Friday, September 29, 2023

Even Saguaro Cacti Have Had Enough Of The Heat: AZ Desert Icons Migrating To Cooler Weather

Extreme Heat And Wildfires Forcing Saguaro Cacti To Seek Cooler Temperatures


Record-breaking heat in Arizona has had a profound and negative effect on their iconic saguaro cacti, with many younger cacti now taking root in higher elevations to escape the heat. Consecutive dry years and extreme temperatures, coupled with invasive buffelgrass, have wreaked havoc on these desert giants. There is now a growing concern among the state's biologists about the future of the iconic cacti.  

Growing exclusively in the Sonoran Desert, also known as the world's wettest desert due to the region's summer monsoons, the saguaro has thrived in this environment for 10,000 years. Climate change has disrupted the annual monsoons, especially the last few seasons. The 2020 season has often been referred to as a nonsoon since only 1.62 inches of rain was recorded. The average rainfall in the Sonoran Desert is 6.08 inches. 2020 also saw a record-breaking heatwave across Arizona, with temperatures rarely falling below 100 degrees.  

While extreme temperatures and drought may not necessarily spell death for a saguaro, it's the fire danger that accompanies extreme temperatures that have biologists concerned. The Bighorn Fire, which raged in the Santa Catalina Mountains north of Tuscon in 2020, burned thousands of acres filled with dense stands of saguaros. This tragedy may only be the beginning of a long trend of the saguaro's decline in Arizona.

Invasive buffelgrass from South Africa has exacerbated the wildfire danger in the saguaro's native range. Buffelgrass and saguaros thrive in the same unforgiving landscape, but buffelgrass is easily susceptible to wildfires and allows these desert fires to ravage entire ranges.

Historically found at elevations ranging from 3,900 to 5,900 feet, young saguaros have been recently recorded in higher elevations and almost nonexistent in lower elevations. The heat-loving cacti are susceptible to freezing temperatures, especially if exposed for 36 hours, making their move to higher elevations a recent phenomenon. The move to higher elevations may indicate the future for the cacti.  

The effect of heat and human disruption of the saguaro is most evident in cities, which are also heat islands in an already extreme environment. Arizona's desert metropolises and their suburbs have uprooted many already established saguaros. Human disruption, compounded by the region's drought and record-breaking, has had dire consequences for saguaros. When a saguaro is relocated, it takes years for its roots to reestablish its roots, and during that time, it is more difficult for the cacti to resist prolonged heatwaves. Arizona cities have essentially become graveyards for saguaros.

On the border of California and Arizona, the far western range of the saguaro may already be too hot for the cacti. Cities have also mirrored this trend as extreme nighttime temperatures place additional stress on the cacti as they cannot recover from the day's heat. The high deserts and mountain ranges of eastern Arizona look to be the cacti's future and maybe even New Mexico if temperatures continue to increase.


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