Tropiaa.Z EaoZogy & l-980. pp. Z287-Z295. THE PREDICTION OF SOIL EROSION LOSSES UNDER VARIOUS LAND USES IN THE TRANSAMAZON HIGHWAY COLONIZATISN AREA OF BRAZIL P.M. Fearnside National Institute for Amazonian Research (INPA) P.O. Box 478, 69000 Manaus, Amazonas, BRAZIL ABSTRACT ., Soil erosion los.ses were predicted as a part of a larger study aimed at producing of human carrying capacity for a part of the Transamazon Highway Colonization Area of Brazil. Erosion measurements were made under annual crops (upland rice, maize, beans, and manioc), black pepper, cacao, pasture, second growth, and virgin forest. Measurements are of the drop in soil surface levels, and therefore include soil compaction. Regressions were developed for prediction of erosion based on such variables as slope and soil clay content. The erosion prediction equations developed were used in computer simulations of the colonists' agroecosystem for carrying capacity by Erosion affects carrying capacity thro.ugh its effect on soil fertility and thereby crop yields. INTROOOCTION An area of planned colonization on Brazil's Transamazon Highway near Altamira, Para offers a unique opportunity to study many aspects of the agroecosystems which were established by the colonists. The huge scale and rapid pace of settlement along the still-expanding network of pioneer highways in the Amazon makes erosion loss prediction urgent. of soil erosion losses were needed as a part of a study of human carrying capacity in a colonization area (Fearnside, 1978, 1979a, b). Carrying capacity depends on crop yields, which are influenced by soil fertility, which in turn are affected by erosion. Computer sUmulations were written modeling the agroecosystem, including a subroutine for soil erosion prediction. Inputs of land use, slope, soil, and weather information were generated in other parts of the program to reproduce the patterns found in field data. The simulations were stochastic in nature, including the probability distributions around the means of many parameters. Soil erosion research in Latin America has recently been reviewed by Lal (1977), who found no studies of erosion in Amazonian Brazil. The only other study involving erosion is that of Smith (1976), who made measurements of soil surface lowering in five plots under annual