Forests cover around 40 % of the European Union (EU) territory and absorbed around 10 % of the EU's human-induced emissions between 1990 and 2022. This process of removing carbon from the atmosphere is commonly referred to as carbon absorberWorryingly, however, current evidence suggests a weakening of this carbon sink, meaning that European forests are absorbing less carbon dioxide from the atmosphere.

A major paper published in the journal Nature, led by the Joint Research Centre (JRC), details the decline in the carbon sink in forests and its causes. According to the EU greenhouse gas inventory published in 2024 by the European Environment Agency (EEA), the average carbon sink of forests decreased by approximately 27 % between 2020 and 2022 compared to the average sink in 2010-2014. The new EU inventory from 2025 suggests an even more significant decline over this period. To illustrate, the average carbon sink of forests fell from -456.9 MtCO2eq/year in 2010-2014 to -374.9 MtCO2eq/year in 2015-2019 and further to -332.6 MtCO2eq/year in 2020-2022.

The causes of declining carbon absorption are diverseOne factor is increased loggingIn addition, Climate change is causing more frequent heat waves and droughts, which reduces tree growth. Climate change also tends to increase the occurrence of disruptive events such as insect disasters, forest fires and tree mortality, which have become more frequent and severe in some areas.

JRC research is investigating the causes of carbon sink decline and looking for the most effective ways to reduce its impact. While reducing greenhouse gas emissions remains the most important strategy for mitigating the effects of climate change, it is also key adjust logging regimes and reconsider forest management methodsto become more resilient to climate change and extreme weather events. It is essential to have available data to develop effective policies and practical measures better and more timely data on carbon stocks and forest health.

The study also identified several knowledge gaps related to monitoring and modelling of European forests. Two priorities are particularly important: first, the urgent need measure carbon flows more accurately and timely by tracking its movement between soil, vegetation, and the atmosphere. Second, refine predictions, how extreme weather events and worst-case scenarios will affect the carbon sink. Addressing these issues is essential for building a comprehensive pan-European forest and carbon sink monitoring system.

Between main areas where further research is needed, include:

• Earth observation: High-resolution satellite imagery, combined with aerial data and ground observation networks, is key for the timely monitoring of EU forests. Many EU countries currently rely mainly on periodic forest inventories, which are insufficient to keep pace with the rapid rate of forest health decline. Existing forest datasets also require greater transparency and standardisation.
• Forest resilience: There is a need to improve understanding of the interactions between biodiversity, resilience and forest management. Developing a comprehensive biodiversity monitoring framework, based on a combination of ground-based data and Earth observations, could help to bridge this knowledge gap. Understanding these interactions could support biodiversity-friendly forest management, taking into account that mixed forest species are better able to withstand disturbances and extreme climatic conditions and have greater carbon sink potential.
• Forecasting and anticipation: Forest management decisions and natural climate solutions have great potential to maintain or even increase the carbon sink of forests. However, it is crucial to anticipate the potentially unintended long-term negative impacts of these solutions, such as the impacts of afforestation on local water resources, in order to increase future forest resilience and adaptation to climate change.
• Expansion: Expanding and improving ongoing research that integrates forest growth models and socioeconomic models would provide policymakers with a clearer picture of how logging and wood products affect the forest carbon sink.

The research outlines possible measures in the field of monitoring, modelling and forest management that could prevent the decline of the forest carbon sink. The study calls for integrated policies that address both climate and environmental objectives, and presents a research agenda to guide these policy decisions. By combining timely regulations with incentives for sustainable practices, the EU can still reverse the decline of its forests' carbon sink and maintain their expected contribution to climate neutrality by 2050. Spring