LLAPALLAPANI, Bolivia — The water receded and the fish died. They surfaced by the tens of thousands, belly-up, and the stench drifted in the air for weeks.

The birds that had fed on the fish had little choice but to abandon Lake Poopó, once Bolivia’s second-largest but now just a dry, salty expanse. Many of the Uru-Murato people, who had lived off its waters for generations, left as well, joining a new global march of refugees fleeing not war or persecution, but climate change.

“The lake was our mother and our father,” said Adrián Quispe, one of five brothers who were working as fishermen and raising families here in Llapallapani. “Without this lake, where do we go?”

Agustina Rios Moya, 22, with her daughter in the ruins of a family house.

David Alejo Valero, 6, with hay for hat-making.

After surviving decades of water diversion and cyclical El Niño droughts in the Andes, Lake Poopó basically disappeared in December. The ripple effects go beyond the loss of livelihood for the Quispes and hundreds of other fishing families, beyond the migration of people forced to leave homes that are no longer viable.

The vanishing of Lake Poopó threatens the very identity of the Uru-Murato people, the oldest indigenous group in the area. They adapted over generations to the conquests of the Inca and the Spanish, but seem unable to adjust to the abrupt upheaval climate change has caused.

Only 636 Uru-Murato are estimated to remain in Llapallapani and two nearby villages. Since the fish died off in 2014, scores have left to work in lead mines or salt flats up to 200 miles away; those who stayed behind scrape by as farmers or otherwise survive on what used to be the shore.

Emilio Huanaco, an indigenous judicial official, is down to his last bottles of flamingo fat, used for centuries to alleviate arthritis. He has never used medication for his aching knee.

Eva Choque, 33, sat next to her adobe home drying meat for the first time on a clothesline. She and her four children ate only fish before.

They and their neighbors were known to nearly everyone in the area as “the people of the lake.” Some adopted the last name Mauricio after the mauri, which is what they called a fish that used to fill their nets. They worshiped St. Peter because he was a fisherman, ritually offering him fish each September at the water’s edge, but that celebration ended when the fish died two years ago.

“This is a millenarian culture that has been here since the start,” said Carol Rocha Grimaldi, a Bolivian anthropologist whose office shows a satellite picture of a full lake, a scene no longer visible in real life. “But can the people of the lake exist without the lake?”

‘We accepted the lake was going to die someday.’

It is hard to overstate how central fishing was to Uru life. When a New York Times photographer, Josh Haner, and I asked Mr. Quispe whether he had made his living as a fisherman, he gave us a strange look before answering, essentially, “What else is there?”

Men spent stretches as long as two weeks without returning to shore, wandering the lake to follow schools of karachi, a gray fish that looked like a sardine, or pejerrey, which had big scales and grew as long as Mr. Quispe’s arm.

Some wives worked alongside their husbands, to pull the nets and do the cooking, making the boats a kind of home.

Fishing season began on the lake’s edge with a ritual called the Remembering. The Quispe brothers were among about 40 Llapallapani men who would pass a long night chewing coca leaf and drinking liquor. Together, the group recited the names of Lake Poopó’s landmarks and how to find them.

“That night, we would ask for a safe journey, that there would be little wind, that there wouldn’t be so much rain,” Mr. Quispe, 42, told us. “We remembered all night, and we chewed our coca.”

Migalena Quispe, right; her husband, Severo Mauricio Quispe; and their son, Nemar.

A mother and child in Llapallapani, whose lifeblood was always fishing.

In the morning, the men would paddle out above the underwater springs known as jansuris. They would toss sweets from the boat as a religious offering. Fishing season had begun.

We were talking on a cloudless morning with a breeze that might have been perfect for a boat ride in another time. Now, the wind only underscored how dry the landscape had become, as tumbleweeds rolled between the boats abandoned on the old lake bed.

Milton Pérez, an ecologist at Oruro Technical University, said scientists had known for decades that Lake Poopó, which sits at 12,140 feet with few sources of water, fit the profile of what he called a dying lake. But the prognosis was in centuries, not years.

“We accepted the lake was going to die someday,” Mr. Pérez said. “Now wasn’t its time.”

Lake Poopó is one of several lakes worldwide that are vanishing because of human causes. California’s Mono Lake and Salton Sea were both diminished by water diversions; lakes in Canada and Mongolia are jeopardized by rising temperatures.

