Fourteen years of anthropization dynamics in the Uapaca bojeri Baill. forest of Madagascar
2018
de Haulleville, Thalès | Rakotondrasoa, OliviaL. | Rakoto Ratsimba, Harifidy | Bastin, Jean-François | Brostaux, Yves | Verheggen, FrançoisJ. | Rajoelison, GabrielleL. | Malaisse, François | Poncelet, Marc | Haubruge, Eric | Beeckman, Hans | Bogaert, Jan
Anthropization of forest landscapes is a major threat to ecosystems and biodiversity. To gather comprehensive information on anthropization dynamics in forest landscapes, fine-scale surveys of deforestation are required, coupled with detailed analysis of both spatial transformation processes and forest patch geometry. We conducted such a comprehensive study in a monospecific Uapaca bojeri (Baill.) forest of Madagascar, between 1999 and 2013. A diachronic set of four maps was produced and deforestation rates were calculated. Spatial transformation processes were described using Bogaert et al. (2004) typology. Forest patch geometry was monitored using largest patch index, mean patch size, and squared mean patch size to describe patch size dynamics, mean shape index and area weighted mean shape index to describe patch compactness, and fractal dimension analysis to describe patch outline complexity. For fractal dimension analysis, an innovative segmented regression model (Muggeo 2008) was used to separately quantify fractal dimensions for multiple ranges of patch sizes. Our results showed a growing anthropization of the U. bojeri forest landscape in the area, through a strong yet decelerating deforestation (from − 59.5% year⁻¹ between 1999 and 2005 to − 2.84% year⁻¹ between 2009 and 2013), clear forest fragmentation, and a subtle yet growing-in-scale simplification of patch geometry for small forest patches. Deforestation was artisanal in nature and, in 2013, large patches were withdrawing to less accessible topographic features. Our results forecast a medium-term loss of resilience of the U. bojeri forest in the area, if no direct forest conservation measures are taken.
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