Decomposers are important because they are crucial for the proper functioning of ecosystems. They recycle the minerals found in dead plants and animals back into the food chain. Ecosystems do not waste energy or materials, and as such, the decomposers capitalize on any remaining energy in a dead organism and make the minerals available to the entire biome.
Without the actions of decomposers, ecosystems would quickly grind to a halt. The green plants, which start the food chain, are unable to grow without nitrogen, potassium and phosphorus. These minerals are released into the environment when decomposers digest their food.
Most decomposers are bacteria. However, many other types of decomposers do exist, including earthworms, protozoans, fungi and millipedes. Earthworms, for example, crawl through leaf litter and soil eating the remains of dead leaves and other organic matter. The earthworms catabolize the energy-rich molecules and excrete the inorganic compounds. In this way, earthworms essentially produce soil.
Fungi are very important decomposers as well. Many grow in wounded, sick or dying trees. Fungi normally exist as tiny filaments that largely remain out of sight in the soil or within the wood of a tree. However, at certain times, the filaments produce a reproductive structure, known as a mushroom. Sometimes, these mushrooms are visible growing from the soil or out of the wood of a decaying tree.