Generations of Uru had watched the water recede and return in what had almost become a predictable cycle. In the 1990s, a dry spell hit that evaporated the lake into three small ponds and destroyed the fisheries for several years. But the lake eventually returned to its previous size.

The Uru passed down knowledge about living on and around the lake. Crowds of large black birds on the horizon were an easy sign that fish were congregated below. They counted three distinct winds that could help or hurt: one from the west, another from the east, and a kind of squall from the north called the saucarí, which can sink boats.

“It awakens from the north and it doesn’t calm down,” Mr. Quispe explained. “ ‘The saucarí is coming,’ we’d say. ‘We can’t go into the water until it calms!’ ”

The lake offered algae called huirahuira, which seemed to relieve coughs. Flamingos were like a pharmacy: In addition to the pink fat used to relieve rheumatism, the feathers fought fevers when burned and inhaled.

Gabino Cepeda, his sister-in-law and his daughter harvesting quinoa.

The villagers would catch and kill the flamingos in April, when the birds lost their feathers and were rendered flightless. The Uru used mirrors to cast sunlight in the birds’ eyes, making them fall asleep temporarily, easy prey.

“We took so many of these from the lake,” said Mr. Huanaco, the judicial leader, pulling out a bright pink wing from the mud hut behind his home. The day seven years ago that he hunted the bird down, he had no idea it would be his last.

‘I will figure out how to make money.’

Mr. Pérez, the researcher, watched with alarm as several threatening trends developed, and began to understand that the lake could evaporate for good.

First, as quinoa became popular abroad, booming production of the grain diverted water upstream, lowering Lake Poopó’s level. Second, mining sediment was quickly silting the lake from below.

And it was getting hotter. The temperature on the plateau had increased 0.9 degrees Celsius, or about 1.6 degrees Fahrenheit, from 1995 to 2005 alone, much faster than Bolivia’s national average.

“We had the possibility that all these factors would hit with a synergy never seen before,” Mr. Pérez said.

Emilio Huanaco with his last flamingo wing.

Feathers have been caked into the dry bed of Lake Poopó.

In the summer of 2014, a rotten smell hung in the air. The surface of the lake had fallen so low that when the saucarí wind hit from the north, the gusts kicked up too much silt for the fish to survive.

“It was enough to make you cry, seeing the fish swimming dizzy or dead,” Gabino Cepeda, a 44-year-old fisherman who has turned to farming quinoa, told us. “But that was just the start. The flamingos are dead, the ducks are gone, everything else. We threw out our nets, there was nothing for us.”

Mr. Quispe and his brothers met one last time on the edge of the dead lake to perform the Remembering. They paddled out as they always had, but returned the same day because there were no fish.

The eldest, Teófilo, turned to his brothers.

“There is no work,” he said. “I will figure out how to make money. And I will tell you how.”

The next week, he left Llapallapani to work in a coal mine an hour’s drive away.

‘The Uru people aren’t made for this.’

Pablo Flores, another Uru fisherman who left Llapallapani, starts a thankless workday before sunrise inside a mill on the edge of the world’s largest salt flat, Bolivia’s Salar de Uyuni. He takes blocks of unrefined salt, grinds them down into a pile as high as he is tall, and puts them into tiny bags, earning 25 cents for each full one.

Some of the Uru-Murato people, Bolivia’s oldest indigenous group, now work in salt flats.

Outside the mill, it is more arduous. In the vast salt flat near the town of Colchani, where two dozen Uru have resettled, day laborers head out with shovels in the backs of trucks. They gather the salt as the heat beats down on them from above and reflects up from the white expanse below.

“The Uru people aren’t made for this,” Mr. Flores, 57, said. “I’m not made for this. We can’t do this kind of work.”

In his village, Puñaka, Mr. Flores was a respected elder. He was once its mayor, and people who knew him from that life still call him by the Spanish honorific “don.” As a fisherman, he was always his own boss.

But at the salt mine, he feels like just another hired hand to exploit.

Alfredo Choque, once a fisherman, now makes his living processing salt.

Erminia Miranda Moya packaging salt from the Salar de Uyuni flats.

“This is a feudal system,” he said. “I can sincerely say this is a bad place.”

