Siliceous karst as a driver of carbon sequestration and geomorphic collapse in a tropical mountain peatland

Peatlands are globally relevant carbon sinks, yet their long-term stability depends on complex interactions between climate, topography, hydrology, and substrate structure. In the Southern Espinhaço Range, Brazil, we investigated the São Miguel Peatland, a degraded tropical mire developed atop quartzites affected by structurally controlled karstification. Using drone imagery, stratigraphic data, documented radiocarbon ages, and carbon content estimates, we reconstructed the peatland’s accumulation history and evaluated its geomorphic transformation. Our results suggest that karstic subsidence created depressions conducive to peat deposition for over 34,000 years, resulting in the sequestration of approximately 987 metric tons of carbon. However, more than 80-90% of this stock has been lost due to post-depositional gully erosion, likely driven by collapse-induced surface destabilization. Stratigraphic alternations of peat and sand at millimetric to centimetric scales further suggest high-frequency depositional variability, governed by both climate shifts and karst–hydrology feedback. We propose the term “karst-controlled peatlands” to describe systems where peat genesis and loss are directly linked to dissolution-driven subsidence. These findings underscore the vulnerability of tropical mountain peatlands to geomorphic instability and call for more nuanced carbon accounting approaches in structurally complex terrains. • First record of quartzite karst driving tropical mountain peatland genesis • Dissolution driven subsidence enhanced carbon sequestration • Defines “karst-controlled peatlands” as a new peatland type for the region • Collapse-driven erosion released >95% of original peatland carbon reserves