water running over the edge of walkway with a city on background.

North America’s most valuable resource is at risk

The Great Lakes helped make the U.S. an economic powerhouse. Now climate change, pollution, and invasive species threaten their complex ecosystems.


Floodwater pours over a walkway at Montrose Beach near downtown Chicago. In the first half of 2019, heavy rains raised the lake level by almost two feet. Scientists expect the frequency of extreme weather to increase across the region in the decades ahead.
This story appears in the December 2020 issue of National Geographic magazine.

For the Anishinaabe, hunting has never been a sport, and life is never taken lightly.

So when the big bull moose approached Tom Morriseau Borg, he felt a mix of gratitude, awe, and humility: The moose was offering itself, a gift of life and meat from the forest that Borg would share with family and friends. Borg, a traditional Anishinaabe trapper, grew up near Lake Nipigon in western Ontario in a home without electricity or running water. The Anishinaabe have fished, hunted, and trapped there for centuries, and after Borg shot the moose, he sprinkled tobacco on the animal and whispered some prayers of thanks, just as his grandfather had taught him.

But as he dressed the carcass—cutting it up to bring home—Borg’s gratitude gave way to revulsion. When he tried to extract the liver, which should have been firm and meaty, it deliquesced into a bloody sludge, sliding goopily through his fingers. Since that hunt, Borg has found similarly diseased livers in several animals. “I notice it in rabbits, beavers, and in partridges,” he said. “The favorite part of the rabbit for me was the rib cage, with the heart and the liver. But now we don’t eat that anymore.”

Borg suspects that the spraying of herbicides by timber companies is hurting the animals in Lake Nipigon’s watershed. “New shoots are the moose’s favorite food,” he said. “They thrive on that new growth.” Or they did until it was poisoned. “That’s the way it works. Herbicides flow into streams to beaver lodges—that’s why their innards are so messed up.

“When I see harm and disruption, it hurts a lot. And the changes I’ve seen in the bush over the last 15 years—I didn’t think changes could come that fast,” Borg said as he finished the story on a cool summer evening at his home in Nipigon.

Borg has graying black hair and is trimly built, fit from a lifetime of hard work maintaining gas pipelines while trapping on the side. In the distance an occasional truck rumbled along the Trans-Canada Highway. From somewhere out in the night came the hauntingly wild cry of a loon.

Borg’s home, which he built with his wife and two sons among tall conifers 33 years ago, overlooks the Nipigon River, an outflow from the lake of the same name. Lake Nipigon covers nearly 1,900 square miles, but on a map it looks pondlike compared with the body of water it drains into: Lake Superior, the largest of the five Great Lakes, or as the Anishinaabe call it, Anishinaabewi-gichigami—the Anishinaabe’s Great Lake. (In Longfellow’s Song of Hiawatha, it’s Gitche Gumee, “the shining Big-Sea-Water.”)

As Borg’s wife, Donna, served us thick slices of bannock with rose hip jam, he lamented the transformation of a land he loves. Even the seasons have changed. Sometimes the lakes still have open water in December; winds are more violent; the winter coats of the animals he traps—beavers, marten, mink, weasels—develop later in the season than they did when he was a boy. “It’s not the same anymore.”

The sorts of changes Borg has seen—and many that he has not yet witnessed in his relatively pristine watershed—are transforming the rest of the Great Lake watersheds. The five lakes—Superior, Huron, Michigan, Erie, and Ontario—are arguably the continent’s most precious resource, incalculably more valuable than oil, gas, or coal. Together they hold more than a fifth of the world’s surface freshwater—six quadrillion gallons—and 84 percent of North America’s.

