Which strategy is best?

What type of forest management is best for the climate? And which strategies are best to fight the climate crisis: decreasing considerably tree harvesting to store carbon in forest ecosystems or intensive harvesting to manufacture wood-based products that retain carbon and replace non-renewable or energy-intensive materials? As often happens at the science-policy interface, the answer to this sort of question is: it depends. However, there is no time to wait and ponder. As the climate crisis deepens, forest owners and managers must act fast to help forests expand their carbon sink potential, compensating at least partly for other sectors where emissions are harder to avoid. So, what is the way forward to fulfil the EU’s policy targets to support increased carbon sequestration?

One process to sequester carbon, three solutions to retain it

Forests in the EU remove approximately 300 million tonnes of CO2 equivalent (Mt CO2 eq) from the atmosphere per year (average 2017-2021). This ‘sink’ compensates for about 8% of the EU-27’s total greenhouse gas emissions. While this contribution occurs through one main process – photosynthesis trapping carbon to promote plant growth – the whole climate benefit from the forest sector depends on three key components: sequestration, storage and substitution.

First, the carbon sequestered into forest ecosystems through photosynthesis is stored in biomass, soil and fauna. Vegetation stores carbon in the leaves, branches, trunks and roots. The carbon pool in forest soils is quite stable under normal circumstances, changing only gradually. However, it can be lost when there are permanent changes in vegetation cover or disturbances to the soil due to erosion and soil preparation.

Second, when harvested wood is used for products such as building materials, furniture or wood-based textiles, then the share of carbon retained in the material is counted towards the EU’s net carbon sink. In recent years (average 2017-2021), the accumulation of carbon in wood products contributed to approximately 45 Mt CO2 eq, on top of the forest carbon sink, resulting in a total carbon sink of approximately 345 Mt CO 2 eq. Although this carbon will eventually return to the atmosphere at the end of the product’s lifetime, the carbon retained in long-life wood products such as construction timber and wood panels can remain stored for decades or even centuries.

The third approach relies on using harvested wood to replace more fossil-intensive materials, for instance when mass timber replaces steel and concrete as building materials, or wood is used as a biofuel replacing fossil fuels such as coal, peat and fossil diesel. This can reduce greenhouse gas emissions, commonly known as the “substitution effect”.

Additional policy measures to increase the net sink will be needed to counterbalance the effects of disturbances and compensate for emissions from land use and other sectors. This is especially important to ensure that the EU policy targets regarding the land use, land-use change and forestry sector (LULUCF) can be achieved. These targets mean that the EU’s lands should sequester 80 MtCO2 eq per year more by 2030 compared to 2021, and help compensate for all emissions remaining in 2050, alongside technological carbon capture solutions. Achieving these goals therefore calls for a substantial increase in forest sinks, a strong reduction of emissions in other land uses, or likely both.

Wood constructions can retain carbon for centuries if timber is prepared properly and installed in a well-designed and built structure. (sculpies/Adobe Stock)

Intensification or extensification of forest management

Historically, land use change and intensive forest use have significantly reduced the size of forest carbon stocks. Recognizing the importance of forest ecosystems for hosting a major part of Europe’s terrestrial biodiversity, landscape quality, wood provision and other forest ecosystem services, reforestation and afforestation programmes have been put in place. While more carbon in the forest means less in the atmosphere, there are concerns about issues that affect the development of European forest carbon sinks. In the case of disturbances such as pest outbreaks or forest fires, which are increasingly common in times of climate change, vulnerable or maladapted carbon-dense forests may be prone to a greater release of carbon into the atmosphere, putting forest carbon stocks at risk. This means that to keep forests’ carbon sinks growing at the necessary speed and magnitude, we need more resilient forests by e.g. rejuvenating part of Europe’s mature forests (which might need to be less carbon-dense to create a sort of “insurance” for existing carbon stocks), restoring degraded ones, while also growing biodiverse forests in new locations

