ORO VALLEY, Arizona – It started with lightning, the fire that swept over the rugged Santa Catalina Mountains on the edge of Tucson. When firefighters got the fire under control, thousands of saguaros, the towering cacti that can reach a height of 18 meters and live to be 200 years, were lit.
The loss was heartbreaking for many in Arizona, where indigenous peoples learned to feed on the arboreal saguaros long before they became a celebrated symbol of the Southwest. Some saguaros still stand in the year-long scar of the bighorn fire, their trunks scorched to the limbs, proof of their reputation as masters of desert survival.
Still, Benjamin Wilder, an expert on saguaros and director of the University of Arizona Desert Laboratory at Tucson, said the lifespan of fire-damaged cacti would likely be shortened.
“I don’t think there will be any more near-misses when we get much bigger fires,” he said.
Forest fires are just one of many threats to saguaros that not only threaten the cacti, but also the mesquite, ironwood, and palo verde plants that protect them. At the same time, the unhindered growth of invasive species, particularly the highly flammable buffalo grass, has created more competition for scarce water resources while fueling fast-paced – and hotter – fires.
Then there is the urban sprawl of Arizona’s cities and towns. While laws generally protect saguaros from being cut down – try Arizona and you can face years of jail time – plant physiologists say that all concrete in metropolitan areas absorbs and holds on to heat. This creates higher temperatures at night than in the open desert, making it more difficult for saguaros to minimize water loss.
Taken separately, saguaros, which can be extraordinarily resilient after their maturity, could potentially react and adapt to any threat. However, scientists warn that climate change could accelerate all threats at the same time and pose an impressive array of challenges against the iconic saguaro. (How do you know if people are new to Arizona? They pronounce the name of the cactus with a hard “g” instead of saying suh-tru-ohs.)
Some disturbing signs are already ringing the alarm bells for admirers of the tallest cactus in the United States. Of the 10,000 saguaros surveyed in Saguaro National Park for a National Park Service report on climate change and saguaro, only 70 were younger than 11 years old and were found almost entirely in rocky foothills.
“The colonization of young saguaros has almost stopped in almost all habitats since the early 1990s,” said the scientists who authored the report when faced with a prolonged drought.
Such results are worrying for a plant that relies on favorable conditions that scientists refer to as “goldilocks” to establish itself. Saguaros, each of which can reproduce hundreds of thousands of short-lived seeds, only grow in the northern reaches of the Sonoran Desert – southern Arizona, southeastern California, and parts of the state of Sonora in northwestern Mexico.
In places with relatively little rainfall, it can take a century for a saguaro to sprout the limbs, which can give the cacti a human-like appearance; a saguaro in Arizona with 78 arms is well over a hundred years old and known as Shiva, after the Hindu deity.
Seeing the saguaro as a person is also rooted in the culture of the Tohono O’odham Nation, whose citizens live on both sides of the Mexican border. According to the oral tradition of the tribe, a mother would leave her child alone while they played toka, a traditional game similar to field hockey.
Alone, the child wandered to an anthill in the desert, then sank into the ground and returned as a towering saguaro. Based on folk tunes that turn the idea of a “food desert” on its head, tribal people still use the sun-bleached ribs of the saguaro, which are made into a stick called the kuipad, to harvest the red fruits of the cactus, which are eaten raw and made into syrup processed or fermented into wine.
Aug 3, 2021, 10:33 p.m. ET
Jacelle E. Ramon-Sauberan, who teaches history and culture at Tohono O’odham Community College in Sells, Ariz., Said the ritual included both catching the fruit and symbolically opening harvest time. “We’re pulling the clouds down to bring the rain,” said Ms. Ramon-Sauberan.
As a key species, the saguaro is also of outstanding importance for other living beings in the desert. Gila woodpeckers and gilded flares drill holes in saguaros for nests that can also house elven owls. Bighorn sheep and mule deer are known to eat saguaro meat, a sought-after source of water in places with little rainfall.
Saguaros, on the other hand, rely on less long-nosed bats and white-winged pigeons for pollination. Coyotes and desert tortoises feed on the fruits of the cactus and disperse the seeds in the feces that are left on the desert floor.
But the man-made changes in the Sonoran Desert disrupt the cycles for saguaros that were honed over thousands of years. One of the greatest challenges is buffalo grass, a drought tolerant plant native to Africa, Asia, and the Middle East that was purposely brought to arid parts of the United States in the 1930s for forage and erosion control.
While rising temperatures could benefit the saguaros by increasing the areas they can survive in, hotter weather could also be a boon to buffalo grass, which has been constantly expanding to the southwest. Buffalo grass infestation has increased since the 1980s, with the size of the spots doubling about every seven years.
The buffalo grass competes with species like Palo Verde trees, which provide shelter for young, vulnerable, slow-growing saguaros – which take about 10 years to grow to an inch and a half. But perhaps more importantly, buffalo grass has turned deserts that were relatively fire-resistant into fire-prone grasslands.
“The buffalo grass fills these spaces between saguaros and provides the fuel to carry larger fires in an ecosystem that really isn’t suitable,” said Don Swann, a wildlife biologist at Saguaro National Park.
In what might be a harbinger, an exceptionally devastating stretch of forest fires in the past year, including the Bighorn Fire in the Santa Catalina Mountains and the Bush Fire in the Tonto National Forest, killed thousands of saguaros and severely damaged many survivors. Relatively heavy monsoons have seen some recovery this year, although Arizona authorities have attempted to contain nearly 20 forest fires across the state in recent weeks.
In the meantime, some who live in the shadow of the saguaros are mobilizing to protect the giant cacti. Some volunteers hand dig buffalo grass in and around Tucson; others spray the invaders with herbicides. In Saguaro National Park, a helicopter crew is performing air jets in some hard-to-reach places in the Rincon Mountains this week.
Patricia Estes, who previously ran the University of Arizona’s Molecular and Cell Biology Laboratory, started a volunteer group called Catalina State Park Buffel Slayers six years ago. She said she got involved in buffalo grass digging after learning how the invasive plant can wreak havoc in arid habitats.
“If you have a buffalo grass fire in an alley in Tucson, it will melt someone’s car or chain link fence,” said Estes, adding, “The biggest threat to saguaros in climate change isn’t the heat or the drought. It is fire that sweeps in and burns extremely hot. “