Climate change impacts on high elevation saguaro range expansion

Severe freeze events have been identified as a primary limiting factor for the saguaro cactus at high elevations in the southwestern United States. With the observed increase in minimum temperatures, it may be expected that saguaros will expand their elevational range. To better understand the factors influencing potential range expansion, we developed a logistic regression model to help explain saguaro presence along its current uppermost elevation. We find that the occurrence of fire decreases the odds of saguaro presence by 78 percent. While less frequent freeze events could allow saguaros to push their current elevational limit, our model suggests that increased fire activity related to the establishment and spread of invasive species could inhibit this range expansion.