Almost 40 million Americans and Canadians live in the Great Lakes watershed. We drink from the lakes, fish on them, transport goods over them, farm their shores, and work in cities that wouldn’t exist without the lakes. And of course, we pollute them. We’ve introduced invasive species that have permanently altered the lakes. The fertilizers we use to grow the corn we feed to the animals we eat and to make the biofuels we pump into our vehicles have contributed to the resurgence of algal blooms so large they can be seen from space. And with our ongoing emission of greenhouse gases, we’ve even managed to reengineer the weather over vast stretches of the Great Lakes watershed, increasing the frequency of severe storms.

“It’s big, what’s happening here,” Borg said over tea. “When you spend time on the land, you know something is wrong. Things are changing. I don’t know if we can stop it.”

As gigantic geographical features go, the Great Lakes are newcomers on the continent. They’re a legacy of North America’s last ice age, when miles-thick glaciers stretched from southern Kansas to the Arctic. When the glaciers retreated 11,000 years ago, they gouged the basins that became the Great Lakes. It was only about 3,000 years ago, though, that the lakes’ current contours and drainage systems evolved, which makes them significantly younger than the oldest Egyptian pyramids. Nothing on Earth rivals the lakes—they’re the world’s largest freshwater system, a gift from one age on the cusp of momentous change to another. They’re connected; one flows into the next.

All the lakes, whether they’re cold and deep with wooded shores, like Lake Superior, or warm and shallow and ringed by industrial cities, like Lake Erie, share a secret life. They’re hosts to a hidden world that most of us will never see. You might, if you’re lucky, glimpse a wolf on Isle Royale in Lake Superior; or catch a moose at dusk near the shore of Lake Huron; or maybe you’ll reel in a 200-pound sturgeon in Lake Erie. But those marquee creatures overshadow a much humbler supporting cast, without which the lakes would die.

“Take a deep breath, and then take a second deep breath. One of those two breaths was made by diatoms,” said Andrew Bramburger, a lake ecologist now with Environment and Climate Change Canada, the agency that administers and enforces much of the country’s environmental policies. Last year he was still at the University of Minnesota Duluth, and on a rainy September afternoon in an empty classroom, he was extolling the life-sustaining role played by diatoms, a type of algae with rigid cell walls made of silica.

“Everyone calls the Amazon rainforest the lungs of the world,” he said. “But it’s actually the diatoms in the oceans, rivers, and lakes of the world that make about half the oxygen in our atmosphere.” Diatoms pump oxygen into the lakes as well—without them, the lakes would suffocate. And they’re the lakes’ primary food source. If the diatoms are healthy, everything else in the lakes will be too.

Bramburger, who is sandy-haired and bearded, has spent 20 years studying algae in the Great Lakes and other large lakes around the world. He grew up near Niagara Falls and could be classified as an aquatic mammal himself. “I love to be in water,” he said. “I learned to surf on Lake Erie. When you tell people you surf on a lake, they look at you kind of strangely.” Then again, in most parts of the world, a lake is something you can see across. Bramburger’s enthusiasm for the lakes was such that he couldn’t help but share it, and not just verbally. He invited me to a special monthly event: a swim in Lake Superior with some friends. They do it year-round, even in the winter, when they’ll jump from ice floes into open patches of water, he told me, cheerfully. And, lucky me, the next frigid baptism would be before dawn in four days. In a craven attempt to opt out, I mumbled that I hadn’t packed a bathing suit. Bramburger cut me off: “You can borrow one of mine.”

While I silently fretted about what I had gotten myself into, Bramburger opened his laptop to show me images of some of Lake Superior’s smallest inhabitants. Researchers have identified about 3,000 species of diatoms in the Great Lakes, and there are probably many more to be discovered. Seen under a microscope, they’re among the most strangely beautiful of all living things, with a kaleidoscopic variety of shapes—rococo orbs, striated lozenges, splayed fans, disks patterned like the rose windows in a Gothic cathedral. Like plants, diatoms and other algae use light to convert water and carbon dioxide into simple carbohydrates. They’re high-quality food for zooplankton—minute, floating grazers—“juicy and rich in fats,” in Bramburger’s description.

