Bird diversity and endemism along a land-use gradient in Madagascar: the conservation value of vanilla agroforests

Land-use change is the most important driver of biodiversity loss worldwide and particularly so in the tropics, where natural habitats are transformed into large-scale monocultures or heterogeneous landscape mosaics of largely unknown conservation value. Using birds as an indicator taxon, we evaluated the conservation value of a landscape mosaic in north-eastern Madagascar, a biodiversity hotspot and the center of global vanilla production. We assessed bird species richness and composition by conducting point counts across seven prevalent land-use types (forest- and fallow-derived vanilla agroforests, woody and herbaceous fallow that are part of a shifting cultivation system, rice paddy, forest fragment and contiguous old-growth forest). We find that old-growth forest had the highest species richness, driven by a high share of endemics. Species richness and community composition in forest-derived vanilla agroforest was similar to forest fragment, whereas fallow-derived vanilla agroforest was most comparable to woody fallow. The open land-use types herbaceous fallow and rice paddy had fewest species. Across forest fragment, vanilla agroforests and woody fallow, endemic bird species richness was positively correlated to landscape-scale forest cover. We conclude that both fallow- and forest-derived vanilla agroforests play an important but contrasting role for bird conservation in the landscape: Fallow-derived agroforests are less valuable but take fallow land out of the shifting cultivation cycle, possibly preventing further degradation. Conversely, forest-derived agroforests contribute to forest degradation but may avoid total loss of forest fragments. Considering the land-use history of agroforests may thus be a promising avenue for future research beyond the case of vanilla.

Methods

1) Species-by-plot matrix from pointcounts across seven land-use types in north-eastern Madgascar (80 plots in total)

2) Plot characteristics (location, elevation, basal area, number of large trees, canopy cover, landscape-scale forest cover)

Methods are described in the paper:

Martin, D. A., Andriafanomezantsoa, R., Dröge, S., Osen, K., Rakotomalala, E., Wurz, A., Andrianarimisa, A., & Kreft, H. (n.d.). Bird diversity and endemism along a land-use gradient in Madagascar: the conservation value of vanilla agroforests. Biotropica.