The carbon exchange associated with accelerated erosion following land cover change is an important component of the global carbon cycle. In current assessments, however, this component is not accounted for. In this paper, we integrated the effects of accelerated C erosion across point, hillslope and catchment scale over the period 4000BC-2000AD to demonstrate that accelerated erosion results in a net sink of carbon. This long-term sink is equivalent to 55% of the eroded carbon and has offset 21 to 48% of the carbon emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced sink strength is limited by ample mineralization (45%) of buried C in terrestrial depositional stores, which lagged burial. The time lag between burial and mineralization implies that the C buried in terrestrial deposits globally during the agricultural expansion of the last 150 years, will become a significant source term in the next decades to centuries. Our analysis exemplifies that accounting for the non-steady-state C dynamics in geomorphic active systems is pertinent to understand both past and future anthropogenic global change.