Bramburger and other researchers have charted an alarming trend stretching back 115 years: Individual diatoms in the Great Lakes are getting smaller. The shrinkage seems to be connected with climate change. As the lakes warm, the diatoms sink, which reduces their ability to harvest light. “The bigger ones can’t stay afloat,” Bramburger said. “The trend is smaller diatoms and less of them, and they’re being replaced by things that are at best low-quality food items and at worst toxic. We don’t know what that’s going to do to the overall food web.” (See how the Great Lakes food web is in trouble.)

Invasive species of mussels, introduced by oceangoing vessels, present an even greater threat to diatoms, causing their numbers in Lake Erie to plunge 90 percent in the past 35 years. The equivalent loss of other keystone plants with higher profiles—the grasses of the African savanna, say—would make global headlines. But diatoms don’t get much press.

For such an abundant and irreplaceable organism, surprisingly little is known about what happens to diatoms in the winter. “Five months of the year the lake is covered with ice,” Bramburger said, “and we haven’t got the foggiest idea of what’s going on down there.”

During the winters of 2017 and 2018, Bramburger and a few colleagues at the University of Minnesota set out to remedy that gap in our knowledge and ventured onto the frozen surfaces of several lakes that drain into Superior to drill some holes in the ice. “We just had our minds blown,” Bramburger said. Instead of the sluggish scene they expected, the waters beneath the ice brimmed with life. “The photosynthetic rates happening under the ice were 60 percent of what they are in the summer. And that was under two feet of ice and two feet of snow. So you think it’s just a cold, dark, boring world down there, but there’s actually a lot going on.” Zooplankton abounded—about 1,500 of them per liter—all swimming about, gobbling up algae.

Without a healthy crop of diatoms to support the zooplankton’s winter feeding frenzy, the lake’s productivity for the rest of the year would suffer. Because small fish in the lakes eat zooplankton, a plunge in the diatom numbers would cause fish populations to crash. “It’s the jump start of the spring food web,” Bramburger said. The solar energy snagged by diatoms provides the calories that become the flesh of ever larger creatures in a daisy chain of embodied light. “If you’re catching big bass in the summer,” Bramburger said, “it’s because these guys were doing their thing in the winter.”

One of the group’s most counterintuitive discoveries was that diatoms were more efficient beneath snow-covered ice than beneath ice that had been cleared of snow. Diatoms need just the right balance of depth and sunlight. If they sink too deep, they don’t get enough light. If they’re higher up in the water column, they can get burned. Snow may be protecting them from excessive sunlight. Under cleared ice, solar radiation may damage the diatoms’ photosynthetic pigments. One explanation: “Their photo systems, their pigments, were basically getting nuked and bleached,” Bramburger said.

It was a worrisome find. “This is something that’s going to affect the Great Lakes as we lose our snow and ice cover and as our winters get warmer but also drier and windier,” Bramburger said. “Drier and windier means we’re going to start losing snow on the ice, and as it gets warmer, we’re just going to start losing ice. In the Great Lakes we see large algal blooms of a species called Aulacoseira. It’s a big diatom, and it likes to be on the bottom of thick, snow-covered ice. If we start losing that, we’ll probably lose one of the really important components of the food web.

“The thing I’m always struck by is that we don’t understand winter, but we’re losing it. It’s a race to figure out what happens in winter before there’s no winter to figure out.”

Heavy rain was forecast for the morning of our swim, which had given me hope that I might yet avoid the ordeal. No such luck. At 5:30 a.m. on the appointed day, 13 of us huddled around a bonfire on a dark, fogbound, rocky beach not far from downtown Duluth, drinking coffee. This group plunge would mark 47 consecutive months of, well, jumping into a lake. Michael Scharenbroich, one of Bramburger’s friends, took the water’s temperature: “Fifty-one degrees,” he yelled. Go time. Without water shoes, I lagged behind the collective charge, and hobbled over stones dropped by glaciers millennia ago. Then the need to relieve the pain in my feet overcame a visceral reluctance to dive in. All around me heads vanished and quickly reappeared above the surface, like a pod of startled otters, wide-eyed with shock and glee.

