Costal Blue Carbon - Understanding results

Dear All,

I’m using this model to understand how carbon storage has changed in Indonesia. I’m only considering mangroves and I’m using two LULC maps, representing the landscape in 2000 and 2018 respectively. After running the model, I used QGIS to understand the total amount (in Megatonnes CO2) of the following outpus:

- carbon_accumulation_between_2000_and_2018 = 425.223.406
- carbon_emissions_between_2000_and_2018 = 67.430.938
- carbon_stock_at_2000 = 1.225.887.507
- carbon_stock_at_2018 = 1.569.643.177
- net_carbon_sequestration_between_2000_and_2018 = 343.755.321

I know that from 2000 to 2018 the total area of mangroves has decreased, so I wonder why the carbon stock in 2018 is larger than the one of the landscape in 2000 (considering that the model does not consider growth and aging of the habitat).

On the other hand, if the model considers that the mangroves that survived until 2018 have continued to capture carbon that those results make sense.

What do you think? Do these results make sense?

Thank you,

Hi Marco -

The model does account for accumulation of carbon, through the model inputs biomass-yearly-accumulation and soil-yearly-accumulation in the Transient Variables Table, and you can see the “carbon accumulation” output from the model too. From the numbers you posted, it looks like there was more accumulation from the mangroves that remain than there were emissions from any that were removed. While I don’t know anything about the total area that remains or was removed, or your carbon accumulation table values, these results do make sense in general.

~ Stacie

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I agree with Stacie :slightly_smiling_face:

Apologies for my late reply, and thank you all for your help!

So, my LULC maps have a resolution of 100m, so each pixel is an hectare. I calculated in QGIS the number of hectares of mangroves in Indonesia in 2000 and 2018, and below you can see that there’s been a consistent decrease between these two years.

Again, since the total area of mangroves was smaller in 2018, I wonder why the carbon stock in 2018 is larger than the one in 2000. Am I missing something? Do you need other info?

Thank you so much.



Hi Marco -

What are the values you’re using in the Transient Variables Table? It’s not just about overall area of mangroves, there are calculations for the amount of carbon sequestered in the mangroves that remain, and the amount of emissions due to mangrove removal, calculated over the 18-year period. The User Guide chapter provides all of the equations that are used in the model - if you want to make sure it’s calculating both accumulation and emission correctly, you can use these to do your own calculations and compare.

~ Stacie

Hi @swolny, thank you for your quick reply,

I attach here the transition table, as well as the carbon_pool_transient and carbon_pool_initial tables. the land-use class “50” are mangroves, the other ones are terrestrial habitats (forest, agriculture, urban)… below you can find their respective classes

I’ll try to do the calculations in the meantime. Thank you!

Marcocarbon_pool_initial_template2.csv (260 Bytes) carbon_pool_transient_template2.csv (705 Bytes) Transitions.csv (1.3 KB)

Hey @marco.guzzetti, this actually sounds consistent with the way the model behaves.

An important thing to remember is that the InVEST Coastal Blue Carbon model assumes that landscape transitions happen instantaneously in the first moment of the transition year (2018 in this case). Until that transition happens, you’ll have accumulation from the baseline year (2000) only, which means that the carbon stocks will be a function of the initial carbon stocks in the year 2000 plus the annual accumulation of carbon until the transition year. There won’t be any emissions until that initial year. As a result, the only thing that the model can do before that first transition year is accumulate carbon, which is what we’re seeing here.