The University of Iowa was named a 2012 Tree Campus USA for the fourth year in a row.

According to a UI news release, the Arbor Day Foundation named the UI in honor of its commitment to “effective community forestry management.” This national organization was created in 2008 to engage students in conservation goals and to honor universities for their forest management efforts.

“Our trees are not only beautiful but serve to purify and cool the air, protect our soil, and absorb carbon dioxide,” said Liz Christiansen, the director of the UI’s Office of Sustainability, in a release. “UI students help us maintain this designation by helping to plant trees on campus.”

The standards for sustainable campus forestry include a tree advisory committee, a campus tree-care plan, dedicated annual expenses for its campus tree program, an Arbor Day observance, and student service-learning projects, the release said.

The UI was Iowa’s first Tree Campus USA institution with more than 7,700 trees to maintain on the main campus and the UI Research Park.