Coastal Blue Carbon

Good morning

I am a MsC Student from Guinea-Bissau at Faculty of Sciences, Lisbon

University.

I am using the Coastal Blue Carbon model to assess the carbon accumulation in

above and below-ground biomass at the mangrove forests in two Parks of my

country.

I ran the Model but the results for carbon emissions seem to be inconsistent.

I am working in the Cacheu (PNTC) and Cantanhez (PNC) Parks, both with

significant mangrove areas.

Land Use Land Cover raster (GDAL-supported) of two parks were used for the

years 2002, 2007, 2010 and 2015, with 25m spatial resolution, made from

supervised classification of Landsat images .

For PNTC we have 35897, 35267, 38634 and 33949 hectares, respectively for

2002, 2007, 2010, and 2015.

For the period 2002-2007we have a decrease in mangrove area of -630ha, for

2007-2010 we have an increase of 3367ha, and for 2010-2015 we have a decrease

of -4685.

For PNC we have 21466, 20636, 23180 and 17909 hectares respectively for the

same years.

For the period 2002-2007we have a decrease in mangrove area of -830ha, for

2007-2010 we have an increase of 2544ha, and for 2010-2015 we have a decrease

of -5271ha.

We used the following input data for Processor:

LULC Lookup table - two classes Mangrove 1 (defined as a Coastal Blue Carbon

habitat ) / no mangrove 0 (defined as no Coastal Blue Carbon habitat)

Carbon pool initial template (MtCO2e/ha) - only Biomass pool was considered:

0.000143 MtCO2e/ha (value obtained from a former study in the country)

Transitions – we considered the following transitions

  1. Mangrove to No mangrove (high impact);

  2. No mangrove to No mangrove (no carbon change);

  3. No mangrove to Mangrove (Accumulation); and

  4. Mangrove to Mangrove (Accumulation)

Carbon pool transient template

Biomass half-life: 15 years (selected from Invest User Guide)

Biomass-high-imp-disturb: 100% biomass lost (selected from Invest User Guide,

but the value inserted was 1 for total biomass lost)

Biomass-yearly-accumulation (MtCO2e/ha/year): 0.0000049 (computed as a

proportion of 3.42% of total biomass, obtained from a published work).

With this input dataset we obtained:

  1. for C accumulation per hectare in the period, in MtCO2e:

2002-2007 – accumulation 0.0000245

2007-2010 - accumulation 0.0000147

2010-2015 - accumulation 0.0000245

(this is just the yearly increase multiplied by the number of years)

  1. for C emission per hectare in the period, in MtCO2e:

2002-2007 – emmision 0.000138531

2007-2010 - emmision 0.0000366

2010-2015 - emmision 0.000176

These results seem to be not correct, because the emission figures are too

high if compared with the obtained for accumulation. For instance, for

2002-2007 we have a little proportion of mangrove areas lost if compared to

the undisturbed area, which continued to accumulate, but the balance remained

negative. Also, for the period 2007-2010, in which the mangrove area

increased, the balance continues negative.

Can you help me in this subject?

Best Regards

Giselle Dias