Fencing the Border and Its Birds

The U.S.–Mexico border in southern Texas is a busy place. The wide, flat streets of Brownsville, Harlingen, McAllen, and (just across the Rio Grande) Matamoros teem with dusty pickups, farm stands, tiny Tex-Mex restaurants, and more than 700,000 people. The region is a hotbed for beautiful and coveted birds, too: 516 species flit through the area’s distinctive mesquite, marshy resacas, and parched arroyos.

South Texas is also a corridor for hundreds of thousands of people trying to slip across the border from Mexico. Along the entire border, the U.S. Border Patrol turns back about one million illegal immigrants every year and seizes about 500 tons of smuggled narcotics. The lower Rio Grande Valley of Texas is perennially in the top three busiest of the Border Patrol’s 20 sectors.

In a move to cut down on illegal traffic, the Department of Homeland Security in 2006 began building 670 miles of steel fence along the border, at a cost of $2 billion so far. By early 2009, just 70 miles remained to be built, most of it in the Rio Grande Valley. Construction is proceeding over the objections of local residents, who have claimed that the fence restricts friendly relations with Mexico, destroys swaths of their land, and sometimes strands their own houses on the south side of the fence (see sidebar).

All but unnoticed amid the human debate, the region’s exuberant wildlife faces exactly the same set of problems.

Exuberant wildlife

Birders come to the Rio Grande Valley for glimpses of tropical species that make their only appearance in the U.S. right here. Species including the improbable yellow-green-and-blue Green Jay and fiery Altamira Oriole. Two unusual sizes of kingfisher live here, the burly Ringed and the almost dainty Green. Flashy Great Kiskadees, intensely mauve Red-billed Pigeons, and so-small-you-might-miss-them Least Grebes and Ferruginous Pygmy-Owls are just some of the species you would otherwise have to leave the country to see. A few don’t occur any farther than a dozen miles north of the border.

Two small wildcat species—the ocelot and the jaguarundi—are also rare inhabitants of the South Texas border. In states farther west, desert bighorn sheep and Sonoran pronghorn live a tenuous existence on limited stretches of habitat straddling the border. In each case, the fence’s twin side-effects, habitat destruction and disconnection, reduce the likelihood that these species will persist in the small patches of habitat that remain north of the border.

Stranded between Mexico and the U.S.

The border fence is largely a struggle between a nation that’s concerned about secure borders and the people who have to live with the fence. It’s not a partisan issue: the legislation had the support of both parties in Congress. Senators John McCain and Barack Obama both voted for it. The Bush administration expedited the building of the fence, waiving more than 30 federal laws that might slow construction. After taking office, President Obama ordered for the remaining authorized and funded sections of the fence to be finished.

But the reality of the fence on the ground is complicated. It stops and starts along the length of the border, covering only about one-third of the full 2,000 miles. In the Rio Grande Valley, stretches of fence go up for a few miles at a time (up to 13 miles), alternating with unfenced areas.

And it doesn’t always follow the border. Partly because of the Rio Grande’s meandering route out to the Gulf of Mexico, planners routed the fence up to 2 miles north of the river, shortcutting the wider arcs. Nearly 200 landowners hold property within that narrow strip. Some have found their driveways cut off from the rest of the United States. Farmers have lost access to fields, and livestock have been cut off from river water. Until a recent agreement, the University of Texas at Brownsville faced the prospect of the fence dividing their campus in two.

These same problems confront the birds and other animals that call the region home. There’s very little natural habitat left to begin with. Most of the 1.5-million-acre Rio Grande Valley has been converted into farmlands and homes. What’s left over are small patches of green space scattered over 200 miles, from the White-collared Seedeaters of San Ygnacio to the Roseate Spoonbills of Boca Chica.

More than 100 of these remnants totaling about 90,000 acres are now protected as the Lower Rio Grande Valley National Wildlife Refuge, the result of three decades of work and planning by land managers. The border fence, its access roads, and the associated construction areas cross these parcels in a half-dozen places, cutting slices from what habitat remains.

Perhaps more problematic for wildlife is the way the fence blocks movement between the few patches that can support them. Animals whose range barely juts into the U.S. may find themselves cut off from relatives, prospective mates, and suitable empty territories. Many terrestrial animals can’t get around or over the fence, and are more vulnerable to predators on its access roads. While birds might seem to have an easier time going over the fence, research has shown that many forest birds are extremely reluctant to cross gaps of unfamiliar or open habitat.

Room for science?

So far, human concerns have taken center stage in the border fence debate. In a post-9/11 world, the argument goes beyond stemming the tide of undocumented workers and narcotics. Advocates point out that already-established smuggling routes could be turned to the purposes of moving terrorists and their weapons across the border.

Critics point to the many gaps in fence along the southern border, the difficulty of maintaining the fence, the spread of tunnels from Mexico into the U.S., and the comparatively unsecured border with Canada. The likelihood of the fence simply rerouting instead of keeping out illegal or terrorist activity, they say, is not worth the monetary or environmental expense.

The official conversation has largely bypassed those environmental effects. The Department of Homeland Security conducted a nonbinding environmental review of the fence route, but waived laws like the Clean Water Act, Clean Air Act, and Endangered Species Act to avoid construction delays. In the view of former Secretary of Homeland Security Michael Chertoff, who waived the laws, the added security of a completed fence outweighed whatever environmental damage might result.

But environmental studies do more than estimate damages. They offer foresight: the opportunity to minimize impacts by identifying slight alterations to routes, materials, and timing. One of the strengths of scientific study is its ability to combine lessons from past work with repeated, careful observations in order to plan for the future.

The 670 miles of fence begun in 2006 are almost finished, and in all likelihood the remainder will go up without major alterations. Then scientists will get a chance to learn about the fence’s effects, albeit in hindsight: to find out how often birds fly over it, or how many ocelots find their way around it; to learn how resident animals cope with restricted movement and missing slices of habitat.

Barring environmental surveys, perhaps the best way to get a sense of that isolation is to visit the Sabal Palm Sanctuary southeast of Brownsville. It’s a standard stop on any South Texas birding trip, where bird watchers count on Plain Chachalacas, Black-bellied Whistling-Ducks, Olive Sparrows, and Buff-bellied Hummingbirds—and hope for semi-regular rarities like Golden-crowned Warblers, Tropical Parulas, and Rose-throated Becards. If construction goes as planned, the sanctuary entrance will be just visible about a quarter mile beyond the fence’s steel bars.