The primary cause of this deforestation is conversion to cropland and pasture. But the reasons for this conversion are varied.
Countries that have extensive tracts of rain forest build roads into remote areas to improve transportation of goods. Legal and illegal logging follows the road expansion. Once an area is logged, it becomes a prime location for agricultural development, which further clears the surrounding forest. These cleared areas are also prone to wildfires, which can further degrade the forest.
Governments sometimes encourage the development of the rain forest with subsidies and tax breaks. Pressure from the global market for timber and soybeans drives the agricultural development.