All these factors make the argument for not focusing exclusively on keeping carbon in forests, but, at least to a certain extent, also storing it in the form of long-life wood products and avoiding fossil-based emissions through the substitution effect. One caveat, however, is the time frame. In the short (1–30 years) to medium term (31-70 years), the carbon benefits of strategies focusing on wood harvest would not be likely to compensate for the reduction of the net carbon sink stored in forest ecosystems, while the substitution effect is set to decrease over time as industries reduce their carbon footprint. There are reasonable arguments for both sides, i.e. to prioritize carbon storage in forests and to store carbon in wood-based products and promote substitution. These actions towards carbon storage are not mutually exclusive and could be combined to a certain extent. If we think about managing forests for multifunctional uses, including for climate change mitigation and harvesting timber, then what would be the most effective option: intensification or extensification of forest management?

From a carbon perspective, intensive forest management could be an advantage as it promotes tree growth and supplies raw material for long-life wood-based products. But this system often supports less biodiversity and negatively affects the provisioning of other ecosystem services. Another option is extensive forest management, which is closer to natural ecosystem dynamics, promoting a more natural forest structure and mimicking disturbance regimes. The delivery of ecosystem services in such a system is high. However, wood production is much lower, therefore requiring larger areas to meet wood demand. A third option, which combines some elements of intensive and extensive management, is the TRIAD approach where the landscape is divided into three areas with distinct objectives: wood production, multiple uses, and conservation. While TRIAD is not a new concept in forest management, it has not been widely tested. 

There is no single best forest management approach, and the choice must be adapted according to the state and objective of the forest. Overall, only local-scale and comprehensive assessments of the complex trade-offs between climate change mitigation options (e.g. harvest more or less) can provide the best solution in each case.

Wood constructions can retain carbon for centuries if timber is prepared properly and installed in a well-designed and built structure. (AVTG/Adobe Stock)

Seeing beyond climate policy – forests’ other roles

While discussion on the climate mitigation potential of forests might be compelling, it is important to remember that forests are much more than the carbon they harbour. Forests also provide other important ecosystem services such as water and air purification, soil protection, and recreational use. Forests harbour most of Europe’s terrestrial biodiversity. The total of all ecosystem services represents a considerable social and economic value. Therefore, it may make more sense to reduce harvest levels to keep carbon fixed in these ecosystems while also maintaining the level of other ecosystem services and preserving habitats suitable to specific fauna and flora species, including those at risk.

Strategies such as climate-smart forestry, which connects climate mitigation with adaptation measures to protect biodiversity and other ecosystem services, as well as setting aside forest areas through protected and restricted areas, can help meet climate and biodiversity targets at the same time. This is being done in countries like Germany, where the National Energy and Climate Plan includes the objective to stop the felling of publicly owned old, semi-natural beech forests. Germany is also planning to use forest restoration and conversion to create species-rich and climate-resilient forests. Similarly, Ireland’s Forest Strategy for 2022-2030 includes forest expansion and restoration as a means to become climate-neutral and protect a range of different forest ecosystems, including ancient woodlands.

Strategies that reconcile different approaches to carbon sequestration can be applied, helping balance societal, economic and ecological needs. Harvested wood can be channelled into long-life wood products and/or activities which bring higher substitution benefits compared to a business-as-usual scenario of wood use. Fostering the cascading use of wood by using wood products at least more than once for material or energy purposes also generates multiple benefits. It not only keeps carbon out of the atmosphere for longer, but it also gives forests more time to sequester the equivalent amount of carbon.

These examples show that, rather than focusing on a narrow set of climate mitigation activities, a range of policy and management strategies, must be considered, including their interactions with other sectors and policies, as well as their regional applicability. There are different pathways to increase the forest sector’s contribution to climate change mitigation, but an ample range of measures to pick from, depending on the local environmental conditions and socio-economic circumstances. Climate strategies can be as vast as Europe’s forests, and as varied as the different territories that comprise the EU.

Resources

Brief on the role of the forest-based bioeconomy in mitigating climate change through carbon storage and material substitution – JRC Publications Repository

EU Member States National Energy and Climate Plans

Land use sector – EU Climate Action

References