Vegetation dynamics and drivers of change in the Central Highlands of Madagascar during the last 6300 years: Pre- and post-human settlement

Abstract

The Central Highlands region of Madagascar is currently dominated by open and mosaic ecosystems, and the region is targeted for afforestation projects. At present, little is known about the origin of these ecosystems and whether or not they are ancient or anthropogenically derived mosaics. This paper provides new insights into the environmental history and drivers of change in the Central Highlands of Madagascar during the last 6300 years through palaeoecological records from Lake Dangovavy. Our results suggested that open and mosaic ecosystems have been present in the landscape for at least 6000 years that is, 4 cal. ka BP before human settlement (2 cal. ka BP). Between 6.3 and 2 cal. ka BP landscapes were characterized by a mosaic ecosystem dominated by a matrix of open montane grassland and ericoid shrubland with extent forest patches, associated with seasonal variation of rainfall, and fire. A matrix of ericoid shrubland remained abundant in the landscape despite an increase of fire regime and herbivory activities between 2 and 1.1 cal. ka BP. Major changes in the vegetation were recorded during the last millennium with a shift towards a more open C4-dominated grassland associated with high fire frequency and herbivory activities, most likely linked to human influence. Our findings support the notion of the natural presence of open ecosystems on the islands. These shed light on the landscape history which should be considered when setting conservation goals with a particular focus on areas targeted for tree plantations and fire bans like the Central highlands of Madagascar.