The bulk of the South American continent's territory is located in the equatorial zone, making nearly all of the northern two thirds of its territory subtropical or tropical. Jungle territory is the most difficult sort of terrain/biome to adapt for human economic activity. Simply clearing the land bears onerous costs. Soils are poor, diseases run rampant. Even if the rivers are navigable, the banks are too muddy for construction (as is the case with the Amazon). Jungle and rainforest are the dominant vegetation of South American and thus it is no surprise that the continent's economic and political history has been problematic. Venezuela, Guyana, Suriname and French Guiana are fully within the tropical zone, and as such have always faced difficulties in achieving stability (the discovery of oil in Venezuela has improved that country's trajectory).