One jump, it turned out, wasn’t enough. We warmed up and went in again. And a third time. As the bonfire dwindled and the sky lightened to a silvery gray, people started to leave, but Bramburger lingered. In a few days he would be moving to Canada to start a new job, and it was clear he would miss mornings like this. “I’ve lived around many places in the Great Lakes, but Lake Superior seems to have a bit of magic for people,” he’d told me. “The sense of identity and attachment to the lake that Duluth has—I’ve never seen on another town on the lakes.”

For all its beauty, Lake Superior can be treacherous. Duluth, with 86,000 people, is the second largest city on Superior, after Thunder Bay, Ontario, and is still recovering from the damage done by a string of punishing storms, including one so-called 500-year storm, that battered the city within the past eight years. A few days after I met with Bramburger, Michael LeBeau, Duluth’s no-nonsense construction project supervisor, gave me a tour of the waterfront, where high lake levels and three intense windstorms had caused extensive flooding damage the year before.

In 2016 one storm knocked out the power for Duluth’s water supply. A city on the edge of one of the world’s largest bodies of freshwater came within hours of running out of water. Looking out over a stretch of prime urban shoreline that soon will be protected by 76,000 tons of stone mined from a nearby quarry, LeBeau worried what the future would bring. “I’m told we’ve almost exhausted the quarry,” he said. “We’re going to be spending close to $30 million for three big storms. For a small and not very wealthy city, it has been a big blow. What we’re building now is the best we can afford. It really is conceivable that if these storms continue or get worse, it won’t be possible to get back to where we were. And no one can understand that.”

Such city-pounding storms are likely to become a costly new normal. Global warming is destabilizing the jet stream, the high-altitude air current that flows from west to east around the planet. The temperature differences between middle and high latitudes that drive the jet stream have declined, slowing that vast river of air. And that has affected seasonal weather patterns: Storms are becoming simultaneously more sporadic and more intense. Some climate models predict that the number of extreme rainstorms worldwide will double with each one-degree-Celsius increase in global warming, a trend that already may be under way. Heavy spring rains in 2019 led to record-high lake levels and widespread flooding across the Great Lakes region.

As we drove along the shoreline on the northern outskirts of the city, LeBeau said that a winter storm early in 2019 had covered the road we were on with four feet of sand and gravel. “We’re looking at another three years of construction—assuming we don’t get another big storm.”

Five hundred fifty miles to the southeast, on another summer day pregnant with rain, a small group of women clustered around a red, diamond-shaped sign on a beach in Maumee Bay State Park, on the shore of Lake Erie a short drive from Toledo, Ohio. What they read troubled them: “DANGER Avoid all contact with the water. Algal toxins at UNSAFE levels have been detected.”

The women, students from Bowling Green State University, had been swimming in the greenish water and had somehow missed seeing the sign before. We were the only ones on the beach, and when I approached, they asked questions I couldn’t answer: Would they be OK? How dangerous were the toxins? “We’ll never come back to this beach,” said Marharita-Sophia Tavpash, visibly shaken, as she and her friends hurried back to their car.

Since the early 2000s, harmful algal blooms have plagued Lake Erie almost every summer. The Great Lakes host a variety of algae and similar organisms, and most of them, like diatoms, are essential for the lakes’ health. But some can choke the life out of lakes. Most problematic are cyanobacteria, ancient organisms present in nearly every body of water. Given the right conditions—warm, polluted water—they grow explosively, forming slimy, green scum. When the algae decompose, they suck oxygen from the water, creating large dead zones, sometimes releasing toxins that can be fatal to wildlife. In humans they can blister the skin and damage the liver.

