Using satellite data, researchers at the Technical University of Munich (TUM) have identified an unprecedented loss of aboveground biomass in Europe's forests since 2018. Forests in Central Europe, which have been heavily affected by drought and bark beetle outbreaks, have been particularly impacted. The study also shows that even small increases in disturbed forest area can release large amounts of carbon into the atmosphere. The findings raise concerns about the European Union's ability to meet its climate goals.
Unlike previous studies that focused solely on changes in tree cover, this study provides the first Europe-wide assessment of changes in forest biomass. To accomplish this, the research team combined satellite data on tree cover change with information on the amount of biomass stored in forests. Their analysis reveals a clear shift: since 2018, biomass losses have increased sharply, leading to substantially greater losses of carbon stored in forests.
This increase in biomass loss coincided with a major rise in bark beetle outbreaks linked to worsening drought conditions. Since 2018, Europe has lost, on average, 46 percent more biomass per year per hectare forest area than during the period from 1985 to 2017. While both timber harvesting and natural disturbances contribute to biomass losses, the researchers attribute the sharp increase since 2018 primarily to climate change-related events. "The changes since 2018 are difficult to explain without climate change. As droughts become more frequent and severe, trees are weakened and bark beetles benefit from increasingly favorable conditions. We expect such events to become more frequent in the future, so they need to be taken into greater account in forest management planning, especially if we intend to rely on Europe's forests as carbon sinks," says Katja Kowalski, a researcher at the Professorship of Earth Observation for Ecosystem Management at TUM and lead author of the study.
Hotspots of carbon emissions
The amount of carbon released depends heavily on the region in which forest disturbances occur. Central European forests contain particularly high amounts of biomass, but they are also especially vulnerable to drought, bark beetles, and storms. In Germany, which has the largest standing timber stock in the European Union, disturbed forests release an average of about 125 tons of biomass or roughly 230 tons of CO₂ equivalents per hectare each year. Before 2018, that figure was approximately 170 tons of CO₂ equivalents per hectare. Mediterranean and Scandinavian forests contain less biomass on average due to their ecological characteristics and growing conditions. As a result, disturbances in these forests release less carbon per hectare. In Central Europe, rising disturbance rates thus have particularly severe consequences for the carbon sink capacity of Europe's forests.
According to the researchers, 18 percent of all biomass losses in Europe between 1985 and 2023 were caused by natural disturbances such as insect outbreaks, storms, and wildfires. Between 1985 and 2017, natural disturbances accounted for 17 percent of biomass losses. From 2018 to 2023, that share had risen to 23 percent.
The much larger share, 82 percent (1985-2023), resulted from forest management activities. "Unlike natural disturbances, we can influence these human interventions," says Cornelius Senf, Professor of Earth Observation for Ecosystem Management at TUM. "In addition, biomass removed from forests does not usually enter the atmosphere as CO₂ immediately. Instead, it is often used as a raw material for buildings or furniture." While timber harvesting increased steadily over the study period, the increase was moderate.
Implications for EU climate targets
The researchers also view their findings in the context of European climate policy. The European Union has set a target of increasing annual carbon removals from forests to 310 megatons of CO₂ equivalents by 2030 in order to offset emissions that are difficult to avoid in other sectors. Yet the performance of Europe's forests as carbon sinks is already declining. According to recent studies, Europe's forests stored about 72 percent less CO₂ equivalents during 2020-2022 than they did between 2010 and 2014. The TUM study suggests that this trend could become even more pronounced.
To counteract this development, Cornelius Senf advocates for adapted forest management practices: "Forests are certainly capable of recovering from disturbances. There is reason to be optimistic, because most disturbed areas will eventually regain their role as carbon sinks. Our task now is to restore their capacity to store carbon and to adapt forests to future conditions."
Further Information:
- The research was supported through the European Space Agency's Climate Change Initiative as part of the RECCAP-2 project, as well as by the EU-funded ForestPaths project. Both projects use satellite data to quantify changes in Europe's forests and their role as carbon sinks.
- Cornelius Senf is a member of the TUM School of Life Sciences and the Center for Alpine Forest Management at TUM.
- In 2026, he was appointed by NASA and the U.S. Geological Survey (USGS) to the Landsat Science Team, an interdisciplinary group of international experts. For more than 50 years, the Landsat program has provided a continuous record of satellite observations, serving as a foundation for research on climate change, land use, ecosystems, agriculture, and urbanization.
