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A bioeconomic modelling of logged tropical forests to simulate low-carbon strategies for Central African concessions. [P-2216-03]

Claeys F., Delacote P., Gourlet-Fleury S., Karsenty A., Mortier F.. 2015. In : Our Common Future under Climate Change. International scientific conference Abstract Book 7-10 July 2015. Paris, France. Paris : CFCC15, p. 269-270. Our Common Future under Climate Change, 2015-07-07/2015-07-10, Paris (France).

Among the contributions expected from forest sectors in policies of climate mitigation, one consists in increasing forest carbon stocks by changing management practices. This activity, generally referred to as Improved Forest Management (IFM), is of major importance in the Congo Basin forests, where 20 millions of hectares are now managed for timber production. The carbon benefit generated by IFM activities is often obtained by a reduction of harvesting pressures on forest resources. In the case of Extension of Rotation Age/Cutting Cycle (ERA) projects, the reduction of emissions comes from the increase of Minimum Cutting Diameters (MCD) and/or the extension of Felling Cycle Duration (FCD). However, such activities have negative consequences for the profitability of timber companies. Climate instruments such as the mechanism of Reducing emissions from deforestation and forest degradation and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks in developing countries (REDD+) promote a compensatory approach to cover these income losses by the valuation of avoided carbon emissions. To determine the feasibility of such a carbon-based compensation, it is necessary to predict over the long term both the dynamics of forest carbon and the time schedule of timber incomes. The two are closely interrelated. Selective logging can alter the structure, the floristic composition, and thus, the carbon stocks of tropical forests. Modelling these forest-logging relationships is challenging. Selective logging implies to deploy a species level representation of timber harvesting but the high diversity of tropical forests, in pair with the scarcity of data, hinders the correct fitting of species-specific models. We developed a bioeconomic approach coupling a mixture of inhomogeneous matrix models for forest dynamics and an object-oriented model for forest logging companies' operations. For forest dynamics, our methodology addresses the challenge of taking into account the high species richness by simultaneously clustering tree species into groups according to vital rate information and selecting group-specific explicative environmental variables. For the logging operations, the object-oriented approach allows us to precisely describe harvest choices under technical and economic constraints, in a highly configurable manner. In the case of a Central African forest concession managed by a typical sawnwood export-oriented company, we predicted the carbon stock evolution for a wide range of ERA scenarios and for a time scale of 100 years. For several categories of carbon credit, we calculated break-even prices that would enable carbon revenues to compensate logger's loss of timber incomes. Our simulations are based on data from the M'Baïki site, in the Central African Republic (CAR), which has been monitored for 30 years through a collaborative partnership with various French and CAR institutional and research organizations. Economic data are taken from several forest concessionaires in Central Africa. We predicted that without any logging, carbon stock would increase naturally. When logging was simulated, the carbon stock decreased during the first felling cycle and although carbon recovery could be boosted by logging, this decrease was too sharp to catch up with unlogged levels. To ensure low break-even prices of carbon credits, ERA activities had to involve both FCD and MCD. In this case, we found a little dependence of the private discount rate and the alternative MCD and FCD, but a strong dependence of the way how carbon credits are accounted. Thus, from the perspective of the forest concessionaire, depending of the chosen type of credits, carbon revenues could compensate timber revenues for a large number of ERA projects. We focused on IFM projects, but our approach remains appropriate for other strategies of forest sustainability improvement such as Reduced Impact Logging techniques or post-logg...

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