On a sunny day in August, more than two dozen brown bears are gathered at Brooks Falls, in Alaska’s Katmai National Park, to feast on sockeye salmon. Thousands of the fish are delayed or stranded here by the six-foot waterfall, a hurdle they must leap over to return to their native spawning grounds upstream. The bears occasionally growl at each other, competing for the best fishing spots.

A huge male known as Lefty, who has white scars on his flank from past battles with rivals, perches on the upper rim and snags salmon out of mid-air. Every few minutes, Lefty catches one and ambles to a wet rock to devour it, leaving behind guts and bones. After eating about 20, he retreats to a shallow spot in the middle of the river to rest, dazed from gorging himself and unfazed by the current, water dripping from his tousled coat.

Mere feet away, on a raised wooden platform, dozens of people jockey for the best vantage point. Cameras and phones out, they watch, spellbound, talking over the rumbling waterfall and the shrieks of glaucous gulls fighting for leftovers.

The bears don’t seem to notice.

“These bears have come to agree that humans are pretty much okay,” says Larry Aumiller, who for 30 years ran the camp at McNeil River State Game Sanctuary and Refuge, to the east, where as many as 80 bears have been seen at once. People involved in bear-watching have discovered that if you’re careful and respectful, the bears view humans as a neutral presence; in turn, the animals present little danger to us, he says. Indeed, no human deaths or serious injuries have happened in the normal course of bear-viewing, adds bear biologist John Hechtel. (At Moraine Creek, to the west of McNeil in Katmai, one large male walked within 10 feet of me to reach a fishing spot, unconcerned by me and my camera-wielding colleagues.)

View Images A female known as T Bear nurses her year-old cubs in the tidal flats of McNeil River State Game Sanctuary and Refuge. Augustine Volcano, which last erupted in 2006, is in the background. Bear advocates worry a proposed mine corridor to the north could negatively affect the animals. Photograph by Acacia Johnson, National Geographic

“To see this many bears in one place is a huge testament to how pristine the entire ecosystem is,” says photographer Acacia Johnson, who’s been visiting these spots for years with her mother Leslie and father Kirk, a former dentist, bear guide, and accomplished bush pilot based in Anchorage, whom I traveled with to see the animals.

On the Alaska Peninsula, a vast area nearly the size of Maine between Bristol Bay and Cook Inlet, brown bears outnumber human residents several fold. About 8,000 to 10,000 brown bears live here, a fifth of North America’s total. These bear populations, the densest in the world, are made possible by the region’s unparalleled abundance and diversity of salmon—hundreds of millions of them, including all five Pacific species, return each year from the ocean to breed in myriad lakes and rivers.

Mine threatens Alaska wild The proposed Pebble Mine has faced heated opposition in the Bristol Bay region. Opponents fear development of the mine and its sprawling transportation corridor would disrupt wildlife habitat and movement and present a risk for accidents like spills of toxic metals. Fairbanks ALASKA Proposed Pebble Mine Anchorage Juneau Bristol Bay Mine poses potential threat to Alaska wild Fairbanks ALASKA The proposed Pebble Mine has faced heated opposition in the Bristol Bay region. Opponents fear development of the mine and its sprawling transportation corridor would disrupt wildlife habitat and movement and present a risk for accidents like spills of toxic metals. Proposed Pebble Mine Anchorage Juneau Bristol Bay Mining claims Sources: Pebble Partnership; Alaska Department of Natural Resources

Male coastal brown bears can weigh up to 1,500 pounds at their fish-fattened peak in autumn, making them among the largest in the world. Though they are very similar to grizzlies, they are bigger and also tolerate being in close quarters with each other, thanks to the fish feast, making them star attractions when they congregate to feed at places like Brooks Falls and McNeil River Falls.

These unique conditions have given rise to a robust bear-viewing industry. Dozens of tour operators fly in tens of thousands of visitors to see the animals each year, bringing in $36 million a year to the region, according to a recent study.

