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Botany Seminar: Monitoring the impact of climate change on desert species in the Joshua Tree National Park region by Lynn Sweet, PhD
Joshua Tree National Park

In the region surrounding Joshua Tree National Park (JTNP), which straddles the Colorado and Mojave Deserts in southern California, previous research has predicted the widespread demise of its namesake iconic species, the Joshua tree (Yucca brevifolia). These climate change predictions point to hotter, drier deserts, which may be a challenge for even drought-adapted species. We have gathered field measurements, with community scientists, from across the Park’s broad elevation gradient for Joshua trees as well as other flora and fauna as part of a research partnership between UC Riverside, JTNP and Earthwatch Institute. We used historic gridded datasets representing the conditions where this species has occurred to predict the distribution of still-suitable conditions (refugia) at the end-of-century under a several future climate change model scenarios. We then used statistical models to identify climate refugia for Joshua trees as well as other mid elevation Mojave Desert species. In order to validate model predictions, using the community science data, we analyzed the demographic patterns of Joshua tree stands from low elevations to upper elevations within JTNP. Recruitment within stands show a strong concurrence with modeled mitigated climate refugia. Mapped refugia provide land stewards with targets for focusing protective management, giving native species a space to persist into the future. As well, collaboration with citizen science NGO’s provides a powerful tool for boosting data-gathering capacity for anticipating and responding to management challenges.