Temperate Forests May Be Losing Their Grip on Carbon Absorption
Forests have long been considered a critical ally in the fight against climate change, but new research suggests their role in absorbing carbon dioxide may be diminishing. A recent study conducted by researchers from Northern Arizona University (NAU) and the University of New Hampshire reveals concerning trends in the carbon absorption capabilities of a New Hampshire forest over the last two decades.
Led by NAU Ph.D. student Darby Bergl, the study utilized a rare 20-year dataset to assess whether temperate forests continue to serve as effective carbon sinks. The results, published in Global Change Biology Communications, indicate that this particular forest’s ability to absorb carbon has significantly declined since 2004.
“We often think of forests as one of our best natural climate solutions because they remove large amounts of carbon dioxide from the atmosphere,” Bergl remarked. “Our findings suggest that mature temperate deciduous forests may no longer reliably remove more carbon than they release under continued global change.”
The study found that the forest’s carbon sink strength has weakened, with the site even becoming a net carbon source in recent years. Interestingly, this decline was not due to decreased photosynthesis but rather increased carbon release through respiration—a natural process involving plants, roots, and soil microbes.
Andrew Richardson, the corresponding author and a Regents’ professor at NAU’s Center for Ecosystem Science and Society, noted the influence of warmer winters on this trend. “Our results clearly show the long-term impacts of changing winter weather on the health and productivity of northern forests,” Richardson said. He emphasized the need for strategies to sustain forest health and resilience, given their societal benefits, including carbon storage and biodiversity support.
Bergl highlighted the implications for global climate models, which often assume forests will continue to absorb substantial carbon amounts. She stressed the importance of long-term ecological research, stating, “The fact that we only detected this weakening carbon sink after two decades of continuous measurements underscores the importance of sustained investment in long-term ecological research.”
The research team also included Mariah Carbone, Yujie Liu, Benjamin Lucas, Scott Ollinger, David Hollinger, Andrew Ouimette, and Pamela Templer, representing institutions such as NAU, UNH, the U.S. Forest Service, and Boston University.
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