Tropical forest degradation underestimated: gaps in emissions inventories

A study supported by the European Space Agency (ESA) shows that losses and the recovery of carbon in tropical forests are often incompletely represented in common carbon models and national inventories. Degradation processes such as selective logging or smouldering fires in particular frequently go undetected — with consequences for emissions accounts and political decision‑making.

Degradation often goes unnoticed

While complete deforestation is relatively well recorded, gradual degradation frequently escapes accounting. This includes tree injuries, partial felling, incomplete burning or accelerated decomposition of dead organic matter. For these shades of disturbance, many countries lack robust figures.

Time‑lagged emissions complicate accounting

Unlike deforestation, which releases large amounts of carbon immediately, degradation leads to partial biomass losses and structural change. The breakdown of deadwood and easily decomposable litter releases carbon over months to decades. These temporally stretched emissions are underestimated or not considered at all in numerous models and reports.

Why national inventories have gaps

Although international guidance calls for capturing degradation, many countries report primarily area losses from clear‑cutting. Reasons include technical barriers, limited capacity and the difficulty of detecting small, scattered damage with conventional remote sensing. Added uncertainty arises when converting observed vegetation changes into carbon fluxes, because soil and deadwood dynamics vary strongly by site and disturbance.

Earth observation as the key

Satellite data can enable more accurate CO2 budgets when used as time series and to provide structural information. Optical sensors detect canopy openings, while L‑band radars (SAR) and LiDAR can “see” into the canopy layer and capture changes in vertical structure. This makes it easier to identify selective logging and partial tree loss. Regular repeat observations over years are crucial to distinguish degradation from regrowth.

Impacts on policy and markets

Incomplete accounting of degradation distorts national emissions inventories and international assessments. Countries that do not report these losses may appear more climate‑friendly than they are. This influences benefit allocation in programs such as REDD+ and leads to a global underestimation of emissions from tropical forests — with implications for assessments of the remaining carbon budget for temperature targets.

What the study recommends

The study calls for a tighter integration of remote‑sensing products with process models. Clearly defined carbon pools (live biomass, deadwood, litter, soil) and realistic temporal dynamics following disturbance are needed. National inventories require practical methods to capture degradation and harmonized standards for monitoring, reporting and verification (MRV). Long‑term field measurements are indispensable to calibrate and validate satellite‑based estimates, for example through permanent plots, measurement networks and flux towers.

Investments and capacity building

Reliable reporting requires investment in technology and institutions: access to high‑resolution, dense satellite data, building national data infrastructures and training programs for local monitoring teams. The greatest added value comes from data fusion of optical, radar and LiDAR sources, because they combine different aspects of forest biomass and its change.