Improved reporting needed on forest carbon emissions

A comprehensive meta-analysis published in Science Advances reveals that forest degradation releases significantly more carbon than current national reporting typically accounts for, and satellite Earth observation is key to closing the gap. The study, led by researchers at the Helmholtz Centre for Geosciences, synthesised 146 peer-reviewed papers covering tropical moist forests, ecosystems that hold roughly 70 percent of all carbon stored in the world's living vegetation.

The findings are striking. Forest fires emit about 50 percent more carbon relative to undisturbed forest. Selective logging accounts for 34 percent more carbon released. Tree loss at forest edges, driven by wind and drier air, caused 31 percent more carbon loss. After 20 years of regrowth, partially damaged forests held only about 75 percent of the carbon of undisturbed forest, while areas that were completely cleared held just 38 percent. Proximity to healthy forest significantly boosted recovery through seed dispersal.

Advances in Earth observation since around 2015 now make it possible to distinguish carbon losses from degradation versus deforestation, and to track recovery over time. ESA's Climate Change Initiative Biomass project produces open-access global maps of above-ground biomass at 100-metre resolution, using data from Copernicus Sentinel-1, JAXA's ALOS-2 PALSAR-2, and NASA's GEDI lidar instrument.

According to ESA's Clement Albergel, the synthesis provides exactly the evidence base countries need to improve their reporting under the Paris Agreement. Current carbon cycle models and national reports inconsistently account for forest degradation and regrowth, often omitting or simplifying these processes. The study's database is designed for direct use by countries reporting forest carbon budgets to the UN.