The UA Campus Arboretum provides scenery, shade and economic benefits to the University.
The UA Campus Arboretum provides scenery, shade and economic benefits to the University.

UA Campus Arboretum: Rooted in the Past, Growing Toward the Future

The UA Campus Arboretum celebrates its 10-year anniversary this year. The largest maintained public green space in Arizona, it includes thousands of trees from arid regions all over the world.
October 29, 2012
White floss silk tree
White floss silk tree
Carnegiea gigantean
Carnegiea gigantean
While the UA was officially recognized as an arboretum in 2002, its history actually began long before that, in the 1800s.
While the UA was officially recognized as an arboretum in 2002, its history actually began long before that, in the 1800s.
The UA's olive trees are believed to be some of the oldest trees on campus, planted in 1895.
The UA's olive trees are believed to be some of the oldest trees on campus, planted in 1895.
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Highlights from the Tree Benefits Assessment:

  • An inventory of 6,070 trees on main campus revealed 44 percent of the collection is represented by 10 species; 37 percent are broadleaf evergreen, 33 percent deciduous, 20 percent palms and 10 percent conifers.
  • Thirteen to 37 percent of trees are newly planted compared with 63-77 percent of trees that have reached maturity.
  • Tree canopies cover approximately 12 percent of campus.
  • The total value of ecosystem services provided by the campus forest is $272,997 each year with an average of $44.95 in benefits per tree. 
  • A conservative estimate of the total replacement value of all campus trees is $28,217,339.
  • By consuming solar energy in the process of evapotranspiration and blocking winter winds, campus trees help reduce energy use by 433MWh, valued at approximately $55,065.
  • Trees reduce the amount of carbon dioxide generated by energy production. As they grow, they also store carbon dioxide from the atmosphere. Together, these processes reduce carbon dioxide, valued at $29,180 from permanently storing 3,890,698 pounds of carbon dioxide and sequestering and avoiding 708,010 pounds of additional carbon dioxide annually. This is equivalent to the reduction in carbon dioxide emissions that would result from decommissioning almost 300 automobiles now and an additional removal of 30 vehicles for each year of the trees’ life.
  • The existing campus forest traps and filters nearly 2,867,671 gallons of storm water each year, with an associated savings of $13,766 for municipal infrastructure and maintenance expenses.
  • The campus trees remove 1,474 pounds of air pollutants, with an estimated value of $13,675.


Support the Campus Arboretum

The Campus Arboretum relies heavily on community donations, which can be made online.


The arboretum will hold a private 10-year anniversary celebration on Dec. 12 to celebrate its progress and to thank dedicated and engaged campus and community supporters.

Walking across the University of Arizona campus on a hot Tucson day, there may be no better respite than the shade of a welcoming tree. Yet, shelter from the desert sun isn’t the only benefit provided by the nearly 8,000 trees on the main campus. A recent assessment shows the University’s trees also have a significant environmental and financial impact on campus.

Taking into consideration factors like trees’ contributions to managing storm water management, absorbing air pollution, reducing carbon dioxide emissions and more, the UA’s Tree Benefits Assessment 2012 found that the campus forest provides approximately $272,997 in ecosystem benefits each year, with an average of $44.95 in benefits per tree. The cost to replace the entire collection would be more than $28 million.

The completion of the assessment coincides with the 10-year anniversary of the UA campus officially being recognized as an arboretum by the American Public Gardens Association in 2002.

“I’m so excited to have these numbers,” said Tanya Quist, director of the Campus Arboretum, which is part of UA Cooperative Extension in the College of Agriculture and Life Sciences. “It’s one thing to walk on campus and have this sense of awe recognizing the history of the landscape, but quantitative data puts into perspective the relevance of these plants as part of our green infrastructure. These values allow us to calculate the return on investment and to guide appropriate landscape development that ensures we continue to have these benefits.”

The data was collected by a team of four students from the School of Plant Sciences, who set out last spring to inventory more than 6,000 trees on the UA main campus. They input species information and trunk measurements into a software program called i-Tree, developed by the U.S. Forest Service. The program then generated information on each plant’s impact on the University.

