Could the pursuit of chocolate play a role in the battle against climate change?
New research from the Paul H. O’Neill School of Public and Environmental Affairs found that planting cacao trees—the source of the beans used to make chocolate—together with other trees and crops on pastureland could significantly increase soil carbon sequestration. Published in the leading soil science journal, Geoderma, the study, “Pruning management drives early accumulation of deep soil carbon following agroforestry expansion,” examines cacao agroforestry systems in southern Bahia, Brazil—one of the world's premier cacao-producing regions. The research was led by Olivia Hurley and Assistant Professor André Franco from O’Neill School’s Soil Ecology Lab.
“This work provides extremely valuable research training opportunities for O’Neill graduate students and connects my research on soil ecology, climate change, and sustainable agriculture with the region where I grew up,” Franco said. “Cacao is central to the history, economy, and culture of southern Bahia. Understanding how cacao production can support farmers while also storing carbon and maintaining biodiversity is a deeply important question for the region and for tropical agriculture more broadly.”
The study examined how transitioning from pasturelands to cacao agroforestry impacts soil carbon, the largest terrestrial carbon reservoir. The findings reveal that the outcome depends strongly on how the land was previously used and how the agroforestry systems are managed. Moderately pruned cacao agroforestry systems promote early carbon accumulation, even in deeper soil layers. Additionally, the research suggests that establishing these systems on treeless pastures yields the greatest potential for maximizing carbon storage.
Shoot pruning is a management technique widely used in cacao farming to achieve an optimal balance between shade and light. However, pruning intensity is not standardized across farms and can vary depending on cultural norms, available resources, and access to information about effective management.
“Agroforestry is frequently championed as a climate solution, but the study demonstrates that context matters,” Franco said. “Where agroforestry is established and how it is managed determine whether it delivers meaningful soil carbon gains. In southern Bahia, moderately pruned cacao agroforests over non-integrated pasturelands offer an important opportunity for climate mitigation.”
Hurley completed the fieldwork in Bahia in 2023 and defended her thesis in December 2024, earning a dual Master of Science in Environmental Science-Master of Public Affairs degree from the O’Neill School.
The research is part of a broader project supported by Mondelez International, and follow-up research is already underway. Franco and current Ph.D. student Christopher Cafasso recently completed extensive fieldwork across four experimental sites in Bahia. Cafasso’s work focuses on the mechanisms behind soil carbon dynamics and on the synergies and tradeoffs among carbon sequestration, biodiversity conservation, and cacao productivity in different production systems, including agroforestry, cabruca, and monoculture cacao.
Cafasso is now processing field samples and conducting laboratory analyses at Universidade Estadual de Santa Cruz in Ilhéus, Brazil, Indiana University’s institutional partner in the project through its Parque Científico e Tecnológico do Sul da Bahia.