Lately I have been seeing a lot of things about the rainforest, and its importance in global warming. The plants in the rainforest consume a lot of carbon dioxide, but the burning of these plants in turn releases carbon dioxide. I saw something recently that the rainforest is actually one of the top carbon dioxide emitters in the world. Of course the rainforest itself isn't doing this -- it the destruction of the rainforest. So it's a bit of a double whammy -- the trees no long have carbon dioxide removing capability, and in fact they are emitting carbon dioxide when they are cut and burned.
There is an article on the WWF website (no, not wresting) about this.