Andrew Hatch, the plant sciences senior who led the assessment team, said he gained a new appreciation for the campus landscape through the project.

“I knew the Campus Arboretum was pretty prestigious, but until you actually go out there and learn about all of these trees you don’t really appreciate it,” he said.

Oldest continually maintained public green space

Although the Campus Arboretum was recognized by the American Public Gardens Association just 10 years ago, its history begins long before then. In fact, the UA is recognized as the oldest continually maintained public green space in Arizona, and much of the earliest vegetation planted on campus continues to thrive today.

For instance, the olive trees extending from North Park Avenue to the Student Union Memorial Center on the north side of North Campus Drive are among the oldest existing trees on campus, planted by faculty member Robert Forbes in 1895. The Joseph Wood Krutch Cactus Garden, originally located on the west side of Old Main in the late 1890s and since relocated to the center of the UA Mall, remains a popular spot for visitors to learn about Sonoran Desert plants. Then there are the UA’s iconic palm trees, many of which are more than 100 years old.

With more than 400 species of native plants and non-native plants, the Campus Arboretum is an integral player in promoting biodiversity and addressing questions of urban sustainability, resource conservation and climate change, all of which are of tremendous relevance to the state, Quist said. In this way, it exemplifies the University’s land-grant mission, said Quist, who also is an assistant professor of practice in the School of Plant Sciences.

“The land-grant mission dictates that we apply our research expertise to the practices we employ on campus so that we serve as a living laboratory; a model of sustainable practices for others in Tucson and throughout arid regions globally to follow,” she said. “Because these trees were selected from arid regions globally, they provide a valuable resource for research.”

Quist said she also hopes to encourage more University researchers on campus to use the plants on campus in their work.

“We have a terrific genetic resource at our doorstep,” she said. “These trees potentially represent genetic adaptations to drought and heat and cold, and that’s exciting. Further, they offer opportunity to explore questions relevant to the social sciences, public health and landscape architecture.” 

The Campus Arboretum offers regular guided public tours, highlighting different aspects of the campus collection, such as its history, sustainable landscapes, edible or medicinal plants and more. A tour schedule is available on the Campus Arboretum website, which was recently upgraded to include a searchable database of all the trees on campus.

Students cultivate new plants for future projects

In the years ahead, Quist hopes to continue to expand the Campus Arboretum and bring in several new plants that the campus does not yet have. Her “wish list” is being addressed by propagating handfuls of seed at a time.

To assist with the expansion of biodiversity on campus, the Campus Arboretum is working with the Desert Legume Program, the research arm of the UA’s Boyce Thompson Arboretum in Superior, Ariz., to cultivate native legume plants that will be grown out and planted on campus. UA plant sciences students also are helping out, by growing plants on Quist’s wish list atop the UA’s Sixth Street Garage, in greenhouse space provided by the College of Agriculture and Life Sciences.

The goal of planting on campus is carefully coordinated with the Campus Arboretum Advisory Board’s collections committee and the UA’s Planning, Design and Construction landscape architects, as well as UA Facilities Management.

“The Campus Arboretum’s role is to encourage more planting and more planning so that appropriate species are selected and placed in the right place,” Quist said. “Planting the right tree in the right place ensures they’ll not only look nice and contribute to the character of our campus, but that they’ll live long enough to reduce our environmental impacts.”

Quist stresses that more recent additions to the campus landscape are just as important as the University’s heritage trees.

For example, the UA's award-winning Underwood Family Sonoran Landscape Laboratory, as well as landscape projects at Likins Hall, Arbol de la Vida and the future ENR2 building, are exciting examples of the UA’s ongoing evolution toward building landscapes that maximize benefits with minimal inputs, she said.

“The Campus Arboretum emphasizes historic preservation,” Quist said, “but builds on our history of experimentation to provide insight, leadership and decisions support needed for a sustainable future.”