UA team studies environmental impacts on cultural resources in the West

Cones encircle an adobe failure on the side of the San José de Tumacácori church. The hole is a result of heavy rainstorms in February, where water got under the structure’s plaster layer and got to the adobe underneath. (Photo by Ava Garcia/Arizona Sonora News Service)

There’s a hole in a 218-year-old building in Tumacácori National Historical Park. It’s the result of rain affecting the historic building’s adobe structure. It’s what can happen when environmental effects impact cultural resources, and it’s the focus of a new study by a University of Arizona team.

The team, comprised of six UA experts hailing from a variety of disciplines and three National Park Service members, is studying how environmental stressors affect cultural resources in the West. These resources include man-made national monuments, parks and historical parks.

“There’s been a lot of work done with climate change or identifying environmental stressors and their impact on natural resources,” said R. Brooks Jeffery, co-principal investigator of the study and professor in the UA College of Architecture, Planning and Landscape Architecture. “What hasn’t been done in the past, though, is the same amount of attention and systematic research around cultural resources.”

These cultural landscapes are spread out all over the West. Funded by a $100,000 grant from the National Park Service, the team is embarking on a three-year study of the inter-mountain west region of the NPS, which includes Montana, Wyoming, Texas, Oklahoma, Colorado, Utah, New Mexico and Arizona.

The UA team is collaborating with the NPS Vanishing Treasures Program, which supports the preservation of historically built architecture and archaeological sites. The program provides technical support and training to staff in parks across the West.

The environmental stressors that affect cultural resources vary depending on their location. Some areas may be more concerned with wildfire and erosion while others face extremes in freezing and thawing temperatures, according to Jeremy Weiss, a member of the team and a research scientist with Cooperative Extension in the UA School of Natural Resources and the Environment.

In a desert environment, much of the damage that affects cultural resources stems from water, in the form of heavy precipitation and flooding, according to Lauren Meyer, program manager of the Vanishing Treasures Program. Fire and wind can also affect cultural resources.

Those stressors can create problems for the preservation of national monuments. Jeffery said extreme weather conditions can have a “disastrous effect” on above-ground adobe structures, and many pre-20th century structures in national parks are made out of similar earthen materials.

“If that material is exposed to an overabundance of water, then the adobe literally melts because it will erode,” Jeffery said.

Flood waters from rain can also create arroyos or drainage patterns that may erode soil structures under the sites, as well as create saturation and degradation, Meyer said.

These environmental impacts don’t just affect cultural resources like monuments and archeological sites. Wilson Hunter, deputy superintendent of Canyon de Chelly National Monument, said cultural resources also include the 80 native families who live in the canyon. Hunter said their farming is being affected by environmental factors such as overgrowth of invasive species of plants and a dropped water table.

And those environmental impacts may not be slowing down anytime soon. Meyer, who has worked with the Vanishing Treasures Program since 2002, said over time she has seen increased severe weather in certain areas in New Mexico and Arizona.

She points to Tumacácori National Historical Park as an example. The park has two monsoon seasons each year, and Meyer said in the last several years they brought in a lot of rain multiple days in a row, leaving the park’s adobe structures with little time to dry out, which has resulted in losses on those buildings.

A close-up of a crack in the trial wash coat of plaster covering the adobe structure of the Convento Ruin in Tumacácori National Historical Park. Cracks like this can be the result of age or rain. (Photo by Ava Garcia/Arizona Sonora News Service)

Roger Dorr, integrated chief of resource management at Tumacácori, said rain affects the park’s historical structures when water gets into cracks in their plaster and wets the adobe beneath it. He said the park’s main structure, a church that dates back to 1800, has had two partial wall collapses this year from a rainstorm in February. Despite the park staff’s monitoring of the walls, the rain found its way into a crack high on the structure.

“The adobe can only take so much before it fails, and that’s what happened,” Dorr said.

To prepare for potential future damage to cultural resources, Meyer said it’s important to understand the unique environmental conditions of each park and what maintenance needs to be done, as well as identifying areas at a higher risk of being damaged to be strategic in how they design interventions.

The research team plans to do just that: They will spend their first year studying the impacts of the individual environmental stressors in the parks and then the next year identifying strategies to prevent damage to the cultural resources. The third year will center on communicating those strategies to the parks so they can carry out mitigation strategies themselves.

“It’s clear that cultural heritage is immobile,” Meyer said. “It sits in the environment in which it was it was built, and it’s not like you can easily pick it up out of that environment and move it somewhere else in order to better protect it. The protections have to be done onsite.”

Some parks already have mitigation efforts that date back decades. Katherine Shaum, archeological technician at Casa Grande Ruins National Monument, said she has seen the effects of UV exposure, heat and monsoon rains on historic structures and ruins in the park. But the Great House, the largest ruin in the park, is covered by a roof-like shelter that was built in 1932. Shaum said the roof protects the ruin from sunrays and heat, and it’s the unprotected lower walls of the ruin that are most affected by the monsoon rains.

“A lot of these prehistoric sites, they had people living in them who were able to take care of the buildings, probably on a daily basis, and then when these people leave and especially when their roofs disappear, makes them open to the elements, their deterioration increases,” Shaum said. “The roof shelter is basically a replacement roof and ceiling system. I think it definitely helps prolong the life of the structure.”

The interior of the San Jose de Tumacacori church in Tumacacori National Historical Park. Construction on the mission church began around 1800. (Photo by Ava Garcia/Arizona Sonora News Service)

These cultural resources can be just as much a part of the identity of the American West as natural features of parks such as Yellowstone National Park, Jeffery said.

“The understanding of Hohokam ruins like in Casa Grande, or Mesa Verde for example, or the Spanish colonial heritage that we have, really begins to help us understand where we came from, what our heritage is,” Jeffrey said. “And the continued legacy of those historic and ethnic groups that are still here and are part of the hybrid identity of places like the West — that is this layered landscape of different ethnic and historic influences.”

Ava Garcia is a reporter for Arizona Sonora News, a service from the School of Journalism with the University of Arizona. Contact her at

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