Saguaro cactuses at the Desert Botanical Garden in Phoenix, Arizona, are facing severe challenges. Temperatures in Phoenix have hit a record-high as a lack of seasonal monsoons take their toll.
The prolonged heat, accompanied by a deficiency of cooling night time temperatures, has left the Saguaros “highly stressed.” According to Chief Science Officer Kimberlie McCue, the stress has caused some cactuses to initially appear normal, only to suddenly collapse. Thus revealing internal rot due to heat-related strain.
Since 2020, the Desert Botanical Garden has experienced an increase in cactuses succumbing to the harsh conditions. The present-day heat records have pushed some previously affected cactuses beyond their limits. This has led to limb loss and complete collapses of the Saguaros.
Phoenix recently witnessed a record-breaking streak of 16 consecutive days with temperatures above 90 degrees. Nonetheless, Thursday is forecasted to surpass 110 degrees, marking the 28th consecutive day of extreme heat.
Critical to the cactuses’ survival is the gas exchange process that occurs at night. The plants open their stomata to take in carbon dioxide for photosynthesis. However, the unusually high night time temperatures in Phoenix caused dehydration in the cactuses, making them more susceptible to infections and insects.
Interestingly, in nearby Tucson, where temperatures are slightly lower but still exceeding 100 degrees, Saguaros have not witnessed the same distress. Erik Rakestraw, attributes this difference to the lack of a “heat island.” effect experienced in Phoenix.
Erik is the curator of botany at the Arizona-Sonora Desert Museum. According to him, reflective heat near walls, particularly affecting domesticated plants, poses more risk than wild cactuses.
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Unfortunately, the future of Saguaros is under threat as rising temperatures over time could hinder new generations of this cactus species from thriving.