Nueva Venecia, Colombia — Leaning over the side of a small speedboat, John Cantillo picks up a thick clump of bright green vegetation, and holds it up before pointing toward the horizon, where the plant stretches across the water as far as the eye can see.
From above, the plant forms dense, almost carpet-like mats that spread over the surface. Upon closer inspection, its long strands extend deep beneath the water, with roots reaching the lagoon bottom, making it difficult to remove completely.
scenes unfold from colombia Ciénaga Grande de Santa Marta, a vast coastal wetland on the Caribbean coast about 30 kilometers (19 mi) from downtown Santa Marta. What until recently was a lifeline for fishing and transportation is now being strangled by dense vegetation, turning it into a looming environmental crisis.
“What we see here today is a problem. It not only affects movement or fishing, but affects the entire community,” said Cantillo, 32, a local environmental and social leader from Ciénaga Grande de Santa Marta.
Over the past year, residents say a fast-growing invasive plant native to Asia – Hydrilla verticillata – has spread rapidly throughout the wetland after first appearing in mid-2025. Dense vegetation, which some locals call “horsetail”, is blocking fishing routes, clogging waterways and restricting access to areas where residents collect water, while increasing costs in communities that depend almost entirely on the lagoon for their livelihoods.
The Ciénaga Grande de Santa Marta is one of Colombia’s most important fishing ecosystems, serving as a nursery for many species.
In Nueva Venecia and Buenavista – two isolated fishing communities built almost entirely on wooden stilts above the water – large stretches of open water are now covered by the invasive plant. The communities themselves are largely informal and exist outside many basic state services.
Nueva Venecia – the older of the two, founded as a fishing settlement in 1847 – is home to about 4,500 people living in 500 colorful houses. Buenavista, which emerged in the 1950s, has about 1,150 residents and 163 equally lively houses, where residents travel between houses, shops and schools by small boats or canoes.
“A year ago, there was fishing here by canoe. Teachers and students would cross the lagoon. Today, what we see is a problem,” Cantillo said.
This is having an impact on already vulnerable communities. Fish catches have declined, transportation has become more difficult and families face rising costs as they are forced to purchase potable water.
In Nueva Venecia, a small-scale fisherman stood shirtless in the midday heat, pulling delicate fibers of dried vegetation from his fishing net, which he had laid out in the sun to make them easier to clean.
“We can’t work because of this plant,” said 61-year-old Sandra Cueto. “It doesn’t let us cast our net – everything gets tangled.”
What was once a routine task now takes much more time.
“The lagoon is completely covered. There is nowhere left to fish,” said Demosthenes Guerrero, a 58-year-old fisherman and representative of the fishing union in Buenavista.
In some areas, groups of residents go out in wooden boats to cut narrow “lifeline” passages through the dense vegetation, allowing canoes to pass without engaging their propellers. These efforts are labor-intensive and largely community-driven, and must be repeated every few days as the fast-growing plant quickly closes the routes again.
The wetland covers approximately 428,000 hectares (1,600 sq mi) of lagoons, mangroves and swamps – approximately the size of Los Angeles – and has been a UNESCO Biosphere reserve since 2000.
Ciénaga Grande de Santa Marta gets food Magdalena River — one of Colombia’s main waterways — that carries untreated wastewater from much of the country, said Julián Arbeláez, a water and sanitation engineer who works in the region.
When water slows down in such wetlands, the flow of nutrients, including nitrogen and phosphorus, creates ideal conditions for invasive species.
“That load causes the river to enter a state of eutrophication,” Arbelaez said, referring to a process in which excess nutrients promote rapid growth of plants.
Vegetation is also blocking access to clean water sources. Residents usually travel by boat to collect fresh water from channels connecting the Magdalena River, but many of those routes are now blocked. As a result, Arbelaez said, people are increasingly collecting water closer to their homes — often in areas contaminated with untreated sewage.
Residents say another invasive plant, Eichhornia crassipes, which floats on the water’s surface, has long been present in the lagoon and also disrupts fishing and transportation, although its impact has been less sudden.
Local leaders say changes in water flow have also contributed to the crisis, with freshwater now dominating areas where salt water once helped suppress or kill Hydrilla verticillata.
Sandra Vilardi, a professor at the Universidad de los Andes who has a doctorate in ecology and has worked in the field for nearly 20 years, said there is still limited research on how the plant came to be and the current explanation remains a hypothesis.
He said one of the most likely routes is marine transport, in which the plant could potentially enter through major river systems before spreading into wetlands via small vessels and dredging activity. Another possibility, he said, is aquarium plants being released into waterways, a common cause of biological invasions globally, though he said that explanation seemed unlikely in this case given the environmental conditions of the region.
“It’s a monster in terms of growth,” Cantillo said, describing how it went from a limited presence at the beginning of last year to entire communities within months.
Even attempting to remove it can make the situation worse, as fragments may break off and spread further. Residents say efforts to remove the plant have been largely limited to small-scale manual cleaning by fishermen and sporadic pilot efforts by authorities, with no effective solutions on a larger scale.
The crisis is now leading some residents to consider leaving altogether.
“We now face a risk that we did not face 20 or 25 years ago – the risk of mass displacement,” Cantillo said.
Protests and road blockades have already taken place as locals grow frustrated with the government’s slow and inadequate response.
Alfredo Martínez, director of CORPAMAG, the regional environmental authority, said that Hydrilla verticillata is not officially classified as an invasive species in Colombia and that national guidelines for its control are still pending. Surveillance and eradication efforts are underway with the participation of the local community, he said, adding that no further expansion has been observed since March and low water levels may slow its spread.
César Rodríguez Ayala, a community leader in Nueva Venecia, said the crisis is affecting almost every aspect of life.
“If the fisherman can’t work, the shop doesn’t sell,” he said. “We are living in a very difficult situation economically and environmentally.”
According to Cantillo, while mechanical removal methods exist, complete eradication is unlikely in the short term due to high costs and limited capacity.
“We are also part of Colombia,” Rodriguez said. “We live on water, but we also deserve to be seen and helped in a moment like this.”
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