ORO VALLEY, Ariz. — It began with a flash of lightning, the fire that swept across the rugged Santa Catalina Mountains on Tucson’s edge. By the time firefighters got the blaze under control, it had torched thousands of saguaros, the towering cactuses that can reach heights of 60 feet and live for 200 years.
The loss was gut-wrenching for many in Arizona, where Indigenous peoples learned to draw sustenance from the treelike saguaros long before they emerged as a celebrated symbol of the Southwest. Some saguaros are still standing within the year-old scar of the Bighorn Fire, their trunks singed all the way up to their limbs, a testament to their reputation as masters of desert survival.
Still, said Benjamin Wilder, an authority on saguaros and director of the University of Arizona’s Desert Laboratory in Tucson, the fire-damaged cactuses would likely have their life spans curtailed.
“I don’t think there’s any more near-misses as we get to the point of much larger fires,” he said.
Wildfires are just one of many threats facing saguaros, menacing not only the cactuses but the mesquite, ironwood and palo verde plants that protect them. At the same time, the unfettered growth of invasive species, especially the very flammable buffelgrass, has spurred more competition for scarce water resources while also fueling fast-moving — and hotter — fires.
Then there is the urban sprawl of Arizona’s towns and cities. While laws generally protect saguaros from being chopped down — try that in Arizona and you can face years in prison — plant physiologists say that all the concrete in metro areas absorbs heat and holds on to it. That creates nighttime temperatures higher than in the open desert, making it harder for saguaros to minimize water loss.
Taken separately, saguaros, which can be exceptionally resilient once they mature, could possibly respond and adapt to each hazard. But scientists warn that climate change may be turbocharging all the threats at once, leveling a striking array of challenges against the iconic saguaro. (How to tell if people are new to Arizona? They pronounce the cactus’s name using a hard “g,” instead of saying suh-wahr-ohs.)
Some troubling signs are already raising 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 the saguaro, only 70 were younger than 11 years old, and they were found almost exclusively in rocky foothill habitats.
“Establishment of young saguaros has nearly ceased since the early 1990s in nearly all habitats,” the scientists who wrote the report said, noting that the population decline in young saguaros took place during a period when temperatures in the Sonoran Desert began rising and the area entered a long-term drought.
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