Restoring Tumamoc Hill, the Heart of Tucson

Support the Save Our Saguaros campaign and help us restore Tumamoc Hill

Article by Kim Franklin, Conservation Science Manager, Desert Museum and Ben Wilder, Next Generation Sonoran Desert Researchers

This past weekend, over seventy-five people showed up on a Saturday morning to help rid “A” Mountain of buffelgrass. For many, this was their first experience with this invasive grass. Some folks, brand new to Tucson, showed up wanting to learn more about this grass they had heard about. Some were Tucson natives who grew up hearing about buffelgrass, but still weren’t sure they could identify it. Others came because they wanted to get outside and move their bodies—pulling buffelgrass can be a fun workout!

All joined our Kickoff Event wanting to help out and save saguaros. These volunteers are also, perhaps unknowingly, protecting all the other Sonoran Desert plant species threatened by buffelgrass, including palo verde trees, brittlebush, and the entire spectacular array of spring wildflowers. In turn, we are also protecting animals that depend on native plants for shelter and food, like the desert tortoise and Western screech owl.

Buffelgrass, an invasive grass native to the savannas of Africa, is transforming the biodiverse shrublands of the Sonoran Desert into monotypic grasslands. Buffelgrass has become the dominant species on thousands of acres of wildlands within southern Arizona. Although complete eradication is no longer feasible, we can still protect and restore the places we cherish most!

This photo shows a rocky slope with buffelgrass in the foreground growing among a mature stand of saguaro cacti and other native plants of the Sonoran Desert.
Looking down on the east-facing slope of Tumamoc Hill in August 2021, note the yellowing buffelgrass in the foreground and the untreated, green buffelgrass patch in the background.

Tumamoc Hill and Sentinel Peak

Two of these beloved places sit right in the heart of the City of Tucson: Sentinel Peak and Tumamoc Hill. The name ‘Tucson’ derives from the O’odham place name Cuk Son, meaning ‘spring at the base of the black mountain.’ Now referred to as Sentinel Peak or “A” Mountain, this 272-acre urban park is the largest natural resource managed by the City of Tucson.

The butte adjacent to Sentinel Peak, Tumamoc Hill, is also connected to Tucson’s first inhabitants. The name ‘Tumamoc’ derives from the O’odham place name Cemamagi Du’ag, meaning ‘hill of the horned lizard.’

A close-up portrait of a horned lizard against a blurred desert floor background.
Regal horned lizard (Phrynosoma solare). Photo by Natalie McNear.

Tumamoc Hill is a volcanic peak with numerous archaeological sites, some dating back at least 2400 years. Since 1903, Tumamoc Hill has been the site of The Desert Laboratory, an 860-acre preserve owned and managed by the University of Arizona in partnership with Pima County. Together, the Desert Laboratory and Tumamoc Hill are designated a National Historic Landmark. In addition to its cultural and scientific importance, Tumamoc is a beloved refuge to a large and passionate community of walkers and runners, with more than 1,000 people climbing the hill each day!

A view of the paved trail on Tumamoc Hill in Tucson with many palo verde trees in full bloom in the background.
This well-trodden path on Tumamoc Hill is used by thousands of people every day. Note the gorgeous palo verde bloom – the yellow flowers. In Spring 2019, we had an exceptional palo verde bloom everywhere in the Tucson Basin. Palo verdes succumb to buffelgrass much faster than saguaros.

Recognizing that this iconic landmark in the center of our city was destined to become a buffelgrass grassland, we launched a long-term effort to restore the buffelgrass-infested slopes of Tumamoc Hill, in partnership with the University of Arizona, Saguaro National Park, and Pima County. Fortunately, restoration requires only that we rid the hill of buffelgrass. The native plant species come back on their own!

We proposed to use Tumamoc Hill as a demonstration site in the center of the City of Tucson to justify greater investments in buffelgrass control efforts—because buffelgrass doesn’t just threaten these two iconic landmarks. So much of the Tucson Basin is vulnerable to invasion by buffelgrass and its close cousin fountaingrass. We hope to generate the necessary additional funding by showing the positive impacts of a successfully restored area in the heart of town.

Treating Tumamoc

So how do we do this? While manual removal works well elsewhere, it is not an option on Tumamoc Hill, since this method is likely to damage Tumamoc’s exceptional archaeological resources. Currently our only viable option on Tumamoc Hill is herbicide application. Each year, with grant funding from federal and state agencies, the Desert Museum hires contractors to carry out this grueling work, which most often takes place in the heat and humidity of our summer monsoon season, because the herbicide is only effective when buffelgrass is green.

Contractors wear personal protective equipment to prevent them from coming into contact with the herbicide, and they spray only the buffelgrass, avoiding any collateral damage to the remaining native plant species. Fortunately, the herbicide degrades quickly and does not end up in our water supply. Moreover, buffelgrass is unpalatable to Sonoran Desert wildlife, so animals are not eating buffelgrass, whether or not it has been sprayed!

Three people in yellow and black clothing are shown from a distance climbing up a steep hill that is covered in green buffelgrass as well as native Sonoran Desert plants.
Contractors extending a hose attached to a spray rig to buffelgrass patches upslope on the east-facing slope of Tumamoc Hill in August 2021.
A close-up view of yellowing buffelgrass, with leafing ocotillos and saguaros in the background.
Yellowing buffelgrass recently treated with herbicide on Tumamoc Hill in August 2021. Note the native plants are unharmed.

After treatment with herbicide, dead buffelgrass decomposes over the course of three to five years, adding carbon back to the soil. The herbicide doesn’t kill buffelgrass seeds, or the seeds of our native plant species. Unfortunately, buffelgrass seeds remain viable for up to five years, meaning that we must return to treat buffelgrass seedlings that sprout up with the monsoon rains. Fortunately, each time we return the work gets easier, because there is less and less buffelgrass to treat.

Our Progress

We are happy to report that the north-facing slope, as well as the top of Tumamoc Hill, are nearly buffelgrass-free! We’ve also made great progress on the east-facing slope that looks down on “A” Mountain. In the next few years we plan to take on the challenging south-facing slope, and after that, the west-facing slope.

With our current funding levels, we expect this effort will require more than ten years.

That is why this year during Save Our Saguaros Month we are asking our community to support this effort with a donation that will be used to help cover the costs of treating buffelgrass on Tumamoc Hill.

A large informational sign off-trail with an infographic titled "Save Our Saguaros." Saguaro cactus and blooming palo verde trees are seen in the background.
A sign display on Tumamoc Hill shows how buffelgrass creates a fire cycle in the Sonoran Desert ecosystem, increasing the risk of wildfires that can wipe out entire stands of mature, healthy saguaros.

Support Our Campaign

For those who cannot get out to manually remove buffelgrass next door on “A” Mountain (or one of the many other pull locations), consider another way to save saguaros: contribute to our Tumamoc Hill restoration efforts with a donation of any amount!

Whether you volunteer at a manual pull, donate to support our efforts to control buffelgrass, or simply share what you’ve learned about the negative impact of invasive grasses in our community, YOU are a vital component of the Save Our Saguaros campaign. Your actions have a real impact on the future of our Sonoran Desert. Give a hoot, and give buffelgrass the boot!

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