• Today, the most important aspect of the urban forest is clearly energy conservation and carbon dioxide absorption.
• Windbreak of trees have been found to reduce residential heating costs 10-15%
• Trees intercept rainfall and reduce run-off, thereby functioning like retention/detention basins.
• The psychological impact of trees on people’s moods, emotions and enjoyment of their surroundings may in fact be one of the greatest benefits urban forests provide.
• Studies show that hospital patients with window view of trees recovered significantly faster and with fewer complications than comparable patients without access to such views.

Environmental Impact
• Each healthy tree can reduce air borne dust particles by as much as 7,000 particles per litre of air, thus a healthy tree is a free standing air conditioner and purifier
• You need about 500 full-sized trees to absorb the carbon dioxide produced by a typical car driven 20,000 km/year

for more informations: http://www.treecanada.ca/publications/trivia.htm