You assume that the carbon in all the volume logged is instantly returned to the atmosphere as CO2. But the rate of decomposition depends on what the wood is used for. Pulp might become CO2 fairly quickly, although not if a large percentage of paper/cardboard is recycled. Lumber can last decades or even hundreds of years when used for construction. For coastal old growth this might still be less than the time the trees would have lived. But perhaps not by much. For the interior, the living trees might have decomposed just as soon, if not sooner, than the lumber. Also, why do you count woody debris in the carbon subsidy? That wood was already dead before logging and will be left there after logging (not much slash burning happens anymore, as I understand it). Roots too will decompose quite slowly and I don't think you should have counted 100% of their carbon. Taking into account the shelf life of wood products, and not counting woody debris, would lower your estimate for the carbon subsidy.
Nevertheless, you're probably correct that there is a large carbon subsidy (externality). It's possible that the value of the forestry industry to provincial GDP is currently greater than the combined subsidies, but even if so, it's probably not by much. And the difference will shrink and likely become negative as the price of carbon rises, as you pointed out. I would just like to see revised numbers that take into account the shelf life of wood products.
Forestry definitely doesn't pay the bills, folks
in Portal: The true cost of subsidies provided to the logging industry
Posted
You assume that the carbon in all the volume logged is instantly returned to the atmosphere as CO2. But the rate of decomposition depends on what the wood is used for. Pulp might become CO2 fairly quickly, although not if a large percentage of paper/cardboard is recycled. Lumber can last decades or even hundreds of years when used for construction. For coastal old growth this might still be less than the time the trees would have lived. But perhaps not by much. For the interior, the living trees might have decomposed just as soon, if not sooner, than the lumber. Also, why do you count woody debris in the carbon subsidy? That wood was already dead before logging and will be left there after logging (not much slash burning happens anymore, as I understand it). Roots too will decompose quite slowly and I don't think you should have counted 100% of their carbon. Taking into account the shelf life of wood products, and not counting woody debris, would lower your estimate for the carbon subsidy.
Nevertheless, you're probably correct that there is a large carbon subsidy (externality). It's possible that the value of the forestry industry to provincial GDP is currently greater than the combined subsidies, but even if so, it's probably not by much. And the difference will shrink and likely become negative as the price of carbon rises, as you pointed out. I would just like to see revised numbers that take into account the shelf life of wood products.