A new study from Sweden finds old-growth forests store up to 89% more carbon than managed forests, with much of the difference coming from carbon locked in forest soils.
Old-growth forests in Sweden store between 78% and 89% more carbon than managed forests, according to research published in Science. The study found that much of the additional carbon is stored in forest soils, suggesting the climate benefits of protecting old forests have been underestimated.
Researchers from Lund University analysed carbon stored in trees, dead wood and soil across Sweden's remaining old-growth forests. They found that soil alone in these forests contains as much carbon as the trees, dead wood, and soil combined in managed forests.
The research is based on nearly a decade of fieldwork. Scientists identified forests with little or no history of industrial logging and excavated about 220 soil pits, some reaching one metre deep, to measure underground carbon stocks.
The team proceeded to compare the findings with managed forests in which trees are cut down to produce timber, paper, and bioenergy. Managed forests still had significantly lower levels of carbon content, even taking into account carbon stored in harvested wood products. It should be added that the carbon stored in wood products has relatively short life spans and will eventually return to the atmosphere.
It is assumed that the difference in carbon storage between old-growth and managed forests is three to eight times higher than in previous assessments. Additional carbon stored in old-growth forests of Sweden equals 211 years of Sweden's current fossil carbon dioxide emissions.
The findings also challenge the common focus on annual carbon uptake. While fast-growing managed forests may absorb carbon quickly, the researchers argue that total carbon stored over long periods provides a more complete picture of a forest's contribution to climate mitigation.
The researchers argued that converting old-growth forests to managed forests leads to greater losses of carbon than was previously understood, mainly due to the release of carbon from the soil. Furthermore, they stated that conservation of old-growth forests and restoration of degraded forests could be useful in ensuring carbon storage over the long term.
This study adds another layer to the existing debate over the management of forests and the implications for climate change policy.
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