Mechanical thresholds constrain global peatland carbon accumulation

Peatlands are vital carbon sinks, yet their long-term accumulation may be constrained by mechanical instability. Here we present a fully coupled two-dimensional model integrating ecohydrological and mechanical processes to assess the mechanical limits to peat growth across landscapes with slope angles from 0° to 12°. By simulating stress distributions and comparing them to reported tensile and shear strength values, we identify the peat depth thresholds beyond which peat bodies become unstable. The model predicts observed failure modes, including bog bursts and peat slides, and reveals that many peatlands may reach mechanical failure before achieving their projected carbon storage capacity. In this work, we show that mechanical constraints limit global peat accumulation to 1.48 times its current volume, significantly below the 1.71-fold increase assumed in future carbon sequestration scenarios. These findings highlight the need to incorporate mechanical thresholds into peatland restoration and climate mitigation strategies.