Unfortunately, we're already "terraforming the Amazon," in the worst possible way:

Global warming aside, southern Amazon forest cover may fall to 20% by 2016
Rhett A. Butler, mongabay.com
September 3, 2008

Forest cover in the "Arc of Deforestation" of southern Amazonia will decline to around 20 percent 2016 due to continued logging and conversion of forests for cattle pasture and soy farms, report researchers writing in the journal Environmental Conservation. The results are independent of impacts resulting from climate change, which some researchers say could dry the Southern Amazon and turn it into a tinderbox.

We're just cutting it down and burning it up. Climate change will finish it off in other couple of decades. (By the way, that's 90 gigatons of sequestered carbon we'll be releasing, once the whole forest is destroyed.)