Decomposers are essential to balancing of ecosystem. They not only decompose dead organic matter and waste from the environment but also extract essential nutrients such as nitrogen and carbon from the waste into the soil.
The soil enriched in these nutrients serve as a source of nutrition for producers (trees, plants etc.) due to which they are able to produce food for primary consumers (which are mostly vegetarian), the primary consumers are then fed upon by the secondary and tertiary consumers which eventually die and are acted upon by decomposers to convert the useful nutrient with in the dead waste of organism into useful nutrients.
Decomposers are thus very important in completing the nutrient and energy cycle and release both nutrient and energy in the environment for reuse by the producers.