Dozens of American bison graze the vast, open fields of El Carmen (Coahuila), a 140,000-acre reserve nearly the size of Mexico City. The country’s northern plains had forgotten the transit of the mammal, which was wiped out 100 years ago after decades of indiscriminate hunting and habitat destruction. In 2021, on the initiative of the Mexican cement company Cemex, the bison returned and roamed the grasslands, soil that accumulates large amounts of carbon and is therefore crucial in the fight against climate change. 19 bison have arrived at the reserve and there are already more than 90 in town. The mammal’s daily life makes it a fundamental player in the regeneration of grass vegetation and the maintenance of hundreds of species living with it.
“The even cutting of the willows [que producen los bisontes al comer] Contributes to increasing the diversity of plants on the ground. It also takes care of the regeneration of ecosystems by transporting and excreting the seeds from one place to another in its digestive system,” explains Rurik List, an environmental scientist at the Universidad Autónoma Metropolitana (UAM). The bison is a sober animal that unintentionally encourages other species to survive in the spaces it inhabits. With its 800-pound weight, it flattens the grass in its path, a change that helps rodents like the prairie dog, which need short grass to be wary of predators.
Cemex conducts various conservation initiatives to offset the impact of its operations. The company has more than 250 active quarries around the world and tries to minimize its footprint from different perspectives: by rehabilitating the exploited sites; They are prepared before they start work to protect their biodiversity and are encouraged to take care of areas like the El Carmen Nature Reserve, where they arrived 22 years ago. “Since the beginning of the reserve, a number of studies have been conducted to find out what works best. An inventory of flora and fauna was conducted to determine which objects of protection we must withhold. And an analysis was carried out to determine the state of the habitat,” says Alejandro Espinosa, director of the El Carmen Reserve.
1,000 kilos and 14 kilometers of walking
The bison is a calm animal that calmly walks across the fields. It is the largest land mammal in the Americas: it stands over 1.6 meters tall and can weigh more than 1,000 kilograms. Espinosa is still curious about the animal: “Did you know that a bison can walk up to 14 kilometers a day?” On their long walk, the bison scratch the trees to relieve the flies’ itch. The hairs released are used by birds for their nests, which in turn helps protect other species.
Their path through the pastures preserves the biodiversity of the area. “They urinate and pass their bowel movements. When they die, it’s 800 kilos of fertilizer to decompose. If they just died, scavengers feed on them too; and when alive they are occasionally eaten by wolves, less frequently by grizzly bears, and still more rarely by cougars. They are also a prey species,” explains List.
American National Bison Association (NBA) director Jim Matheson cites the American mammal’s game instinct as one of its keys. “The bison has never been domesticated and therefore retains its innate herding instinct, making it an ideal ruminant for reclaiming North American grasslands.” he explains. The UAM researcher presents the mammal as a “key ecological species” that has a large impact on the ecosystem in relation to its abundance.
A lung hidden in the plane
Cemex began restoring the protected area 22 years ago with the help of environmental agencies, universities, scientists and support from the United States National Park Service. More than two decades later, the landscape looks different. “Extensive vegetation cover was rarely seen, there were many stones, the whole process of overgrazing was just over. The square was divided into paddocks with fences. One of the first measures was the development of the countryside […] More than 20,000 hectares of grassland infested with bushes were restored and after several years of work we realized it was time for the area’s native species to graze naturally,” adds Espinosa. Bison were one of these methodically selected species. The company tried to select the specimens that were least crossed with other animals – in order to survive, they first bred with cattle. The result was 18 bison (three males and 16 females) introduced from other fields in North America.
Grassland is one of the hidden lungs of the planet. The Food and Agriculture Organization of the United Nations (FAO) argues that these areas allow for the storage and sequestration of greater amounts of carbon than forest ecosystems, capturing up to 30% of the planet’s CO2. To these properties, List adds another: fire resistance. “90% of the carbon in grasslands is underground. When it burns, 10% will burn, but 90% will remain, which will grow again as soon as the rain comes. Unlike forests like those in the Redd+ program, which are used for carbon storage and whose carbon reserves are released into the atmosphere when burned,” affirms the researcher.
The National Commission of Protected Natural Areas (Conanp) estimates that grasslands can absorb up to 45 tons of carbon per hectare. The reserve’s 140,000 hectares multiplies the figure significantly, theoretically reaching 6.3 million tons.
Rare in Mexico, iconic in the US
The Coahuila Reservation saw the birth of the second generation of local descendants this year, indicating signs of their settlement. Espinosa has counted a total of 94 American bison so far. The Conanp reports that there were between 30 and 60 million bison on North American territory 300 years ago, but by 1880 the population had declined to just over 1,000.
Matheson says the IUCN Red List organization, whose job it is to determine the possibility of various species going extinct every five years, has seen the bison stay out of danger. “The herd has not been in danger of extinction for several years, and the herd has proliferated in recent years on all fronts involved – private, agricultural, tribal and conservation. “I think the current bison herd is actually pretty stable,” he says.
The animal, whose existence was an important source of food and fur for the native peoples of North America, has once again set foot in the lands of northern Mexico. In just two years, its population has grown by more than 60 individuals, and its presence is boosting northern grasslands. “You have bison, you have grassland; There is grassland, there is carbon in the soil. You lose the bison and there is a loss of range,” List concludes.
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