Global Carbon Dioxide Emissions from Navigable Rivers

Inland water vessels—barges, tugs, and other ships plying rivers and canals—may be a substantial source of transport emissions, yet their carbon footprint has remained difficult to measure at global scale. Now, a new study uses roughly 20 billion automatic identification system (AIS) records to build a high-resolution picture of where and when these vessels emit CO₂. By combining extensive ship-tracking data with a trajectory completion algorithm that accounts for reporting gaps, the researchers produce a near-global inventory for navigable river routes and inland waterways.

The team estimates that inland vessels released 164.0 ± 1.58 teragrams of CO₂ in 2022. That figure is striking: it corresponds to 24.7% of total global emissions from waterborne vessels, even though inland ships operate on only 0.4% of the planet’s navigable marine and inland water surface area. In other words, the emissions intensity of inland shipping is far higher than a simple area-weighted view would suggest.

Spatially, emissions are not evenly distributed. Instead, the study finds emissions concentrated in a limited number of hotspot river corridors. These bottlenecks arise where major logistics routes, industrial demand, and navigable conditions overlap—turning some river systems into concentrated carbon sources for transport.

Temporal patterns also matter. The researchers report baseline-dependent amplification from 2019 to 2022, meaning emissions change more strongly than would be expected from short-term fluctuations alone. Seasonal variability further shapes monthly and regional emission levels, consistent with how vessel operations respond to shifting hydrology.

The drivers of these patterns are interpreted as the combined outcome of transport demand and hydroclimatic constraints that govern navigability. When rivers remain passable for longer periods—or when operational capacity increases during favorable conditions—more cargo movement occurs, leading to higher CO₂ output along the busiest corridors.

The study’s implications extend beyond shipping inventories. Because inland vessels travel in river corridors where riverine CO₂ evasion is also active, they can add to the carbon entering the atmosphere through the air–water exchange pathway. This makes inland shipping an anthropogenic factor that could influence river-atmosphere CO₂ fluxes, not merely local pollution.

By quantifying emissions at finer spatial and temporal scales, the findings offer a foundation for improving national and global emission inventories for inland transport. They also help identify where targeted mitigation—such as operational efficiency measures, route planning, or policy interventions—could achieve disproportionate climate benefits.

The results provide a roadmap for climate-aware transport planning: as hydroclimate changes under global warming, navigability and demand could shift together, altering the emissions geography of inland shipping.