I have a quick question regarding inputs for the coastal blue carbon model, specifically for a mangrove valuation. Would it be reasonable for the initial volume of disturbed carbon (Dps) under medium impact to be 19, 164, and 35 MgC/ha for the biomass, soil, and litter pools respectively? Compared to the accumulating sequestration (2 and 4.7 MgC/ha for biomass and soil), it seems as if accumulations are vastly outweighed and would result in a negative stock while there is a positive area of mangrove cover.
I’ve only used the Blue Carbon model in its simplest form, not including disturbance, but I have an idea of how it works. First, I’m curious what you mean when you say “the initial volume of disturbed carbon” related to model inputs. The model inputs include the initial carbon stock for each pool (which is in Mg CO2e/ha), and the percentage of that stock that is lost in each carbon pool due to low/medium/high levels of disturbance. You don’t need to specify a specific quantity (in Mg/ha) of carbon that is lost, only the percentage that is lost. The User Guide also provides general guidelines for assigning the disturbance percentage, so you can use that to determine if the values you’re assigning seem reasonable. Or maybe I’m mis-understanding your question?
As for accumulations versus disturbance over time, I’d say that it’s very likely that, if mangroves are disturbed by humans, they’ll lose a lot more than they gain in the disturbance timeframe. This may not always be the case, if the disturbance is very slight. But if it’s a large disturbance, like being cut down or dredged, it will take a long time for that biomass and soil to slowly build back up, and you’ll have negative sequestration over that time, compared with the current state. Now, if your land cover transitions include increasing the area of mangrove over time, obviously that will contribute positive storage/sequestration, which will also be included in the model results.