Do grasslands act as a perpetual sink for carbon?

Soussana et al. (2007) published their findings of a large and careful analysis of flux measurements over European grasslands. The nine sites at which fluxes were measured appeared to be acting as a sink for carbon (C), with a measured flux of -240 ± 70 g C m(-2) y(-1) , equating to a net storage of C of 104 ± 73 g C m(-2) y(-1) (= ~1 t C ha(-1) y(-1) ), when C imports and exports were accounted for. Although not proposed by the authors, but perhaps resulting from the title of a later paper (Soussana et al. 2010), this finding has increasingly been used (particularly by organisations representing livestock producers) to suggest that grasslands are a perpetual sink for carbon, and that just maintaining grasslands will yield a net carbon sink. In this short article, I examine this suggestion by reviewing evidence from repeated soil surveys, long term grassland experiments and simple mass balance calculations, before suggesting a potential explanation for the flux findings, and presenting a series of conclusions and policy recommendations. This article is protected by copyright. All rights reserved.