Hi Morteza,

Soil erosion does not contribute to carbon release, on the contrary. By burying carbon in depositional environments and, at the same time, dynamically replacing C at eroding sites the balance is (slightly) positive, i.e. soil erosion leads to a net withdrawal of carbon from the atmosphere. Read the paper by Van Oost et al. (Science, 2007) for more info.

Kind regards,

Gerard

Regarding the effect, also this discussion may be interesting:

Soil erosion: A carbon sink or source?, By: Lal, Rattan; Pimentel, David, SCIENCE Volume: 319 Issue: 5866 Pages: 1040-1042 Published: FEB 22 2008

Thanks indeed for good references!

R. Lal is a good reference: http://dx.doi.org/10.1016/S0160-4120(02)00192-7

Papers by Lal et al only present one side of this erosion and C argument. For the alternative view (which is much more widely accepted in the scientific community at this point) see:

Stallard 1998 - Global Biogeochemical Cycles

Harden et al 1999 - Global Biogeochemical Cycles

Berhe et al 2007 - Bioscience

Van oost et al 2007 - Science

...... among many other publications.

Now, it is perhaps a good idea to explain a bit better what the difference in vision is, between the papers by Lal et al. on the one hand and the papers by Stallard, Van Oost, Berhe, Harden...on the other side. It is actually not that difficult:

- Lal et al. consider the mineralization of soil organic carbon due to erosion. Erosion leads to soil disruption and aggregate breakdown and, hence, some mineralizationof the SOC that is eroded is indeed to be expected. Lal et al. use a rather large estimate of this effect to come to the conclusion that erosion is a source of carbon to the atmosphere.

- We believe that this vision is too simplistic. A lot of the carbon that is eroded is not mineralized, but buried, possibly for centuries or millenia. On the other hand, soil organic carbon that is removed from the eroding sites is, over the long term, replaced.

The overall balance is therefore positive for the soil: the sum of the buried carbon and the new carbon that replaces the eroded carbon is larger than the total carbon stock that you would expect when the landscape would be entirely stable.

This is not to say that erosion is positive for the soil resource as such: the negative consequences of excessive soil erosion far outweigh the slightly positive effect of additional carbon burial.