New research published in Nature Climate Change reveals that ships traveling on rivers and canals are a surprisingly large source of global carbon dioxide pollution. Although these inland waterways represent less than 1% of the world’s navigable waters, vessels operating on them generated nearly one-quarter of global shipping emissions in 2022. The findings highlight an important source of transportation pollution that has received far less attention than emissions from ocean-going vessels.
Until now, scientists lacked a detailed global estimate of carbon dioxide produced by inland shipping. Researchers in China addressed this gap by analyzing approximately 20 billion ship-tracking records collected between 2019 and 2022. From these records, they identified 12,289 navigable rivers and canals with persistent vessel activity, creating a detailed picture of inland shipping across the world.
Tracking vessels on rivers presents significant technical challenges. Signals can disappear in certain locations, while conventional tracking systems often connect recorded positions using straight lines. On winding waterways, this can incorrectly suggest that vessels traveled across land. The researchers therefore developed a route reconstruction model capable of estimating realistic vessel movements around river bends. They then combined reconstructed routes with information about individual ships to calculate fuel consumption and associated shipping emissions.
The results demonstrate the scale of the problem. Inland vessels produced approximately 164 million metric tons of carbon dioxide in 2022, representing 24.7% of total emissions from global shipping. Inland vessel emissions also nearly doubled between 2019 and 2022, largely because of increasing vessel activity and economic demand, particularly across Asia.
Pollution was highly concentrated geographically. Approximately 69% of inland vessel emissions originated from only 20 major rivers, including the Yangtze, Rhine, Mississippi and Danube. Cargo vessels were particularly important, producing roughly two-thirds of inland shipping carbon dioxide. These findings suggest that targeting heavily trafficked waterways and freight vessels could play an important role in reducing future shipping emissions.
The researchers also compared vessel pollution with the natural carbon released by rivers through processes such as organic matter decomposition and soil runoff. Remarkably, emissions from vessels were approximately 80% as large as estimated natural carbon dioxide emissions from the same navigable waterways.
Emissions also varied throughout the year depending on economic activity, water levels and climatic conditions. Vessel traffic depends partly on whether rivers contain enough water to support navigation, linking transportation activity with changing hydroclimatic conditions. The study therefore describes navigable rivers as hybrid carbon environments where natural river emissions and human-generated pollution occur simultaneously at comparable scales.
Overall, the research suggests inland waterways have been substantially underestimated in assessments of transportation’s climate impact. Better monitoring and cleaner vessels could make reducing inland shipping emissions an increasingly important part of global efforts to decarbonize transportation.
https://phys.org/news/2026-08-river-shipping-emits-quarter-global.html