Deforestation of the Amazon rainforest The completion of the roads was followed by a wave of resettlement; these settlers had a significant effect on the forest as well. Research conducted by Leydimere Oliveira et al. has shown that the more rainforest is logged in the Amazon, the less precipitation reaches the area and so the lower the yield per hectare becomes. Thus for Brazil as a whole, there is no economic gain to be made by logging and selling trees and using the logged land for pastoral purposes. A September 2016 Amazon Watch report concludes that imports of crude oil by the US are driving
Amazon rainforest south as 45°. Climate fluctuations during the last 34 million years have allowed savanna regions to expand into the tropics. During the Oligocene, for example, the rainforest spanned a relatively narrow band. It expanded again during the Middle Miocene, then retracted to a mostly inland formation at the last glacial maximum. However, the rainforest still managed to thrive during these glacial periods, allowing for the survival and evolution of a broad diversity of species. During the mid-Eocene, it is believed that the drainage basin of the Amazon was split along the middle of the continent by the Purus Arch. Water