At the most popular bear-viewing spots, people know the animals as individuals. Millions around the world watch the Brooks Falls webcam, which the National Park Service operates 24/7 in summer. Many of the bears have been given names, and in October, viewers vote in the Fat Bear Week contest, to determine which bear is best prepared for winter. (Lefty was a finalist this year.)

But the bears, and the sustainable industry that’s grown up around them, face a new threat. The proposed Pebble Mine, which would tap into the world’s largest unexploited deposit of gold and copper, would drastically change this undeveloped region and potentially affect the behavior, and even survival, of its unique brown bears.

The mine proposal from Pebble Partnership, owned by Canadian mining company Northern Dynasty Minerals, is working its way through the federal permitting process. The project has ignited intense backlash in the Bristol Bay region, where a majority of residents oppose it, as polls have repeatedly shown. The bay and its waterways comprise the world’s largest sockeye salmon fishery, which provides jobs for 14,000 people.

Many in the salmon industry are concerned that runoff from the mine and the destruction of salmon streams during mine construction would degrade the fishery. In 2014, the Environmental Protection Agency agreed, concluding the mine would present an unacceptable risk to Bristol Bay’s watershed. It would lead to “complete loss” of important fish habitat and irreversible ecosystem degradation, according to the EPA at the time.

View Images The bears at McNeil Falls are uniquely habituated to small groups of bear viewers. Summer permits to visit McNeil River are distributed via a lottery system, allowing only 10 people per day.

Photograph by Acacia Johnson, National Geographic

But Alaska Governor Mike Dunleavy and President Donald Trump have both enthusiastically endorsed Pebble. After the pair met aboard Air Force One in June, the EPA announced July 30 it would no longer oppose the project. The Army Corps of Engineers, which oversees the federal permitting process, is expected to complete a final environmental review and approvals this year. Construction could begin as soon as 2024.

Opponents also fear a catastrophic collapse of one of Pebble’s earthen tailing dams, which would hold hundreds of millions of tons of mining waste. Representatives for Pebble say treated runoff wouldn’t significantly impact the fish and that the dams would be engineered to prevent failure. The mine would employ an average of 850 people during its planned 20-year life.

Anything that would decrease populations of salmon, the base of the food web, could affect the bears. But biologists and guides are particularly concerned about the sprawling transportation corridor that would serve the mine—and edge close to some of the best bear-viewing spots.

View Images A young adult brown bear fishes for salmon underneath the visitor boardwalk at Brooks Camp, in Katmai, where in summer some 400 people a day come to see the animals. A system of boardwalks, trails, and viewing platforms makes it easy to watch the bears. Photograph by Acacia Johnson, National Geographic

The corridor would include a natural gas pipeline and 80 miles of roads that could interfere with bear movement, according to the draft environmental impact statement released by the Army Corps last February. Vehicle collisions could kill bears, and the corridor could create new conflicts between humans and bears. The animals could become more aggressive if they learn to associate humans with food, biologists say; they could also become scared of people and avoid popular bear-viewing spots. Finally, new roads in this undeveloped, remote wilderness could spur future mining, and make it easier to hunt the animals.

Mike Heatwole, Pebble Limited Partnership’s vice president of public affairs, says the mining operation won’t harm bears. “It’s our view that our operation can fully function without degradation to the bear-viewing experience,” he says.

“We’ve spent a lot of time on the bear issue, and I don’t see it as a significant risk from the transportation corridor,” adds Pebble CEO Tom Collier. He says the corridor is far enough away from viewing locations to have a minimal impact.

A route through the wild

In August, bush pilot Kirk Johnson flies Acacia and me over McNeil Falls in a single-engine aircraft. Even at 2,000 feet, we can see dozens of brown bears in the river, feasting on chum salmon.

View Images Visitors watch bears eat sedge grass in the salt marsh at Chinitna Bay, with the dramatic peaks of the Aleutian Range in the background.

