The People’s Palms: Investigating Soil Health, Environmental History, and Community Sovereignty in African Oil Palm Polycultures and Monocultures in Costa Rica’s Zona Sur

In the last two decades, Costa Rica has emerged as a significant site for oil palm production. As global demand for vegetable oils increases, the oil palm sector in Costa Rica is only projected to expand, specifically in the Osa and Golfito cantons in the Zona Sur. However, traditional monoculture oil palm plantations have been found to cause pollution, biodiversity loss, and soil degradation, along with many financial and food security challenges for smallholders in the region. Such has prompted growing efforts to explore oil palm production methods that minimize ecological and societal harms. Over the past ~10 years, the African Palm Laboratory Project (LAPA), a collaboration between the Stanford Woods Institute for the Environment and the Osa and Golfito Initiative (INOGO), has realized a matched-pair experiment comparing the socio-environmental impacts of traditional oil palm monocultures with adjacent, experimental oil palm polycultures. While benefits such as improved biodiversity and financial-security have been associated with the polyculture system, a comprehensive soil nutrient analysis between agricultural systems has yet not been completed. In order to shed light on the soil health differences throughout the LAPA plots, I analyzed the total carbon (C), total nitrogen (N), total plant available N, pH, and select heavy metals in each of the 7 experimental sites. While no overarching trend between soil nutrient concentrations and agricultural system was observed, several sites demonstrated evidence for higher soil C, N and inorganic N in the polyculture system. Furthermore, impacts of fertilizer, past land use history, and current land management practices on soil nutrients and heavy metal concentrations in LAPA sites were observed. Overall, this work sheds light on the soil health dynamics associated with the cultivation of African oil palm, a rapidly expanding crop in Costa Rica’s Zona Sur. This information is key for informing the larger scale feasibility of agricultural systems that can both preserve soil health and meet the growing global food demand.