An international team of scientists from Lund University and Stanford University is highlighting the critical role of soil in climate mitigation, raising urgent questions about the long-term consequences of industrial forestry practices.
In a new study, the researchers take a closer look at Sweden’s old-growth forests and find they store significantly more carbon than the industrial tree plantations rapidly replacing them. Researchers also discovered that a large portion of this carbon is hidden beneath the forest floor.
The research team, which included Rob Jackson, Anders Ahlström, and Didac Pascual, conducted an extensive survey of Sweden’s forests by measuring carbon levels in more than 200 forest plots across the country over a three-year period. The researchers then combined their findings with decades of national forest and soil carbon data. The study represents one of the most comprehensive analyses to date of carbon storage across living trees, dead wood, soil, and harvested timber.
“Unfortunately, the logging of primary forests in Sweden continues,” said study author Anders Ahlström, who spearheaded work on the research over the past eight years – first as a postdoctoral scholar in Jackson’s lab at Stanford and then as a senior lecturer at Lund University in Sweden. “Our results show that protecting the few primary forests that remain has a much larger potential to slow climate change than previously thought. Restoring sites degraded by industrial forestry could also boost biodiversity and store even more carbon.”
Undisturbed primary forests store 72% more carbon per acre than managed forests. When harvested wood products are included, primary forests still hold 83% more carbon. These figures are striking—between two and eight times higher than previous estimates.
According to the study, restoring Sweden’s managed forests to the carbon levels of primary forests could prevent nearly 8 billion tons of carbon dioxide from entering the atmosphere. In practical terms, that is equivalent to Sweden’s total fossil fuel emissions over the past 200 years.
One of the facts that most surprised researchers during this study was that lowland primary forests contained about 64% of the total carbon, compared with 30% in live trees and just 6% in dead wood. “The loss of soil carbon through industrial management is persistent and shocking,” Jackson said.
“Some of the changes we found are intuitive – that the primary forests have larger trees and hold more dead wood. But we weren’t sure what to expect from the soils,” said lead study author Didac Pascual, a postdoctoral scholar at Lund University. “We learned that primary forests stored more carbon in their soil alone than managed forests do in trees, dead wood, and soils combined.”
However, Sweden’s old-growth forests are quickly disappearing. Between 2003 and 2019, unprotected forests were clear-cut at a rate of 1.4% per year, which is six times faster than primary forest loss in the Brazilian Amazon.
“Unfortunately, the logging of primary forests in Sweden continues,” said study author Anders Ahlström, who spearheaded work on the research over the past eight years – first as a postdoctoral scholar in Jackson’s lab at Stanford and then as a senior lecturer at Lund University in Sweden. “Our results show that protecting the few primary forests that remain has a much larger potential to slow climate change than previously thought. Restoring sites degraded by industrial forestry could also boost biodiversity and store even more carbon.”
These implications extend far beyond Sweden, as many countries depend on northern forests to meet climate targets, including through bioenergy production.
“Our goal is to understand what makes the fungi and bacteria in these old-growth forests unique,” Peay said. Fundamentally, this knowledge could potentially pave the way for using microbes to accelerate the transition of managed forest soils to a state where they store more carbon, Peay says, adding that it could do so “without having to wait centuries for old-growth forests to develop naturally.”
The study “Higher carbon storage in primary than secondary boreal forests in Sweden” recently appeared in the journal Science.
Chrissy Newton is a PR professional and the founder of VOCAB Communications. She currently appears on The Discovery Channel and Max and hosts the Rebelliously Curious podcast, which can be found on YouTube and on all audio podcast streaming platforms. Follow her on X: @ChrissyNewton, Instagram: @BeingChrissyNewton, and chrissynewton.com. To contact Chrissy with a story, please email chrissy @ thedebrief.org.