Rivers in the US might be secret weapons in the battle against climate change, especially in the West. But here's the twist: for years, scientists believed rivers release more carbon dioxide than they absorb. A groundbreaking study, led by aquatic biogeochemist Taylor Maavara, challenges this notion, suggesting that many Western rivers could be absorbing more carbon dioxide than previously thought.
Published in Science, the research analyzed every river network in the contiguous US, including those in deserts and shrublands, which have been overlooked. The study reveals that the metabolism of rivers, the balance between carbon dioxide absorption and emission, has been a mystery. Previous monitoring focused on forested rivers in temperate regions, but Maavara's team used machine learning to analyze a broader range of data.
The key insight? Rivers in arid environments, with less canopy cover and organic carbon, can act as carbon sinks. In the western US, around 25% of river reaches absorb more carbon annually than they emit, compared to just 11% in the East. This discovery suggests that previous assumptions about rivers' carbon emissions might be biased by Northeastern US river studies.
The implications are significant. While US rivers still emit more carbon than they absorb overall, the gap might be smaller than we thought. And with 65% of the world's land being arid or semi-arid, these findings could have global relevance.
Intriguingly, climate change might be temporarily enhancing the carbon-absorbing abilities of western rivers. Slower river flows due to hotter and drier conditions allow more sunlight to penetrate, boosting photosynthesis and carbon absorption. However, if rivers dry up, they could become carbon emitters.
Maavara acknowledges uncertainties in river carbon budgets but believes this study brings us closer to understanding the carbon cycle. The findings could be a game-changer in managing atmospheric CO2, sparking a new perspective on rivers' role in climate change mitigation.
