Sustaining biodiversity in forest and cocoa landscapes: Insights from pollinators, pesticides, and land use change in Ghana

Income from cocoa (Theobroma cacao) exports supports the economies of cocoa-producing countries, including many in West Africa. However, cocoa expansion has converted 10 million hectares of West African tropical rainforests to cocoa farmlands over the last 50 years with the most rapid loss occurring between the 1980s and the 2000s. Simultaneously, the extensive pesticide applications to safeguard yields may also pose risks to insect pollinators. This thesis therefore explored the effects of cocoa expansion on insect pollinators and pesticide residues in honeys. Three studies, each study addressing key components of the thesis, were conducted. In Chapter 2, I used a systematic literature approach to evaluate existing studies on the extent of honey contamination from plant protection products approved for cocoa cultivation. The findings showed that only 19% of existing studies were conducted in cocoa-producing countries. Organophosphates, organochlorines, and pyrethroids were the most detected pesticide classes in these countries, while globally, neonicotinoids were most prevalent. In Chapter 3, I analysed residues of key pesticides approved for cocoa cultivation in honey samples from cocoa and forest landscapes in Ghana. Honey samples from fullsun cocoa, agroforestry cocoa and natural forest contained pesticide residues, with imidacloprid being persistent in all honey samples, but concentrations did not exceed the specified EU MRLs. This highlights the pervasive presence of pesticides in the different landscapes. Chapter 4 assessed the influence of natural forest proportions on flower-visiting insects amidst cocoa expansion. Results indicated that proportions of natural forest influenced the abundance of Hymenoptera, Coleoptera, Hemiptera, and Diptera, altering bee community composition, though bee diversity metrics remained stable. To harmonise the economic benefits of cocoa cultivation with biodiversity conservation, I propose integrated pest management, preservation of natural forest patches, and the promotion of agroforestry systems. Such practices can mitigate pesticide impacts, support pollinator health, and ensure sustainable cocoa production.