A lot of people are getting dirty in North America. It’s spring — time to get the shovel, dig a hole, plant a tree, clean the air, beautify the Earth.

The Arbor Day Foundation, an international nonprofit organization, supports and funds tree-planting in private and public places, rural and urban. With government partners at the state and national level, the Arbor Day Foundation has encouraged thousands of U.S. towns and cities to win the designation “Tree City USA,” with official commitments to care for their tree canopies. The foundation also partners on broader efforts to restore forests damaged by fire, insects and disease.

The Arbor Day Foundation also has an extensive international network, spreading its mission to plant, nurture and celebrate trees. The organization has established partnerships throughout the Western Hemisphere and in some European nations, and it is expanding into China, Southeast Asia and Africa with tree-planting projects.

The Nebraska-based foundation reports that more than 5.2 million trees will be planted in 2015 through its funding and partnerships.

Some U.S. regions celebrate Arbor Day on April 24, but the observance varies widely across the United States to coincide with the best seasonal conditions for planting. Germany, Japan and Korea also honor their affection for trees in April.

Many of these tree-hugging activities started well before scientists spelled out the numerous reasons trees are our friends. But the evidence is conclusive that trees contribute to a better environment:

• Trees clean the air of greenhouse gases and other forms of air pollution.

• Trees exude oxygen.

• Trees help purify water.

• Trees can help cool your city and your house, reducing energy costs for cooling.

Trees are working 24 hours a day, seven days a week for a better world. How about you?