The Hidden Role of Fungi

When most people think of fungi, they picture mushrooms growing on a forest floor after rain. Yet a mushroom is only the visible fruit of a much larger organism that lives mostly out of sight. Beneath the soil, fungi spread in vast networks of fine threads, sometimes stretching for great distances, and together they form a kingdom of life entirely separate from both plants and animals. Although they are easy to ignore, fungi play a role in the health of forests that scientists are only beginning to （ 1 ）.

One of the most remarkable discoveries concerns the relationship between fungi and trees. The threads of certain fungi wrap closely around tree roots, helping the trees absorb water and nutrients from the soil. In return, the trees supply the fungi with sugars made from sunlight. Because a single fungal network can connect many trees at once, some scientists have described it, half jokingly, as a kind of underground internet. （ 2 ） this network, trees may even share resources, with larger, healthier trees passing nourishment to smaller or struggling ones nearby.

Fungi do far more than support living trees. They are also among the planet's most important recyclers, breaking down dead wood and fallen leaves and returning their nutrients to the soil for new growth. Without them, forests would soon be buried under their own debris. （ 3 ）, fungi can cause serious harm, destroying crops and killing trees when conditions allow them to spread unchecked. Understanding this hidden kingdom, scientists argue, is essential both to protecting forests and to managing the diseases that fungi sometimes bring.