A new UC Davis study finds that coast redwoods stop photosynthesizing during extreme heat, closing their stomata to save water and slowing carbon uptake. Over time, that could lead to carbon starvation, weaker trees, and less habitat for the species that live in their canopies. The study measured leaves twice a month for two years in Mendocino County, the first work to document this response in coast redwoods. The trees also depend on coastal fog for cooling and hydration, but fog has declined 30 to 40 percent in recent decades. Since redwoods store more carbon dioxide per acre than any other forest, reduced sequestration makes climate goals harder. The article is a clear reminder that protecting mature forests is climate infrastructure, not just conservation.
