A mass balance approach to assess carbon dioxide evolution during erosional events

The accelerated greenhouse effect and the degradation of land resources by water and wind erosion are two major, yet interrelated global environmental challenges. Accelerated decomposition of soil organic carbon (SOC) in cult ivated soils results in decline in SOC stocks over time and also contribute s to increased levels of CO2 in the atmosphere. Off-site transport of SOC i n runoff waters during erosional events also contributes to SOC depletion, but there is a paucity of data in the literature documenting erosional SOC losses and the fate of eroded SOC. In this paper, we present a mass balance approach to compute CO2 evolved from mineralization of SOC during transpor t and deposition of eroded soils. Erosion-induced CO2 emission rates rangin g between 6 and 52 g C m(-2) yr(-1) were computed using data on SOC stocks and dynamics from a series of long-term experiments conducted across a rang e of ecological regions. For the cropland of the world, we estimated an ann ual flux of 0.37 Pg CO2-C to the atmosphere due to water erosion. This flux is significant and suggests that water erosion must be taken into consider ation when constructing global and regional C budgets. Through its contribu tion to atmospheric CO2 increase, water erosion can have a positive feedbac k on the accelerated greenhouse effect. Copyright (C) 2001 John Wiley & Son s, Ltd.