What is the impact of the border fence on Texas animals?

Texas Parks and Wildlife Magazine
August 2011
by Rob McCorkle


On a mild December day in the subtropical Rio Grande Valley, I’m following wildlife biologist Steve Benn along U.S. Highway 281 southeast of Weslaco toward the Hidalgo-Cameron County line. Winter crops like cabbage and onions poke from fecund Rio Grande delta soil along the narrow blacktop that heads south toward the river. An ink-black indigo snake — one of the Valley’s rare species — slithers across the road.

Pulling up behind Benn’s Texas Parks and Wildlife Department truck just north of the levee next to a large gap in the border wall, which rises 18 feet from the dirt, I spot two bobcats about 30 yards away on a bulldozed road that parallels the wall. Cut off to the south by the concrete and steel wall, the cats cast a furtive glance my way before wheeling and dashing north into the thin line of brush adjacent to the bare sugar cane fields just beyond. Had we not been parked next to the gap in this segment of the border wall on TPWD property, where federal government contractors will eventually install a gate, the cats might have slipped through and headed south toward the Rio Grande.

Though I’d read about the fence and seen photos, seeing the border wall with my own eyes bordered on the surreal. Broken segments of the 18-foot-tall, picket-like steel fencing zigzag across the tabletop-flat South Texas landscape, often beginning and ending in the middle of a field, visible at times from the highway, while at other times hidden beyond a distant tree line. While news coverage in the past few years has focused on the wall’s human-related purpose and impacts, little has been communicated about what effects the border fence might have on wildlife, land management practices and ecotourism in one of the state’s most impoverished regions.

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The imposing fence inside the Anacua Unit of the Las Palomas Wildlife Management Area represents but one small part of Texas’ 110 miles of the 670 miles of congressionally mandated Southwest border fence hopscotching across the almost 2,000 miles of border from San Diego to Brownsville to deter drug smuggling and illegal crossings from Mexico into the United States.

In the lower Rio Grande Valley, all but a few of the 22 segments of the called-for 70 miles of pedestrian fencing (as opposed to vehicle fencing) already have been built under the direction of U.S. Customs and Border Protection. Most of the shorter segments measure about a mile in length and were erected adjacent to international bridges or at traditionally heavily trafficked border crossings.

The half-mile-long Anacua Unit segment sits in the middle of 2.52 acres purchased by the federal government under condemnation proceedings initiated by the Department of Homeland Security under authority of the Secure Fence Act. The Texas Parks and Wildlife Commission opposed the land seizure, expressing concern that it would negatively affect wildlife habitat conservation efforts begun some 40 years ago in one of North America’s most important ecological regions, where nature tourism produces a $125 million-a-year economic impact. But federal authorities got the property and installed bollard-type fencing on a 60-foot-wide strip of land in the heart of the unit.

“When finished, and the gate’s put in, bobcats and many other terrestrial wildlife won’t be able to get through this fence here,” explains Benn, project leader for the 3,300-acre Las Palomas WMA, originally purchased by TPWD for white-winged dove nesting habitat with federal excise taxes on hunting equipment and white-winged dove stamp sales. The Anacua Unit is one of 18 units that make up the WMA, and three of them are adversely affected by the wall. “There’s only a 4-inch gap between the steel bars, and with the bars set into a 9-foot-deep concrete trench, animals won’t be able to burrow under it.”

The wildlife biologist worries that the border fence will only compound the Valley’s ongoing habitat fragmentation. He says the wall complicates the area’s wildlife management efforts and threatens indigenous rare species such as the ocelot, Texas tortoise, indigo snake and Texas horned lizard. Benn wonders, too, where animals trapped north of the wall, away from the river, will find drinking water.

Ironically, the wall has gone up in an area where TPWD, the U.S. Fish and Wildlife Service and an army of conservation organizations have spent more than $150 million and several decades acquiring acreage and restoring native habitat in the Valley, where 95 percent of the Tamaulipan thornscrub and riparian woodlands has been eradicated. The result is a sprawling checkerboard of almost 200,000 acres under conservation protection in the Rio Grande delta, a government-protected wildlife corridor that facilitates animal migration and supports plant and animal diversity.

Conservationists fear the border wall will reverse much of that progress and hasten the demise of species such as the endangered ocelot, whose breeding U.S. population — confined to South Texas ranchland and the Laguna Atascosa National Wildlife Refuge — has dropped below 100.

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In the field of wildlife biology, empirical evidence rules. But trying to discern just what kind of impact the still-unfinished border wall is having on wildlife proves to be a less-than-exact science. USFWS and TPWD biologists in 2008 struggled to establish baseline data before fence installation.

