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Research Spotlight: Climate Change and California’s Coastal Redwoods

Emily J. Francis, Gregory P. Asner, Katharine J. Mach and Christopher B. Field (2020). Landscape scale variation in the hydrologic niche of California coast redwood. Ecography. DOI: 10.1111/ecog.05080

The Upshot

Throughout California, the effects of climate change are evident from increasing frequencies of intense wildfires and mudslides to widespread and prolonged droughts. These changes also threaten one of California’s most iconic endemic species: coastal redwoods. Coastal redwoods are not only some of the tallest and oldest trees on Earth, but redwood forests are also capable of storing three times more carbon than any other forests on Earth. 

By combining high-resolution redwood distribution maps with data on moisture availability, researchers were able to identify the environmental factors that shape redwood distribution. Given that some regions within the current redwood distribution in California (south of SF Bay) could become unsuitable for redwoods as soon as 2030, identifying suitable habitats for these vulnerable species is especially urgent, with important implications for carbon sequestration and redwood forest biodiversity. 

The Discovery

The scientists found that redwood habitat suitability significantly varied in relation to moisture availability and fog across different landscape elevations. Redwood habitats were consistently more suitable at sites located closer to streams. The study also found that habitat suitability for redwoods ranged from 22-75% within a single landscape, underlining the importance of considering landscape-scale variation while identifying sites that will continue to be suitable for redwoods, even as surrounding areas become inhospitable due to climate change. 

The Impact

“Habitat suitability of coast redwood has been studied before, but not using high-resolution data at the landscape scale. The approach we employed here could be applied in other forest types to gain new insight into the role of moisture availability in landscape-scale patterns of habitat suitability for many tree species that may be vulnerable to climate change,” said Emily Francis, lead author of the study. 

“This study highlights the value of mapping the composition of our forests at high spatial resolution. Doing so provides leverage to say something about the individual inhabitants within a forest, not just the forest as a blanket average. This, in turn, both enhances our knowledge and presents possible options for managing sensitive ecosystems undergoing climate change,” said co-author Greg Asner, director of the ASU Center for Global Discovery and Conservation Science. 

The Researchers

Emily Francis, the lead author of the study, conducted this research while pursuing a Ph.D. at Stanford University in the Department of Earth System Science. Emily is currently a Postdoctoral Fellow in the Department of Integrative Biology at the University of Texas at Austin. The co-authors of the study include Dr. Greg Asner of Arizona State University’s Center for Global Discovery and Conservation Science, Dr. Katharine Mach, an Associate Professor at the Rosenstiel School of Marine and Atmospheric Science at the University of Miami, and Dr. Christopher Field of the Stanford Woods Institute.