WILDLIFE ON THE BORDERLINE
The barriers along the US–Mexico frontier carve up habitats and age-old migration routes, impacting on a host of species.
At the southern end of Arizona’s Huachuca mountains, the United States meets Mexico on a rocky precipice where a sweeping vista unfolds. To the east, the international boundary reaches towards the horizon through an ocean of pale winter grasses where jackrabbits hide and great horned owls hunt. To the south, the deep grooves of the upper San Pedro River watershed stretch across the border, extending into the foothills of the Huachucas as secret passageways for bobcats and black bears. To the west, the immense San Rafael Valley sprawls southwards as a sea of golden grass where shy pronghorn antelopes roam. And all around, dark mountain ranges tower like islands in the lazuli desert sky, their deepest shadows sheltering the footsteps of jaguars.
This landscape radiates a wild calm, but beneath the surface are two conflicting realities: the borderlands region encompasses one of the most biodiverse ecosystems in North America, while rapidly becoming one of the world’s most militarised and divided places. Over the past decade, just over 1,000km of border wall have been constructed along this 3,200km-long frontier. Most construction has been exempted from environmental laws that would have protected critical habitat and migration pathways for endangered species. And in January, the new US president vowed to expand border wall construction and to intensify militarisation of this land.
Yet from a steep mountainside overlooking the border, geopolitical tension drifts away on a fresh westerly wind. This immense landscape remains the kind of special space where wildlife can thrive, and humans can find that unique brand of respite particular to vast open spaces.
STANDING IN THE WAY
Seeking out some of this wild solace, I hike a trail from the Montezuma Pass in Coronado National Memorial, a protected area managed by the US National Park Service, through the mountains to the border, where a monument was placed in the 1850s when the United States bought this land from Mexico under the Gadsden Purchase.
ONE OF THE MOST BIODIVERSE ECOSYSTEMS IN NORTH AMERICA IS RAPIDLY BECOMING ONE OF THE WORLD’S MOST DIVIDED PLACES.
Such monuments were erected all along the border, from the Pacific Ocean to the Gulf of Mexico. But today this particular one carries a weighty importance – it is situated on one of the few migration pathways remaining to a suite of transnational grassland species.
The US–Mexico border, a line drawn in the sand by two nations, is fundamentally defined by a natural boundary at the overlap of the temperate and tropical zones. Here the north and south meet and mingle, sharing an assortment of trees, cacti, wildflowers and grasses that don’t coexist anywhere else. Natural borders like this are unusual places, prone to biological extravagance.
Prior to the Gadsden Purchase, this land was claimed by Mexico, and before that Spain. In the millennia that preceded Spain’s conquest of North America, it was the domain of native people; and before that, it belonged to the jaguar.
Strength, adaptability and stealth earned the jaguar its position as an apex predator in the Sonoran Desert. “Jaguars evolved here in North America before they moved south into the tropics. So in a very fundamental sense they belong here,” says Randy Serraglio, a conservation advocate for the Center for Biological Diversity. And somewhere out within this grassland sea, or padding through shadows in the river corridor, the jaguar still roams. Only now the big cat is fighting for its existence in an arid world at the boundary of two nations.
In the early 20th century, jaguars started to disappear,
largely due to hunting and habitat loss. In 1963, the last known female jaguar in the United States was killed near the Grand Canyon, and for decades the largest cat in the western hemisphere was feared to have been driven to extinction in the US. But then, in the 1990s, a ray of hope appeared in the form of a photograph captured in south-east Arizona. Since then, there have been hundreds of photos and sightings of male jaguars. “We don’t know where the nearest female is,” Serraglio admits. “We know there is a breeding population around 200km south of the border, but we don’t know if there are some closer, even in the United States. Jaguars are so cryptic.”
IN SEARCH OF A MATE
Researchers know that young male jaguars are coming to the US to find new territory. They live here for a few years until a biological urge kicks in, and then head back to Mexico to find the nearest female. “They have to go back,” Serraglio says. “They have to find a female.”
Jaguar researchers believe that when the northernmost female jaguars begin to branch out, if migration pathways are open to them, they will find their way to the United States. And when that female pioneer arrives, Seraglio says, it will be a game-changer. In the meantime, conservation organisations have been working to raise awareness and create a plan for restoration. Central to jaguar conservation are two basic needs: space and pathways for travel.
“Like most apex predators, jaguars need large areas of wilderness,” Serraglio explains. “And they travel long distances to find what they need. Connectivity is critically important for jaguars.” This puts the future of this cat at the mercy of the prevailing US policy of building walls and expanding militarisation of its southern border. “If jaguars are ever going to recover in the United States, the breeding population in northern Mexico must be able to expand north,” Serraglio says. And jaguars are not alone.
The US began intensifying border enforcement in 2005 when Congress approved several measures aimed at fast-tracking the construction of a wall. In addition to mandating 1,120km of wall, the federal measures removed environmental and other bedrock protections for land, people and wildlife. Since that time, about one-third of the border has been walled, largely over landscapes set aside specifically for wildlife and wilderness.