Photograph by Acacia Johnson, National Geographic

In the distance, the dramatic peaks of the Aleutian Range ring the coast along Cook Inlet, sloping down to rolling tundra and wetlands. The land is wet and green, with thousands of lakes and streams flowing through meadows and stands of pine and alder.

Thirteen miles to the north of McNeil Falls, Pebble plans to build a port at Amakdedori Beach, on Cook Inlet, to transport concentrated copper and gold.

Waves, wind, and storms pummel this wild coast. A massive driftwood berm created by the tempestuous weather stretches the length of the beach; extreme tides have pushed logs and other detritus miles inland. Bob Shavelson, who runs the environmental organization Cook Inletkeeper, says this is “one of the nastiest places for running a boat.” Both the weather and the shallows of Kamishak Bay, just offshore, make it “one of the most unforgiving navigational settings in the world.”

View Images Flowers bloom along Amakdedori Creek and Beach, the proposed site for Pebble Mine's industrial port. Here, barges would be loaded with containers of concentrated metals from the mine, 55 miles northwest. The barges would bring the containers to a ship anchored in the bay, which is known for shallow reefs and violent weather.

Photograph by Acacia Johnson, National Geographic

Regardless, the bay could soon be a docking station for barges and ships at the end of the mine’s transportation corridor—which bear advocates worry could be more disruptive for bears than the mine itself.

The corridor would begin some 55 miles northwest, at the mine site, where copper and gold ore would be turned into concentrate, creating acidic waste that would be stored there in perpetuity. The concentrate would be sealed in containers and trucked to a new port on Lake Iliamna, Alaska’s largest. From there, an ice-breaking ferry would carry the containers across the water, to another port, where they’d be transferred to trucks and driven to the proposed shipping port at Amakdedori Beach. Barges would take the ore to an ocean-going vessel anchored in the bay, and that ship would bring the concentrate to a smelter for further processing.

On that last stretch of road, the 37 miles from Lake Iliamna to Amakdedori Beach, vehicles would pass every 18 minutes. The route would cut through roadless wilderness and prime bear denning territory, says Dave Crowley, a biologist who oversees the region for the Alaska Department of Fish and Game. At its closest, the road would come within less than a mile of McNeil River State Game Refuge, and it would bisect an important wildlife corridor running between Katmai National Park to the south, the McNeil refuge to the southeast, and Lake Clark National Park to the north.

Many of the bears that fish at McNeil in the summer move north of the proposed corridor route to den, Aumiller says. With a road there, bears would be at risk of getting hit by cars and killed, and some deaths are inevitable, says Sean Farley, a biologist with the fish and game department.

James Fueg, another Pebble spokesperson, says the company would limit driving speeds to 35 miles per hour, teach employees to avoid wildlife, report sightings, and stop traffic if necessary to avoid collisions.

The draft environmental impact statement says potential consequences from the road include “loss of habitat due to land conversion, increased mortality from vehicular collisions … and behavioral changes based on avoidance of humans.” Even with this warning, the report has a major shortcoming, says biologist Derek Stonorov, who was stationed at McNeil River Camp from 1990 to 2000 and has studied coastal brown bears for more than 50 years. The assessment only considered impacts to bears within a three-mile radius of the road, which is insufficient considering they travel up to 80 miles a year, he argues.

“It’s a travesty that they would want to put a road in there,” Stonorov says. “It’d be the end of that whole area.”

Unpredictable mammals

At bear-viewing hotspots, attacks are essentially unheard of, says Aumiller. While he has been charged a couple times, he’s never had to use his shotgun or bear spray, which guides carry. “Bears have the reputation of being dangerous and unpredictable, and they are neither of those,” says Chris Day, a long-time bear-viewing guide.

