The storm’s environmental impact and its consequences for the water and carbon cycles

The physical environment and silvicultural regime of the southern maritime pine production forest– West, together with land-use planning and the sharing of the rural area in question with agricultural land and rapidly expanding urban areas, make it particularly vulnerable to storms and partly explain the severity of the damage observed following recent storms. The water cycle, hydrology and carbon cycle of the storm-damaged forests have been significantly altered by Storms Martin and Klaus. Their evapotranspiration may be halved, winter soil waterlogging may be exacerbated, and runoff to surface waters may increase. The ecosystem’s net carbon balance is reversed; the damage sustained can transform the ecosystem from a carbon sink into a carbon source by reducing its capacity for photosynthesis and increasing the mineralisation of organic carbon and the amount of biomass added to the soil. Exceptional storms such as Lothar, Martin, Gudrun, Klaus and Hurricane Katrina have thus significantly weakened the net carbon balance of continental Europe and the United States, respectively. Given the uncertainty surrounding the intensification of storm patterns, it is therefore prudent to identify and assess the various options for adapting the forests of the Landes de Gascogne massif to storms.