Coast Redwoods Slow Photosynthesis In Extreme Heat

A study shows that high temperatures limit carbon uptake in California's iconic coastal redwood trees.

Updated on Oct. 20, 2026 in Botany

Macro view of damp redwood needles and textured bark, capturing the quiet biology of a coastal forest. — A study published on September 22, 2026, finds that coast redwoods in California reduce carbon absorption when exposed to extreme heat. AI Illustration. Upload story photo >

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Is the local environment in your area getting healthier or worse due to rising global temperatures?

Research published on September 22, 2026, reveals that coast redwoods experience inhibited photosynthesis when exposed to extreme heat. Data from a 28-month study in Mendocino County indicates that needle temperatures can soar significantly above ambient air levels.

Why it matters

As temperatures climb, these trees partially close their stomata to conserve water, which inadvertently reduces their capacity to absorb carbon dioxide. This sensitivity suggests that rising heat could diminish the long-term carbon storage potential of the species.

Laboratory tests on lower canopy samples showed photosynthesis rates consistently declined across a temperature range of 72 to 110 degrees Fahrenheit. Field measurements taken once or twice monthly over 28 months confirmed that needles can reach 18 degrees Fahrenheit hotter than the surrounding air.

The players

Journal of Geophysical Research: Biogeosciences

This is a peer-reviewed scientific journal that publishes research on the interaction between biological and physical processes in Earth's environment.

The details

Researchers at the Garcia River Forest monitored the trees by measuring needle temperatures and testing how heat stress limits vital physiological functions. The findings demonstrate that coast redwoods are highly sensitive to thermal fluctuations within their native range, which spans from central California to southern Oregon.

July 2022: Field measurements began at the Garcia River Forest site.
October 2024: The 28-month data collection period concluded.
September 22, 2026: The study was published in the Journal of Geophysical Research: Biogeosciences.

The Big Picture

This research follows the findings published in the Journal of Geophysical Research: Biogeosciences regarding coast redwood temperature sensitivity. The data marks a shift in understanding how specific tree species respond to thermal stress, potentially updating legacy hypotheses regarding their resilience to climate change.

Understanding these physiological limits helps researchers predict which forest areas may struggle as temperatures rise in the coming decades. This could eventually impact how land managers in California and Oregon prioritize conservation efforts to maintain healthy redwood ecosystems.

The takeaway

The study highlights that even massive, ancient trees like the coast redwood face significant physiological constraints due to rising temperatures. Protecting these forests requires acknowledging that heat stress can fundamentally alter their ability to serve as carbon sinks.