Biologists trapped and collared bobcats in several areas, including the Anacua tract, so they could track their movements as the wall went up. At TPWD’s Champion Unit in Hidalgo County, managed by the USFWS, biologists did a series of three-minute bird counts before fence construction began to see how bird populations might be affected by any habitat destruction, as well as the noise associated with building the fence and future U.S. Border Patrol operations. Although birds can fly over any barrier, conservationists note that destruction of riparian habitat for wall construction means many bird species would have less habitat in which to survive.

Much of the Valley’s wildlife exists in the USFWS South Texas Refuge Complex. The Santa Ana, Laguna Atascosa and Lower Rio Grande Valley national wildlife refuges include 100 tracts totaling 180,000 acres. Biologists and volunteers sampled wildlife and bird populations along wall segments being built inside the complex.

USFWS wildlife biologist Mitch Sternberg coordinates biological programs for the refuge complex. He oversaw pre- and post-construction wildlife track surveys conducted along roads at the base of four sections of the fence in Cameron County south and east of Brownsville in the Sabal Palm Audubon Sanctuary, the Southmost Preserve and Boscaje de la Palma.

Biologists found numerous animal tracks from coyotes, lizards, snakes and raccoons skirting the end of the fence segments, which typically abut roads used to access the river levee. In addition, biologists found that the wildlife crossings (8-by-11-inch “cat holes”) were being frequented primarily by raccoons. While the more than 300 passages incorporated into the various Valley fence segments at the request of USFWS can accommodate smaller terrestrial creatures, they are too small to allow passage of larger animals, such as coyotes, bobcats or tortoises.

In the summer of 2009, Sternberg conducted bobcat tracking surveys at several future fence construction sites. He set up infrared cameras near several wildlife corridors along natural drainages. Sternberg followed the movements of a bobcat mating pair and their kitten as construction got under way. When an adult female came into their territory, the bobcat pair killed her.

“In December, I saw both the male and female dead by Highway 281,” Stern recalls. “Their territory had been squeezed down to 400 square yards of agricultural fields and brush near the wall and highway. They were likely searching for more territory. There are 600 acres of brush south of the wall, but it was a mile to the gate opening and they didn’t find it.”

In Arizona, the border fence has been in place long enough for conservation scientists and others to track some of the consequences caused by fragmented habitat for specific wildlife populations. Aaron Flesch, senior research specialist with the University of Arizona’s School of Natural Resources and the Environment, documented some of the effects of habitat connectivity issues on desert bighorn sheep and ferruginous pygmy owls in an article published in Conservation Biology.

Of the diminutive owls that tend to fly only a few feet off the ground, Flesch wrote: “They tend to avoid large vegetation openings. And when they encounter large vegetation openings greater than 200 meters, they tend to turn around.” He concluded that large vegetation gaps coupled with tall fences “could limit trans-boundary movements” of the owls.

Flesch’s team also concluded that the “disruption of trans-boundary movement corridors by impermeable fencing would isolate some populations [of female bighorn sheep] on the Arizona side,” likely having a negative effect on the overall population living in the resulting fragmented Arizona habitat.

Flesch and his team suggested additional funding was needed to support research among governmental agencies, universities and other organizations to find the best ways to balance border security and the needs of wildlife species.

To that end, a team of University of Arizona researchers working with the U.S. Geological Survey in 2010 developed a protocol for monitoring the border wall’s potential effects on wildlife to help identify locations that need to have mitigation actions. It has been submitted to the U.S. Department of the Interior and the Department of Homeland Security and is still under review.

“What we’ve got now is anecdotal information and studies that look at one species or one section, but we really need a comprehensive analysis of the impacts over a large stretch of the area,” says Laura Lopez-Hoffman, assistant professor of the university’s School of Natural Resources.

Nancy Brown, public outreach specialist for the South Texas Refuge Complex, estimates the border wall has affected 60 to 75 percent of the complex’s land. Three-quarters of the federally owned acreage fronts the Rio Grande, which snakes for 275 miles through the Valley. In her Santa Ana NWR office is a map of the green swath of the river corridor marked with red squiggles that look like tiny worms, denoting the proposed segments of the wall to be built between Brownsville and Lake Falcon.

In Hidalgo County, contractors built roughly 20 miles of concrete wall — not along the river, but atop the meandering earthen levees that protect the southern part of the county from floodwaters. Here, no wildlife passages exist at the wall’s base.

The opposite end of the county is home to the Valley Nature Center. Overseeing the center’s operations in the heart of Weslaco is Martin Hagne, who moved to the Rio Grande Valley in 1979 and serves on the board of the Friends of Santa Ana NWR.

