Pacific Views

Fungi: An Invisible Decline

Before I took up botany, I had two things in mind when I thought of fungi: mushrooms & moldy food. I thought of them as parasites, spoilers, organisms whose limited uses would hardly be missed if they all disappeared tomorrow. I would have considered shiitakes, wine, and brie a good sacrifice for ridding the world forever of gangrene, crop rot, and fungal or yeast infections.

But the joke is, they are disappearing, and it turns out that we would miss them tremendously.

There's first the obvious task they perform, decomposition. Without the activities of fungi, as well as the bacteria whose behavior is similar, dead organic material would break down only through meteorological processes. The bodies and waste of dead plants and animals through the ages would stay where it fell until wind and water had their way. It would be very difficult for life to continue, as more of the ingredients it needs became locked away in dead tissue.

We're now learning to further harness their decomposition power, with the Northwest's own Paul Stamets leading the way with pioneering work in mycoremediation:

...The first significant study showed that a strain of Oyster mushrooms could break down heavy oil. A trial project at a vehicle storage center controlled by the Washington State Department of Transportation enlisted the techniques from several competing bioremediation groups. The soil was blackened with oil and reeked of aromatic hydrocarbons. We inoculated one berm of soil approximately 8 feet by 30 feet by 3 feet high with mushroom spawn, while others employed a variety of methods, ranging from bacteria to chemical agents.

After four weeks, the tarps were pulled back from each test pile. The first piles employing the other techniques were unremarkable. Then the tarp was pulled from our pile, and gasps of astonishment and laughter welled up from the observers. The hydro-carbon-laden pile was bursting with mushrooms! Oyster mushrooms up to 12 inches in diameter had formed across the pile. Analyses showed that more than 95 percent of the PAH (polycyclic aromatic hydrocarbons) were destroyed, reduced to non-toxic components. The mushrooms were also free of any petroleum products.

After eight weeks, the mushrooms had rotted away, and then came another startling revelation. As the mushrooms rotted, flies were attracted, feeding on the mushroom spores. The flies became a magnet for other insects, which in turn brought in birds. Apparently the birds brought in seeds. Soon our pile was an oasis, the only pile teeming with life. ...

Understand that a mushroom is very much the tip of an iceberg when considering a fungi. They exist as an extensive mat of threaded cells which periodically produce reproductive structures, or fruiting bodies, and some of these are known as mushrooms. For a mushroom to exist, there must be a relatively (and sometimes objectively) huge mass of fungal tissue.

Basically, for much of their life cycles, fungi are invisible to us. This makes it easy to miss what they do, not through any fault, but a tremendous difference of scale.

Root Symbiosis

The plants we depend on are much easier to notice. We can stand in their shade, admire their flowers, live on their fruit and seeds. And the vast majority of our food comes from the flowering plants, the group of plants that evolved ways to get animals to handle reproduction and seed dispersal for them. A full 80% of these important species rely on fungi to survive in the wild.

That sounds kind of odd, because we typically think of fungi as plant parasites, attackers of the most insidious kind. But some fungi live so closely with plants that in the natural state, neither would be found without the other.

The conifer species, to take another example, are very dependent on their associated fungi, and this was discovered during a mine tailing reclamation in Georgia. Nursery grown Loblolly pines were planted at the site and would not get much taller than the day they were brought in. Around five years after the beginning of the project, a small Loblolly pine removed from a roadside was brought in to replace a dead nursery tree. The next year, its growth had taken off.

The tree was studied for some time without giving any clue to its success where other trees were stunted and failing to thrive. Until a giant puffball was discovered growing at its base. The roadside tree had its roots naturally innoculated with the spores of a fungus that actually brings the plant nutrients and water in exchange for sugars. The symbiosis formed is referred to as a mycorrhizae, literally 'fungus root.'

