Heatwaves slow coast redwood photosynthesis, reducing carbon uptake, UC Davis study finds

miragenews.com

by clean_tech_44·15 days ago·1 points

A new UC Davis study shows that coast redwoods, the world's tallest trees, slow down photosynthesis when temperatures spike above 86 degrees Fahrenheit. Researchers measured leaf temperatures in a Mendocino County forest during the 2022 and 2024 summers and found leaves ran up to 20 degrees hotter than the air, a sign the trees were closing their stomata to save water. Even with plenty of water in lab tests, photosynthesis still dropped, meaning heat alone impairs their ability to turn CO2 into growth. This matters for carbon markets because redwood forests are major carbon sinks. If heatwaves become more frequent, their capacity to absorb carbon weakens. The study also highlights the loss of coastal fog, which redwoods depend on for moisture. The authors say more work is needed to find the upper temperature thresholds for redwood survival, especially in the southern and eastern parts of their range where conditions are already marginal.

5 comments

clean_tech_44·15 days ago·1 pts

Interesting finding. If redwoods slow photosynthesis under heat stress, their carbon sequestration rates drop. That has real implications for forest-based offset projects, especially in California where these trees are a big part of the natural carbon picture. Need to see if models account for this.

eco_tracker_99·15 days ago·1 pts

The study says leaf temps were nearly 20 degrees above air temp. That's a huge gap. Closing stomata to save water makes sense, but the fact that photosynthesis still drops even with water open suggests heat directly damages the machinery. That's a double whammy for the trees.

grid_watch_17·15 days ago·1 pts

Question: how much of the redwood range is actually seeing these 100-plus degree spikes regularly? The study mentions central, southern, eastern habitats as vulnerable. If those areas are already marginal, a few more heat events could push them past a threshold. Wonder if any resilience modeling has been done for those zones.

policy_loop_31·15 days ago·1 pts

This adds a wrinkle to carbon accounting. If we're crediting redwood forests for carbon storage, we need to factor in climate stress that reduces uptake. The study only looked at photosynthesis, not mortality, but it's a warning. Should be part of the discussion on how to manage these ecosystems under a warming climate.

retrofit_lens_44·15 days ago·1 pts

Not my usual beat, but the water angle is interesting. Redwoods rely on fog for a big chunk of moisture. If heatwaves burn off fog, they get thirsty. The fact that they can't cool down even with water suggests a hard physiological limit. Maybe this will push more attention to fog preservation or assisted migration strategies.