The spread of the adventive Lumbricidae into the temperate zones of the world has, like any good adventure story, elements of fitness, luck, conquest, failure, and a good deal of exaggeration.
—WILLIAM FENDER, “Earthworms of the Western United States,” Megadrilogica, 1984
SPRING WAS WINDING DOWN and summer was on its way. The earth warmed a little, and most days, the fog started to lift around noon. One Saturday I sat outside in the dirt pulling weeds. It was satisfying work, clearing some space for the sunflowers and zinnias that were only a month old but already tall and well rooted. After a while I looked up and pushed some hair under the brim of my hat. It was a fine feeling to be outdoors in the summer, with the fog slowly burning off and the sturdy green plants reaching for the sun. As I sat and surveyed the bed I’d just weeded, a fat red worm moved across the soil towards me. My heart leapt a little at the sight of it. I dropped my spade and picked the worm up, rolling it over in my hand. It was a large specimen, red on top with a translucent underbelly, a barely developed clitellum, and a flat, spoon-shaped posterior. Lumbricus terrestris, the nightcrawler.
I have an old British earthworm textbook that includes a section on “Mesmerizing Worms.” The author contends that crabs, lobsters, fish, and snakes all like to be stroked; it is, he claims, a well-known fact. He described stroking a nightcrawler on its back one day and finding that it “instantly settled down to be petted.” A few days later, he picked up another one, and although it squirmed around at first, it later “became perfectly quiet when stroked, and lay still afterwards as if it were waiting for further play.”
Until I read that passage, it had never occurred to me to stroke a worm. I would not have thought that a worm longed for physical contact, although I’d seen them mass together in the bin in a way that showed they were not afraid of crowds. But why would a nightcrawler tolerate exposure to air and an unfamiliar human touch? And how would I know if the worm was mesmerized or merely playing dead?
I pulled my glove off and ran a finger along the worm’s back, from head to tail. It stretched as I touched it, lengthening each segment under the pressure of my finger. Still, it didn’t seem to be trying to escape, just extending itself. I stroked it a few more times, slowly, guessing that a faster stroke would only alarm it. Soon it was perfectly still in my hand.
What can I make of this interaction between me and the nightcrawler? Surely it doesn’t know a thing about me. If it could see me, it would have every reason to be frightened. I can only guess that everything above the surface of the earth is outer space to a worm, and that humans are aliens. Why would it tolerate me stroking it? Maybe the pressure on its body reminds it of the comforting closeness of an earthworm burrow, where the sensation of gritty earth sliding along the skin must feel like home.
An earthworm’s skin is fragile; I didn’t see the point in handling it any longer. But when I looked around the garden, I couldn’t tell where it came from. There was no burrow nearby that I could see. I set it down in some loose soil and sat next to it, waiting for it to bury itself. At first it didn’t move. Maybe it was still mesmerized. Then it pushed a little soil aside and found a way back into the earth, its flat iridescent tail waving as it ducked away from the light and continued its work.
AS FAMILIAR AS THAT nightcrawler may seem, it is not indigenous to North America. In fact, many of the worms commonly found in American garden soil today are not native. Canada, the northernmost parts of the United States, and northern European countries such as Sweden and Norway were covered by ice and snow during the last Ice Age about ten thousand years ago. If earthworms existed there before the advance of the ice, there were none to be found after. And the native worms that lived below the southern limit of the glaciers have gradually been displaced through the disruption of their habitat and the introduction of exotic (non-native) species. Those native worms are still out there, but they are poorly understood and increasingly difficult to find. Dig up an earthworm from any backyard in the United States, and that worm will mostly likely be non-native.
Lumbricid earthworms like the nightcrawler followed the route of immigrants into North America. Some ecologists have called these worms “weed species”—creatures, like cockroaches and flies, that follow humans wherever they settle. They have also changed the nature of the landscape, and the possibilities for agriculture, everywhere they’ve gone.
European immigrant farmers coming to the United States might not have thought to deliberately transport such a ubiquitous creature as an earthworm to the new world, but transport them they did—in the soil of potted plants, the ballast of ships, the hooves of horses, and the wheels of wagons. Whether they came as stowaways or invited guests, there is no doubt that foreign species of earthworms, namely Lumbricus terrestris, the nightcrawler; Eisenia fetida, the red wiggler; and Aporrectodea caliginosa, the field worm, came west with settlers and helped turn the already rich valleys and plains of the Midwest into some of the best farmland in the world. In two hundred years, European settlers managed to transport earthworms nearly three thousand miles across the continent, a feat that would have taken the worms about 1.5 million years to accomplish by themselves had they simply been released on the East Coast and allowed to migrate towards California at their leisurely rate of a few yards per year.
