Ralison, J. M. | Search bioRxiv

bioRxiv2020

It's not just poverty: unregulated global market and bad governance explain unceasing deforestation in Western Madagascar

Madagascar is recognized both for its unparalleled biodiversity and the high level of threat suffered by this biodiversity, associated in particular with anthropogenic deforestation. Despite sustained efforts to fight poverty and curb deforestation, forest cover in Madagascar is rapidly decreasing. To try to explain why it is so difficult to stop deforestation in Madagascar, we analysed the recent deforestation process in Western Madagascar through satellite image analysis and field surveys. We show that deforestation has increased from less than 0.9%/yr on 2000-2010 to more than 2%/yr on 2010-2017. We identified two major causes of deforestation, which were not associated with subsistence agriculture: slash-and-burn agriculture for the cultivation of cash crops (maize and peanut), and uncontrolled fires to create open pasture. Maize production is mainly at the destination of the domestic market and is used in particular for livestock feeding. Peanut production has boomed since 2013 and more than half of it is now exported towards asiatic countries. The money earned by farmers is principally invested into zebu herd acquisition. Trade of agricultural commodities benefits several intermediaries, some of whom have political responsibilities thus creating conflicts of interest. On the other hand, agents from institutions in charge of the management of the protected areas have no means to enforce laws against deforestation. In the absence of an efficient strategy to stop deforestation, we predicted that 38-93% of the forest present in 2000 will have disappeared in 2050. Forest loss, apart from biodiversity loss and climate-change global issues, will be at the expense of local population. In order to stop deforestation, international aid should be used to improve local governance to enforce environmental laws and pressure should be put on trading companies to buy certified agricultural commodities that are not derived from deforestation.

ecology↗

bioRxiv2020

Phylogeographic analysis of Goodman's mouse lemur reveals historical interconnectivity of Madagascar's Central Highlands and eastern rainforests

The Central Highland Plateau of Madagascar is largely composed of grassland savanna, interspersed with patches of closed-canopy forest. Conventional wisdom has it that these grasslands are anthropogenic in nature, having been created very recently via human agricultural practices. Yet, the ancient origins of the endemic grasses suggest that the extensive savannas are natural biomes, similar to others found around the globe. We use a phylogeographic approach to compare these two competing scenarios. By sampling multiple populations of Goodmans mouse lemur (Microcebus lehilahytsara), a small-bodied nocturnal primate, we reconstruct the phylogeographic and demographic history of these "environmental metronomes" to estimate the time at which their populations diverged, and thus proximally, when their habitats would have become fragmented. We applied coalescent methods to RADseq data to infer phylogenetic relationships, population structure, and migration corridors among sampling sites. These analyses indicate that forest fragmentation occurred rapidly during a period of decreased precipitation near the last glacial maximum and would have affected both the Central Highlands and eastern forests. Though there is clear genomic structure separating the populations of the Central Highland from those of the eastern rainforests, there is also evidence of historical migration between them. Findings support the hypothesis that the Central Highland savanna predates human arrival, indicating that it is a natural landscape that has long impacted the population dynamics of Goodmans mouse lemur, and by extension, other forest-dwelling organisms in Madagascar.

evolutionary biology↗