A comprehensive survey of saguaro cactus populations across southern Arizona has found that the iconic desert giants are holding steady and even expanding in some areas, offering encouraging news amid broader concerns about climate change impacts on Sonoran Desert ecosystems.
The survey, conducted by researchers at the University of Arizona and the National Park Service over the past three years, counted and measured saguaros at 50 monitoring plots spanning Saguaro National Park, the Tucson Mountain District, and several sites in the Tonto and Coronado national forests.
“The overall picture is more positive than many people expected,” said Dr. Laura Merritt, the study’s lead author. “We’re seeing healthy recruitment of young saguaros in most areas, which means the populations are sustaining themselves.”
The saguaro, which can live 150 to 200 years and grow over 40 feet tall, is the defining symbol of the Sonoran Desert and a keystone species that provides food and shelter for dozens of bird, bat, and insect species. Concerns about their future have grown as climate change brings hotter summers, more variable rainfall, and increased wildfire risk.
The survey found that a series of wet winters in recent years have benefited young saguaros, which are most vulnerable during their first decade of life when they depend on “nurse plants” like palo verde and mesquite for shade and protection. The wet conditions promoted robust growth of these nurse plants, creating favorable conditions for saguaro seedlings.
However, the researchers also noted areas of concern. Several monitoring plots in lower-elevation desert showed signs of stress in mature saguaros, including increased rates of bacterial infection linked to unusually hot summers. The 2023 extreme heat event, when Phoenix exceeded 110°F for a record 31 consecutive days, coincided with elevated saguaro mortality in some urban-adjacent areas.
“Climate change is a real threat to saguaros, but it’s a slow-moving one,” Merritt said. “The question is whether the species can adapt fast enough, and right now the answer appears to be cautiously yes — but we can’t take it for granted.”
Saguaro National Park plans to continue annual monitoring and is expanding citizen science programs that enlist volunteers to help track saguaro health across the park’s two districts.
