Bacteria and fungi are called decomposers because they break down the dead and decaying organic matter into simpler substances such as carbon dioxide, water, simple sugars, and mineral salts and provide the nutrients back to the soil. The advantages of decomposers to the environment are that they act as natural scavengers (an animal that feeds on carrion, dead plant material,) and they also help in recycling nutrients.
Advantages
(i) Decomposers degrade garbage and the organic wastes which would otherwise cause environment problem. It prevents foul smell and checks spread of disease.
(ii) Decomposers recycle the nutrients through biochemical cycle.