Pallade Veneta - Study Finds Climate Change Threatens Cacti More Than Previously Thought

Cacti, widely regarded as some of the most resilient plants on Earth, are facing a severe threat from climate change that exceeds previous scientific expectations. A new study published Wednesday in the journal Nature indicates that the combination of rising temperatures and extreme drought events could eliminate suitable habitats for more than a quarter of analyzed cactus species by the end of the century.

The research challenges a long-held assumption in botany that cacti would likely be "winners" in a warming world. Brian Enquist, a professor at the University of Arizona and co-author of the study, noted that while these plants are adapted to hot, dry environments, the current climate is shifting into a new regime that many species have not encountered during their evolutionary history.

"Even in these really hot, dry environments where you see cactus species, the climate now is shifting into a new climate regime that these species haven’t encountered in their evolutionary history," Enquist said.

The study integrated new spatial data on severe drought with climate models to track how future conditions might affect nearly 1,000 cactus species. The researchers analyzed approximately 650,000 records of cacti globally, including community science data from the app iNaturalist, which more than doubled the number of species included in the analysis. This dataset spanned ecosystems ranging from tree-hanging Christmas cacti in tropical rainforests to the massive saguaros of the Sonoran Desert.

The findings revealed that drought and heat would have the most severe impacts on species in concentrated cactus hotspots, including Chile, Argentina, Peru, Ecuador, and countries in Central America. While some regions, such as the Mexican Pacific coast, showed modest gains in cactus diversity, these were offset by significant losses in neighboring areas.

The study’s results suggest that habitat declines will lead to substantial losses in cactus diversity in certain regions. More than 80 percent of all analyzed species could lose most of their suitable habitat by 2100. This figure is significantly higher than estimates derived from considering only rising temperatures and projected average precipitation, highlighting the critical role of extreme drought events.

Cacti are already among the world’s most imperiled plants, with more than 30 percent of species considered threatened due to habitat loss and illegal trade. The popularity of cacti as houseplants has fueled a collector market that contributes to this decline. Recent unprecedented droughts have already caused widespread die-offs of species such as Copiapoa cacti in Chile’s Atacama Desert and saguaros around Phoenix and Tucson.

Michiel Pillet, a postdoctoral researcher at the University of South Florida and co-author of the study, stated that these recent events are precursors to what may occur if climate change continues to drive longer, more intense periods of heat and dryness. "We were extremely surprised by how intense our results were," Pillet said.

Pillet added that the impacts identified in the study are likely an underestimate due to insufficient data on rare species, which face disproportionate risks from climate change. He illustrated this vulnerability with the example of a cactus species living in a single coastal spot that could be wiped out entirely by a hurricane.

The research extends beyond understanding the climate vulnerability of cacti. David Williams, a botany professor at the University of Wyoming who was not involved in the study, noted in an email that the work will guide future studies uncovering species-specific ecological, demographic, and physiological processes that shape persistence across shifting climatic conditions.

The researchers suggest their modeling approach could be applied to other plant species. They also propose that the findings can help experts develop more targeted conservation efforts in a warmer, drier world. One potential strategy is "assisted migration," which involves artificially dispersing seeds into new environments that fit a cactus’ climate niche to establish more stable populations for at-risk species.

Enquist highlighted the widespread public interest in cacti as a positive factor for conservation. The abundance of citizen-science observations generated by this interest helped make the research possible. "There are a lot of people that care about these plants," Enquist said. "What’s wonderful then about that is that there is a lot of opportunity for intervention."

Pillet emphasized that raising awareness for the cactus species most at risk and gathering more data on them can help determine where to spend limited conservation resources effectively. "Get the best bang for our buck," he said, referring to the strategic allocation of funds to protect biodiversity in the face of accelerating climate change.

G.Riotto--PV