Sustainable vanilla provision using crop wild relatives in a joint land sparing / land sharing approach

The vanilla sector faces several challenges that negatively affect its stable supply. Domestication bottlenecks, vegetative propagation, and manual pollination instigated a strong genetic erosion in the crop species Vanilla planifolia. Moreover, practices involving intense monocultures and supply chains with asymmetrical revenue partition further exacerbate the vulnerability of this sector. The Neotropics host several Vanilla crop wild relatives (CWRs). Alike the closely related V. planifola, Vanilla CWRs produce fragrant fruits, better known as beans or pods. Furthermore, they hold untapped diversity for potential use in crop improvement and breeding, yet, are threatened by extinction. There is an urgent need to protect these Vanilla species, and simultaneously evaluate their possible contribution to counteract the abovementioned production problems. This PhD thesis aimed at providing initial insights into the use of Vanilla CWRs within an approach that endeavors a joint effort of (a) the conservation of the natural habitat of Vanilla CWRs and their associated pollen and seed dispersers, and (b) the sustainable cultivation of the vanilla spice in agroforestry systems surrounding these protected areas, promoting the integration of promising Vanilla CWRs and natural pollinators. We define this as the Vanilla land sparing/sharing (SPASHA) approach, whereby the produced vanilla beans are ideally traded via direct supply chains that involve organized farmer groups and responsible businesses. We conducted an interdisciplinary study to explore the application potential of the proposed Vanilla SPASHA approach within our study region Área de Conservación Osa (ACOSA) – a biodiversity hotspot in southwest Costa Rica holding several Vanilla CWR populations. As such, this PhD implemented four work packages to acquire information on the distribution patterns, pollination mechanisms, and cultivation potential of Vanilla CWR’s, as well as on the perceptions of the vanilla supply chain members towards the proposed innovations.

In the first work package (Chapter 2), we applied species distribution modelling to provide spatially explicit recommendations for the implementation of the Vanilla SPASHA approach in ACOSA. The maps, modelled at the extent of Costa Rica, showed interspecific variation in suitability, most likely influenced by species-specific functional plant traits or certain biotic interactions. ACOSA proved highly suitable for the four modelled CWRs, and suitability maps were overlaid with land use maps to define (a) low- and high-priority conservation areas, i.e. forested areas respectively with or without protection status, both with high Vanilla suitability, and (b) potential cultivation areas, i.e. fallow and degraded lands that could be reforested with the integration of promising Vanilla CWRs, or existing agricultural lands that could be transformed to agroforestry systems with vanilla as an (additional) cash crop. In this context, cultivation areas may serve as biological corridors between the protected areas, encouraging the exchange of ecosystem services between forest and farmland. The spatially explicit recommendations resulting from this study fit within the scope of the National Bio-Corridor program that seeks to develop sustainable land use practices within the corridor network.

In the second work package (Chapters 3 and 4), we assessed the potential integration of natural pollinators within vanilla cultivation systems, as an alternative to the widely applied manual pollination technique. We identified pollinators and pollination mechanisms, examined pollinator habitat requirements, and evaluated natural fruit set. We found that Vanilla pompona is pollinated by Eulaema cingulata, and displays a dual pollinator attraction mechanism that combines floral fragrance rewards with food deception to induce pollen removal. Vanilla hartii rewards its floral visitors with sucrose-rich nectar, and is pollinated by Euglossa species that morphologically fit with the flowers. Combining our results with an in-depth literature review, we presume that all the Neotropical fragrant Vanilla CWRs are pollinated by Euglossini, with the latter demonstrating specific habitat requirements. Overall, the low natural fruit set, even of nectar-rewarding Vanilla species, favours the continuation of manual over natural pollination. Yet, we highly encourage the development of agro-ecological landscapes that consist of Euglossini-friendly vanilla cultivation systems surrounding Euglossini refuges (i.e. intact forests), whereby vanilla beans produced in these landscapes could be certified and sold at specialty markets.

In the third work package (Chapter 5), we obtained insights into the cultivation potential of the four modelled Vanilla CWRs. We established experimental field sites in both forested lands and existing agro-systems (i.e. cacao plantations) available in ACOSA, and developed models that predict the measured plant performance traits with Vanilla species (the four CWRs, a commercially-used hybrid, and the crop species V. planifolia), land use system, and several environmental variables. The hybrid and CWRs outperformed V. planifolia in terms of vitality, whereas the latter and the hybrid had the highest growth rate. The performance of each species, however, depended on land use system and light intensity, enabling us to identify species-specific preferences. Disease-suppressive and growth-promoting bacteria positively affected vanilla plant survival, vitality, and growth. Moreover, we observed significant effects of certain soil chemical variables and functional tutor tree traits on vanilla plant performance – emphasizing the important interactions between the vanilla orchid and its environment. Additionally, the quantified aromatic potential of the beans of the different Vanilla species demonstrates possibilities for market diversification. Our results demonstrate potential for the inclusion of Vanilla CWRs in cultivation systems that mimic their natural habitat. Yet, an evaluation of the feasibility (e.g. labour, production, revenues) of these systems within the proposed SPASHA approach is highly required, alongside further research on the spatial arrangement and associated management of the different Vanilla species and the other, additional crops (e.g. cacao).

In the last work package (Chapter 6), we carried out a discrete choice experiment with 186 farmers living in ACOSA, to better understand the perspectives of the supply chain members towards innovations within the vanilla sector. Combining our results with a study on market preferences, we see great value in the development of a supply chain between (a) farmers willing to form part of a vanilla cooperative and interested in agro-ecological practices involving Vanilla CWRs, natural pollinators, and agroforestry, and (b) responsible businesses seeking sustainable vanilla sourcing and market diversification. In this context, farmer cooperatives will most likely play a central role in capacity building, farmer organization, and the provision of market outlets.

In conclusion, we provide insights into possible measures that could contribute to the mitigation of the identified production and socio-economic problems within the vanilla sector; by probing the potential of a strategy that combines the conservation and sustainable cultivation of Vanilla CWRs. We combined the data acquired from the four work packages and developed a practical scheme for the implementation of the case-specific Vanilla SPASHA approach in ACOSA – an approach that coincides with the national land use policies for this biodiversity hotspot as well as the perceptions of a large part of the questioned farmers. Yet, further evaluation of this approach in terms of production feasibility, biodiversity conservation, and market integration of new vanilla varieties is highly required.