'Groundbreaking' Study Stresses Need to Protect Global Forest Carbon Sink

In what one researcher's group on Thursday hailed as a "groundbreaking" study, scientists from 11 countries highlighted "the critical role of forests in mitigating climate change" and how various threats are imperiling Earth's vital climate sink.

"Despite facing regional threats like deforestation and wildfires, the world's forests continue to be a powerful weapon in the fight against climate change," the U.S. Forest Service (USFS)—which co-led the study published in Nature—said Wednesday in a statement announcing the paper. "These vital ecosystems have consistently absorbed carbon dioxide for the past three decades, even as disruptions chip away at their capacity."

The study shows how the world's forests have consistently absorbed carbon dioxide over the past three decades, "even as disruptions chip away at their capacity."

Researchers examined long-term ground measurements combined with remote sensing data and found that "forests take up an average of 3.5 ± 0.4 billion metric tons of carbon per year, which is nearly half of the carbon dioxide emissions from burning fossil fuels between 1990 and 2019."

According to USFS, other key findings from the study include:

• Boreal forests in the Northern Hemisphere, spanning regions like Alaska, Canada, and Russia, have experienced a significant decline in their carbon sink capacity, dropping by 36%;
• This decrease is attributed to factors including increased disturbances from wildfires, insect outbreaks, and soil warming;
• Tropical forests have also seen a decline, with deforestation causing a 31% decrease in their ability to absorb carbon;
• Regrowth in previously abandoned agricultural lands and logged areas has partially offset these losses, keeping the net carbon flux in the tropics close to neutral; and
• Temperate forests, on the other hand, have shown a 30% increase in their carbon sink capacity, a rise largely due to extensive reforestation efforts, particularly in China.

"Our research team analyzed data from millions of forest plots around the globe," USFS researcher Yude Pan said in a statement. "What sets this study apart is its foundation in extensive ground measurements—essentially, a tree-by-tree assessment of size, species, and biomass. While the study also incorporates remote sensing data, a common tool in national forest inventories and land surveys, our unique strength lies in the detailed on-the-ground data collection."

The study's other lead author, Richard Birdsey of the Woodwell Climate Research Center in Falmouth, Massachusetts, said that "the persistence of the global forest carbon sink was a surprise given global increases in wildfire, drought, logging, and other stressors."

"But it turns out that increasing emissions in some regions were balanced by increasing accumulation in other regions, mainly re-growing tropical forests and reforestation of temperate forests," Birdsey added. "These findings support the potential for improving protection and management of forests as effective natural climate solutions."

The study's recommendations include reducing deforestation, promoting reforestation, and "improving timber harvesting practices to minimize emissions from logging and related activities."

The world lost around 3.7 million hectares of primary tropical forests last year—a rate of approximately 10 soccer fields per minute, according to data from the University of Maryland's Global Land Analysis and Discover Lab. While this marked a 9% reduction in deforestation compared with 2022, the overall deforestation rate is roughly the same as in 2019 and 2021. Felling trees released 2.4 metric gigatons of climate pollution into the atmosphere in 2023, or almost half of all annual U.S. emissions from burning fossil fuels.

In the United States, green groups cautiously welcomed the USFS introduction last month of a draft environmental impact statement for the proposed national old-growth forest plan amendment, which followed President Joe Biden's 2022 directive to protect old-growth forests.