Coastal blue carbon model - transition timeframe

NatCap Software Support
1

Hi,

I’m using the coastal blue carbon model to assess the carbon implications of marsh shift with sea level rise. The future LULC raster I’m using has transitions from blue carbon habitat to non-blue carbon habitat (e.g., marsh becoming open water) and transitions from non-blue carbon habitat to blue carbon habitat (e.g. agricultural land becoming marsh). I know that the timeframe of carbon release following the first type of transition is set by the half-life parameter for the transition, but I’m not sure how the timeframe of transitions to a blue carbon habitat are handled within the model.

For example, if a certain area is agricultural land in the baseline LULC (for year 2000), but transitions to marsh in the 2025 snapshot LULC, is that area assumed to have transitioned to marsh immediately after the baseline year and accumulated carbon for the 25 years until the snapshot? Or does it not transition to marsh until the snapshot year (so no accumulation in that area would occur between 2000 and 2025)?

Any clarification would be appreciated. Thank you!

2

Hi @kwarnell, sorry about the delay on this!

The model assumes that transitions happen completely within the one timestep/snapshot in which they are reported. So in your example, the model would assume that the area that was agricultural (assuming it’s not a blue carbon habitat) in the year 2000 will not accumulate any carbon from year to year. Then, in the year 2025, that area would transition completely to marshlands (a blue carbon habitat). This blue carbon habitat would thereafter accumulate carbon annually according to the associated rate in the yearly-accumulation column in the LULC lookup until the next transition boundary year.

Let me know if that doesn’t clear things up and sorry about the delay!
James