Forests remove carbon dioxide from the atmosphere and store carbon in living biomass and soils. But that is only part of their relationship with the climate.
When trees are harvested, carbon remains stored in wood products after it leaves the forest. How long it stays there depends on what the wood becomes and how long the product remains in use. Wood can also replace other fossil-based materials, creating a positive climate effect through substitution.
Carbon stored in the forest, carbon held in harvested wood products, product lifetimes and substitution are related, but they are not the same thing. Keeping those distinctions clear is essential if we want the discussion to be meaningful. Assessing the climate impact of forests and wood means being clear about where carbon is stored, for how long, what happens to forest carbon stocks, and what is being compared across the wider value chain.
On 16 September 2026, Teaming Up 4 Forests will publish the Productive and Biodiverse synthesis study, examining how Europe’s forests can remain productive while maintaining biodiversity. One part of the study looks at forest carbon and the value chain, including how different forms of carbon storage and potential substitution effects should be understood together.
Assessing climate impact means looking beyond the forest itself
Forests store carbon in several places. Living trees capture carbon as they grow, while forest soils can hold substantial carbon stocks that build up over long periods but can be lost much more quickly when forests are severely disturbed. Both can be affected by management, forest health and disturbances such as fire, storms and pests.
Harvesting does not necessarily mark the end of carbon storage. When wood is used in products, some of that biogenic carbon moves from the forest into the value chain and can remain stored for decades or, in some applications, much longer. Forests are also naturally regenerative systems, meaning they can grow back and continue storing carbon after harvesting.
The type of product therefore changes the picture. Wood used in a long-lived structural application stores carbon for a different period from wood used in a short-lived product. A climate assessment that stops at the point of harvest would miss that distinction.
But extending the boundary beyond the forest does not mean ignoring what happened there. The report is clear that the climate impact of harvested wood products must be considered alongside changes in forest carbon stocks and emissions associated with producing those products.
Carbon storage and substitution need to be assessed separately
Using wood can affect climate outcomes in another way: through substitution.
Substitution refers to the potential emissions difference when wood is used instead of another material or energy source. That effect depends on what is being replaced and on the emissions associated with both alternatives. It is therefore a comparison between systems, not another form of carbon storage.
This distinction is important because carbon stored in a forest, carbon retained in a wood product and emissions potentially avoided through substitution answer different questions.
The climate case for a wood product therefore cannot be established simply by pointing to the carbon contained within it. The wider assessment also has to consider changes in forest carbon stocks, emissions from production and any substitution effect. The report expresses this directly: the net climate benefit depends on the combined effect of long-term carbon storage and substitution exceeding emissions from production and losses from forest carbon stocks.
The climate impact of carbon storage depends on time as well as quantity
Carbon stored biologically is not necessarily stored permanently. Forest carbon can return to the atmosphere through natural carbon cycles, harvesting or disturbance such as wildfires, while carbon held in a product is released when that product reaches the end of its life unless that product is recycled.
Temporary storage can still contribute to climate mitigation by delaying emissions, but it should not automatically be treated as equivalent to permanent removal. The study examines this explicitly through the concept of temporality: the need to account for how long carbon remains stored when assessing its mitigation value.
This is why the timeframe of an assessment matters alongside the amount of carbon involved. A snapshot may show how much carbon is stored at one moment; it cannot by itself tell us how durable that storage is, what happens elsewhere in the system or how the overall climate effect develops over time.
Taken together, these distinctions lead to a simple but important conclusion: the climate impact of forests and wood depends on the boundaries and timeframe of the assessment, and on keeping different climate mechanisms separate enough to measure them properly.
The Productive and Biodiverse synthesis study will examine these relationships in greater depth when it is published on 16 September.
Join the Teaming Up 4 Forests launch webinar to hear the researchers introduce the study and the evidence it brings together. Register to the webinar here: https://tinyurl.com/TU4F-16-September
