High-resolution mapping of anthropogenic impacts on erosion and sediment flux in the Northern Andes

Human activities have profoundly altered erosion rates and river sediment transport, yet the magnitude and individual drivers of erosion change remain insufficiently quantified—in part because long-term (natural) rates of erosion are rarely quantified. Here, we assess changes in erosion and river sediment transport in the Northern Andes of Colombia by comparing short-term erosion rates—derived from suspended sediment load measurements and bedload modeling—for 139 catchments with long-term natural erosion rates inferred from cosmogenic nuclide data. On average, short-term erosion exceeds natural rates by 78% for the years 1980–2000 and by 111% for 2000–2022. Because suspended sediment was sampled only monthly, these figures likely underestimate the true increase. The largest increases occurred along the flanks of the Eastern Cordillera and, post-2000, in the northern and central segments of the Central Cordillera.A random forest model identified agriculture, mining, and deforestation as dominant drivers of erosion, while natural variables like rainfall show weaker but possibly amplifying effects. Modeled soil erosion rates broadly align with observed short-term sediment export, indicating high sediment connectivity and minimal storage in these steep catchments. Despite rising sediment flux, satellite imagery shows limited river morphological change, possibly due to floodplain buffering or human confinement. However, we document cases of river aggradation impacting infrastructure and downstream ecosystems. Our results highlight the accelerating influence of agriculture, deforestation, and mining on erosion and sediment flux in the Northern Andes and underscore the need for improved monitoring and land management strategies to mitigate the geomorphic and ecological consequences.