By Laura Cruz
The construction of buildings, shopping malls and roads increasingly hinders the route that blue crabs take every year from the mangrove to the ocean to reproduce.
Urban development and poor ecological planning translate into habitat loss for this threatened species.
Crabs are key to maintaining mangrove health and experts warn that their disappearance could cause the entire ecosystem in the area to collapse.
Every year, thousands of blue crabs emerge from the mangroves of the Riviera Veracruzana and make their way to the beach. It's a spectacle that happens at nightfall, even in the midst of concrete and urban noise. Between June and September, thousands of blue crabs (Cardisoma guanhumi) are guided by the full Moon to the ocean where the females, after being fertilized, release their larvae that, later, return to the mangroves to grow and complete their life cycle. The problem is that today this journey is a race full of obstacles. Crabs must cross illuminated avenues, busy roads and walled subdivisions [built-up areas divided into lots or houses with their own infrastructure such as streets, services and common areas].
The Veracruz Riviera is a coastal strip that has experienced the biggest real estate boom in the state of Veracruz in the last decade. There, the Veracruz-Boca del Rio conurbated area, located between the municipalities of Medellín and Alvarado, has been gradually transformed with luxury real estate developments.
Progress is measured in oceanfront towers and shopping malls that promise exclusivity and social status. However, a silent battle is being waged on the asphalt and the perimeter fences: the survival of the blue crab, an emblematic species of coastal ecosystems.
Off the coast of Veracruz, you can see tall buildings that affect the blue crab route. Photo: Laura Cruz.
Real estate expansion, driven by the tourist boom, together with urban development lacking ecological planning, fragments the blue crab's habitat and alters the natural cycles that have sustained their existence. Specifically, urbanization has invaded mangroves, destroyed burrows and obstructed migratory routes, leaving blue crab no space to complete their life cycle.
From 2005 to date, the Ministry of Environment and Natural Resources (Semarnat) has approved a total of 58 subdivisions and, according to environmentalists, this has meant that this species faces its greatest threat today.
“What for some represents progress, for this species means a countdown,” warns Carlos Alberto Butrón Valenzuela, a marine biologist with the association Justice and Citizen Awareness, an organization that has managed to obtain protection and file lawsuits on key environmental issues for the region.
The risk, in addition, is that the blue crab plays a key role for ecosystems that could be affected by the decline of the species.
“The blue crab not only oxygenates the earth, it also regulates ecological balance and supports vital processes for biodiversity. Its disappearance would involve much more than biological loss, it would be the beginning of an environmental collapse in the region,” warns César Meiners Mandujano, a researcher at the Institute of Marine Sciences and Fisheries of the University of Veracruzana.
Blue crab habitat loss
In the Veracruz Riviera, more and more subdivisions are being built a few meters from the mangrove, an ecosystem protected by the General Law of Ecological Balance and Environmental Protection and the Official Mexican Standard NOM-059-SEMARNAT-2010. In this way, more fences [a structure built to delimit, protect or divide spaces, commonly used in land, houses or facilities] stand in the way of the blue crab, blocking its path to the sea and putting its life cycle at risk.
“Previously, habitats changed over 40 or 50 years, allowing species to gradually change their way of life or their migration trajectories. However, with the new urbanization, an environment changes in a matter of months and there is no time for species to adapt, causing tremendous chaos”, warns biologist Carlos Butrón.
The obstacles not only arise in the journey that crabs undertake every year to reproduce, but on a daily basis, their survival has also become a challenge.
In this year 2025, 58 subdivisions have been authorized in the area. Photo: Laura Cruz.
“They need an open space to build their burrows and go out at night to look for food,” Meiners explains. “In addition, with less space, there are fewer burrows and fights begin between themselves over territory and food,” adds the expert.
One of the most important habitats for the species is the Mandinga Lagoon, belonging to the municipality of Alvarado, which is part of the Riviera Veracruzana. This environment has been profoundly altered. Natural dunes have been leveled for the construction of subdivisions, plant species alien to the ecosystem have been introduced and, according to Butrón, “large subdivisions dump their wastewater into the lagoon in the background, which is the Mandinga lagoon”. According to the expert, “although they are supposedly treated waters, they damage the environment, they change the pH and the ecological balance of plants and fish that live and that deposit their young in those areas”.
Mandinga Lagoon is one of the most important habitats for blue crab. Photo: Laura Cruz.
Mongabay Latam tried to consult the Alvarado City Council to confirm the information provided by Butrón, but until the publication of this note, we received no response.
What is a fact is that the Mandinga Coastal Lagoon System (SLCM) underwent significant transformations in the last 17 years.
According to scientific research published in 2021 by the Autonomous Metropolitan University, the area of the mangrove forest decreased by 107 hectares between 2000 and 2017, representing an annual loss rate of 1.02%. According to the study, the main factor contributing to that loss is the growth of human settlements.
Scientists around the world have been warning about the importance of conserving mangroves for decades. The fact is that these are key ecosystems for the fight against the climate crisis since they protect the coasts from storms, are great carbon storers and are the habitat of numerous species, including the blue crab.
Every time there are new buildings in the Riviera Veracruz. Photo: Laura Cruz.
