Population projections of an endangered cactus suggest little impact of climate change
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Population projections coupled with downscaled climate projections are a powerful tool that allows predicting future population dynamics of vulnerable plants in the face of a changing climate. Traditional approaches used to predict the vulnerability of plants to climate change (e.g. species distribution models) fail to mechanistically describe the basis of a population’s dynamics and thus cannot be expected to correctly predict its temporal trends. In this study, we used a 23-year demographic dataset of the acuña cactus, an endangered species, to predict its population dynamics to the end of the century. We used integral projection models to describe its vital rates and population dynamics in relation to plant volume and key climatic variables. We used the resulting climate-driven IPM along with climatic projections to predict the population growth rates from 1991 to 2099. We found the average population growth rate of this population between 1991 and 2013 to be 0.70 (95% CI 0.61–0.79). This result confirms that the population of acuña cactus has been declining and that this decline is due to demographic structure and climate conditions. However, the projection model also predicts that, up to 2080, the population will remain relatively stable mainly due to the survival of its existing adult individuals. Notwithstanding, the long-term viability of the populations can only be achieved through the recruitment of new individuals.
KeywordsAcuña cactus Climate projections Long-term demography Temperature Precipitation
The authors thank the Ecological Monitoring Program of Organ Pipe Cactus National Monument and the National Park Service for providing the long-term demographic database and Charlotte Brown, Charles W. Conner, and other NPS staff and volunteers who helped collect data. EL would like to thank Pilar Navas-Parejo for providing help with the figures. The authors thank the Southwest Border Resource Protection Program for funding this study (Cooperative Agreement P16AC01027, Plant demography and vulnerability to climate change at Organ Pipe Cactus National Monument and Pinacate Biosphere Reserve).
Author contribution statement
EL analysed the data and wrote the manuscript; EJG analysed the data and wrote the manuscript; PCR and PH lead fieldwork and analysed data; AP performed fieldwork. All authors contributed critically to the drafts and gave final approval for publication.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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