• On Mexico’s Pacific coast, sea level rise and infrastructure projects have eroded 8.4 meters of coastline per year since 1967.
• In the community of Cuauhtémoc, San Mateo del Mar, at least 900 Indigenous Ikoots people are increasingly affected by flooding, as homes and streets give way to the sea.
• The community voted to relocate in May 2025, but bureaucratic delays are hindering the process, and many lack the funds to leave the community on their own.

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CUAUHTÉMOC, Mexico — On a wind-battered beach in San Mateo del Mar, Mexico, four figures haul a net into shore. Frigatebirds (Fregata magnificens) mark the fishers’ position in a high, twisting column that follows their progress from the water onto the beach. One of the men tosses a small fish onto the sand. It barely comes to rest before a dark bird wheels down from the sky to claim it.

The man is José Rangel Edison, 57, a fisher from the community of Cuauhtémoc, an Indigenous Ikoots community of 900 people in the municipality of San Mateo del Mar, on Mexico’s Pacific coast.

“In the past, the sea used to be over there,” Edison says, pointing to the horizon across the cresting waves. “But since I was 18, when I started fishing, it’s been coming in little by little. Now it has almost wiped out Cuauhtémoc.”

Edison’s community is perched on a slim stretch of land between the ocean and a large lagoon system. Now, rapid se level advance is displacing residents and disrupting daily life. According to a report from the Autonomous University of San Luis Potosí, the Pacific Ocean consumed 8.4 meters (27.5 feet) of Cuauhtémoc’s land per year between 1967 and 2014, while locals describe a larger encroachment of around 1 kilometer (0.6 miles) since the first half of the 20th century.

Two Cuauhtémoc residents walk past a dead tree as they make their way toward the ocean. Image by Euan Wallace for Mongabay.

The effect on the landscape has been profound. By the shoreline, the concrete bones of old houses lie half-buried and abandoned. Strong northerly winds whip clouds of sand onto the dry husks of dead trees and rough shrubbery.

“I can clearly see how it was before: the houses, the streets, the people who lived there,” says Gabriel Pinzón Leyva, 51, a police officer and the local authority in Cuauhtémoc. “I carry them in my mind because I lived them — I grew up in this place, on those streets.” Beneath a palm-leaf canopy at the local police station, Leyva looks toward the ocean, now only 100 m (328 ft) from where he is sitting.

In 2007, Felix González Piamonte, 55, was the first from the community to be displaced. “You can’t see my house anymore,” he says, speaking of the home he once shared with his wife and children. “Now it’s beneath the waves.” Piamonte says they were forced to move to another plot of land around 1.5 km (0.9 mi) from the beach.

“I was worried for my children; they were still small. I was afraid that a wave could come and pull us out of the house or sweep us away,” he remembers. “When the waves fell, the house would shake.”

Today, locals report community-wide flooding taking place twice per year, between March and April and again in September, that leaves residents stranded in their homes, unable to work or attend school. The well that once served the community has now been contaminated with saltwater, leaving residents to rely on the nearby Tehuantepec River for drinking water. But locals say it isn’t reliable. “[The water] arrives one day per week,” Edison says. “It isn’t enough for us.”

Gabriel Pinzón Leyva, a police officer and the local authority in Cuauhtémoc, sits on the wall of an abandoned home. Image by Euan Wallace for Mongabay.

Complex causes

Despite increasingly precarious living conditions in Cuauhtémoc, uncertainty remains around their causes.

According to a 2024 report published by the Ministry of Agrarian, Territorial and Urban Development, “The locality has been affected year after year by rising sea levels, accompanied by heavy surf caused by the ‘mar de fondo’ phenomenon.” This phenomenon consists of powerful waves formed by offshore storms.

But some scientists say climate change and natural phenomena alone cannot explain the extent of the coastal erosion seen in Cuauhtémoc.

According to José Antonio Ávalos, 65, an investigator at the Autonomous University of San Luis Potosi who led a 2023 government-commissioned study on the problem in San Mateo del Mar, sea level rise due to human-caused global warming does not exceed global averages, totaling around 16 centimeters (6.3 inches) in the area between 1902 and 2015. He says that’s not enough to cause all the flooding Cuauhtémoc residents are experiencing. “Of course climate change has an influence,” he says, “but only a marginal one.”

Instead, Ávalos points to the construction of the Benito Juárez Dam on the Tehuantepec. The 947-million-cubic-meter- (33,400-cubic-foot-) capacity dam began operations in 1961 and is owned and operated by government water authority CONAGUA. “Before the construction of the Benito Juárez Dam, the Tehuantepec River carried a very significant amount of fine sediment,” Ávalos says. “Because a dam was built upstream, all of those sediments are trapped in the reservoir. They no longer move down toward the beach.”

Satellite images of Cuauhtémoc in 2004 and 2025 indicate an extensive loss of land to the sea. 2004 image by Maxar Technologies, INEGI via Google Earth. 2025 image by Airbus, INEGI via Google Earth.

Ávalos argues that the lack of sediment replenishment is the key driver of coastal loss in Cuauhtémoc. He notes that erosion lessens progressively with increasing distance from the Tehuantepec’s discharge area.

