Biodiversity assessment of vanilla plantations and surrounding areas in the SAVA region of Madagascar

Abstract

Conversion of land for agriculture can have catastrophic impacts on natural ecosystems and can drastically reduce biodiversity, especially in the tropics. However, different crop cultivation methods have different effects on biodiversity, with ecologically sympathetic production and management regimes often exhibiting the lowest species loss [1]. Madagascar’s vanilla plantations are one example of a valuable cash-crop where large areas of forest have been converted to agroecosystems. However, the impact of vanilla production on Malagasy biodiversity is unknown. Much of the world’s vanilla is produced in Madagascar’s north-east SAVA region using a variety of cultivation methods, ranging from small-scale plantations grown in and around existing forests, to large intensively-farmed plantations grown on an industrial scale. We undertook a series of rapid biodiversity assessments of vanilla plantations (n=17) in the SAVA region. At each plantation, we surveyed the species richness of plants and vertebrates. Surveys were also performed in nearby natural forest fragments (n=9), to act as uncultivated controls.

We observed over 500 plant species and nearly 200 vertebrate taxa. Plant and animal species richness tended to be lower in plantations compared to natural forests, suggesting that conversion of forest to plantation was detrimental to biodiversity. However, the location and management regime of different plantations had significant impacts on resident flora and fauna. Species richness for both plants and animals was significantly higher in traditionally maintained vanilla plantations grown in or adjacent to natural forest fragments, compared to more intensively farmed, anthropogenic sites. Vanilla plantations also harboured numerous threatened animal species (n=9), suggesting that they are valuable habitats for these taxa. The most surprising result was the observation that five different species of lemurs inhabited vanilla plantations [2,3], including the newly described dwarf lemur Cheirogaleus shethi [2]. Lemurs were significantly more likely to be found in traditionally maintained plantations compared to intensively farmed sites [3]. While vanilla plantations may not be ecological substitutes for pristine forests, we show that they harbour significant levels of biodiversity, particularly when maintained with ecologically sympathetic management techniques. Appropriately managed and located vanilla plantations therefore act as viable habitats for many species, including primates. Given their financial worth, creating vanilla plantations may provide a more profitable and sustainable way for local people to use and potentially expand existing forests, rather than the traditional slash and burn removal of forest for other agriculture or grazing.

[1] Perfecto, I. & Vandermeer, J. (2008). Ann. New York Acad. Sci. 1134: 173-200 [2] Hending, D., et al. (2017). Folia Primatol. 88: 401-408 [3] Hending, D., et al. (2018). Int. J. Primatol. in press