Fishers, scientists restore mangroves on a Mexican isle wrecked by salt mining

  • For decades, salt mining has deteriorated the wetlands and natural flood patterns of Isla del Carmen, part of Bahía de Loreto National Park in Mexico.
  • Collaboration between two conservation organizations and a community of fishers on the mainland are working to restore the mangroves of Isla del Carmen by rehabilitating its hydrology and constructing “vegetation terraces” for the trees.
  • The project also involves training and educating communities about the importance of conserving the ecosystem for the sake of wildlife, the local economy and protecting against the effects of climate change.

In recent decades, salt extraction has taken its toll on the mangroves and wetlands of Isla del Carmen, in the Mexican municipality of Loreto. Since the start of the 20th century, salt mining even led to the creation of a town for workers traveling back and forth every day by boat. The industry boom ended in the 1980s, leaving only the ruins of buildings, machinery, a church and a dock. The island, situated in the Gulf of California, hasn’t been the same since. The severe environmental deterioration has left its mark.

“That activity has undoubtedly created deterioration on the island,” said biologist Arturo Peña, director of the Loreto office of Vida Silvestre (OVIS), a conservation NGO that has spent three decades helping protect the area. “In the process, they had to flood certain lagoons and allow the sun to do its job evaporating the water, to get the salt.”

Bahía de Loreto National Park was created in the 1970s to protect five islands, including Isla del Carmen. But the salt mine rush hit the southeast part of the island, called Bahía Salinas, where black mangroves (Avicennia germinans) grew.

“When salt extraction ended, the island was abandoned and the people who lived there returned to the mainland to form the community of Ensenada Blanca,” Peña said. Today, the children and grandchildren of the salt workers live there. And since 2021, they’ve been the ones restoring the Isla del Carmen ecosystems.

“There are 12 of us in the community — five women and seven men — and we’re fishermen. I’m in charge of organizing the trips and equipment,” said Alejandro Castro, community leader in Ensenada Blanca. A year ago, the group started cleaning the coastline in collaboration with CONANP, the federal agency that oversees protected areas. It was through CONANP that they made contact with OVIS and started working on the mangroves.

“We train and learn about the work that the mangroves do,” Castro said. “Now we know what they’re for. The plants produce oxygen. They’re what cleans the air and protects a lot of species, and also the coastline from hurricanes.”

In coordination with OVIS and the North American Center for Environmental Information and Communication (CICEANA), an NGO based in Mexico City, they’re working to rehabilitate the wetlands by cleaning the natural canals that were affected by the salt mine. They’re also building “vegetation terraces” out of sediment from the canals for planting mangrove seeds in. To date, they have 11,000 mangrove propagules.

Restoration in the community

Seen from the mainland, Isla del Carmen is an impressive 27 kilometers (17 miles) long and 9 km (5 mi) across, with desert vegetation serving as a home to a diverse species of bushes and halophytic plants. Mountain ranges of volcanic rock and alluvium make up 15,100 hectares (37,300 acres) of the area, with hills and plateaus rising up to 479 meters (1,572 feet) above sea level.

According to monitoring by OVIS, the fauna of the island includes 47 mammal, 19 reptile and one amphibian species. But the most abundant group is birds, with 86 species. The island is an important habitat for brown pelicans (Pelecanus occidentalis), magnificent frigatebirds (Fregata magnificens) and blue-footed boobies (Sula nebouxii). The area is also a nesting site for seabirds like the yellow-footed gull (Larus livens), osprey (Pandion haliaetus) and the American oystercatcher (Haematopus palliatus).

The geographical location of the wetlands also makes them important for migratory seabirds traveling along the Pacific migratory route.

Black mangrove seeds that sprouted in the 2023 season. Image courtesy of Gaspar Bautista/OVIS.

“The mangroves, wherever they are, are important,” Peña said. “They’re associated with coastal waterbodies that are also part of the life cycle of many important species for commercial fishing, starting with shrimp.” Mangroves on Isla del Carmen, among some of the northernmost islands in Mexico, also provide food to large mammals like blue whales (Balaenoptera musculus) and gray whales (Eschrichtius robustus).

The restoration site covers an area of 50 hectares (124 acres), where there are patches of mostly black mangroves. The project in Bahía Salinas intersects the flooded lagoons that were used for salt extraction and where the normal daily tidal flows were interrupted, modifying the ecosystem.

As Peña described it, “What we did was determine what the natural water flows flooding lagoons were like when they were completely open and active [with salt mining].”

The first step was allowing the passage of seawater into the lagoons again. The team of community members and specialists, working with picks and shovels, cleared the main and secondary natural canals to allow water to enter. Then came a tidal water pumping system, involving the installation of a pipe connecting the ocean with the lagoon.

