The Secret Lives of Fungi
These versatile organisms are some of the most pervasive—and powerful—forces of nature.
Text and photography by James Sogaard
You are surrounded. Above you, below you, even on you, live thousands of organisms that are neither plants nor animals, but fungi, members of their own kingdom.
We live in a fungus-filled world. The earth is home to perhaps 1.5 million fungus species, though scientists have identified only about one-tenth that many. Mushrooms, molds, mildews, smuts, rusts, and yeasts"fungi are incredibly varied in form and ecology. Many are microscopic.
Fungi have historically been mysterious to humans. Mushrooms have been described as productions of Zeus's thunderbolts or of the devil, and even as houses built by animals. Ancient Egyptians banned commoners from eating mushrooms because these fungi were considered food of the gods. Pliny the Elder—a scholar in the days of the Roman Empire—believed that poisonous mushrooms resulted from the breath of venomous snakes.
Today, science has revealed the importance of fungi in the natural world. Some fungi act as decomposers. Others are parasites or beneficial partners (mutualists) to living organisms. Sometimes these roles overlap.
Fungi recycle dead wood. Wood is a challenging diet—dry, hard, and low in nitrogen. Another big problem with wood is the nature of the chemical bonds in cellulose—no animal has the enzymes needed to degrade those, so that job belongs to fungi, as well as bacteria and protozoans.
Many wood-decaying fungi get nitrogen by consuming bacteria, roundworms, rotifers, amoebas, and other tiny animals found in wood. Using various ingenious microscopic traps, lures, and poisons - such as sticky knob traps, poison "lollipops," adhesive-coated nets, and baited constricting rings—they dissolve and absorb these creatures as well as other fungi, slime molds, and algae.
Many fungi are parasites. As such, they can change ecosystems, landscapes, even history. Certain fungi live inside the leaves and stems of plants, and can be either a boon or bane to their hosts. Some produce chemicals that make plants toxic to insects and mammals, while others cause diseases such as Dutch elm disease. Fungi caused the potato blight that led to the Irish potato famine in the mid-1800s.
A lichen is a symbiotic union of a fungus with an alga or a cyanobacterium, often called blue-green algae. Important colonizers of bare rock and soil, lichens can change the color of entire landscapes. About 4,000 kinds are known in North America and more than 15,000 worldwide.
In a lichen, the fungus makes up most of the mass and determines the structure. The fungus harvests up to 80 percent of the energy produced by the alga through photosynthesis.
Lichens containing cyanobacteria chemically bind atmospheric nitrogen and make it available for lichen-eating animals, thus procuring a nutrient usually in short supply.
Ubiquitous but endangered?
Fungi are beneficial root associates of 90 percent of vascular plants—plants with vascular systems that allow transport of water and nutrients. As such, they contribute hugely to the fixation of atmospheric carbon dioxide into living tissues. A single tree may have hundreds of thousands of miles of microscopic, threadlike fungal structures called hyphae on its root hairs. These structures take up most of the water and minerals needed by the plant.
The hyphae often serve as a bridge between tree root systems, even connecting trees of different species. Some tree species, such as oaks and pines, have up to a thousand kinds of fungal root partners.
Many fungi produce familiar mushrooms found under particular tree species. A dramatic decline in the diversity and abundance of such mushrooms in Europe has been attributed to air-pollution input of nitrogen, which is disrupting the mutualistic partnership. The consequences for forests are unknown. In North America, experiments show that some fungal die-offs may also be occurring here.
James Sogaard is a naturalist and freelance photographer who is fascinated with mycology.