In 1984, on the outskirts of Paragominas, a bustling and violent cattle town in the eastern Amazon, I walked through a pasture, brown and dusty from drought, into a 500-acre island of virgin forest. The moist greenness of the leaf canopy that reached more than 100 feet above my head and the squishy dampness of the humus, dead leaves, and branches on the ground were a world apart from the parched African grasses and gaunt white zebu cows I had just seen. Although I didn't realize it at the time, it is in understanding the differences between these two worlds -- the rainforest and the cattle pastures that are replacing them -- that we begin to realize how the lives of people around the world are tied to the fate of Amazon forests.