Arbor Day is celebrated on the last Friday of April. The tradition of planting trees on this day began in Nebraska in 1872. Soon, other states passed legislation to set up Arbor Day in their states, and the tradition began in schools in 1882.

There are an estimated 3 trillion trees on Earth. Here are some interesting tree facts:

— Trees help clean the air — they absorb pollutants such as nitrogen oxide, ammonia, sulfur dioxide, and ozone. Trees filter particulates out of the air by trapping them on leaves and in the bark. Global forests removed almost 33 percent of fossil fuel emissions annually from 1990 to 2007.

— Trees absorb carbon dioxide — they remove and store the carbon and release the oxygen back into the air. In one year an acre of mature trees can absorb the amount of carbon dioxide produced by your car driving 26,000 miles.

— Trees provide the atmosphere with oxygen — in one year an acre of mature trees can produce enough oxygen for 18 people. More than 20 percent of the world’s oxygen is produced by the Amazon rainforest.

— Trees help conserve energy — trees strategically placed around a home can cut air conditioning needs.

— Trees provide shade — shade can reduce the surface temperature of city streets by 10 degrees. Shade from trees also reduces water evaporation from lawns.

— Trees reduce water runoff and soil erosion.

— Trees muffle sound and provide wind breaks.

— Trees harbor wildlife.

— Trees provide timber for construction, fuel for heat and cooking, and food.

Other interesting facts are: a tree-lined street will slow traffic, the value of commercial property is increased with landscaping and trees mark the seasons.

The NFL planted 2,400 trees to combat the greenhouse gas emissions produced by the Super Bowl in Detroit.

The city of Iron Mountain has an annual tree sale. Six varieties are provided, with watering instructions and a hole dug by the city before the tree arrives. If interested, contact the city Tree Board or the Iron Mountain city clerk.

To quote Theodore Roosevelt: “to exist as a nation, to prosper as a state, and to live as a people, we must have trees.”

— Dennis Bal, Iron Mountain Tree Board member