When these new species arrived in North America, they found a welcoming climate: rich, damp soils; a comfortable pH level; and temperate weather. There is almost no part of the United States where European earthworms have not made a home for themselves. Over the last few decades, earthworm censuses have found over a million worms per acre in Geneva, New York; Frederick, Maryland; and LaCrosse, Wisconsin.
I can only assume that the worms in my backyard are recent immigrants themselves. Eureka was established late because of its inaccessibility. Dense redwood forests made the area hard to reach by land and it was barely visible from sea, where only a narrow opening led into the bay. As timber and fishing industries began to flourish in the mid-1800s, settlers began cutting down forests to make room for a town.
My house was built around the turn of the century by a family—the Chapmans—who had owned the land since about 1880. When they dug a well in my backyard to serve the three houses they would build on this block, they might not have found any nightcrawlers; the European worms were also recent arrivals and probably hadn’t established themselves yet. For that matter, they might not have found any worms at all, considering that they were building on cleared forest land. Not much is known about the native species that lived in the redwood forests at the time. Whatever species did exist probably disappeared as the forests were cleared to make way for a grid of streets and houses. The nightcrawlers in my garden could have arrived a hundred years ago in the potting soil of Mrs. Chapman’s rhododendron, or they could have been introduced over the last few decades when the previous owners of this house returned from a fishing trip with extra bait.
ALTHOUGH A GOOD DEAL of forest was cleared to make way for the town of Eureka, redwood trees can still be found in people’s backyards, and the town is surrounded by wilderness. In fact, the northern entrance to the Headwaters Forest is only about a fifteen-minute drive from my house. I go there from time to time in the summer. There’s a comfortable, paved trail leading into the woods, and it makes for a nice walk in fair weather. Sometimes I’ll see hawks and songbirds there; when it’s damp I may see a red-legged frog or a dusky yellow banana slug. But now, when I walk through the woods, I wonder about what I can’t see. I wonder about the worms in the forest.
It seems as though no one around here is neutral when it comes to the Headwaters. To timber companies the forest represents jobs and lumber, and to environmentalists it represents a priceless resource: some of the last stands of pristine old-growth redwood forest. Few have forgotten the protests that took place a few years ago to save this forest. After all, this is the place where Julia Butterfly Hill lived for two years in a tree named Luna, and where police officers swabbed the eyes of antilogging protestors with Q-tips dipped in pepper spray, prompting a civil rights lawsuit that is still working its way through the courts. At the end of all the protests and negotiations, the federal Bureau of Land Management and the State of California joined together to purchase the 7,400-acre forest, allowing them to halt logging and protect such endangered and threatened species as the marbled murrelet, spotted owl, and coho salmon.
Most of the Headwaters forest is off-limits to visitors. From the southern entrance, forest rangers lead small groups on a four-mile hike along what used to be a logging road. Although there are some old-growth trees along the hike, most of the forest near the trail has been logged at one time. At the northern entrance—the one closest to my house—people can walk about five miles into the forest, but along the way they’ll see more maples, willows, and alders than they will redwoods. The most pristine parts of the forest begin where those trails end. This is where the marbled murrelet makes its home. Most tourists who visit will not see the endangered shorebird, or the old groves it inhabits, where ancient trees reach three hundred feet into the sky.
I’ve never been into those restricted areas, but I’ve hiked through plenty of redwood forests and I can imagine what these are like. Like tropical rainforests, the trees in redwood forests tend to regulate the climate. The tree canopy shelters the forest from sunlight and filters rainwater as it comes down, keeping the forest cool and moist but never drenched. I have walked into a redwood forest during a rainstorm, only to find I didn’t need my umbrella once I was under the canopy. Even on the hottest afternoons, under the trees it is always chilly and damp. Some trees are so enormous that five people can’t link arms and reach around them, and they are so tall that it is impossible to stand at the base and see the top.
A redwood measures its life span in centuries, not decades. Time seems to stand still inside a redwood forest—it is easy to imagine that you have dropped into some distant past, centuries ago, when these forests ran in a narrow band along much of the West Coast—but at the same time, life begins again so quickly that you can almost watch it happening. When lightning strikes a tree, a fire burns down through the center of it. Around it, dozens of new redwoods spring up from the cinders. When one falls, it becomes host to mosses, ferns, and young redwood saplings. Even the smallest creatures seem primeval, otherworldly: I have seen red-legged frogs looking up at me from a damp creek bed, and banana slugs, mustard yellow and longer than my finger, move across the trails at an infinitesimally slow pace. A redwood forest is powerfully alive. When I visit one, I put my hands on the largest tree I can find, and I almost believe I can feel a heartbeat. Even in my most pragmatic moments, when I acknowledge that I live in a house built of redwood, filled with wood furniture and thousands of books printed on wood-fiber paper, I can’t help but shudder at the thought of even one of these trees being cut down and hauled out of the forest.
