Giving Credit where Credit is Due. A Practical Method to Distinguish between Human and Natural Factors in Carbon Accounting

Net carbon emissions from the biosphere differ from fossil-fuel based emissions in that: (i) a large proportion of biospheric carbon exchange is not under direct human control; (ii) land-use decisions often have only a small short-term effect on net emissions, but a large long-term effect; and (iii) biospheric carbon exchange is potentially reversible. Because of these differences, carbon accounting approaches also need to be different for fossil-fuel and biosphere-based emissions. Recognising that, the international negotiators at COP 7 adopted a range of guiding principles for accounting for biospheric carbon exchange, including: that accounting excludes removals resulting from (a) elevated carbon dioxide concentrations above pre-industrial level; (b) indirect nitrogen deposition; and (c) the dynamic effects of age structure resulting from activities and practices before the reference year. In this paper, we highlight some of the challenges in biospheric carbon accounting for Canada, the U.S.A, New Zealand and Australia, four nations for which biospheric net carbon exchange is large relative to fossil-fuel based emissions. We discuss an accounting scheme that is based on assessing changes in average carbon stocks due to changes in land use. That scheme is tailored to the special needs of biospheric carbon management and is consistent with the accounting principles adopted at COP 7. The paper shows how the accounting scheme would resolve many of the biospheric carbon accounting anomalies identified for the four nations we studied.