As recently as 25 years ago, algal blooms seemed to be a problem of the past. Before Congress passed the Clean Water Act in 1972, blooms had blighted the lake year after year. But the legislation imposed strict regulations on sewage treatment plants and led to the removal of phosphates from laundry detergents. Algae thrive on phosphorus; without large influxes of the element, the blooms can’t grow. For one halcyon decade, the lake remained bloom free. (Too much fertilizer is harming the Great Lakes.)

So why have the blooms returned? To meet the people who solved that mystery, I drove to Heidelberg University, in Tiffin, Ohio, whose 125-acre campus in the state’s corn belt houses what some scientists call a national treasure: a meticulous, 45-year record of the chemicals that flow into Lake Erie from two large tributaries, the Maumee and Sandusky Rivers. The collectors and proud curators of that trove are two women who have devoted more than 40 years to the task of diagnosing Lake Erie’s ills.

“We predate the EPA,” said Ellen Ewing, over lunch at one of the university’s dining halls. “We’re older than Earth Day!”

Ewing, who has short gray hair and the crisp, assured manner of someone who knows her work inside and out, was talking about Heidelberg’s National Center for Water Quality Research, founded in 1969. She has worked there since 1976, right after graduating from the university. Ewing started two years before her longtime colleague and fellow Heidelberg alum, Barbara Merryfield, sitting next to her at our table. Their job titles are lab manager and research associate, respectively—neither has a Ph.D.—but the data they’ve amassed over the decades have enabled researchers to understand the puzzling resurgence of Lake Erie’s algal blooms.

Every week for more than 40 years, Ewing, Merryfield, and their small team have collected water samples from the Maumee, Sandusky, and other watersheds. “I used to drive 500 miles a week,” Merryfield said. “I was out three days a week. Quite a few involved being stuck in the mud up to our axles.” With her strong build and denim shirt, she still looked capable of dealing with a mired four-by-four.

“When Barb had a work anniversary, I calculated the number of samples she had processed,” said Laura Johnson, an environmental scientist who has directed the center since 2016 and whose own work has been pivotal in unraveling the algal bloom conundrum. “It was way over two million, and I know that’s an underestimate.”

Every year they collect roughly 10,000 samples, testing each for 11 different parameters, Ewing noted, between bites of a salad. “We’re wickedly efficient.”

All that sampling revealed that a conservation practice that was supposed to improve the lake’s water quality has had the opposite effect. In the 1990s many farmers in the lake’s watershed incorporated “no-till” agriculture. Instead of plowing fertilizer into their fields every spring, farmers started to spread pellets onto the fields’ surface. The reduction in plowing did reduce soil erosion, but it unexpectedly has increased the amount of algae food flowing into the lake. When phosphorus was plowed eight inches or so into the ground, it remained tightly bound to the soil. But with phosphorus pellets sitting in the upper inch or two of the soil, the phosphorus dissolves and washes into the lake whenever the soil becomes saturated with rainwater. Researchers now use spring rainfall data to forecast the severity of algal blooms.

The number of days with two inches of precipitation or more has more than doubled in the past two decades, Johnson said: “That’s the big problem.” But, she added, it’s a problem we can fix. Johnson’s mentor, Jennifer Tank, an ecologist at the University of Notre Dame, has been working with farmers on ways to reduce runoff from their fields—and to prepare them for the rigors of a new climate era.

The same heavy spring rains that washed phosphorus into Lake Erie forced farmers in the region to delay their spring planting in 2019. Fields were so wet and muddy that farmers fell weeks behind.

“A record number of acres weren’t planted this year [2019],” said Kaleb Kolberg, a 26-year-old farmer in Hartford, Michigan, about 12 miles from the shore of Lake Michigan. Most people couldn’t plant on one-quarter of their land. Pointing to one of his own fields behind his home, he said, “That corn would normally be twice as high. We planted in conditions we never planted in before. We usually harvest corn in mid-September. This year it will be mid-October.”

