Thu 8 November: Next PhD discussion meeting on Agriculture-Climate-Forests-Food

The effect of forest management for wood production on atmospheric carbon concentrations and eventually on climate remains highly contested, especially in the tropics where it is associated to deforestation and degradation. To know whether wood harvesting in forests causes a change to the natural carbon cycle, we estimate the carbon balance from natural tropical forests in Costa Rica using a lifecycle accounting approach. System boundaries include all major lifecycle processes at a regional level and one rotation period (15 years being the minimum under local regulations) as recommended in the literature for an attributional lifecycle assessment of bio-products. We use a mass flow analysis based on information from all logging operations in the Costa Rican NW region (2010-2016), a sample of industries transforming wood into final products and national data for the end of life of wood products. Based on this, we estimated a surplus of carbon stored within the boundaries of the system, i.e. -3.06 Mg C ha^-1 15 yr^-1. However, once we allow the random interaction of parameters through Monte Carlo simulations, the balance becomes -2.08 Mg C ha^-1 15 yr^-1 with a 95% CI of -5.08 to 1.39. This confidence interval reveals probabilities of a net increase in atmospheric carbon due to harvesting although these are smaller than those from a system that acts as a reservoir.  Anthropogenic reservoirs (products in use and solid waste disposal sites) play a determinant role delaying carbon losses and explain most differences with previous accounts of the carbon balance of tropical forest management. We find that it is the multifunctionality of wood through short and long-term final uses that lead to this outcome. Given that the carbon balance is mostly sensitive to changes in length of the rotation period, we discuss the validity of this timeframe to approximate the carbon balance for tropical forest management.