Locals also blame the construction of new breakwaters in the nearby port of Salina Cruz, around 17 km (10.6 mi) from Cuauhtémoc. Inaugurated by former President Andrés Manuel López Obrador in February 2024, the breakwaters form part of the Isthmus of Tehuantepec Interoceanic Corridor, a government megaproject aimed at creating a trade and transit link between Mexico’s Pacific and Atlantic coasts.

The breakwaters are intended to facilitate the entry of larger commercial vessels into the port, and many locals suspect the diversion of ocean currents has led to increased coastal erosion in the vicinity of Cuauhtémoc. “When they began building the breakwaters, it accelerated,” says Leyva, the police officer.

A view over the breakwater recently constructed in the port of Salina Cruz. Part of the Isthmus of Tehuantepec Interoceanic Corridor (CIIT), the breakwater is designed to allow larger ships to enter the harbor, but residents of Cuauhtémoc say it is contributing to coastal erosion. Image by Euan Wallace for Mongabay.

Time to relocate

While uncertainty persists around the causes of sea level advance in Cuauhtémoc, consensus remains around one issue. The community “must be relocated,” Ávalos says, “because within a decade, the entire neighborhood will be flooded.”

In May 2025, a community assembly in Cuauhtémoc voted in favor of relocation. But Cuauhtémoc faces many challenges before the move can become a reality.

“Many people are still here, but there’s no way for them to relocate because of money,” Leyva says. “People can’t leave.” Though some residents have been able to buy land farther from the beach, many cannot afford the roughly 50,000 pesos ($2,895) that locals say an adequate parcel of land costs.

The municipality has requested support from the federal government, and local authorities say federal officials first visited the community to discuss it in 2023. But progress is slow. “Just meeting the bureaucratic requirements will take time, and then there’s the funding needed to carry out the projects,” says Raúl Rangel González, 42, the municipal president of San Mateo del Mar, who holds a doctorate in advanced studies in human rights. “The requirements they set for us to be able to do this feel like a wall that cannot be passed.”

Although the location of the new settlement has already been identified — an area known as Polygon 3A roughly 5 km (3.1 mi) from Cuauhtémoc — it includes land owned by people outside of the community. González says negotiations must take place with the owners of this land before the relocation can be finalized. Once the location has been confirmed, local authorities remain hopeful that federal funding will cover the costs of the infrastructure needed to build and sustain the new community.

Meanwhile, some residents are frustrated by continual delays. “They’ve been talking about relocation for more than five years now, I think — but no, nothing,” Piamonte says. “A village like ours — especially since we’re Indigenous, a community with our own mother tongue — that doesn’t matter to the government.”

Though relocation is widely accepted as a necessary step, the prospect of leaving a long-inhabited home carries an emotional cost for many residents. “We don’t want to leave,” says Gualteria Leyva, 74, who was born in Cuauhtémoc and has lived here ever since. A strong wind whips her hair as she speaks. “We’ve lived here our entire lives,” she says. “We aren’t used to living anywhere else.”

Like many here, Gualteria Leyva has seen friends and neighbors move away from the community. “People have already left,” she says, “and now the sea floods their homes.” Soon, Leyva accepts, she may have to join them.

Felix González Piamonte was one of the first to be displaced in Cuauhtémoc. A baker by trade, here he is pictured in the tuk-tuk he drives around the community. Image by Euan Wallace for Mongabay.
Homes abandoned due to the advance of the Pacific Ocean lie half-submerged by sand on the beach in Cuauhtémoc. Image by Euan Wallace for Mongabay.

The next generation

As they move into a precarious future, the thoughts of many residents are with the next generation.

Camilo Pinzón Edison, 48, is standing opposite the community church. A young girl is pulling at his sleeve as children file out of the nearby school, arranging themselves in small groups across the church’s weather-beaten steps. “We’re almost going now, we’ve already lived our time here,” he says. “What worries us are our children, the ones who are coming after us.”

In a house a few blocks away, Isidro Pinzón Leyva, 42, props up a large painting against his desk. A local artist and brother of Gabriel, he has tracked the progressive erosion of the coast by painting three maps of the community, each showing the position of the shoreline at a different moment in time.

His finger traces the length of a blue line on the canvas. It represents the Timiti’u’d Canal, a water channel that many years ago was consumed by the sea. “In this canal, we used to go fishing, and sometimes we’d pull little fish out from among the tree trunks,” he says. “It’s something that no longer exists. And maybe these children are able to play and enjoy themselves here now, but tomorrow their children won’t be able to. They will have a different kind of childhood.”

In the light of the lowering sun, Isidro Leyva’s own young boy plays on the floor of his studio. Above the wind can be heard the sound of distant waves.

Isidro Pinzón Leyva, a local artist, in his home in Cuauhtémoc. Behind him, three of his paintings depict maps of the community at different times, tracking the progress of coastal erosion. Image by Euan Wallace for Mongabay.

Banner image: Ikoots fishers haul a net into shore off the coast of Cuauhtémoc, San Mateo del Mar, Mexico. Overhead, frigatebirds attempt to steal fish from the net. Image by Euan Wallace for Mongabay.

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