Estimation of economic value in blue carbon model

Software Support
1

Hello, I’m sorry that I’m having trouble using the model again – When I count the layers the model outputs, the annual net carbon sequestration in this region is a positive sum in terms of the grid number, but the value of carbon, when summed in grid numbers, is negative – Why is that?

In the layer’s attribute table, a grid with a net sequestration of -1148642 has a carbon value of -24229, and a grid with a net sequestration of 239173 has a carbon value of 1955. The negative ratio is 2.6 times the positive ratio.net_sequestration1990-1995 value1990 Why is the lost carbon more expensive than the accumulated carbon?

Here is my workspace
workspace.zip (540.0 KB)

As you can see, I have been asking a lot of questions on this forum recently, and I am very grateful to the platform for helping me.

I feel that I have encountered many difficulties in learning the principles of this model, which are still unsolved. There are only a few simplified formulas in the help document. I can not match the input parameters, the formulas in the documentation and the values in the model output, such as the calculation of carbon emissions and the calculation of carbon value, is there a more detailed formula?

I also could not find the answer after reading some of the references in the help documentation. Is there a more detailed description of the operation and formulas of the Invest Model? It's important for me to learn how it works, otherwise I can't verify that my results are correct and reliable.

Thank you again for your patience!

Selina

2

Hi Selina,
I suspect that is due to the timing of changes. Values are presented as net present value, so if your lost carbon happens sooner than the gained carbon, these values will be greater/unit, due to discounting.
Regards,
Rob

3

Hi Rob
Thank you for your answer！
My time step was set at five years. How could a 5% discount over five years lead to such a big difference? And isn’t NPV calculated on the basis of net sequestration-emission(=accumulation-emission)? The net sequestration has been positive for the past 5 years, so there shouldn’t be a time difference?I’m sorry, I still don’t understand.
Selina

4

I believe the “value1990” raster is the NPV of all changes from baseline year to your end date, not only for 1990-1995.

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5

Oh, okay. Thank you Rob.