Street trees that are planted on city streets come from forests and nurseries where life and growth is easy for them. It takes a strong, brave tree to survive in our urban forests.

The trees that line our sidewalks are like natures soldiers.

They protect our air by cleaning and trapping pollutants, dust and dirt. They remove CO2 from the air and help stop global warming which threatens to raise the Earth's temperature and change our climate in harmful ways.

Lots of pollutants threaten street trees -- smoke, ozone, sulfurous and nitrous oxides.