Scientists studying satellite image data from the fires in the Amazon rain forest said that most of the fires are burning on agricultural land where the forest had already been cleared.
https://www.nytimes.com/interactive/2019/08/24/world/americas/amazon-rain-forest-fire-maps.html
https://www.nytimes.com/interactive/2019/08/24/world/americas/amazon-rain-forest-fire-maps.html