Inconsistent outcome of the Carbon model

Dear developers,

I applied the carbon storage and sequestration model but I have an outcome that is not coherent and I think is not correct. Assessing land use changes from 1990 to 2012 (attached file), the main change is a reduction of surface area of agricutural areas and an increase in forest and semi natural areas (CORINE Land Cover). According to the literature, the conversion from croplands to forest implies an increase in carbon stock. However, my results are different and according to the output of the model there is an increase in carbon stock of agricultural areas and a reduction in the carbon stock of forest and seminatural areas (when it was supposed to be the other way around). Can you explain me why is this happening?

Thanks

Comments

  • RichRich Administrator, NatCap Staff
    Hi, without the biophysical carbon pool table I can't be sure, but I might guess there could be subtleties in the sub landcover classification?  Like is the loss of "Land principally occupied by agriculture, with significant areas of natural vegetation" a carbon stock that's weightier than the increase of "Natural grasslands"?  

    Anyway, it would helpful if you could post your carbon pool table here.

    Also, I don't know if it's a typo and/or relevant, but the area headers for your table are listed as 1990 and 2012, but the difference table says 1990 and 2000.
  • Hi Rich,

    I am not sure I understood what you said. However, attached you can find the carbon pool table for you to take a look. Please do not pay attention to classes with SLM (for instance, vineyards SLM) because they are part of a different analysis and dont influence this particular outcome.

    By the way, yes it is a typing error sorry about that. Though is not important.

    I will be pending on your answer.
  • RichRich Administrator, NatCap Staff
    Hi @Casta, annoyingly your original land breakdown table is no longer attached to this thread.  I think the forum only keeps the most recent attachment or something.  But I *do* remember that you had a decrease in "Land principally occupied by agriculture, with significant areas of natural vegetation" and an increase in "Natural grasslands".  The carbon pool table you attached shows that the agriculture landcover type has more carbon (106.04) than natural grasslands (104.81).  In just that example you'd expect a carbon loss by conversion from agricuture to grasslands, even though conceptually you might not.

    I also see some other surprising numbers, like "olive groves" and "bare rocks" both have more carbon stocks than "agro forestry".  At any rate, I'd guess if you ran through the actual numbers of areas of landcover multiplied by their carbon stocks, you'd find that for the given carbon pool stocks you have and the amount of landcover change, you just so happen to have a carbon loss because that's how the numbers worked out. 

    Could you try calculating the total carbon stocks given your carbon pool table and your spreadsheet you attached earlier and see if this is the case?  I'm not sure what else to look for at this point.

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