Morphodynamics of the world’s large tropical rivers drive a carbon pumping mechanism  

This study investigates the eco-morphodynamic activity of major tropical rivers in the Tropics, aiming to quantify the carbon flux originating from riparian vegetation into inland waters. Employing a comprehensive multi-temporal analysis of satellite data, developed on the Google Earth Engine cloud computing platform, spanning from 2000 to 2019, at a spatial resolution of 30 meters, we focused on all tropical rivers with a width exceeding 200 meters. Our research reveals the existence of a highly efficient Carbon Pump mechanism, where river morphodynamics play a pivotal role in driving carbon export from the riparian zone. This, in turn, stimulates net primary production through a synergistic process involving floodplain rejuvenation and colonization. The quantification of this unique pumping mechanism underscores its substantial contribution, alone accounting for an annual mobilization of 12 ± 0.96 million tons of carbon in these tropical rivers. We identified distinct signatures of fluvial eco-morphological activity that serve as proxies for assessing the carbon mobilization capability linked to river dynamics. The study also delves into the interplay between river migration and carbon mobilization, shedding light on the potential impacts on the carbon intensity of planned hydroelectric dams in the Neotropics. We highlight the significance of the river-carbon nexus, emphasizing the necessity for a comprehensive approach in formulating effective water policies that consider the intricate relationships among river dynamics, carbon flux, and environmental phenomena.