Does the natural decomposition of deciduous tree leaves form methane and contribute to global warming?
First it should be known that both deciduous and evergreen trees lose their “leaves”. Deciduous flora lose their leaves all at once (more or less) and evergreen flora lose and replace their “leaves” at about the same rate (which is why in most forests with pines, spruces, furs, etc you find needles all over the forest floor but no bald trees). To address methane production the answer is that it depends. Methane is primarily produced from anaerobic microbial facultative organisms which use alternate electron receptors for respiration. Since methane, even in rumanents, is produced by these organisms, a lack of oxygen is necessary for methane production. That said, if the tree leaves are decomposing in an oxygen-free environment they are giving off methane gas. This is common in the tundra up north where the warming of the Earth and the thawing of the land is heating up the soil enough that this type of decomposition can occur and millions of tonnes of methane are given off. However, on a