Dismissal of environmental law along much of the border has jeopardised populations of numerous species, including the jaguar, ocelot, collared peccary, pronghorn antelope and black bear. For many species, the wall poses a direct threat by blocking access to scarce water and food resources. Barriers have also isolated individuals from mates on the opposite side of the
border, which worries biologists.
CENTRAL TO JAGUAR CONSERVATION ARE TWO BASIC NEEDS: SPACE AND PATHWAYS FOR TRAVEL.
A 2011 study found that black bears in the Sierra Madre mountains are genetically linked with bears across the border in south-east Arizona; any barrier that separates bears in Mexico from those in the US will threaten this isolated southern population. “Black bears are much less abundant in Mexico,” says Juan Carlos Bravo, who directs the Mexico Program for the Wildlands Network, an organisation focused on restoring landscape connectivity. “They depend on open corridors into the United States for genetic diversity.”
TRAGEDY FOR TOADS
The fallout from this may not become apparent for years, as genetic poverty takes its toll on the bears. But for some species, the growing divisions in this landscape have already hit hard. Immediately after the border wall was built in the Organ Pipe Cactus National Monument, scientists filmed Sonoran Desert toads jumping against its steel, time after time, until they were taken by predators or died of dehydration. In 2012, a herd of pronghorn in the San Rafael Valley began disappearing. An investigation found that after the border barrier was put up, all of the breeding males were isolated on its southern side.
All of these impacts were predictable outcomes of adding large obstacles to the landscape, Bravo notes. “It goes against modern conservation practice to build a barrier.”
The construction of a border wall has
destroyed and fragmented critical habitat all along the border. In Texas, where the Rio Grande delineates the frontier, more than 95 per cent of the native habitat has been lost to human development. The remaining five per cent is located almost entirely on wildlife refuges along the river corridor. This scant remaining habitat provides a lifeline for endangered wild cats, imperilled reptiles and insects, and globally important bird populations.
More than 500 species of bird depend on the Lower Rio Grande Valley. Many make their homes along the river, while others rely on its relatively lush surroundings to rest and refuel after gruelling flights over the Gulf of Mexico or the vast deserts to the west. Every remaining acre of native habitat here may make the difference between death and survival for migratory birds such as northern cardinals, altamira orioles, green jays, kiskadees and many more.
Bobcats also use the Rio Grande. But in 2009 researchers found that after the border wall fragmented wildlife refuges in southern Texas, bobcats were killing bobcats and dying on roads as they fought over shrinking territory and roamed the Lower Rio Grande Valley searching for new homes.
For conservationists, the rise of border walls constitutes a tragedy of epic proportions for thousands of wild species. And this threat to global biodiversity goes well beyond the borders of North America, as more nations reinforce their borders worldwide.
Here in the Huachucas, looking out over the San Pedro River and the mountains rising above the Mexican grasslands, the intention of newly elected president Donald Trump to expand the US–Mexico border wall casts an ominous pall. For now, however, the border at the foot of the Huachucas is defined by a 2.5m-high barbed-wire fence. It poses little obstacle to the jaguar, which can jump over this barrier or sneak under if need be.
Recent evidence shows jaguars are doing just that. In late 2016, a camera-trap captured the image of a new jaguar in Arizona – one whose sex could not be determined. The mere possibility it may be that longawaited female caused jaguar conservation hopes to soar. But to the east of the Huachucas, an 11m-high wall has already been built right up into the foothills, a wall that stretches for dozens of miles across the San Pedro Valley.
I myself have witnessed numerous species trapped by this wall, including collared peccaries, animals with an important ecological role as both a prey species and seed distributor. The imposing edifice also blocks the passage of pronghorn, mule and white-tailed deer, cottontail rabbits and indeed every other terrestrial animal, through one of the most critical passages in the region for wildlife.
Climate change can only worsen the situation, as it begins to exacerbate droughts and intensify heat in the desert. “With such huge uncertainty due to climate change, we have to preserve the options for these species to adapt,” Serraglio says. “One of the best ways to do that is to maintain connectivity.”
The borderlands represents the only viable future for the jaguar in the US, and for so many other species entwined in the region’s web of life. Each creature here has adapted to survive in a desert, but their greatest test may yet rise before them. “For thousands of years jaguars were revered by indigenous cultures as superhuman,” Serraglio says. “But they can’t climb that wall.”
FOR CONSERVATIONISTS, THE RISE OF BORDER WALLS CONSTITUTES A TRAGEDY OF EPIC PROPORTIONS FOR THOUSANDS OF WILD SPECIES.
Clockwise from top left: the best hope for the continued survival of bighorn sheep is open travel corridors; the border wall has fragmented bobcat habitat; kangaroo rat populations are being split by walls built through the California dunes; elf owls are facing habitat destruction in the borderlands; migration corridors are being severed by border barriers.
Clockwise from above: the border wall now bisects the grasslands of the Coronado National Memorial and San Pedro River corridor; a gila monster on a conservation property in Mexico; altamira oriole in Lower Rio Grande Valley; a male jaguar in southern Arizona.
Above: a desert cottontail at the border wall during its construction in southern Arizona. The barrier restricts the passage of the species and other land mammals.