Coastal Redwoods Cut Back Gas Exchange as Heat Waves Intensify

California's towering coast redwoods are showing a marked physiological response to extreme heat, curbing both respiration and photosynthesis when temperatures surge above 100°F (38°C). The slowdown, observed by researchers monitoring the iconic trees, highlights how rising climate variability may stress a species long adapted to cool, maritime climates.

Redwoods traditionally thrive in coastal fog belts where the average annual temperature hovers near 59°F (15°C). Their massive trunks and shallow-rooted, moisture-loving foliage are tuned to a narrow thermal window, allowing continuous carbon uptake and growth throughout the year.

During recent heat waves, scientists recorded a pronounced decline in the trees' gas exchange rates. The term “breathing” refers to the trees' respiration, while “eating” denotes photosynthetic carbon fixation. Both processes slowed as leaf temperatures climbed, indicating that the trees were conserving water and limiting metabolic activity to avoid damage.

Such responses are not unique to redwoods, but the magnitude of the decline is concerning given the species' ecological role. Coast redwoods sequester large quantities of carbon, support diverse understory habitats, and serve as a natural buffer against coastal erosion. A persistent reduction in their carbon uptake could diminish these ecosystem services.

The findings arrive amid broader concerns about climate change’s impact on forest health across the western United States. Warmer winters, reduced fog, and longer drought periods have already stressed many tree species, increasing susceptibility to pests and disease. For redwoods, the combination of higher peak temperatures and fewer cooling fog events may compound stress.

Researchers stress that while redwoods can tolerate occasional heat spikes, the frequency and intensity of such events are projected to rise. Continued monitoring will be essential to determine whether the trees can acclimate over time or if management interventions—such as protecting fog corridors or reducing nearby heat sources—will be required.

Policy makers and conservation groups are watching these developments closely, as redwoods are emblematic of California’s natural heritage and a focal point for climate resilience strategies. Protecting the microclimates that sustain them could become a priority in regional climate adaptation plans.

Future studies aim to quantify how long the trees remain in this reduced metabolic state and whether repeated heat events lead to lasting growth setbacks. Understanding these dynamics will inform both scientific models of forest carbon budgets and practical efforts to preserve the majestic redwoods for generations to come.