A new analysis by Lund University and Stanford University reveals that old-growth forests in Sweden store dramatically more CO2 than industrially managed ones. The peer-reviewed work, published in Science, found that the substantial difference in carbon storage is mostly credited to soils.
Studying forests in Sweden, the team of researchers mapped old-growth forests across the country and then measured CO2 at more than 200 forest plots over the course of three years.
This field data was then combined with decades of national forest and soil CO2 inventory data and statistical models, creating a first-of-its-kind analysis that quantifies carbon in vegetation, dead wood, soil, and harvested timber.
Results showed that undisturbed primary forests store 72% more carbon per acre than the managed forests that are replacing them, typically with single-species plantations.
The publication clarifies that this figure gives managed forests credit for all the CO2 stored in goods from harvested wood, such as bioenergy, paper, and building materials. When these harvested wood products are excluded, primary forests store 83% more carbon per acre.
As highlighted in the publication, the difference is 2.7 to 8 times larger than current official estimates. This means that if the CO2 storage in Sweden’s managed forests is to be restored to the level of primary, old forests, this effort would require keeping nearly 8 billion tons of carbon dioxide out of the atmosphere.
The researchers were surprised to find the CO2 storage difference lies in the soil, and Rob Jackson, senior study author and professor of Earth system science at the Stanford Doerr School of Sustainability, shared that there’s far more carbon in the soil than in the trees in these old-growth boreal forests.
He highlighted, “The carbon storage capacity that an old-growth forest loses once it’s been heavily furrow-cut and logged can’t easily be recovered. The loss of soil carbon through industrial management is persistent and shocking.”
Relevant: New Study Finds Removing Livestock From Grasslands May Compromise Soil Carbon Sinks
The increased use of northern forests as a climate change mitigation tool, especially for bioenergy production, forms part of most models for stabilizing global temperatures. The findings of this new study suggest that those projections may overestimate climate benefits from forest-derived biofuels, especially if slowly growing boreal forests take centuries to build up those benefits.
Looking ahead, researchers will study what exactly drives this carbon storage capacity in old-growth Swedish forests, looking to identify elements that can be replicated in other boreal forests around the world.
Read more: New Study: EU Forests Are Losing Their Carbon Absorbing Capacity
