Study Finds Coast Redwoods Halt Photosynthesis During Heat Waves

Research published on September 22 in the Journal of Geophysical Research: Biogeosciences indicates that coast redwoods, the tallest trees on the planet, might halt photosynthesis during periods of elevated temperatures. The study, led by ecologist Lily Klinek from the University of California, Davis, observed trees in the Garcia River Forest, California, from July 2022 to October 2024, encompassing two heat waves. The needles were found to be as much as 18 degrees Fahrenheit warmer than the surrounding air, suggesting stress. The researchers believe that stomata may have closed to retain moisture, thereby reducing carbon dioxide absorption. Laboratory experiments confirmed that photosynthesis rates decreased as temperatures rose. The tallest redwood, Hyperion, identified in 2006, has been off-limits to visitors since 2022 due to these challenges.