Authors: Marcus Lindner (EFI), Hans Verkerk (EFI)
Forests play an important role in the global carbon cycle that can help to mitigate climate change via three pathways:
- Forests remove carbon dioxide from the atmosphere and store carbon in biomass and soil.
- In forests managed for wood supply, part of the carbon (mainly in tree stems and major branches) is extracted from the forest during harvest. If the wood is used for materials, the carbon is stored in wood products and only released at the end of their life (which may include one or more phases of recycling).
- In addition to carbon storage in forest ecosystems and in wood products, using wood can avoid or reduce fossil greenhouse gas emissions by replacing (substituting) products or fuels that emit more greenhouse gases during their production, use and disposal (e.g. steel, concrete).
Possible approaches for forests range from no management with the (sole) aim to store carbon within forest ecosystems to active management aiming either to strengthen carbon storage in forest ecosystems (e.g. through tree species selection, breeding, thinning, cutting regimes, etc.) or to strengthen carbon storage in forest ecosystems and in wood-based products and avoiding emissions through substitution effects. An open key question is if forests which are left unmanaged provide larger CO2 emission reductions than forests managed for the production of wood (with carbon storage in wood products and substitution effects).
Scientific studies to tackle this question may even appear contradictory because they reflect different views and approaches. The carbon effects of managed and unmanaged forests are generally found to be affected by the assumed forest dynamics (growth rate, mortality, disturbances). In the case of managed forests, other relevant factors include the types of forest management, of wood products considered, and the non-wood products that are substituted, and how these products have been produced. In addition, the comparison of managed and unmanaged systems is hampered by limited information on the natural dynamics of unmanaged forests and by uncertainties on the impacts of climate change. Europe’s forests are affected by climate change and this is expected to continue in the future with changes of productivity, tree species suitability and extreme events and disturbances.
Especially in a transition from a managed to an unmanaged forest, it is unclear how ceasing management would affect forest development and its carbon balances under climate change. The present rate and magnitude of climate change (including the effects of natural disturbances) exceeds the speed of natural tree species migration and their capacity to adapt to the changing conditions. Ending management limits the possibility to strengthen forest resilience to climate change through adaptive forest management – for example by increasing species diversity, introducing better adapted species and provenances - implementing sanitary fellings to contain invasive pest species, reducing the amount of burnable materials in fire-prone areas, etc.
When looking at carbon balances, it is also essential to consider consequences beyond the local level. Reducing wood production may lead to gains in carbon storage in forest ecosystems at one location, but these gains may be offset through the international trade of wood and wood products causing deforestation or degradation elsewhere (a “leakage effect”). There is an increase in material demand due to a growing world population and rising levels of prosperity. The reduced production and use of forest products may result in increased use of competing, nonrenewable materials, often with larger carbon footprints, such as steel and concrete.
In most of the EU regions, selling timber is the dominant source of income from forests to fund the costs of the establishment and adaptation of forests to new climate conditions. Changes in forest management limiting the supply of wood have consequences for the economic performance of forest owners, but also for the wood-processing industries and regional economies.
A holistic evaluation is therefore needed to understand the full consequences of changing forest management in supporting climate policy. To strengthen the long-term contribution of forests and forestry to climate change mitigation, as well as the resilience of forests to climate change, the best strategy will therefore be a mix of measures that takes into account regional conditions. This mix combines conservation approaches to strengthen carbon storage in forest ecosystems, as well as active management approaches to store carbon in forest ecosystems and wood products, and avoid emissions through substitution.