Decomposers are the choppers, shredders, plowers, and dissolvers of the biological world. They break down tree leaves, dead flowers, grass blades, old logs in forests, and plant roots into small parts, and, finally, into carbon dioxide, water, and numerous basic chemical compounds in soils, water bodies, and sediments. Organisms involved in decomposition vary from earthworms that drag leaves into their burrows, chew up parts of the leaves, and pass them through their guts to microscopic bacteria that make the final breakdown of fragments into basic chemicals. Some decomposers are specialized and act most effectively on only, for example, oak leaves or maple seeds. Others decompose parts of many plant or animal remains that fall on the soil or into a stream or lake. Most decomposers are often not visible, but in some lawn areas, especially under deciduous trees, we can see little volcano-like earthworm mounds. Mushrooms in our...