Giant old saguaros can be resilient. It's baby saguaros researchers are worried about.
A woodpecker living in a Saguaro at the Desert Botanical Garden in Phoenix on June 28.
Caitlin O'Hara for NPR
In 2020, a new fear sprouted in metro Phoenix.
Amid the utter turmoil of the COVID-19 pandemic and a record-hot summer, the area's mighty saguaros were toppling at a rate that alarmed casual observers. In recent years, photos and videos of ancient giants crumbling have permeated local media and social platforms.
But experts say it's not those regal old cactuses people should be so worried about — rather, it's the young ones that aren't germinating. Human-caused climate change driven primarily by the burning of fossil fuels is robbing the Sonoran Desert of the conditions needed to help baby saguaro take root and thrive. So, as the desert grows warmer and drier, scientists are turning to that same saguaro-loving community for help establishing future generations of the cactuses.
Saguaro falls
Worry about the saguaros led locals to feverishly call cactus expert Tania Hernandez of the Desert Botanical Garden back in 2021.
"People's impression was the saguaros were dying, they were collapsing in the street," Hernandez said.
But were they really dying at an unprecedented rate?
"I didn't have any answer," she said. "... but we are working on that."
She launched metro Phoenix's grassroots Saguaro Census. Volunteers use an app to log photos of the cactuses they see and their general health. It's a survey years in the making.
"The first year (2022) was a complete success," she said. "We had really a lot of people helping us. That talks about the importance of the plant."
Since then, thousands more have made observations for the census, and Hernandez is cleaning and compiling that data. But one observation has stuck out.
"Very few of them are babies," Hernandez said. "And that means to us that when these old folks die ... we're not going to have babies to replace them."
It's an observation researcher Peter Breslin of the Arizona Institute for Resilience at the University of Arizona has also made when he surveyed thousands of saguaros that spike up from Tumamoc Hill, a volcanic outcropping in Tucson, in 2022 and 2023.
"There was no evidence, from this survey anyway, that the mortality rate of the older saguaros had increased," he said.
"But on the other hand, we have found extremely low numbers of new or young saguaros coming into the population," he added. Of roughly 4,000 cactuses catalogued, there were fewer than 20 that had germinated and established since 2012, Breslin said.