Saving an endangered ecosystem in the Lower Rio Grande Valley

By Krista Schlyer; All photos by Krista Schlyer

A beautiful, scenic bridge found on the Santa Ana National Wildlife Refuge.

A WINTER FOG BLANKETS THE LOWER RIO GRANDE VALLEY, OBSCURING all but the heights of the forest canopy where the outstretched arms of ebony, ash and hackberry reach through a cottony mist. From atop the hawk tower at Santa Ana National Wildlife Refuge in South Texas, no roads, no farm fields, no buildings are visible, only a deep lush forest loud with the dawn chorus of kiskadee, green jay and oriole that has rung out on this land for ages beyond count. Enveloped in this misty morning, one can imagine another time, not so long ago, when jaguars stalked this forest by night, jaguarundis hunted its deepest shadows by day, and ocelots poured their mercurial bodies through small gaps in the dense thornscrub on the heels of cottontail and dove.

But as the sun ascends, the fog dissipates revealing the reality that has over the past centuries displaced jaguar, ocelot, bird and butterfly, ebony and ash until almost none were left: roads, utility lines, bare fields, buildings and border barriers.

“We’re down to less than 5 percent of the native Tamaulipan thornscrub habitat and less than 3 percent of riparian forests,” says Robert Jess, who directs the South Texas Refuge Complex for the U.S. Fish and Wildlife Service.

Ibis flock
An Ibis flock glides above the water at Santa Ana NWR, South Texas.

Most of the habitat originally fell to farming. In 1880, there were 2,000 acres of cultivated land in Hidalgo County; by 1924, that figure had grown to more than 125,000 acres. By 1943, the year the Santa Ana refuge was established, it had become an island of remnant habitat in a sea of cropland. Once-common species, like plain chachalaca and hooded orioles, had almost disappeared. Ocelots and jaguarundis were endangered, and the last jaguar in Texas was killed in 1948.

But in 1979, a seed of an idea was planted in the form of the Lower Rio Grande Valley National Wildlife Refuge, explains former refuge complex manager Ken Merritt. More than a refuge, the project was a grand endeavor to restore and stitch together disjointed pieces of natural land into a whole cloth of habitat that could save an expansive community of imperiled species.

“The refuge aimed to preserve the habitat,” says Merritt, “but also to create a travel corridor for a variety of species, especially the ocelot.”

Queen butterflies
More than half of North America’s butterfly species — some 330, including these queen butterflies — can be seen floating about South Texas.

In this way the refuge could serve as connective tissue between isolated tracts of land owned by private citizens, nonprofit organizations and governments along the last 275 miles of the Rio Grande River. Two keystone refuges would anchor the corridor project: the Laguna Atascosa — a critical stronghold for endangered ocelots on the Gulf Coast — and Santa Ana, some 60 miles west on the Rio Grande, which protects the largest remaining riparian thorn forest in the United States.

This ambitious endeavor has included an investment of millions of dollars and many thousands of volunteer hours — the blood, sweat and tears of a community that simply would not let this landscape die. They knew there was no place else like it in the world.


Native habitat in the Lower Rio Grande Valley includes picturesque wetlands.

The richness of this river delta derives from its geographic location. The Rio Grande lies within a natural borderlands, where the boundaries of four significant climate zones overlap. The north, south, east and west of North America’s natural world meet here, blending tropical species, like ocelots and green jays, with their more temperate counterparts like bobcats and white-throated sparrows. Likewise, precipitation zones that define the eastern and western portions of North America overlap here, so cactus grow as comfortably as Spanish moss. Many unique species are adapted to these four extremes and coexist here at the edge of their respective ranges.

The Valley attracts scores of migrating species, especially birds and butterflies, as they attempt to make their grueling seasonal journeys. The Gulf of Mexico and Chihuahuan Desert flank the Valley to the east and west, effectively creating a migratory funnel for birds trying to avoid the dangers of flight over the Gulf or the desert. Of the more than 320 North American migrating bird species, some 80 percent can be found resting and refueling within the Valley. More than half of North America’s butterfly species — some 330 — can also be seen floating about South Texas.

Green jay
The gorgeous green jay is just one of the many birds tourists come to see in the Lower Rio Grande Valley.

“Many bird species means many seed distributors,” explains refuge restoration ecologist Kim Wahl. “Many butterfly species and bee species mean many pollinators. It all works together to create an incredibly diverse place.”

South Texas claims 1,200 documented plant species, organized into 38 unique plant societies — from the rich wetlands and lowland river forests shaded by black willow, Texas ebony and Mexican ash, to thick brushlands, grasslands and coastal dunes. These plant communities have for millennia sustained a complex wildlife community, including indigo snakes, Texas tortoises, aplomado falcons and malachite butterflies.


A significant challenge arose, as Wahl explains: “How do we go from an open field to something we can call habitat?”

The initial plantings in the 1980s and 1990s consisted of broadcasting seeds for fast-growing plants like Texas ebony, huisache and tepeguaje. The success rate was low due to dry, bare soils, but much was learned in the process.

The extreme heat, drought and winds of a South Texas summer would have been buffered by a sheltering forest in a natural setting, but on farmland, tender seedlings are at the mercy of the elements. It became clear that given the damage the land had endured, plants needed a head start. Especially when the ecological integrity of the land had been so deeply wounded.

More care for individual plants was essential, but this would require more time and more financial resources in an era when budgets for national wildlife refuges are consistently declining. Budget shortfalls meant optimal planting methods could only be used as key resources were available, Wahl explains.

