Landscapes Forest and Global Change - ESA - Escola Superior ...

H.R. Ratsimba et al. 2010. Multi-scale analysis of carbon stocks and deforestation monitoring
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4. Discussion
Although deforestation occurs in practically all developing countries (FAO, 2006), the actual
rate of deforestation makes REDD initiatives more and more important to maximize reductions
of greenhouse gases. In this way, it is important to create methodologies to assess and to
monitor the deforestation and the carbon stock together. The REDD initiatives suppose that
countries has to be able to assess both degradation and deforestation processes. However, the
degradation analysis seems to have some limitations regarding the cost effectiveness of the
methodology. Rakoto Ratsimba et al. (2010) have shown that this kind of assessment is possible
at a small scale (local level) while the upscaling process demonstrates that only deforestation
monitoring is possible over large areas. It is due to loss of spatial accuracy (the diversity of
value of 23 * 23 pixels of SPOT image are included in a single pixel of MODIS image).
This study reports that it is possible to report a forest map through biomass stock assessment. It
gives the opportunity for policy makers to have not only the total area of the forest (2 754 905
ha for the humid forest of the Eastern of Madagascar), but also the mean carbon stock per area
(126 ± 12 t/ha) (see Figure 5). If we refer to other studies done in the region, Sussman et al.
(1994) estimated the forest area of the region at 3 800 000 ha in 1985. Moreover, the same
assessment can be done in other images (2000 for example) in order to model the deforestation
process. The accuracy assessment gives a total value of 28,85 % which is an acceptable value
regarding other carbon assessment (Samalca et al., 2007 – 41,27 % ; Rakoto Ratsimba et al.,
2010 – 31,35 %). Thus, depending on REDD objective in Madagascar and the country priority, a
small scale or larger scale initiative could be implemented.
Figure 5: Forest map of the Eastern Humid Forest of Madagascar (biomass stock 126 ± 12 t/ha)
Projection: Laborde (Hotine Mercator Oblique) – Ellipsoïde International 1924
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