I am assessing change in carbon in mangroves between two timepoints 1985 and 2015. The model seems to run fine. However when I look at the carbon stock raster for 2015 I see some negative values. Is that possible? The 1985 carbon stock raster does not have negative values.
Thanks
Matt
Hi @mreiter, Very interesting! It does sound unexpected. How negative are the values? And could you upload your logfile so we can take a look?
Thanks,
James
Hi,
I met the same problem,too.It is odd that the output of carbon stocks has very few negative values.
I would be very grateful if you could reply to me.
Thanks
Selina
InVEST-Coastal-Blue-Carbon-log-2020-07-12–14_36_42.txt (9.4 KB)
HI @Selina, Very interesting! It does sound unexpected. How negative are the values? I don’t see anything out of the ordinary in the logfile, so there’s something else going on here.
Thanks,
James
I used the model to get carbon stocks for 1990-2019, but there were negative values in the last two timesteps, rarely less than 10 grids, which is a bit odd。
Hi @Selina, this issue has come up a couple of times recently, and I don’t have a fix for you yet. We are working on it, though, and I’m glad that it’s only affecting a few pixels. Could you share your complete set of input data so I can take a look? There’s a chance I might be able to see what’s happening here by taking a look at your inputs.
I hope to have a fix for this before too long, and thanks for your help,
James
Hi @Selina, I’d like to first apologize for how long it’s taken me to get back to you about this issue. I confirmed that this was indeed an issue with the model back in July, just after you sent your data to me, but the fix proved to be very tricky and between this issue and a number of other issues with the model, we ended up rewriting the model entirely. The corrected version of the Coastal Blue Carbon model will be released in InVEST 3.9, which should be coming up in the next couple of weeks. I’ve also confirmed that the updated model works as expected on your inputs, with no negative stocks across any of the years I sampled in your analysis, and the results look reasonable given your inputs.
I’m so sorry for the delay on this, and please feel free to let us know if anything else comes up!
James
Hi James,
I am having the same problem as Selina and Matt, but this time with outputs of the net present value. The outputs of carbon stocks, accumulations, emissions, and net sequestration look good (Analysis period 2015-2040). But the net present value for pixels with land use/land cover changes shows negative numbers even in the year of baseline LULC raster (2015)
When the pixel has no changes in the study period (accumulation process), it seems that the code is working well and shows positive numbers of the net present value for both years (2015-2040).
We are using the “Price table” option. The table is the same as suggested in the InVest guide. Running with InVEST 3.8.9 version.
Log file looks good:
InVEST-Coastal-Blue-Carbon-log-2020-11-10–17_03_44.txt (4.7 KB)
I would be very grateful if you could give me a glimmer of hope 
.
Thanks
Carlos
These are the values for a pixel with no LULC changes
Hi @borochi,
We’ve had enough issues come up with Coastal Blue Carbon that we ended up rebuilding it, which you can find in this development build:
We are much more confident in the correctness of this latest version of the model, so could you try running this latest version of the CBC with your inputs and see if the valuation is still negative? Note that the inputs have a slightly different structure (which are described in the User’s Guide and demonstrated in the sample data that’s installed with the development build).
Let us know how it goes!
James
Hi James,
Thanks for the swift response. We ran the new version of CBC and the results for carbon storage seem to be right, and match the ones we generated with the previous version. However, when using only two years (2015 and 2040) there was no output raster for emissions in that period, and the total net carbon sequestration raster and net present value rasters had zero as the value for all pixels (fig.1). We tried again using an intermediate year (e.g. 2030) and it generated a net present value map with values that seem to make sense for 2030 and 2040, but it only generated one carbon emissions map for the second period (2030-2040). We do not understand if adding an intermediate map is a requirement of this new version, or if there is something else we are missing.
Can you please help us?
Thank you again
Figure 1
Hi @borochi,
Could you send me your inputs so I can take a close look at what the model is doing? That will be easier than trying to debug a potential issue exclusively over the forums
If your inputs are large, it might be easiest to send them via a file sharing service like dropbox or google drive, and if you’d rather keep them private, feel free to send them to my email, jdouglass@stanford.edu.
Thanks!
James
Thanks for sending your inputs @borochi!
For emissions, you’re right that the model isn’t producing emissions outputs between the baseline year and your first transition, and this is correct for how the model is supposed to work. The way that the model handles carbon emissions doesn’t allow us to start the modelling run in a state of emission. So instead, all carbon in natural habitats will accumulate until the first transition period. In the first transition year, the model will start emitting carbon for whichever pixels enter a state of emission. So in this case, you may want to extend the analysis year out past the first transition year to see the effects of some of the carbon emissions.
I’m actually really glad you mentioned this, because this turned up a small bug in the CBC model that is now fixed in this development build:
Could you try out this dev build and let us know if anything else looks out of place?
Thanks!
James
Hi James,
“New” outputs look ok. We still have not found a possible bug
I think I am missing something in this part of the first transition period of the CBC model. My baseline is 2015, my first transition period is a raster map modeled from the probability of changes to 2040 (25 years later). For this year 2040 my land use/cover map already had changes, gains and losses of blue carbon habitats. Accumulation is calculated, but why emissions are omitted? What happened to the emissions from the mangrove covers that existed in 2015 but no longer in 2040? that’s my conflict.
On the other hand, when the analysis of the second transition period (in my specific case) from 2040 to 2050 is carried out, how are changes in land use/cover calculated? (There is no a raster map for 2050).
Some of the pixels of the results of this second period present negative values (I suppose due to loss of blue carbon habitats and consequently emissions). I still have the doubt that if emissions are not calculated in the first transition period (25 years), the Total-net- sequestration values and the net-present-values are being overestimated.
Thanks for your support and patience!!!
Carlos
Great! Well, let us know if and when something else comes up that doesn’t quite look right and we’ll take a look.
The Coastal Blue Carbon model assumes that landcover changes happen instantaneously and completely in the year when the transition occurs. So in your example you have the baseline landcover at the year 2015 and your first landcover transition happening at 2040. The model assumes that the landcover that exists at the year 2015 remains the same through the end of the year 2039, and then in 2040 there’s a landcover transition to what you have in your 2040 snapshot raster. If there’s a carbon disturbance in the year 2040, then you’ll start to see carbon emissions in some pixels on the landscape in years after 2040.
The only time the landcover changes is at a transition year. There’s no gradual change of landcover here at all … landcover transitions happen completely in the year of the snapshot raster where a transition takes place.
It sounds like you might be describing an analysis year at 2050, right? If so, you’ll see carbon emissions between 2040 and 2050. There’s no change in landcover classification, the emissions are happening from the 2040 transition event itself.
Yes, total sequestration could be negative over the 2040-2050 period when carbon is being emitted. I’d expect to see positive sequestration when carbon is being accumulated.
Hopefully this clarifies some things and let me know if you have any other questions!
James