That’s why it always gives me an uncomfortable feeling to walk into the Headwaters from the northern entrance and see the remains of the old logging operation. The town of Falk once stood on a hillside about a mile into this forest. It was a lumber town, owned by the Elk River Lumber Company and occupied by about four hundred people at its peak. People lived in Falk from about 1884 until just after the Great Depression. By 1940, it was a ghost town, complete with an abandoned general store that held nothing but empty shelves and old receipt books. Hikers used to go out there looking for artifacts, and the empty buildings attracted plenty of campers over the years. In 1979 the last of the old buildings was knocked down. The forest has begun to move back in, reclaiming its territory, covering up the signs of human occupation. A pile of brick and rubble—perhaps a house or an outbuilding?—has sunk into the forest floor. Moss and fern almost completely obscure the pile of bricks from view. Redwood saplings have started to spring up among them. Over time the remnants of this town will be completely buried under the forest floor. Right now, little remains but the plants that Falk residents brought in to plant around their homes. Garden plants like yew trees, daffodils, and breath of heaven shrubs can all be found along the trails.
I got to thinking about those plants after I’d been to the Headwaters a few times. If earthworms migrated across the country in the roots of plants, as many believe, does that mean that the Falk townspeople brought earthworms into the Headwaters forest? Is it possible that the exotic plants growing alongside the trail are just the tip of the iceberg? What would it mean to this forest—or any forest—if an unfamiliar species of earthworm moved in?
I drove out to the northern entrance one Sunday afternoon in May and walked into the forest, taking a self-guided tour brochure with me. The second stop along the tour was a pair of yew trees that once marked the entrance to the home of Loleta and Charlie Webb, Falk’s caretakers. The column-shaped trees were strikingly out of place in the forest. Between them, a path led to the site of the caretakers’ former home, but the path was off-limits to visitors. A short post held a plaque that explained the site’s significance. At the base of the post were a couple of bricks. I kicked over one of the bricks. Under it, three earthworms squirmed out of sight.
I grabbed a stick and dug them out of their burrows. They looked like ordinary pink worms to me, smaller than a nightcrawler, lighter in color than the red wigglers that lived in my worm bin. I couldn’t begin to guess whether this was a native or an exotic worm. Sam James would know. I wrapped my hand around the worm and kept walking. A little while later I came to the spot where the old mill had stood. The cookhouse and loggers’ homes once stretched up the hillside behind the mill. No one was allowed to climb up the hillside, but I turned over a few logs near the trail and found a couple more worms. The next morning, I shipped them off to Sam James and waited for the results.
I knew that the worms I sent to Sam were in no way representative of all the worms living in the forest. One scientist wrote an article about earthworms of the Pacific Northwest several years ago in which he warned that “many species preferentially inhabit game trails and other compacted soils. . . . Do not fall into the habit of collecting only the easiest habitats.” He suggested getting at least twenty yards away from roads before collecting specimens, but I didn’t dare wander that far off the trail in the protected Headwaters forest. Even if I had, I might not have found any native worms. Another taxonomist wrote that the absence of native worms in some areas of California “now shows that they were unable to compete there once the adventive Lumbricidae arrived.” If native worms were to be found, they were most likely deep in the pristine old groves, far away from human interference from the likes of me and the long-gone Falk townspeople.
Sure enough, Sam reported a week later that the worms I’d sent belonged to the Lumbricidae family. I’d uncovered Lumbricus rubellus, redworm. The other worm I’d dug up was Aporrectodea caliginosa, the common field worm that also lives in my garden. Both are non-native worms, and both thrive in the damp soil of the Pacific Northwest. Because they’re both so common to this part of the country, it is impossible to tell how they arrived in the forest. They could have moved in along with the residents of Falk, or they could have come in later, as heavy equipment rolled in to pave the trail or raze the last of Falk’s buildings. Even a muddy hiking boot could have deposited a worm cocoon along the side of the trail.