The purposeful innoculation of tree roots at reclamation sites has yielded impressive successes (pdf), emphasis mine:

...Since its inception in 1982, the Ohio Abandoned Mine Lands Reforestation Program has planted over 5 million PT-innoculated pine and oak seedlings on over 3,000 acres of unreclaimed AML sites.... The typical site is baren, eroded with a mixture of bench slopes... or steeper terrain.... The sites also are highly acidic (pH 2.9-3.4), and no soil amendments... are used. Tree survival has averaged over 85% in the PT-innoculated tree plantings with less than 5% tree failures as compared with less than 50% survival and over 75% failures in previous plantings with the same noninnoculated tree species.... From 1982 to 1998, the Ohio AML reforestation project with PT-innoculated trees has cost approximately... $300.00/acre. In 1998, approximately 340,000 PT-innoculated seedlings were planted on 242 acres at a cost of... $805.00/acre. This represents an approximate 87% cost reduction as compared with conventional mine land reclamation methods ($6,000/acre)....

These relationships are what allowed the first plants to leave the water and live on land. They provide a root system many times larger, more absorbent, and far reaching than the plant could grow on its own. The mere presence of the fungi around the root deters other microscopic root predators from attacking. And perhaps this relationship has prevented many plants from evolving roots that are more functional, but it's too late to argue with millions of years worth of evolution at this point.

Exit, Stage Left

You can read more about the nature of these intimate interspecies relationships in this mycorrhizae overview. Yet as the essay points out, just as we're learning how important these organisms are, scientists all over the world have noticed that the diversity and numbers of fungal species are in decline. Part of the problem stems from modern agriculture:

...Mycorrhizae are destroyed when the soil is fumigated, sterilized, solarized or drenched with most of the pesticides used to control nematodes, grubs, or weeds. They are also sensitive to high levels of chemical fertilizer. There is a difference of opinion as to the mechanics. ...Others research workers say that the high levels of chemical fertilizer, especially phosphorus, cause the plant roots to shift feeding patterns away from the mycorrhizae. ...There is, however, general agreement that avoiding high levels of chemical fertilizer, particularly phosphorus, promotes a more vigorous feeding through the mycorrhizae. ...

While it isn't clear if those are the only causes, it's becoming more urgent to find out what those causes are. Not only for the health of the trees, but the animals that live among them, and for humans to whom these organisms represent an untapped source of useful chemical processes.

...Squirrels, voles, deer, bears, and other animals eat these types of mushrooms. The flying squirrel, which lives throughout the forested areas of Canada, is very dependent on the underground fungi.

Mushrooms, above and below ground, are good sources of nutrients, often containing 25 to 30% protein. They vary in vitamin and nutrient content and a diverse population of fungi helps create a balanced diet for the animals that utilize them.

...In Europe, dramatic declines (in the order of 50%) in the number of species of ectomycorrhizal fungi in forests have been reported. The reasons for this are unclear but factors that have been suggested include pollution, over harvesting of mushrooms, and fertilization of forests.

Many of the forests of Europe are currently in a state of decline. It is not known if the decline in ectomycorrhizal species is contributing to the decline in the forest or if stress to the forest is causing decline in types of mycorrhizae. ...

Waste And Folly

There's a word for land that's not immediately being used for human activity. It's called 'undeveloped land.' A term that, like timber land, implies that the sole useful purpose of an area can be measured in direct human uses.

If the work ethic that pervades our culture for good and ill is to be turned to some use in this, there needs to be broad recognition that work is not the exclusive province of Homo sapiens. It must be seen that useful, even essential, functions may be carried by 'idle' land and the organisms that populate it. Even when we can't see them.

The degradation of fungal habitat, just like the habitat of any other organism, is a waste. We've barely started to tap the resources available to us in this diverse kingdom of lifeforms, and through neglect are allowing their destruction. It would be the equivalent of finding the start of a gold vein in a mountain, and blasting through with dynamite to clear space for a backwater byroad. The value obtained doesn't compare with the longterm potential value of the destroyed resource.

Ultimately, fungi are important partners in our ecosystem. They could be of even more use to us if there was broader recognition of their unique contributions to the life cycle. Paul Stamets has an even grander dream, one that makes this science fiction fan giddy with the possibilities:

..."I have a strategy for creating ecological footprints on other planets," he says. "By using a consortium of fungi and seeds and other microorganisms, you could actually seed other planets with little plops. You could actually start keystone species and go to creating vegetation on planets."

"I think that's totally doable."