why are decomposers important to ability of ecosystem to thrive?

Decomposers eat dead and decaying things. The world would overflow with leaves if we didn't have them. Well anyways, Decomposers eat the stuff and leave waste in the soil that fertilizes plants and helps them grow. Then Consumers such as deer, humans, etc eat the plants to get energy. Then Predators eat us or we die and decay. Then the Decomposers eat us. It goes on and on. That's pretty much it.

decomposers do exactly that---they decompose -----take the organic matter in the form of the dead parts or the waste materials from metabolic activities of living organisms and break them down (sometimes the word decay is used here) to the nutrient molecules that can be absorbed by the producers for their own living purposes. eventually these structural and energy nutrient molecules are transferred to other organisms in the food chain. Producers, plants are not able to absorb these nutrient molecules in any other form so the decomposer organisms play a key role in the cycling of nutrient matter in ecosystems