Forest fires cause global cooling from particulates. Plus a healthy rainforest produces lots of methane. Look at a picture of global methane (sorry lost my link) and you will see the most massive amounts coming out of the rainforests.
I think you'll find that wetlands by far produce the most methane followed by forest termites, and oceans. They are the top three sources of (natural) methane.
Land fills, refineries (and similar) and the bowels of cud-chewing domesticated livestock are the three largest 'man-made' sources of methane.