Soil quality under coca cultivation: Evidence from Peru’s largest coca-growing region challenges degradation narratives and maintains alternative crop opportunities

Abstract

While drug control institutions and national governments are increasingly denouncing the negative impacts of coca (Erythroxylum sp.) cultivation on soil degradation, empirical evidence on its effects on soil quality remains limited. Here, we present a first analysis comparing the physicochemical properties of soils that have been under coca cultivation for different time periods, compared to reference soils under rainforest. Using 125 soil samples collected in 2023 in Valle de los Ríos Apurímac, Ene y Mantaro (VRAEM), we assessed key soil properties at the surface level (0–20 cm). Compared to reference rainforest soils, soil pH was slightly higher (+0.3–0.5 pH units) in recently (< 10 years) cultivated coca fields likely related to liming practices and increased base cation cycling. Electrical conductivity was lower in all cultivated fields, and total nitrogen was only slightly lower in fields under cultivation for 11–20 years. Promisingly, soil degradation under coca cultivation could not be evidenced in terms of bulk density, cation exchange capacity, soil organic carbon concentration and cumulative carbon stock (0–60 cm depth), phosphorus nor exchangeable aluminum. In conclusion, the findings suggest that the effects of coca cultivation on soil degradation are not as severe as presumed, challenging prevailing narratives on its environmental impact and indicating that crop substitution programs could also mitigate these issues using agro-ecological approaches.