Sustainable forest management

Forests act as significant carbon sinks, as trees absorb CO2 during photosynthesis and transform it into biomass. Young forests sequester CO2 at a faster rate compared to older forests, which experience diminishing carbon sinks as they mature.

Forests in the EU are growing, yet the carbon sink is decreasing. There is more than one cause. The consequences of climate change such as forests fires, drought, storms, insect outbreaks, impact the capacity of EU forest to capture CO2. In addition, the natural ageing of these ecosystems has reduced the yearly carbon absorption rate.

Some people mistakenly believe that bioenergy is the major driver of the decline of the European Union's carbon sink. Biomass for bioenergy primarily comes from residues from forest management (thinnings, tops and branches after harvesting) and forest-based industries (typically sawmill by-products like sawdust and chips). 

Despite misconceptions regarding bioenergy's role in carbon sink decline, evidence suggests that strategic forest management and bioenergy production can coexist, sustainably.

A reduction of harvesting will have a positive impact on the carbon stocks, however its impact on the carbon sink will depend on many factors. In addition, our society needs biomass for materials and energy, and there is no reason why we should not use this renewable source in a sustainable way. Studies show that the regional climate change mitigation potential of sustainably managed forests is about 10 times as high as that of forest taken out of management, based on lifetime of trees under unmanaged conditions (Schulze et al. 2020).

So, the real question should be, can we enhance the forest carbon sink while at the same time substituting carbon intensive materials and fossil fuels with biobased products and bioenergy? The answer is yes, thanks to sustainable forest management.

Removing biomass for forest management purposes leads to an immediate drop in carbon stocks. This is a fact. But unlike humans, forests have a longer lifespan and operate on timescales spanning decades or even centuries. To better understand the carbon balance, it is essential to consider the long-term effects of sustainable managed activities. 

As showed in this image, time is undeniably crucial, yet equally significant is the considered area. Although the stock diminishes in the harvested area, the rest of the forest experiences growth that outweighs the harvesting impact and increases the forest carbon sink. Moreover, the harvested portion will keep on storing the CO2 in materials for a long time, while the residues will substitute fossil fuel for energy production

In the context of assessing the carbon balance of forest operations, one should keep a holistic approach.  It’s extremely important to pay attention to the boundaries of the system. Indeed, what happens at stand level should not be extrapolated to the whole of the forest. As shown in the figure below, the carbon stored in the forest vary quite drastically when considering only a fraction of the forest (left), while the trends are much smoother at forest level (right).

Furthermore, recent research shows that, during the development of unmanaged part of the forest, many trees die because of competition (natural process), no matter the quality of the site they’re located in or the species they belong to. Forest stands that were aged between 100 and 150 years could lose up to 40% of their total volume because of competition induced mortality (Pretzsch et al., 2023).