Turn up the volume! Listen to the howler monkeys crossing an aerial wildlife bridge on the Palenque-Playas de Catazajá highway in southeastern Mexico. This is one of the few successful wildlife crossings (specifically designed for this purpose) in the country. Video courtesy of Biota Corporativo Ambiental

In Mexico, one of the five most megadiverse countries in the world, wildlife crossings are essential to protect thousands of species living in ecosystems fragmented by roads and other development. However, they are scarce and often ineffective in the country. The Mexican state’s insufficient action, legal and regulatory gaps, and public lack of awareness are some of the obstacles preventing the establishment of more structures to reconnect habitats and ensure the safe movement of wildlife for biodiversity conservation.

Note: This story was updated on October 21, 2024, to include information about the publication of the N-LEG-3-24 standard. See The Legal Gap section.

Welcome to Mexico, a biodiversity paradise that hosts 10% of all species on the planet. This country is home to the world's largest variety of reptiles (864 species) and ranks second in mammal diversity, only behind Brazil (496 species). With around 360 species of amphibians, 1,800 butterflies, 1,150 birds, and 23,424 vascular plants, Mexico is a treasure trove of wildlife. Additionally, its richness extends to fungi and microorganisms.

However, this extraordinary biological wealth is in grave danger. In the past 30 years, Mexico has lost nearly 40% of its wildlife, and more than 2,600 species are at some level of risk of extinction- due to climate change, pollution, deforestation, and ecosystem fragmentation. The rapid expansion of linear infrastructure megaprojects, such as the Tren Maya and the Isthmus of Tehuantepec Train in the southeast, or the so-called “ghost train” in Ímuris, Sonora, as well as roads, gas pipelines, border walls, and other projects, are fragmenting habitats and disrupting the connectivity crucial for the survival of numerous species.

Over the past 10 years, Wildlands Network has led the first road ecology program in Northwestern Mexico, documenting the severe impacts habitat fragmentation has had on Sonora's wildlife due to infrastructure projects, primarily roads. Simultaneously, it has promoted wildlife crossings as the most accessible and effective solution, not only to mitigate these effects and ensure wildlife can continue to thrive but also to prevent accidents that affect people.

Various wildlife species crossing through culverts and tunnels, captured by Wildlands Network cameras in Sonora

It was good news when, in November 2023, an article was added to the Federal Highways, Bridges, and Motor Transport Law making wildlife crossings mandatory in the country's road infrastructure. This marked the beginning of a paradigm shift in favor of ecosystem connectivity.

The changes to the law bring hope for promoting effective wildlife crossing practices in Mexico, which, as of now, can barely be counted on one hand. “The current state of wildlife crossings in Mexico consists of isolated cases, projects, and efforts that are not being communicated with each other,” explains Mirna Manteca, co-director of Wildlands Network's Northwest Mexico Program. “Real wildlife crossings, like those in other countries, with fences, sidewalks, or overpasses? Those practically don't exist, except for a few rare cases. There are drainages and tunnels used as wildlife crossings, but they were not built with that intention and are not always useful for wildlife.”

Promises vs. Reality. In Southeast Mexico, a region of immense floral and faunal diversity, with jungles, underground water systems, and mangroves, the government is promoting the Tren Maya (“Mayan Train”), a 1,525 km railway project.

Home to jaguars, anteaters, ocelots, monkeys, foxes, turtles, and snakes, among 170 species at risk, the Mayan jungle is being fragmented like never before. Although the train was announced as “the most environmentally careful project in Mexico,” with over 500 wildlife crossings, environmental groups have denounced that so far only a few transversal drainages without the minimum characteristics to protect animals' free passage have been documented. The displacement of wildlife caused by this megaproject has also increased the number of roadkill incidents. Photos by: Fonatur/Tren Maya (left), Guillermo D´Christy/Sélvame el Tren (right)

The Legal Gap

However, despite these changes in the law, the main obstacle to the effective implementation of wildlife crossings in Mexico remains, curiously, the legal gap. These reforms require a framework that clearly details how wildlife crossings should be implemented in Mexico. "Ideally, there should be regulations that define the characteristics of the structures according to the type of wildlife, the studies to be conducted before and during implementation, the necessary maintenance and its frequency, as well as the penalties for those who do not comply with the law, among other things,” explains Gina Chacón, Director of Public Policy for the Mexico Program.

To date, we have only seen progress in the publication, in June, 2024, of the N-LEG-3-24 standard which explicitly states that a transportation infrastructure project must include the implementation of wildlife crossings. “It does not mention details about the characteristics of the wildlife crossings, the maintenance and the budget to be taken into account for their implementation and sustainment, which leaves many questions and legal gaps,” explains Gina.

This legal gap is exploited by construction companies and the authorities themselves to avoid building the necessary wildlife crossings or to do so "at their discretion" and, at best, following the general guidelines of the SICT, which signify progress but are clearly insufficient.

Solidifying a standard legal framework is, therefore, urgent. According to Gina, “there is no valid excuse to justify the authorities' lack of action on this issue. It reflects that the Mexican state does not prioritize environmental policy and still sees it as an agenda for only for times in which there is extra budget.”

