Floral species richness, structural diversity and conservation value of vanilla agroecosystems in Madagascar

Abstract

Agricultural landscapes provide financial livelihoods for farming communities in rural areas. However, such agroenvironments can significantly impact the local floral biodiversity and introduce harmful invasive species to the ecosystem. Despite the prominence of plantations throughout the tropics, their effects on local flora are limited to only a few specific cash crops and geographical regions. Here, we compared the species richness and structural diversity of vegetation in natural forest fragments and three types of vanilla plantation within the Sava region of north‐east Madagascar ranging from those within or adjacent to existing forests, to intensively cultivated plantations. We recorded data on plant species abundance, diameter at breast height and canopy cover within multiple sites of each habitat. We used abundance data to calculate species richness indices, and we compared these metrics between habitats. Forested habitats contained a significantly higher floral species richness, structural diversity and more endemic and regionally native species than nonforested, anthropogenic vanilla plantations. However, our results suggest that the high floral species richness and structural diversity of natural forests can be partially achieved in vanilla plantations, depending on the site's management regime; traditionally managed vanilla plantations located close to natural forests can support diverse floral communities. These encouraging findings for plant conservation and sustainable agroforestry in Madagascar suggest that that newly created vanilla plantations and already existing nonforested plantations should endeavour to follow the more traditional forested approach to enhance the future sustainability and promote floristic diversity.

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

“…The conservation value of vanilla agroforestry can, however, only be assessed relative to other land uses, and, most importantly, in comparison to the land use the agroforest was derived from. This important distinction lacks in previous studies (Hending et al, 2018(Hending et al, , 2019.…”

“…The lack of ecological research in vanilla agroforests is surprising given our knowledge on the contributions of other agroforests to biodiversity conservation (Bhagwat et al., 2008). The only studies available for vanilla are from a recent rapid biodiversity assessment (Hending, Andrianiaina, Rakotomalala, and Cotton, 2018; Hending, Andrianiaina, Maxfield, Rakotomalala, and Cotton, 2019): The authors reported fewer lemur sightings in vanilla agroforests than in forests and a diverse plant community in traditionally, less intensively managed vanilla agroforests in proximity to forests. Similarly, we find vanilla agroforests to host fewer bird species than old‐growth forest and show that landscape‐scale forest cover is essential for endemic birds.…”

“…The lack of ecological research in vanilla agroforests is surprising given our knowledge on the contributions of other agroforests to biodiversity conservation (Bhagwat et al, 2008). The only studies available for vanilla are from a recent rapid biodiversity assessment (Hending, Andrianiaina, Rakotomalala, and Cotton, 2018;Hending, Andrianiaina, Maxfield, Rakotomalala, and Cotton, 2019):…”

Land‐use history determines stand structure and tree diversity in vanilla agroforests of northeastern Madagascar

“…Within vanilla agroforests, smallholders use small-statured trees as a support for the climbing orchid, while a variety of taller trees form the canopy above (Havkin-Frenkel & Belanger, 2018). Hence, vanilla agroforests comprise a wide range of tree densities and tree canopy cover (Hending et al, 2020). Furthermore, household surveys in northeastern Madagascar found that vanilla agroforests particularly differ in their land-use history: around 30% of agroforests are forest-derived, established by cleaning the understorey, thinning the forest, and planting vanilla under the canopy of the already established trees (Hänke et al, 2018).…”

“…This definition embraces a broad range of different management schemes with trees and large woody perennials that already existed prior to the agroforest establishment, but also encompasses spontaneous regrowth or actively planted trees or other tall woody plants (Schroth et al, 2004;Bhagwat et al, 2008). Recent studies show that vanilla agroforests can provide habitat for native wildlife (Hending et al, 2018;Hending et al, 2020;Martin et al, 2021), but it remains unclear to what extent the habitat structure and tree diversity are determined by land-use history.…”