Coast Redwoods Show Signs of Heat-Induced Stress as Temperatures Rise

A team from the University of California, Davis monitored coast redwood leaves in Mendocino County over a two-year period, recording physiological responses twice a month. They discovered that during extreme heat the leaves heat up faster than the surrounding air, prompting the trees to close their stomata to avoid water loss. While this protects the trees from dehydration, it also stops photosynthesis, leading to a potential carbon-starvation cycle that could stunt growth and reduce carbon sequestration.

The researchers note that declining fog—an essential water source and cooling mechanism for these trees—is already 30-40 % less frequent, compounding heat stress. Experts say the combined stressors could diminish the forest’s unique canopy ecosystems, affecting salamanders, marbled murrelets, and other organisms. Although the trees recovered after cooler periods in the study, the authors caution that more frequent, hotter heat waves may overwhelm their ability to bounce back.