In 1997, American Forests joined the effort in South Texas to help provide those key resources and keep restoration on track. Since then, the organization has provided more than $1 million to support the planting of more than 2 million seedlings.


“American Forests covers the cost of many of the plants, so we are able to spend more money on how we plant,” Wahl says. “We can go from just putting plants in the ground to creating habitat.”

With more thoughtful planting methodologies, seedling survival and diversity has increased, resulting in more natural plant communities in a shorter period of time. It’s been a community effort. Private nurseries grow three-quarters of the seedlings, assisting the refuge and also fueling a micro-economy around restoration. And, every October for 20 years, the refuge has held the Rio Reforestation event, enlisting thousands of volunteers to plant seedlings and learn about the value of returning native habitat to the landscape.

The benefits of restoration are expansive, well beyond the direct economic impacts.

“Forest restoration is also a great investment for people,” notes Eric Sprague, vice president of forest restoration at American Forests. “You get water benefits for a drought-prone area and climate benefits that come from trees.”

It would be difficult to overestimate the value of this work for the future of wild species. At least 24 globally imperiled plant species are native to the Valley. They include ashy dogweed, South Texas ambrosia, star cactus and Walker’s manioc. Many of these were widespread in the Valley historically, but now their global range is restricted to a few small patches in South Texas. Some 85 species of animals are threatened with extinction or already lost, like the Smyth’s tiger beetle and Eskimo curlew. Once-common hooded and Audubon’s orioles have disappeared from large portions of the Valley, and Altamira orioles have been in decline for decades along with elf owls, red-billed pigeons and varied buntings.

Ocelots are now critically endangered, plagued by habitat loss and fragmentation that isolates their populations. Only about 50 ocelots are left in the wild in the United States, and without significant effort, this small cat is likely to be extinct in the country within 50 years. These cats need the densest thorn forest, a habitat type that now comprises less than 1 percent of the Valley. With every new fragmentation they are forced into smaller and smaller islands of habitat, where a shallow gene pool and limited prey threaten their future. But travel in search of survival can be treacherous. In 2015, five ocelots — about 10 percent of the known population — were killed on roads.


The border wall on the Lower Rio Grande Valley refuge
The border wall on the Lower Rio Grande Valley refuge.

Historically, the U.S. population of ocelots was linked to those in Mexico. When they needed to find new territory or mates, they could swim across the Rio Grande. But, as the border between these two nations hardens, animals of all ilk are being blocked from essential migrations.

In 2017, President Donald J. Trump announced plans to expand construction of a border wall in the Valley. Proposed wall construction, and other border enforcement activities, compound upon a host of ongoing threats to restoration of Valley ecosystems, making the ultimate success of the conservation effort far from certain.

“Most, if not all, of the native forests and subtropical brushlands in the expansive 2.7 million acres of the Lower Rio Grande Valley are threatened by ongoing human activities,” according to a 2015 U.S. Geological Survey report.

An armadillo
An armadillo blends into its habitat in the Lower Rio Grande Valley.

Invasive species, like bufflegrass, giant reed and salt cedar, crowd out native species and thwart restoration of native plant communities. Climate change is increasing the frequency of extreme drought and flooding, and causing sea level to rise while eroding coastal habitats. Dams on the Rio Grande have taken a toll on the health of the river landscape by depriving forests of essential nutrients and water. Conversely, levees have caused the delta to be inundated for extended periods of time, killing mature trees. Added to these threats are ongoing development pressures, such as Space X, proposed liquefied natural gas facilities and a rapidly expanding wind energy industry.

But the greatest of all these threats is likely to be the ever-expanding human population and resulting urbanization. Since 1940, population in the Valley has increased by more than 1 million people, making it one of the fastest-growing regions in the nation. If current trends continue, the population will double by 2050 to more than 3 million people. More people means more roads, more vehicles, more pressure to urbanize forest and grassland.

“If you could sum all the threats up in one word,” Jess says, “it would be fragmentation.”

Endangered species are already reeling from a highly fragmented landscape. Their survival requires an expansion of habitat, and development pressures are making that increasingly difficult.

“When you deal with endangered species, there is a sense of urgency,” Sprague says. “You want to see results fast.”

A red-banded pixie butterfly
A red-banded pixie butterfly soars through The Valley.

But restoration takes time — and there’s the rub.

“It’s now a race between expanding development and protecting the habitat and migration corridors that connect important blocks of thornscrub,” Sprague says. “We’re trying to make these connections while we still have a chance.”

Back on the hawk tower in Santa Ana, the rising light shines upon spider webs that glisten in the forest canopy. The departing fog has revealed the hard reality of this nearly vanished ecosystem, but something else has become equally apparent: The dawn chorus continues, hawks fly past, kiskadees pluck ripe orange hackberries, chachalacas rustle clumsily on branches far too thin for their chicken-like forms and a beautiful red-banded pixie butterfly stops to rest on a nearby leaf. Their presence here is evidence of an ardent effort carried out over the past four decades to save this endangered landscape. Each is a piece of the naturally lush fabric of the Lower Rio Grande Valley, and a poignant reminder of the preciousness of what’s at stake here. This habitat may have diminished to near nothing, but to those that remain, it is everything.

Krista Schlyer has been documenting the ecosystems of the U.S.-Mexico borderlands since 2007. Learn more about her work at