From windblow to wood products: storm impacts on forest and HWP carbon trajectories in Ireland

Forest climate mitigation potential is strengthened when biogenic carbon is retained in long-lived wood products via temporary storage. In Ireland’s national greenhouse gas reporting, Harvested Wood Products (HWP) are accounted for using IPCC first order decay methods, and Irish assessments indicate that product breakouts strongly influence HWP carbon stock and emissions trajectories. Forest harvest volumes vary under normal management conditions and potentially even more under disturbance conditions. Storms have repeatedly caused windblow in Irish forests and can force salvage harvests, which can alter the distribution of harvested carbon among product classes, shortening carbon storage duration in HWPs, and limiting climate mitigation potentials. This study coupled inventory-driven forest simulations with the Ireland HWP model (IHWP-1.0) to quantify how a national storm event reshapes the forest-to-product carbon pathway for Irish conifer forests on mineral soils. Applying CBM-CFS3 (Kurz et al. 2009) as a forest carbon modelling tool and National Forest Inventory data, two scenarios were compared: (1) business-as-usual (BAU) management with regular thinning/clearfell cycles and replanting; (2) windstorm disturbance applied to eligible stands via stand attribute rules, followed by operational response (parameterised salvage timing/intensity and reforestation sequence after a short period of downed biomass decomposition). Harvest outputs from these forest growth simulations were mapped to HWP carbon dynamics pathways to create the IHWP-1.0 model, for which additional simulations were run using the Abstract Network Simulation Engine (ANSE). The IHWP-1.0 model’s flow network dynamics were based on Knaggs and O'Driscoll (2019) and used the IPCC decay parameters (half-lives of 35 and 25 years for sawn wood and wood-based panels, respectively). The HWP stock-in-use trajectories and payback time (years required to return to carbon storage under BAU trajectory) were analysed. This framework investigates how storms can affect long-lived product carbon storage, and the resilience of the forest climate benefits in an increasingly disturbance-prone context.