Smallholder vanilla agroforestry in Madagascar: biodiversity, ecosystem services and yields in a land-use context

Abstract

Land-use change threatens biodiversity and ecosystem services worldwide. Tropical areas are currently particularly affected: natural ecosystems are being transformed into largescale monocultures or small-scale mosaic landscapes characterized by smallholder agriculture. In both cases, the conversion of natural ecosystems into agriculturally used areas can greatly increase yield, at least in the short term.A rapid change in land use is currently taking place in north-eastern Madagascar, driven by two main factors: the cultivation of rice through shifting cultivation and the conversion of forests and fallow land into vanilla agroforestry. The result of these processes is a smallscale and very heterogeneous agricultural landscape. This dissertation shows what this land-use change means for biodiversity and ecosystem services, how realized harvests and profitability influence land use decisions, and where there are opportunities for nature conservation through targeted policy interventions in north-eastern Madagascar. Importantly, this is a greatly under-researched topic, given that research on the conservation value of converted lands in Madagascar is still in its infancy. Indeed, nearly nothing has been published on biodiversity, ecosystem services, and yields in vanilla agroforests.To compare different forms of land use, we selected 80 plots in 10 villages and in Marojejy National Park where we collected a large part of the biodiversity and ecosystem service data that underpins this dissertation. The seven land-use types were old-growth forest, forest fragment, forest-derived vanilla agroforestry, fallow-derived vanilla agroforestry, herbaceous fallow, woody fallow, and rice paddy. To obtain more precise data on tree dynamics and harvests in vanilla agroforests, we additionally researched a chronosequence with 209 vanilla agroforests. Furthermore, this thesis also contains a review on the importance of 1.1 Land-use change as a key diver of biodiversity loss ……………………………………………..15 Box 1: My PhD journey -Interdisciplinarity and diversity……………………………………..… 18 1.2 Trade-offs between biodiversity, ecosystem services, and yields in tropical smallholder agriculture, with a focus on agroforests …………………………………………………19 Box 2: My PhD journey -Transdisciplinarity ………………………………………..………………… 22 1.3 Natural history, land-use change, and conservation in Madagascar ………………………23