Human influence on the distribution of cacao: insights from remote sensing and biogeography

Abstract

Cacao (Theobroma cacao, Malvaceae) is an important tree crop in Africa and in the Americas. Current genomic evidence suggests that its original range in Tropical Americas was smaller than its current distribution and that human-mediated dispersal occurred before European colonization. This includes regions like Mesoamerica and Eastern Amazonia where cacao is supposedly naturally occurring. In this study, we utilize remote sensing and land use data to examine the influence of human activities on cacao-growing regions and explore patterns between cacao distribution and anthropized areas. By evaluating nearly nine thousand preserved specimen collections, we worked with a comprehensive occurrence dataset that considers taxonomy and distribution. We then analyzed remote sensing images of specimen locations and compared land use profiles of regions into which cacao was introduced with documented native areas. Our findings revealed a clear association between anthropized areas and cacao specimens, with the majority located in areas strongly affected by human activities. Conversely, regions closer to the proposed native range of cacao exhibit less human impact. These results, while accounting for sampling bias, reinforce the idea that humans may have played a significant role in cacao’s dispersal, even in parts of the Amazon where its native status remains uncertain. The discussion on cacao’s native range and identification of introduced areas hold implications for jurisdiction, access to genetic resources, and conservation efforts. Additionally, it is relevant to debates surrounding the repatriation of genetic data of economically important crops. Understanding the historical human influence on cacao’s distribution is crucial for addressing issues of crop improvement, conservation, and sustainable use.