As climate change intensifies the Sonoran Desert is getting hotter and drier, threatening many species. The saguaro cactus (Carnegiea gigantea), an iconic desert species is adapted to extreme conditions, but new research published in the Annals of Botany Special Issue on Plant Reproduction in a Changing Global Environment suggests that saguaro populations are expected to decline by 2099.
To understand how saguaros might respond to a climate change, researchers studied 13 populations across the species’ range. They used field data (2014–2016) to develop an integral projection model (IPM). This model used future climate projections (two representing different levels of climate change and one assuming no change) to predict how saguaro numbers might change between 2017 and 2099.
The results were alarming, as all saguaro populations are expected to decline by 2099, primarily due to drought limiting recruitment (the establishment of new individuals). Saguaros reproduce by producing thousands of small seeds, but for these to germinate and grow into new cacti, they need the right conditions (moisture, shade, and protection from herbivores). Unfortunately, with rainfall becoming more erratic and more frequent droughts, fewer seedlings are surviving long enough to replace older cacti.
The pattern of future saguaro population dynamics suggests that the projected climatic changes for the present century will have negative effects on the status of saguaro populations, especially when we compare them with the projected null scenario where there is no climate change.
The research led by Ricardo Félix-Burruel, also suggest that the impact of climate change won’t be uniform across all Sonoran Desert. Populations near the coast will decline faster due to more severe droughts. Inland populations may be more resilient but will still decline over time. Conservation efforts must consider these localized effects to protect saguaros for the future.
For now, the saguaro remains in the desert, but without successful recruitment of new individuals its future is uncertain Saguaros shape desert ecosystems, providing food and shelter for many species. Their decline could have cascading effects on biodiversity.
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Félix-Burruel R., Larios E., González E. and Búrquez A. (2024) Annals of Botany. Population decline of the saguaro cactus throughout its distribution is associated with climate change. Annals of Botany. Available at: https://doi.org/10.1093/aob/mcae094
Image: Sarah Covshoff
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