# Heatwaves Force California Redwoods to Halt Photosynthesis

- Topic: science
- Source: [Wired](https://www.wired.com/story/californias-tallest-and-most-iconic-trees-are-getting-heat-stroke/)
- Published: 2026-10-11
- Original: https://www.wired.com/story/californias-tallest-and-most-iconic-trees-are-getting-heat-stroke/
- Language: en
- Image: https://media.wired.com/photos/6ac8bfc343102e19d08d1486/master/pass/GettyImages-2271228456.jpg

## At a glance

- UC Davis researchers discovered coast redwoods close leaf pores and halt photosynthesis to prevent dehydration during severe heatwaves.
- Shutting stomata stops carbon absorption, raising concerns that persistent heat events could trigger fatal carbon starvation in younger trees.
- Declining coastal fog removes a natural cooling mechanism that redwoods rely on to survive beyond their typical temperature range.
- Drying conditions within upper branches threaten elevated ecosystems of soil and ferns that shelter rare salamanders and seabirds.

## Sources

- [Wired](https://www.wired.com/story/californias-tallest-and-most-iconic-trees-are-getting-heat-stroke/)

## The story

A two-year investigation by researchers at the University of California, Davis, shows that coast redwoods shut down photosynthesis during periods of extreme heat. By tracking trees in Mendocino County twice each month, scientists found that redwood needles heat up much faster than surrounding air. To conserve vital moisture when temperatures soar, the trees seal their stomata rather than cooling down through transpiration.

Closing these surface pores saves water but prevents trees from absorbing carbon dioxide, halting essential energy production. Ecologists warn that repeated shutdowns could trigger carbon starvation, leaving redwoods without sufficient stored energy to produce new foliage. Younger second-growth groves that dominate the region are particularly vulnerable, as their rapid development demands substantial carbon intake.

Rising temperatures also coincide with a steep decline in coastal fog, which historically provided redwoods with canopy hydration and cooling shade. Researchers note that drier microclimates threaten canopy soil mats that support arboreal wildlife, including wandering salamanders and marbled murrelets. While redwoods recover once heatwaves subside, chronic stress could stunt their growth and diminish their unmatched ability to sequester carbon.

> Summary by Daily Read Bytes. [Read the original source](https://www.wired.com/story/californias-tallest-and-most-iconic-trees-are-getting-heat-stroke/)