The European Union (EU) climate policies rely on a functioning forest carbon sink. Forests cover about 40% of the EU area and have absorbed about 436 Mt of carbon dioxide equivalent per year between 1990 and 2022, which is about 10% of the EU’s anthropogenic emissions. However, the ability of forests to act as carbon sinks is rapidly declining owing to increasing natural and anthropogenic pressures, threatening the EU’s climate goals and calling for prompt actions. Here we provide actionable research recommendations to improve the monitoring and modelling of forest resources and their carbon sink, and to better inform forest management decisions. We suggest a timeline for the development of these measures to better support the implementation of strategies and policies outlined in the European Green Deal.