| dc.description.abstracteng | In my doctoral research, I combined a literature review with field experiments to investigate the pollination ecology of cocoa, the third largest export commodity worldwide. The aim of my work was to elucidate the potential of ecological intensification, through pollination services, for increasing yields and improving farmer income in the region of Napu Valley, in Central Sulawesi, Indonesia. I divided my doctoral dissertation into four chapters, formatted as peer-reviewed scientific manuscripts. In Chapter I, I compiled all available scientific literature from the past 65 years to elaborate an exhaustive review on the neglected role of cocoa pollination. In Chapter II, I report the results of my field studies to quantify the relative importance of landscape, farm, and plant performance, as well as soil organic litter for species richness and abundance of cocoa flower visitors. In Chapter III, I present results of a large-scale hand pollination experiment and contrast the contribution of pesticide and fertilizer uses with that of pollination on fruit set and yield for improving farmer income. Finally, in Chapter IV, I present recommendations on how to translate gene-editing technologies from the laboratory to the farm, expanding the scope to three perennial crops: cocoa, citrus, and coffee.
My findings in Chapter I and II provide evidence that mainly ants and to a lower extend dipterans are the main flower visitors of cocoa. This suggests that neglected ants may play a larger direct and indirect role in cocoa pollination than previously acknowledged. Multi-strata vegetation surrounding the farms (e.g. forests, agroforests), the shade provided by the tree canopy cover in the farm, and the amount of tree flowers are the main factors explaining flower-visitor species richness and abundance. Contrary to my initial hypothesis, increased amounts of soil litter in my experimental approach did not affect flower visitors. In Chapter III, the hand pollination experiments show that pollination, and not pesticides or fertilizers, is the main driver of fruit set and yields. Moreover, I found that hand pollinating 13% of cocoa flowers in a tree increases yields by 51%, and hand pollination of all flowers (100% of flowers/tree) by 260%. These yield increases have a direct effect on farmer livelihoods as their income increases by 69%, 50% and 85% at the local (study region), regional (Central Sulawesi) and national (Indonesia) level. Finally, in Chapter IV, I give comprehensive recommendations on how to integrate innovative gene editing technologies with traditional ecological intensification strategies, such as pollination services and grafting. These recommendations aim to bridge the gap between lab and farm implementation.
In conclusion, I found that pollination services play a major role for increasing cocoa yields. While I prove that hand pollination can increase yield notably, it is still highly labor intensive. Thus, a well-structured working plan and the creation of innovative pollination tools are needed to reduce the implementation costs. On the other hand, natural pollination by enhancing flower visitation through management adjustments at the landscape and farm level should become an ecological alternative to hand pollination, but future studies need to detect the still hidden identity of pollinators and their ecology. The results from my work suggest that the preservation of multi-strata vegetation in the surroundings and high canopy cover enhances flower visitor populations and flower visitation, and this presumably improves yields. As litter amount did not appear to affect pollinator species’ richness and abundance, further studies should focus on soil litter quality rather than quantity. Finally, I argue that in the future cocoa stakeholders need to find alternative management practices to agrochemical intensification. These practices should successfully integrate ecological, such as pollination services, and promising gene editing approaches for increasing cocoa production sustainably, improve farmer livelihoods, and preserve biodiversity in times of climate change. | de |