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Correctly assessing forest change in a priority West African mangrove ecosystem: 1986–2010 An answer to Carney et al. (2014) paper “Assessing forest change in a priority West African mangrove ecosystem: 1986–2010”

Andrieu, Julien, Cormier-Salem, Marie-Christine, Descroix, Luc, Sané, Tidiane, Diéye, El Hadji Balla, Ndour, Ngor
Remote sensing applications 2019 v.13 pp. 337-347
decision making, ecosystems, environmental policy, estuaries, forests, georeferencing, image analysis, mangroves, paper, remote sensing
In order for decision-makers to adjust environmental policy appropriately, it is essential that they utilize reliable data. Now, on a global scale, mangroves are considered endangered, yet there is a general consensus among recent scholars that mangroves in Saloum and Casamance estuaries are currently experiencing regeneration. In contrast with the results of these papers, Carney et al. (2014) published a paper in Geoforum mapping and quantifying a massive mangrove loss. However, remote sensing and mapping shortcomings have been identified. The 2010 map used in the Carney et al. (2014) paper is accurate, however, as a result of errors in georeferencing, window extraction and classification, their 1986 map is not. Mangrove and mudflats are grouped in the same class. The addition of a stacked classification to the image processing used by Carney et al. (2014) enables the realization of a correction of the map, and thus the production of results similar to other studies. The supposed loss of mangroves appears to have been the consequence of this classification error. In fact, we observe a progression of 8804 ha instead of the regression of 37,196 ha assessed by the authors. This published discrepancy, which is in opposition to any other study of this area, must be discussed in order to clarify for scholars and policymakers the actual dynamics of mangrove change in the studied region.