Mexico reintroduced 47 bison in 2025 after more than 100 years: Just months later, the ecosystem is restoring itself

In northern Mexico, the reintroduction of dozens of bison in part of the Chihuahuan Desert is positively impacting the surrounding ecosystem in several major ways, says the body that is the driving force behind the initiative.

Last year, nearly 50 bison were brought into Cuatrociénegas, a UNESCO-recognized nature reserve in Mexico’s Coahuila state. Renowned for its gypsum dunes and its bright-blue pools of water, the 400,000-hectare habitat is home to several hundred plant and animal species – including multiple flora and fauna that are “critically vulnerable or endangered”, UNESCO warns.

“A fundamental species that was there before and should be there”

But the bison’s introduction in Cuatrociénegas’s El Santuario Reserve, a protected area run by the Fundación Pro Cuatrociénegas, is helping to “reactivate the dynamics and the health of an ecosystem”, says Gerardo Ruiz Smith, the Fundación’s director. “It offers you so much hope,” he told the Mexican media outlet Vanguardia, to see the impact of “simply bringing back a fundamental species that was there before and should be there”.

Having been extirpated from the area by human activities in the 19th century, the bovines returned in August 2025, when three bison were introduced in El Santuario, in a collaboration between the Fundación Pro Cuatrociénegas and Coahuila’s Museo del Desierto. In November, the Fundación then announced the introduction of 44 more bison, in a multi-group effort that also involved the Mexican Fund for the Conservation of Nature.

“After [bison] were hunted to the point of extinction in this area around 200 years ago, the return of a key species to the region of Cuatrociénegas is a historic moment,” Ruiz Smith wrote on social media at the time. In a subsequent post, he added: “This event represents much more than the reintroduction of an emblematic animal: the bison is a true ecosystem engineer, capable of regenerating soils, improving water infiltration, reducing wildfire risk and strengthening the biodiversity of the Chihuahuan Desert.”

“Molding and regenerating”

Speaking to CNN, Ruiz Smith explained that the bison in El Santuario will help to prevent the outbreak and spread of fires by eating dry vegetation. Thanks to the animals’ grazing, blazes will have fewer potential fuel sources.

Weighing up to around 1,700 pounds, the bovines are also promoting the generation of plant life in the area – thanks, in part, to the impact of their hooves on the surface. By turning up the ground as they run, Ruiz Smith said, they unwittingly till the soil, creating openings that let in water. The upshot: more favorable conditions for flora to grow.

In addition, bisons act as inadvertent spreaders of plant seeds, Ruiz Smith told Vanguardia. This happens because seeds can become entangled in the animals’ fur, before being shaken loose as the bison move around.

Ruiz Smith also noted that the bisons’ manure is aiding the fertility of the Cuatrociénegas soil, by attracting dung beetles. As explained by biology experts in the MDPI academic journal, dung beetles improve the nutrient content of soil by burying the excrement they encounter. In addition, their burrowing plays a key role in aerating the subsurface.

As the bison promote a healthier landscape in El Santuario, hidden cameras installed in the area have captured the return of previously-absent animals such as pumas, lynxes and the collared peccary, Ruiz Smith revealed to Vanguardia. What’s more, local bird species have been seen using the bison’s fur to build nests. “[Bison] are landscape architects,” Ruiz Smith concluded, telling CNN: “They set about molding and regenerating their surroundings.”

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