| Mission with CartONG - Vietnam |
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Jason San Souci, GISCorps Volunteer In December 2009, CartONG; a French based non profit organization requested the assistance of a Following a series of analysis and field work, CartONG and their team of collaborators had learned of inconsistencies in the carbon content levels that were measured in 2004 and 2009. In order to verify that information they decided to request a remote sensing specialist’s assistance to analyze Spot satellite imageries from those two years. Shortly after the request came in an email broadcast was sent to the volunteer database and 15 individuals from 10 countries applied for the project. The review of the resumes and interviews resulted in selecting Jason San Souci, GISP from AFE Advisors LLC. in The following is a summary of that report. Executive Summary When comparing fieldwork results from 2004 and 2009 on determining carbon content of one village in the Vietnamese Highlands, the carbon ranges differed enormously, suggesting that either the methods of fieldwork have changed or that the carbon stock was depleted through deforestation and degradation. However, analyzing SPOT satellite images from 2004 and 2009 on carbon content, verified the findings of the fieldwork and demonstrated that the carbon stock had declined through both, deforestation and degradation. The Need for Satellite Imagery Analysis After the fieldwork started and was completed in one of the villages; it was found that whereas the newly collected data would give a good overview and provide a good base for the Carbon stocks model projecting future carbon contents under different forest management scenarios; the data on carbon content which could be obtained through past forest inventories was fragmented and verification was needed. Especially the range on carbon content was reported to be much higher in 2004 than 2009. Whereas this was to be expected, the differences were striking and raised questions. The decision to verify these inconsistencies was taken at a late state of the project and there was no budget available to pay a specialist for the analysis. Hence, CartONG asked if Method • Converting the Digital Number values to at-satellite reflectance; some input was given by the SPOT technical team When comparing the overall computed results it becomes evident that the trend identified during the fieldwork with a strong deforestation and degradation since 2004 can be confirmed through the Satellite Image Analysis. The Carbon range in the satellite images is slightly below the carbon range determined through fieldwork in 2004 and 2009. This can be explained through the fact that trees with a bigger diameter will store more Carbon, which the mixed pixel value of the image can’t reflect to the same extent (Figure 1).
On the left hand side graph Amount of Carbon shows the Carbon range prevailing in 2004 in Thon (village) 6; as can be seen, none of the forested areas are below 751 Tones/Ha. On the right hand side the situation in 2009 is depicted. Here none of the forested areas contains more than 750 Tones/Ha. This trend is reflected in the results of the satellite image analysis as well. In 2004, the lowest carbon value is ranging between 501 – 750 Tones/Ha; in 2009 the highest value is not exceeding 500 Tones/Ha. The boundaries are not as defined which is linked to the fact that the boundaries shown in the plot analysis have been obtained by interpolating (kriging) – Figure 2.
When roughly estimating degradation for Thon 6 from the results of the satellite analysis; the following figures were established:
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