And budget is scarce, not only for environmental programs but also for road infrastructure. Mexican roads currently receive less than half the budget they had five years ago, and just last February, the Road Conservation Program was announced as canceled, with the news that these tasks, previously handled by contractors, would now fall under the responsibility of the military. “Budget cuts translate into a lack of quality road projects,” explains Mirna. “To restore ecological connectivity, we not only need scientific data and appropriate legislation. We also need to allocate sufficient funds for the implementation of mitigation measures where they are needed.”

Rare video footage of a jaguar caught on camera using a bridge to cross under a highway in Sinaloa, Mexico. Video by Wildlands Network and partners

What Is Not Counted Does Not Exist

In addition to the legal gap, there is a lack of official statistics. “We have not been able to find sufficient data on wildlife roadkill or complete information about its impact,” says Mirna Manteca. “The SICT has very little information; in some cases, they only report these as ‘accidents with moving beings.’” The lack of vehicle insurance (only 27% of cars in the country are insured) and the fact that such incidents are not reported to insurers, as they are in the United States, Canada, or other countries, is another factor to consider.

While there are several initiatives to report road-killed wildlife, such as this collaborative platform by INaturalistMX in which Wildlands Network participates, or the Wildlife Road Mobility and Mortality Observatory for Mexico (a project of the Mexican Transportation Institute, closed to the public), they are partial efforts to document a problem that is far more serious.

One of the news headlines following Wildlands Network's report on the roadkill of a female black bear on the Ímuris-Cananea section of Highway 2 in Sonora. Headline by ADN40

Just looking at the news gives an idea of the impacts of habitat fragmentation and the lack of wildlife crossings. For example, in the two years following the construction of the Villahermosa-Escárcega highway in the state of Tabasco, the population of howler monkeys, an endangered species, was halved in an 8-kilometer stretch. In Sonora, Wildlands Network's monitoring between 2016 and 2019 on a section of Federal Highway 2 documented over 330 road-killed animals belonging to 43 species, seven of which are under some category of protection. This highway crosses the Sky Islands region, an important ecological corridor for jaguars, black bears, and ocelots.

Without statistics and data, it is difficult for the Mexican state to recognize that this is a public issue that deserves immediate attention: “We need to assess and conduct a real count of what it means for wildlife crossings not to exist and recognize that habitat and ecological corridor fragmentation ultimately affects the quality of life of communities and people,” says Gina Chacón.

The research and monitoring work of the Wildlands Network Mexico team on Federal Highway 2 in Sonora

Step by Step

Biologists Mirna Manteca and Cecilia Aguilar from the Wildlands Network team have been invited to dozens of meetings with hundreds of government officials, SICT engineers, contractors, and “whoever will listen,” as Mirna says, to explain, with scientific information presented in an accessible way, why ecological connectivity is important and the urgency of developing good practices for wildlife crossing construction in infrastructure projects. “There are information gaps in Mexico about wildlife movement that need to be filled,” she explains.

This is a dissemination effort, “planting seeds” among the new generations of professionals, but also “catalyzing these conversations among people in power” around road ecology, which is gradually bearing fruit. According to Mirna, “Mexico is at the point where it will start doing things right. Fortunately, there is increasing interest and awareness, at least among SICT officials, and we see that it is recognized as an issue among decision-makers.”

Mirna Manteca, Wildlands Network Northwest Mexico Program Co-director, explaining the importance of ecological connectivity at one of the symposia of the Mexican Association of Road Engineering (AMIVTAC)

Gradually, some success stories are also emerging, thanks to affected communities demanding that governments place "well-made" wildlife crossings. Additionally, environmental impact assessments for some projects, prior to the execution of works, are being conducted by technical teams (biologists, ecologists, engineers) with more preparation and knowledge about road ecology.

Another good piece of news is that more organizations are working on road ecology. Given the interest and growing participation around the topic, Mirna Manteca wants to promote a civil society working group to share data, knowledge, and technology, advocate, and promote public access to information.

“My dream is to have an interactive and collaborative map of all existing wildlife crossings in Mexico. Like the one Wildlands Network created for California, United States, which includes 244 wildlife crossings and 62 priority sites for new projects. A map of this type would show all the work that remains to be done, but also demonstrate that we are making progress, little by little,” she says.

Gina also sees opportunities in this context. She hopes that the pending standard will be an opportunity to do things right: strengthen the legal framework and open the doors to technical collaboration between different government levels, organized civil society, and other institutions that have much to contribute. Besides raising the issue to public policy design, “I think more conversations should be opened with the population and develop environmental education programs at all levels.”

Yes, there is a long way to go, but for Gina Chacón, today, more than ever, “there is political will to implement well-planned, executed, and monitored wildlife crossings in both ongoing and completed projects. The priority must be to guarantee habitat connectivity in this country with immense biological diversity.”

We thank Patricia Cruz from Biota Corporativo Ambiental and Gilberto Pozo-Montuy from Conservación de la Biodiversidad del Usumacinta A.C. (Cobius) for providing valuable information for this story.