Table 3. Regional variation in the environment and production systems in four different regions settled by Andean indigenous colonists. Colonization region Physiography Date of first settlement Area (ha) Mean annual precipitation (mm) Major crops Alto Beni and Yacumo Syncline valley and foothills 1960 287,172 2000 Rice, coffee, cacao, fruits Chapare Piedmont and foothills 1960 623,906 4000–6000 Coca Yapacaní† and Santa Rosa Piedmont 1960 475,002 2000–4000 Rice, soybean San Julian† Alluvial plain of the Río Grande 1968 460,915 1500–2500 Maize, sunflower, soybean Note: See Appendices 1 and 2 for an overview and the spatial distribution of each subgroup. †The colonization zone has incipient mechanization.