Trees help to modify local climate by lowering air temperature,
increasing humidity, influencing wind speeds and reducing glare.
In the warmer months of the year, urban areas realize lower air
temperatures when trees are strategically planted along streets
and near buildings. These trees provide shade and evaporation of
water through the transpiration process. The evaporation from a
single large tree can produce the cooling effect of 10 room-sized
air conditioners operating 24 hours a day. Communities in which
homeowners utilize trees in their landscaping also benefit. When
homeowners properly place trees in landscaping they benefit from
savings on daytime air conditioning. For example, three or more
large trees strategically placed on the sunny sides of a house will
provide enough shade to reduce air-conditioning costs by as much
as 30 percent. Trees also help with energy costs in the winter by
blocking cold winds thereby reducing the strain on heating units.
These energy savings, when spread over many houses, neighborhoods
and urban areas, can reduce the demand for power production by utility
plants, which also reduce the amount of air pollutants produced
by these power plants.