For this reason, mangroves are protected under the Official Mexican Standard NOM-059-SEMARNAT-2010, where they are classified as a “Threatened” forest species.
In 2016, Sergio Armando González, president of the Earth Mission Association, led the first blue crab rescue campaign in the Riviera Veracruz. The campaign consists of helping crabs to cross from one side to the other and raising awareness among the inhabitants of the area to respect the natural and reproductive cycle of the species.
One of the people who decided to participate in the rescue in 2025 was Ana León, a university student and creator of the blog Let's Talk About Biology. Along with other volunteers, he was stationed at the entrance to Mandinga for several nights—before, during and after the full moon in August—to help the female crabs on their way to the sea to spawn and carefully return the males to the mangrove.
“The truth is that it is impossible to go down Mandinga, which is where the most crabs come out. The first thing they run into is the road. If they cross the road, they cross a shopping plaza, and then they cross another subdivision. It's impossible for a crab to get past all these obstacles. What we do is make their way easier,” he explains.
The number of copies rescued has been decreasing over the past three years. In 2023 there were 7000 and in 2024 only 2000. This year was the most critical since it is estimated that only 500 crabs managed to be assisted in a period of three months.
An ecological clock in countdown
The blue crab is a true ecological engineer that supports life in mangroves. By removing soil during excavations, it oxygenates it, accelerating the decomposition of organic matter and favoring other species. Therefore, its disappearance could trigger the collapse of an entire ecosystem, Mainers warns, affecting fishing, coastal protection and biodiversity.
“It's not that the blue crab is completely disappearing, because its distribution ranges from Massachusetts to Brazil, including the Gulf of Mexico. But in that specific location, their presence could be extinct,” he says.
In this area of the country, the blue crab is at risk. Photo: Laura Cruz.
Currently, blue crab fishing has a ban that coincides with their spawning season. The goal is to get their populations back on their feet. Margarito Enríquez, representative of the Boca del Rio Fishermen's Federation, recalls that previously the catch of blue crab was abundant. “In a single night, we could collect 20 to 30 dozen crab hands [front legs that serve primarily for food and defense]. Today the figure has fallen by 90%,” he laments.
The decline is such that several years ago the dozen sold for up to 80 pesos (4.36 dollars), but currently their market price exceeds 200 pesos (10.89 dollars). Although many fishermen have redirected their efforts to catch other species, they recognize that the loss of mangroves and the decline in the blue crab population have profoundly affected their profession.
“Previously, we caught blue crab with our hands. We went to the banks of the rivers, near the mangroves and there we would find him,” says the fisherman.
Authorities and Developers: Between Progress and Conservation
Dozens of real estate agencies are promoted on the internet and with large advertisements offering luxury and exclusivity, but since 2008 the municipality of Alvarado has no updated land planning program, which limits adequate planning for urban and environmental development in the region. According to the Semarnat Ecological Gazette, 14 real estate, tourism and commercial projects were evaluated between January and September of this year.
Blue crab specimens have to cross roads to reach the sea. Photo: Laura Cruz.
In the Riviera Veracruzana there are no wildlife passes, nor concrete actions to counteract the damage, but there are citizen proposals. This year, a campaign was launched on Activate, a digital platform that encourages social participation to generate concrete actions. With the collection of more than 7000 signatures, the inhabitants of the Veracruz Riviera asked the Semarnat and the National Aquaculture and Fisheries Commission to grant immediate legal protection to blue crab spawning areas, declaring themselves as temporary shelters, as well as the prohibition of fishing and construction activities during their breeding season.
They also asked the Alvarado City Council and the Government of the State of Veracruz to require subdivisions and real estate developments to include ecological corridors or tunnels for wildlife, so as to protect blue crab migratory routes. The Federal Attorney's Office for Environmental Protection and the Municipal Police of Alvarado were asked to apply sanctions against illegal fishing, carry out night operations and establish fines for those who catch or trade this species out of season. It was also proposed to the Institute of Ecology and the Ministry of Environment of Veracruz to implement a program for the repopulation of blue crab.
With the exception of the Alvarado mayor's office, Mongabay Latam did not receive a response from the Government of the State of Veracruz to know if progress is being made in concrete actions to protect the species.
In Alvarado, Veracruz, there are people who are making efforts to rescue the blue crab. Photo: Laura Cruz.
According to the municipal government of Alvarado, “the Riviera grew disproportionately in years before [the current administration] and right now all we have left is to look for the best opportunities.” According to Mayor Lizzete Álvarez Vera, “all we have to do is respect our wetlands, our mangroves, respect the habitat area of the blue crab, but those who have land in the Riviera Veracruz and want to develop it don't have to restrict the development of a city. We cannot restrict the development and growth of a municipality, a city or an area, because the blue crab passes along the road or travels along the road.”
As a representative of the Green Ecologist Party of Mexico, the mayor emphasized her commitment to a “green” government. However, in practice, the city in the Riviera Veracruz continues to grow with new subdivisions, many of them approved through Environmental Impact Manifestations (MIAs) whose legitimacy has been questioned.
For Butrón and Meiners, the decision to protect the blue crab should involve municipal, state and federal governments, since if the species disappears, the balance of an entire ecosystem would be threatened.
* This text is part of a journalistic alliance between Mongabay Latam and Causa Natura.
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