Looking over the heap of salt, he remembered an old legend, about a flood that destroyed the world — except for the Uru, who escaped on their balsa rafts and hid on a hilltop when the water began to recede. Disasters were meant to take the form of deluge, not drought, he said.

Some Uru men have left alone, sending money back to relatives who remain on the lake. But others, like Mr. Flores, have taken their families into a new world that has already begun transforming life in ways large and small.

Fifteen Uru live in Machacamarca, a dusty town of several thousand that was once a stop along an old railroad line to the lake. María Flores Ignacio and her two teenage children moved this spring into a rented apartment, a first for Ms. Flores, whose adobe home in Llapallapani was handed down through generations.

Juana Choque has begun selling handicrafts to make ends meet.

Ms. Choque’s family, like so many others in Llapallapani, used to depend on fish.

“I am living in someone else’s house,” she said with a long sigh.

To pay the rent, Ms. Flores makes straw handicrafts that she sells to tourists in the state capital, Oruro, at a Saturday market. There are hats, baskets, bracelets, earrings and small boats like the ones the Uru used to navigate Lake Poopó.

‘We fight each other now.’

Back in Llapallapani, Mr. Cepeda, the fisherman-turned-farmer, wants out, too. But he doesn’t have the money.

When the fish died, Mr. Cepeda staked his hopes on quinoa, an ancient crop in the Andes that is now in vogue in Western countries.

The dry bed of Lake Poopó near Llapallapani.

He had inherited two hectares of land — about five acres — from his father. He did not quite know how to plant quinoa, but he scattered the seeds in the ground and hoped for the best.

Instead of luck, Mr. Cepeda got a devastating frost, which struck in March. Picking up a handful of the quinoa, he showed us his meager harvest, mostly pulverized. It blew away from his palm. Only a few grains remained that weren’t dust.

Severina Choque, 27, carried bundles of quinoa from the fields.

Former fishermen have begun growing quinoa instead, but a frost cut the harvest in half.

The lake had always been what mattered to the Uru, not the ground, Mr. Cepeda told us. But that was changing.

“We fight each other now,” he said. “Here is my land. But someone says, ‘Now you are encroaching.’ And then someone else says, ‘No, that’s mine.’ ”

‘I want to teach my child to fish. But I can’t.’

Francisco Flores, now 26, was a child when his grandparents told him about the day the Uru-Murato first tasted meat.

It was the start of the 20th century, and the Uru had decided to leave the lake’s floating islands made of reeds and mud and settle on its edge. They wore shoes for the first time and gave up dresses made of feathers or wool for Western clothes. After centuries of eating only fish, they tried lamb, Mr. Flores recalled being told, and “it was tough.”

A century later, the Uru have hit a crossroads again, but one not of their choosing.

“I want to teach my child to fish,” Mr. Flores said, stopping on the dirt road that leads to the cemetery filled with his forebears. “But I can’t.”

Another day, Mr. Haner and I followed Felix Condoni, Llapallapani’s mayor, to a city market to buy vegetables for the first time. He used to barter with the Aymara Indians, whose pastures lie north of the village, trading fish for potatoes and quinoa straight from his boat.

Now, instead, he counted out bills from a wad with his wife and mother, the three looking confused.

The mayor, who carries a cane used to punish village delinquents, reached out with his other hand to buy a bottle of Axe deodorant spray.

“This is all new to us,” he said.

Simona Seceda buying vegetables in nearby Challapani. People used to come to Llapallapani with produce to trade for fish.

Felix Condori, left, the mayor of Llapallapani, with his wife, mother and daughter. He now works in construction.

On the highway back from the salt flat with Adrián Quispe one day, we saw a flamingo perched on the side of the road, by a stream 100 miles from Lake Poopó. It made Mr. Quispe suddenly remember the soup his mother used to make.

We stopped the car, got out and walked into a watery landscape with snowcapped mountains in the distance and birds in front of us.

“This is what Lake Poopó once looked like,” Mr. Quispe said.

An hour before, I had been in the salt mill with Mr. Flores, the former Puñaka mayor who moved to Colchani with his wife and two young children two years ago.

When he last took them back to Llapallapani for a visit, his 6-year-old daughter said something that gave him chills. She was staring at what used to be the lake, having never really known it not to be dry.

“Let’s go to Colchani,” she said. “Let’s go home.”

To some children, Llapallapani does not feel like home.