The forest carbon cycle: How different forest types capture and store carbon

Covering about one-third of the Earth's land surface, forests provide essential ecosystems services, from soil conservation, and water management , timber and raw materials for hundreds of millions of people, and climate regulation.

How do forests help to remove carbon dioxide from the atmosphere?

Through tree growth, carbon dioxide (CO₂) is captured and stored in the form of wood, deadwood, fallen leaves (litter) and in forest soils (‘carbon sequestration’). Trees also release CO₂ again into the atmosphere, as a result of natural processes (decomposition of deadwood by bacteria and fungi), harvesting or natural disturbances (windthrows, wildfires¹).

It’s clear that forests are important to regulate climate. They function as carbon sinks, when they absorb more CO₂ than they release. However, they can also become carbon sources when they release more CO₂ than they absorb.

Is carbon sequestration different in managed vs. protected forests?

In 2022, Mondi and the Austrian University of Natural Resources and Life Sciences (BOKU) teamed up for a research project to better understand how different forest types and management practices impact the ability of forests to capture CO₂. The project focused on European forests (included a comprehensive literature review, meta-analysis, and expert interviews.

The study highlighted the complexity of carbon dynamics in forests and explored impacts of forest management and structure on carbon sequestration. It has compared managed forests (young, middle aged, until 100-150 years old) and unmanaged forests (mature, old growth), often set aside for protection, asking:

• What are the differences between the two forest types when it comes to carbon sequestration and storage?
• What happens to a forest’s ability to store and capture CO₂ if the management practice is changed (for example, when we preserve a previously managed forest or start actively managing a previously unmanaged forest)?

Based on the available data, several findings from the research were identified:

• Sustainably managed forests are efficient in removing CO₂ from the atmosphere, acting as a so-called ‘carbon pump’.
• Unmanaged forests have the highest carbon storage, but low to negligible carbon sequestration.
• Managed forests left without human intervention (i.e. those managed forests converted to protected lands) can become unstable. The reason for this instability stems from the fact that formerly managed forests are less adaptable to changing conditions.
• Healthy and stable unmanaged forests provide good carbon storage, but carbon sequestration is likely to decrease in future as they approach maturity. The risk of carbon losses will increase, in part due to climate change.

The study made it clear that there is still a lot of work to be done in this area when considering the carbon sequestration potential of managed vs protected forests and implications of a switch from one type to another. A lack of data on carbon stocks, stand structure of unmanaged forests, and harvested wood products were identified as possible directions for further research.

At Mondi, we believe that sustainable working forests provide many benefits, including commercial value to landowners, while protecting ecosystems and biodiversity, and reducing reliance on products derived from fossil fuels. Plantation forestry can also reduce pressure on protected forests as plantations provide a higher yield, which helps to meet rising demand for fibre-based products. Planted forests make up 7% of the world’s forest cover², while meeting nearly half of the global industrial roundwood supply.

Science and business team up to improve forest resilience

We collaborate with the scientific community to address climate change challenges, gain broad access to research and convert it into practical applications, for Mondi and the forest sector overall.

This includes Mondi’s role as a founding member of the TEAMING UP 4 FORESTS science-business platform and our latest study, on the factors affecting future wood supply in Europe, including climate change, land use and policy developments. Learn more about TEAMING UP 4 FORESTS here.

Explore our latest Sustainable Development report to discover more topic. about how Mondi promotes resilient forests while taking action on climate.

^{[1]https://unece.org/forests/carbon-sinks-and-sequestration
[2]https://www.fao.org/forestry/newsroom/news-detail/planted-forests-key-to-achieving-global-goals---fao-journal/en}