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The region around Altamira, Brazil, located in the Eastern Amazon, has experienced rapid landcover change since the initiation of government sponsored colonization projects associated with the construction of the Trans-Amazon Highway. The 30 years since colonization (1971) have been marked by a net loss of forest cover and an increase in the amount of cultivated/productive land, particularly for pasture and annual/perennial crop production. This research presents a parcel-level model of landcover change for smallholders in the Altamira study area. The utility of specific land-use activities is calculated to identify those land-uses that are most optimal at each time point, and labor is allocated to these activities based on the availability of household and wage labor. The model reports the proportion of the parcel in the following landcover classes at each time point using a 1- year interval: mature forest, secondary successional forest, perennial crops, annual crops and pasture. A graphical user interface is used for scenario testing, such as the impact of high/low (population) fertility, the increase of out-migration to urban areas, or changes in cattle and crop prices. The model shows a rapid reduction in the amount of mature forest in the 30 years following initial settlement, after which the parcel is composed of a mosaic of secondary succession, pasture and crops. The nature and rapidity of this landcover change is the function of a variety of household and external variables incorporated in the model. In particular, the model produces different landcover compositions as a function of demographic rates (fertility, mortality) and agricultural prices. (C) 2001 Elsevier Science B.V. All rights reserved

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