Satellite analysis finds biomass losses per hectare have risen 46% since 2018, while a separate study projects a decline in the continent’s forest carbon sink.
Europe’s forests are losing more biomass as drought, pests and other disturbances increasingly affect some of the continent’s oldest and most biomass-rich forests, according to new research.
A study published in Nature Geoscience found that above-ground biomass losses from forest disturbances increased sharply after 2018. For each hectare of disturbed forest, 46% more biomass has been lost since 2018 than in the preceding period.
The research, supported by the European Space Agency’s (ESA) Climate Change Initiative through its RECCAP-2 project, uses satellite-based datasets to assess forest biomass losses across Europe.
The study is the first to quantify biomass losses from forest disturbances across the continent rather than measuring only the area affected. This distinction is important because the amount of biomass lost can vary substantially between forests. A disturbance affecting a large area of relatively open woodland, for example, can result in less biomass loss than one affecting a smaller area of dense, mature forest.
Europe’s forests cover about 39% of its land area and hold an estimated 10.6 billion tonnes of carbon in above-ground biomass, including trunks, branches and leaves. Between 1985 and 2023, forest disturbances resulted in an estimated 6.5 billion tonnes of above-ground biomass loss across Europe, although some of this has since been offset by forest regrowth.
Measuring biomass loss
The study combined annual maps of tree-cover loss derived from the Landsat satellite archive with a high-resolution map of forest biomass. By overlaying the datasets, the researchers reconstructed changes in biomass losses from forest disturbances across Europe between 1985 and 2023.
“What surprised me most was how differently disturbances translate into biomass loss across Europe. Two events can look almost identical on a map yet have very different implications for the amount of carbon stored in forests. Until now we’ve largely been flying blind on that difference,” said Katja Kowalski, lead author of the study and a postdoctoral researcher in the Earth Observation for Ecosystem Management group at the Technical University of Munich.
The results point to a marked change from around 2018, when severe droughts affected parts of central Europe, notably Germany, the Czech Republic and Poland. The drought weakened trees and increased their vulnerability to pests, including the European spruce bark beetle, which can kill a mature tree within weeks.
Logging accounted for about 82% of biomass loss between 1985 and 2023, while natural disturbances accounted for the remaining 18%. However, natural disturbances have driven much of the increase in biomass losses since 2018.
Forest recovery under pressure
A separate study supported by the RECCAP-2 project has highlighted the implications for Europe’s forest carbon sink. Published in National Science Review, it combined national forest reports with satellite-based disturbance and biomass data to project the development of Europe’s forest carbon sink to 2030.
The study estimates that the carbon-sink capacity of European forests will decrease by 39% between 2010 and 2030, as disturbances outpace the ability of forests to recover.
“Europe can increase its forest area but still lose carbon sink capacity. The real question is whether growth and recovery can keep up with disturbances and harvest. Right now they can’t — and closing that gap means managing our forests differently, above all by harvesting less as natural disturbances keep rising,” said Philippe Ciais of France’s Laboratory of Climate and Environmental Sciences, a co-author of the study and science leader of ESA’s RECCAP-2 project.
