Trees are a great investment for both property and the environment.  Shade trees can reduce air conditioning costs and consumption for homes and offices.  Asphalt and concrete surfaces that absorb and radiate heat from the sun (referred to in cities as the heat-island effect where it is more predominant) are kept cooler by shade from trees.  Carbon from CO2 is absorbed and oxygen is released back into the air. 

According to Tree Canada, one large tree can release enough oxygen for a family of four in just one day!