It had been a stressful year—on top of all the normal challenges of farming life. “It costs $600 to raise an acre of corn,” said Kolberg, a muscular former college linebacker and self-described farm nerd. A single tractor costs $300,000. “You take all the risks up front and hope it pays off in the fall.” Kolberg fared better than most. Working with Colleen Forestieri and Erin Fuller of the county conservation district and with Jennifer Tank, Kolberg had been planting cover crops of ryegrass and crimson clover for several years to protect his land during the off-seasons. Driving around southwestern Michigan with Kolberg in his pickup on a hot August afternoon, across a landscape planed by glaciers, even a lifelong urbanite could spot the farms that had planted cover crops. The corn grown on fields without them was noticeably shorter, sometimes by several inches; some fields weren’t planted at all—they were just too wet for tractors. Some still held pools of standing water.

Kolberg said he was able to plant on more of his farm than his neighbors were able to plant thanks to cover crops, which pulled moisture out of the ground. “With cover crops, we’re ready for the two extremes,” he added, “too much water and too little.”

Besides keeping farmers such as Kolberg in the black, the widespread use of cover crops would cut off the flow of nutrients that fuel algal blooms. “We need to protect every square inch of ground,” Tank said. “That would be a game changer. We need watershed-scale cover crops.”

For all their advantages, cover crops are a hard sell. “Cover crops require all the same care as regular crops,” Tank said. Farmers don’t make money on cover crops.

For now, fertilizer runoff from many farms remains unregulated under the Clean Water Act, even after a phosphorus-fueled bloom shut down the water supply of a major city.

On Friday, August 1, 2014, at about 7 p.m., Toledo’s director of public utilities received a call from the department’s chief chemist. Routine tests of the city’s water showed that it had been contaminated with microcystin—an algal toxin. Advising residents to boil their water wasn’t an option—it would only concentrate the poison. So at 2 a.m., the city issued a “do not drink” advisory. For more than two days, until the water was treated, nearly half a million Toledo residents couldn’t drink from their taps.

Six years later, the catastrophe still rankles Wade Kapszukiewicz, Toledo’s current mayor. “It caused businesses to close,” he said. “It caused hospitals to not be able to do surgeries—if there’s no water, there’s no surgery. It was a traumatic event for our region.”

His office, 22 floors above downtown Toledo, overlooks the Maumee River. Three years ago, he said, when a bloom on Lake Erie spread upriver, the Maumee looked as if it had been dyed green. The city has spent more than a billion dollars to upgrade its stormwater system and water-treatment plant, including improvements to filter and eliminate microcystin and a buoy with special sensors that monitor the extent of algal blooms near the city’s water-intake pipe in Lake Erie. So a repeat of the crisis is unlikely—a reassuring bit of knowledge during a pandemic. Imagine a city without water now.

But Toledo, Kapszukiewicz said, is still paying a price for the unregulated release of phosphorus and other fertilizers into the lake. The problem is that not all farmers are as conscientious as Kolberg. “I don’t need to be awake at 5:10 tomorrow morning to know that the sun will rise in the east,” Kapszukiewicz said. “I also don’t need to make yet another visit to yet another farm to know that agricultural runoff is polluting Lake Erie. Everyone already knows that. The only question is: What are we going to do to stop it?” he said. “I am not anti-farmer. I am antipollution. I know that many farmers are trying often very bold technologies to reduce agricultural runoff. The biggest problem is caused by these megafarms, especially CAFOs. This is not mom-and-pop farming.”

CAFOs, concentrated animal feeding operations, are essentially factories for raising animals—a pig, poultry, and beef industrial complex. When the number of animals on a CAFO exceeds EPA limits, the CAFO must comply with clean water laws, but many operate just under the legal limits and escape regulation. A recent study found that from 2005 to 2018, the number of farm animals in the 8,300-square-mile Maumee watershed, the largest in the Great Lakes, more than doubled from nine million to 20 million. The amount of manure applied to fields during that same period—a rich source of phosphorus—increased by about 40 percent.

