Swidden cultivation is one of the most widespread agricultural systems in the tropics. Due to socioeconomic changes, swiddens are either abandoned, substituted for other agricultural systems, or intensified. In the region of the middle Amazon river, Brazil, the high market demand for cassava flour (farinha) combined with land scarcity is inducing agricultural intensification. We define agricultural intensification as an increase in the frequency of swidden-fallow cycles and a decrease in the fallow period. In this study, we evaluate the consequences of agricultural intensification for management practices and swidden productivity in one of the main cassava producing areas of the Brazilian Amazon. We used ethnographic and biophysical surveys to characterize the current management practices and to evaluate the effect of repeated swidden-fallow cycles within a short fallow period regime on swidden size, weed infestation and life-form composition, weeding effort and cassava productivity. Our results show that with repeated swidden-fallow cycles cassava yield decreases, weed cover increases and weed composition changes from a tree-dominated to a graminoid-dominated community. Such changes in the weed community result in increased weeding effort, to which farmers respond by cultivating smaller swiddens. Therefore, the ongoing agricultural intensification leads to lower swidden productivity and household income without ensuing clear benefits for farmers. Limited access to fertilizers, herbicides and technical assistance combined with the market demand for a single product hinders adaptation. Broadening market opportunities and improving technical assistance to farmers could raise the diversification of production and sources of income and guarantee higher resilience to the system. (C) 2015 Elsevier B.V. All rights reserved.
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