Evaluating the socio-environmental impacts of monoculture cashew expansion in the Northern Western Ghats, India

• Main Author: Anushka Rege
• Other Authors: Lee Ser Huay, Janice Teresa
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Science::Biological sciences::Ecology
• Online Access: https://hdl.handle.net/10356/163037
• Institution: Nanyang Technological University

Agricultural expansion is one of the largest global threats to biodiversity. Cashew (Anacardium occidentale L.) crop is grown across 33 countries covering 7,101,967 ha but little is known about its socio-environmental effects. India is the second-largest producer of cashew in terms of area under cultivation (1,115,434 ha) and the production quantity (772,779 tonnes). Southern Maharashtra is the largest cashew producer within India and falls in the Western Ghats global biodiversity hotspot. Cashew in this region is grown dominantly by smallholders with an increasing reliance solely on cultivar varieties of cashew. The forests within the Sawantwadi-Dodamarg landscape in southern Maharashtra are mostly privately owned and are being cleared for monoculture cashew expansion, posing a unique conservation challenge. I aimed to evaluate the socio-environmental effects of cashew cultivation through a dual global-local lens. I first conducted a global literature review, followed by a spatial modelling exercise to synthesise the effects of cashew on biodiversity and livelihoods, and understand where global biodiversity is most vulnerable to cashew cultivation. I found that literature was concentrated from Indian and West African regions, showing that cashew harboured a subset of generalist fauna found in reference habitats. Cashew farming was dominated by male smallholders and the increasing reliance on cultivar cashew varieties may put farmers’ livelihoods at risk. The South and Southeast Asian, West African and Latin American regions were most vulnerable to cashew cultivation due to overlaps with threatened vertebrates. I developed a farmers’ typology and sought to understand land management practices in the Sawantwadi-Dodamarg. I used semi-structured questionnaires to interview 65 cashew farmers and reviewed literature to construct the historical overview of cashew expansion in our study site. Agricultural subsidies introduced from the 1980s to the 1990s encouraged cultivar cashew expansion and also influenced land-use conversion from rice and privately owned forests to cashew. Farmers preferred cultivar cashew varieties since they produced higher yields faster, although they required more agrochemical inputs and were susceptible to pests and wildlife depredation. About 80% of farmers had planted cashew farms by clearing privately owned forests in the past 30 years and expressed an interest to continue the same. Farmers avoided applying for government-sponsored compensation for crop losses due to wildlife depredation and instead chose to expand cultivar cashew at the cost of deforestation. I detected and mapped the spatial extent of cashew plantations in the Sawantwadi Dodamarg landscape using Sentinel-1 and Sentinel-2 imageries alone and also in combination. I also compared the performances of the algorithms Random Forest, Classification And Regression Tree and Support Vector Machine. The mapping exercise showed that the Random Forest algorithm using both optical and radar datasets was best suited to detect and map cashew plantations. The area under cashew cultivation as of 2020 in the Sawantwadi-Dodamarg landscape was 53,350 ha. Lastly, I compared bird diversity across cashew plantations, privately owned forests and government-controlled forests, using both acoustic methods and point count methods. I further examined how landscape-level covariates influenced the bird species richness and abundances. I detected a total of 109 bird species. The indices Normalised Difference Sound Index (NDSI), Bioacoustic Index (BI) and Total Entropy (E) best explained the bird species richness and abundances measured using point count methods. The bird species richness and abundances across all land uses were broadly comparable and influenced by the variables land-use type, forest cover within 100 metres and distance to nearest human settlement. NDSI, BI and E were influenced by land-use type, forest cover within 100 metres and distance to nearest human settlement, while BI was influenced by elevation as well. Cashew crop has globally expanded over thirteen-fold in the past four decades. With further biodiversity research and equitable stakeholder participation there is potential to manage cashew land use sustainably and secure dual goals of biodiversity conservation and safeguarding of local livelihoods. Research along such socio-environmental lines can possibly contribute to the development of sustainability and certification initiatives for cashew. There is an urgent need to pay research attention to crops like cashew that are grown by smallholders and contribute to apparently small-scale yet consistent forest loss.