La politique optimale de séquestration du carbone par les sols agricoles en France

The Kyoto Protocol, which came in force in February 2005, allows countries to resort to "supplementary activities" consisting, in particular, in the sequestration of carbon in agricultural soils. Considering the importance of its agricultural land and its weak possibilities of low-cost reduction in GHG emissions (given the high nuclear share in electricity generation), France can exploit this opportunity. This paper analyzes the optimal path of carbon sequestration in French agricultural soils. Our model takes into account one of the essential characteristics of the dynamics of carbon storage in agricultural soils: the asymmetry of the sequestration/de-sequestration process. The calibration of the model on French data gives a clear-cut result: the adoption of sequestration practices must be permanent. A temporary sequestration is never optimal. Numerical simulations also show the sensitivity of the optimal policy to sequestration costs and to the bounded number of units of land on which a change of practice can take place at each date. The numerical results demonstrate that a permanent sequestration policy leads to temporary emission reductions. These annual reductions are very limited as compared to the Kyoto objectives for France.