50
Slash and burn ag is so stupid...
From Wikipedia:
The productivity of the soil following forest removal for farming lasts only a year or two before the fields become infertile and farmers must clear new areas of forest to maintain their income. In 1995, nearly half (48%) of the deforestation in Brazil was attributed to poorer farmers clearing lots under 125 acres (0.51 km2) in size.
They typically grow crops on the land at first, then due to poor soil management it becomes useless for crops so they put cattle on it and burn down more forest to grow more soy or whatever.
Then again. Big picture time.... We're globally releasing enough GHGs that it's equivalent to burning down the entire Amazon rainforest every two months.