Concept preview

What you will be able to do

1. 01Explain the role of fungi as decomposers in nutrient recycling.
2. 02Describe mycorrhizae and lichens as fungal partnerships.
3. 03Give examples of fungi used in food and medicine.
4. 04Distinguish parasitic from mutualistic fungi and give disease examples.

If every fungus on Earth vanished overnight, the world would not simply lose its mushrooms — it would drown in its own dead. Fungi are the planet's foremost decomposers, and this single role makes them indispensable to nearly every land ecosystem. When a leaf falls, a tree dies, or an animal's body is left in the forest, it is chiefly fungi — working alongside certain bacteria — that break it down, using the absorptive, enzyme-secreting feeding you met earlier to digest the dead tissue and reclaim the nutrients locked inside it. What makes fungi so uniquely important here is their almost unrivalled ability to digest lignin and cellulose, the tough structural molecules of wood. Very few other organisms can break lignin at all, so without wood-rotting fungi the dead trunks of forests would pile up more or less forever, and the enormous stores of carbon, nitrogen and minerals they contain would stay locked away, unavailable to the living. By rotting this material, fungi complete the great nutrient cycles: they return carbon to the air as carbon dioxide and release nitrogen, phosphorus and other minerals back into the soil, where growing plants take them up again. Every fertile soil, every healthy forest, rests quietly on this invisible labour of decay.