While the wall’s present impact on the Valley ecology and wildlife is just now becoming known, at least anecdotally, Hagne frets over the long-term effects of closing off wildlife corridors in so many different places, where the river sometimes takes wicked twists and turns.

Although the Valley Nature Center is far enough inland not to be impacted, the wall has affected operations at two of Cameron County’s most significant nature preserves bordering the Rio Grande.

Uncertainties surrounding the wall’s construction and access issues forced Audubon in May 2009 to close its Sabal Palm sanctuary, home to the nation’s last substantial stand of the subtropical sabal palm. The 527-acre nature preserve did reopen in January 2011 when a private group, the Gorgas Science Foundation of Brownsville, stepped forward to help fund and run the refuge.

A few miles downriver lies the 1,034-acre Southmost Preserve, another major native sabal palm sanctuary as well as a native plant nursery, organic citrus operation and critical native wildlife habitat for rare snakes, cats and other critters. The Nature Conservancy has filed suit contesting U.S. condemnation and seizure of eight acres that today hosts a 6,000-foot-long, 60-foot-wide strip of land bisected by the border fence. Its location cuts off the northernmost part of the preserve, isolating 900 acres between the wall and Rio Grande in what critics call a “no man’s land.” Preserve operators find themselves grappling with myriad land management challenges.

“My concern now is how do we manage the property, operate the nursery where we’re growing 80,000 seedlings under contract with the USFWS and keep the wetlands and resacas pumped full of water,” says John Herron, the Nature Conservancy’s director of conservation.

Herron says many people don’t realize that the fence doesn’t follow the river, that huge gaps exist between fence sections and that hundreds of acres end up stranded between the wall and river.

“The fence is exempted from environmental laws, so there hasn’t been any assessment of the environmental impact,” Herron says. “Who should pay for that? The USFWS hasn’t been given any money for that, nor have we. Here we are three years into it and there are lots of areas with no clarity.”

Fifth-generation South Texan Max Pons, who manages the preserve and lives on the property, hopes the wall’s presence doesn’t threaten the preserve’s wildlife that thrives amid the native Tamaulipan thornscrub and ancient stands of Sabal mexicana. The native palms once forested much of the Rio Grande Valley, but are now found only in deep South Texas and northern Mexico. Each palm, which can grow up to 40 feet tall, creates a micro-habitat of its own.

“You can have a population of southern yellow bats living under its leaves,” Pons explains, “and turkeys and other birds nesting and roosting. Invertebrates collect in leaf litter at the base, which attracts lizards and snakes such as the endangered indigo. Wood rats live in the trees and hop from one tree to the other.”

Pons credits the federal government, however, with working with him and other conservation agencies to try to mitigate some of the wall’s impact on wildlife. On a drive along a recently installed wall segment, he gets out to show me a hard-to-spot, notebook-paper-size opening that has been cut out at the bottom of the steel fencing to allow snakes and other small critters to pass through. In another concession to conservation organizations, he says federal contractors dug up several hundred sabal palms in the fence right-of-way for replanting at Southmost Preserve, Sabal Palm Audubon Sanctuary and Bosque de la Palma NWR.

Some representatives of the Valley’s lucrative nature tourism industry, a business fueled by world-class birding that draws enthusiasts hoping to add such local specialty birds as the green jay and chachalaca to their life lists, worry about the wall’s impact on local economies.

Nancy Millar, director of the McAllen Convention and Visitors Bureau, says news of the border wall has already resulted in one British birding company canceling future tours to the area. And, she says she gets plenty of questions about the impact of the fence when she attends travel shows in the U.S. and abroad.

For Keith Hackland, president of the Friends of the Wildlife Corridor and owner of the Alamo Inn and Outdoor Store in Alamo, concerns remain about what impact the border wall will have on prime birding spots in riparian forests farther upriver.

“The greatest fear I have is for the part of the wall being built from Rio Grande City to Falcon Dam in Starr County,” Hackland says, “because the plan is to place it along the river. Clearing the narrow strip of riparian forest on the banks would be an ecological disaster, eliminating the red-billed pigeon, Audubon’s oriole, Muscovy duck and all of the rare nesting birds.”

He contends that such habitat destruction in such an ecologically rich region blessed with more than 500 bird and 300 butterfly species will have a huge impact on wildlife,
conservation efforts and the economy.

“If nature tourists lose confidence in this area and can’t access the river forest,” Hackland says during my visit to his inn, “I’ll be looking for new use for this building. They are the ones who pay the bills and help make this enterprise work.”

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