Oh yeah, I remember now. Animals produce carbon dioxide and plants produce oxygen. That's primary school biology. Christ, I can be dense sometimes.
Actually, some recent research has shown plants themselves (along with animals) produce a lot of "greenhouse" emissions - so simply re-foresting may not make things any better...
I will dig up the ref.
But as the planet heats up the recycling (rotting) process gets accelerated so more carbon is released...