Fungi primarily play the role of decomposers in ecosystems. They break down organic matter, such as dead plants and animals, returning essential nutrients to the soil and facilitating nutrient cycling. This process is crucial for maintaining the health of ecosystems, as it enhances soil fertility and supports plant growth.
While fungi do not typically fit the definitions of producers (which include plants that perform photosynthesis) or consumers/predators (organisms that consume other living organisms), some fungi can engage in symbiotic relationships with plants (mycorrhizae) or even parasitize living organisms. However, their primary and most significant ecological role is as decomposers.