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Tuesday, July 2, 2013

Continental Divide


A photographer documents the ecological impacts of the border wall between the United States and Mexico

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Drought conditions in the Janos, Chihuahua, grasslands will force many species to move northward, like bison (below right).

Crouched in a photo blind near the border between the United States and Mexico, Krista Schlyer heard voices—beneath her. As if checking for a heartbeat, she pressed her ear to the ground to diagnose the source of the sounds. What she got was an earful of squeaks and chirps from a prairie dog family scurrying about in their burrow.

"I just lay there for an hour listening to them chatting back and forth," Schlyer says. "It was an incredible moment."

To untrained eyes, or ears, not much appears to live in the lands straddling the border between the United States and Mexico. And yet this region is one of the most biologically diverse in all of North America. The varied ecosystems include deserts, grasslands, "sky island" mountains and the Rio Grand Valley—the midpoint between the tropics to the south and the temperate zone to the north. More than half of North America's bird species, 3,000 plant species and more than 100 different mammals inhabit the borderlands.

"If you were just looking at a place for its biodiversity, you have all the reasons you need to conserve this special part of the North American continent," Schlyer says.

While most photographers rely on their eyes to help them understand a place, Schlyer interprets the U.S.-Mexico borderlands with all of her senses. It's a good strategy in this arid desert region. Ground surface temperatures can soar to 160 degrees Fahrenheit, and according to Schlyer, "Most life is lived out of sight, under ground or by shadow of night."


The last remnants of habitat in South Texas remain a haven for the plain chachalaca. Wall construction will put the preserve in a
no-man's-land between the border wall and the Rio Grande.
How have so many species adapted to the harsh climate of the region? The desert tortoise can survive a year or more without access to water because its bladder stores large amounts of fluids. The Gila monster, a venomous lizard, consumes its annual energy needs in just a handful of large meals and spends 95 percent of its life underground. Trees such as mesquite, blue palo verde and ironwood have roots that penetrate deep into the soil to find moisture. Most cactus species have huge masses of shallow wide-spreading roots that can soak up water quickly. The mighty saguaro cactus has pleats that enable it to expand and contract as it takes up and uses water. Endemic and iconic to the Sonoran Desert, saguaros can live for more than 150 years and reach heights of 40 to 60 feet, providing much needed shade for other plants and animals.

While the survival of many species in the borderlands depends on conserving energy by staying put, others can only survive by constantly moving. Large mammals including coyotes, bobcats and foxes must travel to seek water, food and mates. Whether they venture into the United States or Mexico is irrelevant as long as they find what they need. But what if their survival depends on being able to move freely between the two countries? And what if they run smack into a giant concrete and steel wall? This is the issue that Schlyer addresses in her new book, Continental Divide: Wildlife, People, and the Border Wall (Texas A&M University Press).

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