Back Forty: We have a fungus problem

Back Forty will bring you periodic reviews, interviews and reporter insights about the stories they wrote. We hope you enjoy it as a companion to our main content on TheFERN.org and our Ag Insider policy news site. You can subscribe to the newsletter below.

By Rowan Jacobsen

These are heady times for fungi. Other than the rare breakout star like penicillin or truffles, life’s “other kingdom” has been content to creep through the cultural shadows, letting plants and animals hog the limelight. That seems natural for a life form that often exists as a single cell or as microscopic tendrils threading through the soil, but lately fungi have captured our imagination. On the hit HBO show The Last of Us, a fungus called Cordyceps, which in real life snakes through ants’ bodies until it controls their minds, has figured out how to do the same to humans, crashing the population. Scary stuff.

And now comes Blight, Emily Monosson’s equally chilling book about what fungi are really up to. The good news: nothing truly apocalyptic yet. The bad news: they’re getting there.

Consider Batrachochytrium dendrobatidis, or Bd, a fungus that has put the world’s frogs in a Last of Us situation. A native of the Korean Peninsula, Bd popped up in the Americas in the 1980s and ’90s, killing frogs and other amphibians in shocking numbers. Researchers suddenly couldn’t find a frog to study. Zoos were emptied of their displays. Bd has now infected 500 species of frogs and caused the extinction of as many as 90.

We have become disturbingly numb to such decimation of wild populations, but until the frog apocalypse, this was unheard of, says Monosson, a toxicologist and the author of three previous books on the impact of modern chemicals on living things. “In 2019 dozens of scientists … wrote of the destruction caused by Bd: ‘This represents the greatest documented loss of biodiversity attributable to a pathogen.’ Before Bd, no one knew any disease could be so bad. Now they know.”

And researchers keep seeing bad ones. If Bd were a freakish one-off, it wouldn’t be that big of a deal (unless you’re a frog), but most of Blight is a steady drumbeat of horror stories documenting the devastation wrought by fungi on the warpath.

Pseudogymnoascus destructans, the cause of the infamous white-nose syndrome, has put a Bd-like hurting on North American bats since 2007, killing more than 90 percent of the populations of little brown bats, tricolored bats, and northern long-eared bats, its white fur creeping over their skin while they hibernate like mold on a forgotten cheese. As with the frogs, no one had ever witnessed such a massive die-off of bats before. If that’s one you think you can safely cross off your to-worry-about list, Monosson notes that bats, with their voracious appetites, provide American agriculture with $23 billion worth of free pest control every year.

But Blight also makes it clear that fungi are coming directly for our food supply, too. We already lost the first big banana, the Gros Michel, to a fungus known as Race-1. In the early 20th century, Race-1 quickly spread across the entire Banana Belt, from Asia to Latin America, and would have wiped out the industry if a suitable replacement hadn’t been found.

Fortunately, the Cavendish, the banana we know and love, came to the rescue. It wasn’t susceptible to Race-1, and while it wasn’t quite as sweet or durable as the amazing Gros Michel, it was good enough. Today, virtually all of the 100 billion bananas consumed each year—a $40 billion industry—are Cavendish.

So of course, a new relative of Race-1, known as TR4, is now coming for the Cavendish. This time, there is no obvious heir apparent, and banana production could suffer mightily. This may not sound like a tragedy, but bananas, globally, are one of the big four staple crops, along with wheat, maize and rice, and a lot of jobs and food security in developing nations are dependent on them.

Wheat, too, is under threat. Just one gene, known as sr31, is responsible for protecting most of the world’s wheat crop from wheat stem rust, a fungus that has triggered famines in the past, and forms of wheat stem rust that can overcome sr31 have already emerged. So savor that toast a little longer tomorrow morning.

In the good old days, our food supply was about as close as fungi could get to threatening us directly. We might suffer the occasional fungal insult—athlete’s foot, thrush, etc.—but fungi almost never killed healthy mammals. We just burn too hot for organisms that prefer the chthonic chill of the underground. Bats are the exception that proves the rule—white-nose syndrome attacks them when they are torpid, having cooled their internal temperature from around 98 degrees to 45 or so.

But then something named Candida auris came along and broke the rules. It feasts happily on our cells at a balmy 98.6 degrees. (Unnervingly, this is also a plot point in The Last of Us; global warming has trained Cordyceps to adapt to warmer prey.)

The weirdest thing about C. auris is that it came out of nowhere. Previously unheard of, it popped up in hospitals in dozens of countries in the 2010s, spreading from patient to patient and killing an alarming percentage of them, in part because it mysteriously arrived on the scene already resistant to most anti-fungal drugs. Instances have exploded in the U.S., going from less than 500 in 2019 to 1,474 in 2021, and 2,377 last year.

It’s no mystery why so many fungal pathogens are suddenly emerging as cosmopolitan scourges: Global trade and transport. For almost all of these invaders, the story is the same. A fungus that lived in a state of equilibrium with its host in some corner of the world was unintentionally whisked around the planet and went wild on related species that had no defense. The white-nose fungus likely jumped from a European cave to a Northeastern one on some spelunker’s boots. The African clawed frog, a popular laboratory research animal, probably spread Bd around the world. The white pine blister rust, which has devastated several species of American pines, arrived on pine trees shipped from Europe.

Part of the problem is that fungi are very good at this. They produce gazillions of spores, which are much tinier than seeds and much better at catching a ride on a breeze, bird, or bulldozer. And they are devilishly good at staying dormant for years until an opportune moment arises.

Considering the tsunami of living things being relocated on a daily basis, it’s no wonder fungi are ascendant. Two hundred million animals, comprising two thousand different species—pythons, tiny fish, brilliantly colored lizards—reach the United States each year through the pet trade. More than a billion plants and pieces of plants are shipped internationally every year. Almost none of them get inspected. Neither do we as we travel the globe, and we are virtual vending machines of fungal spores.

Monosson calls it one huge conveyor belt of disease. “We are relentless travelers and traders,” she writes, “and as a result we have brought species, which for tens of millions of years or more, lived apart—separated by the planet’s oceans, islands, and mountains—crashing together. We are jumbling the world’s biota, often to devastating effect.”

What can be done? Not much. This is the most discouraging part of Blight. Monosson makes the obvious recommendations. We need better inspection at ports. Nurseries should be required to certify their stocks as pathogen-free before sending them overseas. The illegal animal trade should end—and even the legal one should be curtailed. We need more seed banks, fewer monocultures, and a greater diversity of plant varieties being grown for food, so we won’t get stuck in a genetic deadend. We should also curb indiscriminate use of anti-fungal sprays in agriculture, which can lead to drug-resistant fungi like C. auris.

But barring a sudden and massive shift in how we move goods, plants, animals, and ourselves around the planet, fungi are going to find their way everywhere. They are just too well adapted to the modern moment. “We haven’t simply opened Pandora’s box,” Monosson writes, “we have swung it around and shaken out the contents.” Still, we can each follow best practices. Don’t import exotic plants or animals. Learn to love those little red bananas. And occasionally, check yourself for new tendrils in strange places.