This giant fungus is eating entire forests

The Armillaria ostoyae, or the Humongous Fungus, spans 2,385 acres of the Malheur National Forest. Blue whales and giant sequoias are tiny compared to this single mushroom.

Most of the organism is invisible, living underground as a massive web of black, shoe-string-like filaments called rhizomorphs. These threads creep through the soil, seeking out the roots of evergreen trees.

Once it finds a host, the fungus invades the root system and begins to decay the tree from the inside out. It siphons nutrients to fuel its own expansion across the mountain range.

The only visible clues to its presence are small clumps of honey-colored mushrooms that sprout from the base of infected trees in the fall. These mushrooms are genetically identical across the entire 3.7-mile stretch.

Estimates for its total mass vary, with some scientists suggesting it could weigh as much as 7,500 to 35,000 tons. It grows at a glacial pace, slowly conquering the forest floor pixel by pixel over millennia.

Despite its destructive nature, the fungus is essential to the forest's life cycle. It clears out old, weakened trees, creating gaps in the canopy that allow light to reach the floor and trigger new growth.