View Images Fireweed blooms in the foreground as visitors watch brown bears walk through the edge of the McNeil River campground. Photograph by Acacia Johnson, National Geographic

Almost all attacks are caused by humans behaving badly, such as leaving food out or startling bears, says Michael Saxton, a Brooks Camp ranger. “It's very challenging to learn how to operate around large, unpredictable mammals, but somehow the bears seem to have figured it out,” he says.

But this peaceful coexistence could be threatened if people traveling and working along the corridor feed the animals or leave out garbage, which could cause the animals to associate humans with food. On the other hand, non-lethal deterrent techniques, such as projectiles and noise-making devices, commonly used to keep bears away from human-occupied areas, could cause bears to avoid people and bear-viewing spots, Aumiller says.

“Bears that are negatively habituated to the project, or have become food conditioned, may become a danger to the public at bear viewing areas,” the Army Corps’ statement notes. When an animal becomes “food conditioned,” it means they associate humans with treats, which can make them bolder around people and thus more dangerous.

Pebble’s Heatwole says the company has a plan to “ensure this does not become an issue, and our approach to operations will be in line with [best] practice among Alaska industries.”

“We will do things such as fencing off the port and ensuring safe and appropriate handling and disposal of all food and waste,” he says.

Besides harmful associations, the road would create easier access for hunting, both legal and illegal, says state biologist Crowley. “Any time you open up a road in bear country, harvest and illegal killing tends to go up and reduce the bear numbers.”

For Aumiller, any loss of bears that have come to view humans as a neutral, safe presence would be “beyond tragic.”

“It’s like a betrayal of trust,” he says.

Gem of gems

At Brooks Falls, I meet people who know the bears like old friends. Kyle Mendel, a young man from Houston, loves to watch the webcam with his mom Kathi, who paints the bears in watercolors. He’s a fan of Otis, a bear who’s now sitting in a frothy hollow beneath the falls, stealthily feeling for salmon. Peter Brown, 80, a retired computer programmer from California, has been returning for decades. “This place kind of gets in your blood, and you want to come back,” he says.

View Images In the evening light, a brown bear called Fluffy grazes on sedge grass near the McNeil campground. Bear advocates worry that Pebble could lead to the deaths of animals that have learned to view humans as a neutral presence. That would be "beyond tragic," says Larry Aumiller, who ran the camp at McNeil River Falls for three decades. Photograph by Acacia Johnson, National Geographic

Naomi Boak, who does outreach for the park, comes to the Brooks Falls platform daily to answer questions. Originally from New York City, she learned about the bears in 2014 from the webcam.

“When I started watching,” Boak says, “I couldn’t walk, I didn’t have a job, and I had to have my hip replaced.” She got hooked. Earlier this year, a job in public relations opened up at Brooks Camp. Within weeks, she got the job and found herself moving to Alaska.

“I never thought I’d be here,” Boak says. “It’s the most incredible privilege.”

Watching the bears helped cheer Boak up. “I just think they’re fascinating creatures. They’re resilient, they’re smart, they’re playful, they have great stories.”

The Army Corps of Engineers is expected to finalize its environmental impact statement this summer. Soon after, Pebble hopes to receive a Record of Decision from the corps approving a permit under the Clean Water Act, the final major approval the company needs to move forward. Pebble would then go through state and local permitting process, Heatwole says, which takes three to four years.

While I’m speaking with Boak and the Johnsons, a large blonde female bear with large ears, called 128 Grazer, climbs onto the rim of the falls next to Lefty. In spring 2016, Grazer brought a trio of new cubs here. Previously more docile, she began challenging even the largest and most dominant males for access to prime fishing spots. The gambit could’ve killed her; instead, it worked. She successfully raised all three cubs, who finally left her side in 2018.

These kinds of surprises keep people coming back for a lifetime, Kirk says. “This is the gem of gems. It doesn’t get any better than this anywhere on the planet.”

Editor's note : Reporting for this story was assisted by a fellowship with the Institute for Journalism & Natural Resources .