Mountainous Soils Hold Twice as Much Carbon as Previously Estimated

For decades, scientists have assumed that mountainous terrain was a poor place to look for stored carbon. The logic seemed sound: steep slopes erode quickly, soil washes away into rivers, and what little remains is thin and shallow. But a new study from the University of Oregon has overturned that assumption entirely. Mountainous landscapes, it turns out, are actually impressive reservoirs of soil carbon—holding roughly twice as much as previous global models predicted.

The finding emerged from painstaking fieldwork in the Oregon Coast Range, where researchers examined the aftermath of nearly ten thousand landslides, some dating back as far as 480,000 years. These ancient disturbances, now stabilized, offered a natural laboratory. By drilling into a representative sample of six landslides and measuring carbon density, the team built a timeline and extrapolated a model across the entire study area. What they discovered challenged a fundamental assumption: soil in these mountainous landslides often reaches depths exceeding five meters—more than sixteen feet—compared to the thirty centimeters that earlier models had assumed.

The thickness matters enormously. Deeper soils accumulate higher carbon stocks, a consequence of thousands of years of rock weathering that creates fine-grained material with vastly more surface area to trap and hold carbon. As rock breaks down over millennia, it becomes a better carbon sink. The older and more weathered these deep zones are, the more carbon they can store. This discovery reframes how scientists should think about where carbon naturally concentrates in the landscape.

The research was led by Brooke Hunter, then a doctoral student in the lab of earth scientist Josh Roering, who specializes in geomorphology—the study of how landforms develop and change. Hunter is now an assistant professor at Appalachian State University. The work appears in Science Advances. "When we think about terrestrial carbon, soil contains more carbon than vegetation and the atmosphere combined," Hunter noted. Understanding where that carbon lives and in what quantities is essential for accurate carbon accounting and for designing effective climate interventions.

Mountainous regions have historically been understudied for carbon content, partly because the terrain is difficult to traverse and partly because measuring soil depth and composition in steep, unstable landscapes requires specialized effort. That knowledge gap has had real consequences: it's been harder to identify and protect areas that function as natural carbon reservoirs, or to design interventions like mineral spreading or soil seeding that might enhance carbon sequestration.

Roering and his team argue that better geomorphic mapping—models that account for landscape shape and how it has evolved—can change that calculus. By understanding where high-carbon soils are concentrated, land managers could prioritize conservation and management practices that preserve them. The researchers emphasize that there is no single climate solution, but incorporating these more accurate models into decision-making could help identify which specific approaches might work best at specific sites.

The implications extend beyond basic science. There is growing momentum around natural climate solutions—techniques ranging from enhanced rock weathering to nutrient seeding designed to pull carbon from the atmosphere and lock it into soil. Knowing how much carbon is already stored in the landscape, and where it's most concentrated, allows scientists to model how much additional carbon might be sequestered through these efforts. It's a form of bookkeeping that matters: you cannot manage what you do not measure. For mountainous regions that have been largely invisible in global carbon accounting, this research suggests they deserve a second look.