If all of the decomposers were suddenly removed, then nutrients would not be able to cycle back into the soil so that nutrient uptake by producers could be achieved, or at least not as fast or at as great a level, as it would probably soon enough become inorganic and unusable. Nutrients would be rapidly lost in the ecosystem and would not be able to be put back into the system.
Decomposers are important to the stability of an ecosystem because they return vital nutrients back into the environment. If all the decomposers were removed, plants would run out of nutrients, affecting the entire ecosystem.
