increase the property value of your home by 15% or more.
Ref: Tree Importance | Value of a Tree | Tree Benefit