What does it mean that these non-native worms inhabit the forest floor? It’s a question that ecologists are just beginning to explore. An invasive plant species can move into a forest and displace native plants, change the food source and habitat available to birds and other denizens of the woods, and even—through the gradual thinning of native trees and shrubs—alter the climate inside the forest. One could speculate that exotic earthworms displace native earthworms by consuming their food source or pushing them out of their habitat. A native earthworm may have a symbiotic relationship with a particular native plant, or it may be a food source to a specific bird or snake. It may help maintain a particular balance of nutrients in the soil, one that forest plants rely upon. If that earthworm disappears, is it possible that the forest itself could change?
Answers to these questions are not easy to find. Sam James wrote that there are “serious deficiencies” in our understanding of native North American species and lamented the fact that there may not be “sufficient social or political interest to foster conservation of earthworm biodiversity.” After he identified the worms for me, I called him to ask if it was possible for a non- native species to harm the Headwaters forest.
“Hard to say,” he said. “But it’s an interesting question. You don’t really think of earthworms as being destructive, but that’s what brought me down to the Philippines the first time.” He’d heard that earthworms were destroying rice crops there and offered his services to identify the worms and help local farmers come up with a solution. He first traveled to the Banaue rice terraces in the Ifugao province of the Philippines in 1999.
The terraces, which have been in place for upwards of two thousand years, climb up the sides of green mountains that rise about four thousand to six thousand feet above sea level. The terraces are flooded during the growing season, but when the season ends, the fields are drained and the farmers grow other crops along the terraces. “It’s a modern economy there,” Sam said. “They can’t rely on rice alone to support themselves, so they drain the terraces and plant vegetables and flowers.” Sam and his crew arrived to learn that foreign earthworm species—some from South America and some from Asia—had come into the area as roads were built and new plants were imported. They were active burrowers that filled the terraces with holes as soon as they were drained. “It’s like Swiss cheese out there,” Sam told me. “The floods don’t hold. Used to be they’d keep them flooded year-round, and the worms never had a chance to get in.”
That’s not the only worm problem facing these farmers. “There’s another worm that lives in the terrace walls itself,” Sam said. “Some of the farmers live out there on the terraces and these worms are attracted to the garbage that piles up. The worms are building burrows that break down the terrace walls. It’s a native worm that’s hard to identify because it has no sexual organs. We rely on those organs and their location to identify most species of worms. But this worm is parthenogenic. It clones itself. Hard to say for sure what it is.”
There’s no easy solution to this problem of earthworms in the rice terraces. It points out, once again, how small acts have unintended consequences. “There are plenty of scientists out there studying the ecology of invasions,” Sam told me. “Until recently, earthworms weren’t really on their radar screen. But you never know what the consequences will be of bringing a few worms into a new environment.”
I mentioned the eucalyptus trees that grow along the California coastline. They’re not native, they grow like weeds, they kill anything that lives underneath them except other eucalyptus, and they are a serious fire hazard because of their high oil content. They were brought here from Australia over a hundred years ago as a timber source and windbreak. “I think most people can relate to the idea of an invasive exotic. Everybody in California knows about the problems with eucalyptus trees. But they’re big and obvious,” I told him.
“Exactly,” he said. “But what about the earthworms that came over in the roots of those trees? Nobody thought about that.”
I asked if he had ideas for ridding the rice terraces of the worms that had colonized there. After all, you can’t just round up worms and send them home. “That’s the hard part,” he said. “There’s not much you can do. You can’t poison them without poisoning the soil. The fact is, the worms may be filling the terraces with holes, but it was an economic decision to drain them in the first place. It may take a government program to pay the farmers to grow rice year-round the way they used to, just to preserve that way of life.
“But you know one thing that will get those worms out of the ground? Wasabi. You know, the really spicy green stuff you eat with sushi. They can’t stand it; they’ll do anything to get away from it. But can you imagine what that would smell like? A whole field of wasabi?”
He starts laughing, the ironic laugh of someone who has seen earthworms get the better of two thousand years of rice farming in one country while transforming the soil and making productive farming possible in others. Sam James is perhaps one of the few people who gets the joke: earthworms can change the course of human civilization and do it all silently, in the dark, unseen.
ONE WORM THAT I didn’t find in the Headwaters forest was the common nightcrawler, Lumbricus terrestris. While they thrive in my garden and are often found in rich soil wherever humans live, they have a low tolerance for the acidic soils of coniferous forests like the Headwaters. They do seem to be fond of deciduous forests, like the hardwood forests along the East Coast and near the Great Lakes, where annual leaf fall makes for a thick pile of worm-friendly compost. A few days after Sam James called me with the news about my Headwaters earthworms, I heard about a couple of scientists at the University of Minnesota who were studying the earthworms’ destruction of hardwood forests. Before long, I was on my way to Minneapolis.