Quantifying the impacts of human activities on reported greenhouse gas emissions and removals in Canada's managed forest: conceptual framework and implementation

The land sector is expected to contribute to strategies aimed at mitigating global temperature increases and this necessitates an improved understanding of human actions on land sector emissions and removals. Current Intergovernmental Panel on Climate Change guidelines for the land sector of national greenhouse gas inventories are based on the assumption that all emissions and removals in managed lands are caused by humans. In Canada, however, natural disturbances in managed forests can result in large and highly variable emissions and subsequent removals that mask the impacts of management activities. Here we describe methods to isolate and quantify the impacts of management on trends in estimated anthropogenic emissions and removals in Canada's managed forest by partitioning fluxes from two land components: fluxes from lands dominated by natural disturbance effects and fluxes from the remaining managed forests. The sum of the flux estimates of the two land components is equal to net emissions and removals in managed forest lands. Separating highly variable natural disturbance fluxes from the remaining fluxes in managed forest lands increases the understanding of how human activities impact flux trends. Comparing these anthropogenic emissions and removals with those from natural disturbances quantifies their relative contributions to global atmospheric C[O.sub.2] concentrations. Key words: carbon, greenhouse gas inventory, anthropogenic, managed forest, climate change mitigation, CBM-CFS3. On s'attend a ce que le secteur terrestre contribue aux strategies visant a attenuer l'augmentation de la temperature a l'echelle du globe, ce qui necessite une meilleure comprehension de l'impact de l'activite humaine sur les emissions et les absorptions associes au secteur terrestre. Les directives actuelles du Groupe d'experts intergouvernemental sur revolution du climat pour le secteur terrestre concernant les inventaires nationaux des gaz a effet de serre s'appuient sur l'hypothese que la totalite des emissions et des absorptions sur les terres amenagees sont d'origine anthropique. Au Canada cependant, les perturbations dans les forets amenagees peuvent entrainer d'importantes et tres variables emissions et captures subsequentes qui masquent les impacts des activites d'amenagement. Nous decrivons dans cet article des methodes pour isoler et quantifier les impacts de l'amenagement sur les tendances des emissions et des absorptions d'origine anthropique estimes dans les forets amenagees du Canada en repartissant les flux associes a deux composantes terrestres: les flux dont la provenance est dominee par les effets des perturbations naturelles et les flux associes au reste des forets amenagees. La somme des flux estimes pour les deux composantes terrestres est egale aux emissions et captures nettes sur les terrains forestiers amenages. La separation des flux excessivement variables associes aux perturbations naturelles du reste des flux sur les terrains forestiers amenages ameliore la comprehension de la facon dont l'activite humaine influence revolution des flux. La comparaison de ces emissions et du piegeage d'origine anthropique a ceux qui sont associes aux perturbations naturelles quantifie leurs contributions relatives aux concentrations globales du C[O.sub.2] atmospherique. [Traduit par la Redaction] Mots-cles: carbone, inventaire des gaz a effet de serre, anthropique, foret amenagee, attenuation des changements climatiques, MBC-SFC3.
1. Introduction The purpose of the annual reporting of national anthropogenic greenhouse gas (GHG) emission and removal estimates to the United Nations Framework Convention on Climate Change (UNFCCC) is to [...]