On estimating tropical forest carbon dynamics in Papua New Guinea
Bryan, J and Kirkpatrick, JB and Shearman, PL and Ash, J, On estimating tropical forest carbon dynamics in Papua New Guinea, Annals of Forest Science, 68, (2) pp. 213-216. ISSN 1286-4560 (2011) [Refereed Article]
One of the few initiatives to address ongoing global warming that did not completely stall at the UNFCCC climate change negotiations was the reduction emissions from deforestation and forest degradation (REDD). REDD has a focus on the forests of the tropics. Unfortunately forest mensuration in most tropical countries has been inadequate to accurately determine forest carbon stocks, much less the effects of land use and changes in land use on them (Houghton et al. 2009; Bryan et al. 2010a). Whilst tropical logging is known to be widespread, the exact areas of tropical forest subject to logging have not been accurately mapped (Asner et al. 2009) or mapped with sufficient regularity to provide adequate data on the areas subject to this activity. Biomass losses due to logging have usually been derived from limited plot data, or derived via various models from estimates of regional biomass and timber extraction volumes (Houghton et al. 2009) and thus encapsulate considerable uncertainty. For these reasons the carbon impact of tropical logging remains an open question, and one that needs to be closed before any international institutional arrangement considers promoting forms of timber extraction as a tool for controlling carbon emissions. Here, we examine the current state of forest carbon research in Papua New Guinea (PNG) to illustrate the problems that can arise by developing forest management policy prematurely from incomplete forest research.
The question of the effects of logging on carbon stocks in Papua New Guinea has been addressed by Shearman et al. (2008, 2010) and Bryan et al. (2010a), who concluded that the available data were inadequate to derive accurate conclusions on the quanta involved. It has been most recently addressed by Fox et al. (2010) who are confident that their analysis of permanent sampling plots (PSPs) ‘provides a sound basis for estimating C dynamics associated with LULUCF’ (p. 7), LULUCF being land use, land use change and forestry. In the present paper, we examine the attributes of data that would provide such a sound basis, examine the data of Fox et al. (2010) in this context, and comment on the possible political implications of accepting the type of data used by Fox et al. (2010) as valid in the context of REDD.
To understand the effects of changing the manner in which forests are used or managed on carbon balances, data are needed on stocks and flows. The starting point is to understand the carbon stocks in forests that have not been subject to human modification within a timeframe relevant to rates of regeneration. As Bryan et al. (2010a) and Fox et al. (2010) emphasise, confidence in this outcome requires adequate unbiased sampling of forests undisturbed by humans and extrapolation of the results of this sampling using accurate spatial data layers representing the different types of undisturbed forest.