“The salinity is really strong there because that water is stagnant; that’s one reason the mangroves haven’t grown,” Castro said. “That’s why the first step is making the canals to control the salinity from the ocean, so that the water comes in and out, and doesn’t become stagnant.”

“Although the different mangrove species can withstand high salinity levels, in a flooded lagoon for salt mining, we’re talking about 80 to 85 parts per million of salt concentration, which is hazardous to the species,” Peña said. “That’s why the idea is to introduce water that reduces the concentration of salt and allows the establishment of mangrove seedlings.”

The second step consists of making the terraces around each canal and planting them with mangrove seeds.

The vegetation terraces are made of sediment taken from the canals, Castro said. They’re rectangles of 4-5 m (13-16 ft) in length and 2 m (6.5 ft) in width, height enough that seawater doesn’t cover them. Each terrace is separated by 1 m (3 ft) from the next so that the water flows freely through each canal.

There are currently 40 terraces of that size and another along the open canals for feeding the new black mangroves, whose seeds were collected from the previous season by the community team. They’re in charge of spreading them using the “broadcast seeding” technique, which involves spreading the seeds randomly by hand.

“We also have red mangroves [Rhizophora mangle] in Bahía Balandra, on the other side of the island where we collect seeds, but they’re planted in a different way,” Castro said. “The seed is like a bullet. Then they are cut and buried at a more or less reasonable distance apart, a meter or a meter and a half [3-5 ft],” he said.

The project has been successful to date. Of the 18,000 propagules or germinations of black mangrove and 2,000 red mangroves, around 11,000 have managed to survive and grow.

The work also involves monitoring the current salinity of the wetlands to obtain technical information that can be useful for analyzing changes in water quality. Specialists measure the physiochemical characteristics of the water, including salinity, temperature and total dissolved solids at 11 different sampling sites each month.

The results have been positive. As of November 2023, the salinity has decreased considerably, according to OVIS studies. Results for the next studies, started in February 2024, will take some time to get back.

Educate to conserve

But the mangrove restoration project wouldn’t be complete without involving the community. In Ensenada Blanca, high school and college students, fishers, tourism workers and community leaders learn about the importance of conserving the ecosystems.

CICEANA specializes in environmental education and allied itself with OVIS. It worked on the social component of the project with the goal of acquiring financing from the SíMiPlaneta Foundation, which advocates for greater environmental awareness.

“If the community is going to live there forever, why not work and foster it with a culture of conservation?” said CICEANA operations director Arisbeth Rosales, a biologist specializing in conservation and community development. “This goes beyond saying that you shouldn’t litter or cut down mangroves. Instead, reflecting on why it is how it is, [why it’s] deteriorating. The community should know that context and how much it’s lost.”

Several workshops in the community have shown people the importance of conserving mangroves and the health of the oceans. The workshops include audiovisual components as well as dialogues, with opportunities for reflection.

“Disseminating this message goes beyond the people you speak to [in the workshops],” Rosales said. “For example, on the professional level, some students will go on to become teachers and they’ll finish their training and start working with other students, and they’ll replicate the message of doing things better for the good of the environment and our ecosystem.”

The same happens with tourism workers, who share what they’ve learned with visitors and other artisanal fishermen who, even though their fishing practices aren’t that invasive, are always looking to improve.

But the most touching work, Rosales said, is with children. A lot of them didn’t know the story of their own community. Now they know that a salt mine existed and that it caused the erosion of the island and the loss of the mangroves.

“Now there’s a sense of pride in the community, but they’re also aware that not everyone lives in a landscape like the one they live in and that it’s about to disappear if we don’t do something,” Rosales said.

This year, Rosales and other organizers hope to involve schools in the volunteer program. “We want them to plant mangroves or help with the activities. Let them sweat it out in the project so they become a little more aware of [what it involves]. They should know it’s a difficult thing to restore and that’s why we need to conserve it.”

In the future, said community leader Castro, he imagines Isla del Carmen with green landscapes and big mangroves where other species can live and reproduce without being threatened. To make that happen, they need to sow the seeds of sensibility and responsibility in new generations of residents.

“We’re even going to give talks at schools so that younger people have that on their minds, something we didn’t have as children. Before it was about taking them out to see the ocean. It’s not just about going out on the boat and making money. Now it has to be different,” the fisherman said. “One of the dreams I’ve always had is to give something back to the ocean. I’ve been on it for 30 years, because I’ve been fishing since I was 11. I want to instill in younger generations that good things can be done.”

Banner Image: Planting mangrove seeds on the main canal. Image courtesy of OVIS.

This story was reported by Mongabay’s Latam team and first published here on our Latam site on March 26, 2024.

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