Without more stringent restrictions on phosphorus runoff, algal blooms will become a permanent fixture of Lake Erie. One scientist told me that if current trends continue, the occurrence of blooms will double by 2040. “This is not a money problem,” Kapszukiewicz said. “It’s an accountability problem. All the money in the world isn’t going to solve it without accountability.”

The lakes’ immensity belies their fragility. Over the course of several months I visited all the lakes except Huron. Being young, in geological terms, they’re not as ecologically diverse as the oceans; they’re immature, more susceptible to threats. Each lake deserves its own story: Michigan and Huron, which are in effect two lobes of a single lake, have the opposite problem from Lake Erie: They’re too clean.

Hundreds of trillions of invasive mussels have nearly denuded their waters of plankton; the mussels can filter the amount of water in Lake Michigan in a week or less. Mercury and PCB levels in the Lake Ontario watershed are so high that many fish there are unsafe to eat. I met with dozens of researchers who have devoted entire careers to understanding and protecting the lakes. Charter boat captains told me how algal blooms have gutted their livelihood. And I learned that harmful algal blooms have started to appear on Lake Superior, the least spoiled of the lakes.

So where does that leave us? The fate of the lakes—and of the millions of people who depend on them—might best be described by an Anishinaabe word: zaasigaakwii, which has no real English equivalent.

“It refers to birds arriving in spring, then [they’re] hit by a big storm,” says Michael Wassegijig Price, a traditional ecological knowledge specialist at the Great Lakes Indian Fish and Wildlife Commission. “It’s what happens when you get hit with the unexpected in nature.” Like multiple 500-year storms in a decade or algal blooms on a northern lake.

Eighteen years ago Tom Borg had his own experience of zaasigaakwii. On a February day he drove his snowmobile onto the frozen lake near his home, something he’d done on countless other winter days. He wasn’t far from the forested shore when the ice suddenly gave way beneath him. Luckily the water was only three feet deep—“but just as darn cold as 30 feet,” Borg said. “The pain was extreme, like daggers into my legs.” Somehow he managed to pull his snowmobile from the lake and drive back to his cabin, where he started a fire that warded off certain hypothermia. “If it wasn’t for my grandfather’s teachings to keep my wits about me and don’t panic, I might not have survived.”

On a cool September morning, Kama Bay, an inlet on the northern edge of Lake Superior, looks serene, untainted—not endangered by anything at all. It soon vanishes from view as Borg and I ascend a steep, maple-lined trail off the inlet’s shore. Some maples seem to glow, the season’s alchemy turning their leaves flame red. We pass a stream and small waterfall, whose waters would soon reach the Anishinaabe’s Great Lake and eventually spill over Niagara Falls. With each step up the trail, the threats to the continent’s five freshwater seas momentarily recede, becoming problems of some other world, some other time.

Borg pauses and suggests that I take a maple leaf home as a gift from the watershed, a talisman as fragile and lovely as the lake below us. Later, reflecting on the day he almost died from exposure, he said that perhaps he hadn’t been as careful as he should have been—maybe he could have looked more closely at the ice, maybe he would have seen the danger ahead. “Nature isn’t mean,” he said. “It’s unforgiving.”

Tim Folger wrote about the Arctic’s dwindling sea ice in the January 2018 issue. Keith Ladzinski photographed America’s changing national parks for the December 2016 issue.

This story was updated on July 30, 2021.

The Nature Conservancy works with farmers to reduce the flow of phosphorus into the Great Lakes by planting cover crops and other practices. nature.org
Friends of the Detroit River is restoring waterways and land in Michigan and Ontario, with a focus on the Detroit River. detroitriver.org
The Ojibwe (an Anishinaabe tribe) consider wild rice sacred and have grown it for centuries. Purchasing it from the tribe injects cash into the local economy and helps promote sustainable development. LLwildrice.com

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