Wetlands brimming with wildlife serve as the centerpiece of a new South Texas park.
By E. Dan Klepper
A peculiar scent of soot and fermentation permeates the damp Tamaulipan thorn scrub along the Rio Grande Valley floodplain. The wet scrub, a tangle of mesquite and palmetto that gives way to ball-mossed ebony before tumbling into marsh, emits an odd, unsettling perfume. The scent seems to override all other senses with its distinct notes of smolder and decay. Once the body enters a moisture-laden thorn scrub the nose begins to work overtime in compensation for diminishing eyesight.
The thorn scrub, a snarl of hundreds of botanical species, weaves a thick, dark mat that leaves little room for daylight. Sun rays, blazing unimpeded across the Rio flatlands, are reluctant to penetrate the scrub. Once the beams collide with the scrub's green wall, their radiance is all but snuffed out. Only dim fragments of light remain, lingering like curling whiffs of smoke.
Resacas, with their marshy habitats composting in remnant floodwaters, are important components of the Rio Grande's Tamaulipan thorn scrub and are invariably the source of both its dampness and decay. These ancient river channels provide conduits for floodplains to negotiate periodic and natural inundations. The resulting resacas form arterial, snake-like patterns across the landscape. Before the advent of dams along the Rio Grande, resacas performed nature's own flood control and assisted wildlife that depended on their peculiar environs to survive and thrive.
Nature, in fact, loves a resaca. It is the womb from which all manner of bugs and beasts are born. Its water harbors shore, song and sea birds; the nimble branchwork above it gives rise to nests, eggs and wings; and its mud coddles and then recycles frogs, turtles and insects. Quietly watching a resaca in scrub shadow grants witness to a semitropical world in full swing – green jays chatter and feed, dragonflies strafe the water's edge, bobcats drink, then scatter.
But once daylight lags, darkness comes quickly to a resaca's thorn scrub, and night is its inhabitants' milieu. Great horned owls haunt the canopy, ocelots stalk prey, Mexican treefrogs squeak like bed springs, indigo snakes thread the resaca cattails, and Rio Grande lesser sirens (a type of salamander) surface the mud with a click-click-click of odd, amphibian song. Fireflies ignite and beacon a crazy course through an impenetrable morass so remarkably dense that humans are no more hamstrung by it in darkness than they are by the light of day.
Perhaps therein reside the metaphysics behind the human assault on the Rio Grande Valley's Tamaulipan thorn scrub and its attendant resaca wetlands. For the past 100 years, these native Texas habitats, with a unique expanse of vegetation once covering vast swaths of the state's deep south, have been systematically cleared, plowed, dammed and drained to accommodate agriculture, flood control and unimpeded urban sprawl. Today, less than 5 percent remains. What survives consists of a patchwork of fragile and compromised habitat, home to dozens of species of endangered plants and wildlife including ocelots and a bit of Texas ebony-anacua woodland that is considered one of the most threatened plant communities in the United States.
Efforts have been made in the last several decades to kickstart Tamaulipan preservation and restoration before the remaining fraction vanishes altogether. The Texas Parks and Wildlife Department has been working alongside other organizations, including the World Birding Center, to establish parks and preserves that protect this endangered ecosystem.
In fact, TPWD's latest and grandest effort in this push for preservation can be found within a few miles of Brownsville. Called Resaca de la Palma State Park for the sabal palms that dot the drier savannahs above its resaca, these 1,700 acres of rich, semitropical diversity represent the largest contiguous tract of native resaca and thorn scrub habitat in the World Birding Center's lower Rio Grande Valley preserve.
Today visitors will find a small fretwork of trails constructed across the park's scrubland that weaves quietly through the mesquite-palmetto savannahs, ebony-anacua woods, and resaca wetlands. All trails lead to comfortable wildlife-viewing benches or observation decks that hover indiscreetly over the resaca banks. A wooden boardwalk levitates visitors above the resaca itself, allowing an opportunity for a more intimate examination of the resaca's dark and pungent waters.
The park's bird list numbers more than 250 species including the aforementioned Valley favorite – the green jay – as well as summer tanagers, great kiskadees, anhingas, white-tailed kites, cerulean warblers, peregrine falcons and buff-bellied hummingbirds. The birds and other wildlife are free to roam the park, unimpeded by the dangers of traffic because vehicles are not allowed beyond the visitor center. Instead, a 3-mile, single-lane tram road circumnavigates the park, and visitors are encouraged to bike, walk or ride the unobtrusive tram to view the park. Hikers can take the tram to one of the trailheads and, after their hike, catch the tram again for a ride back to the visitor center parking area. The outdoor recreational activities available at Resaca de la Palma include picnicking, wildlife viewing, and butterfly watching and all are consistent with its true mission: to preserve, restore and interpret this unique and disappearing habitat.
While it took foresight and vision to secure this threatened bit of the state's original natural world, it is the long-term plan for the restoration of the park's main attraction – its degraded resaca – that makes this project a truly remarkable and challenging environmental endeavor. The park's resaca, like most, once functioned under a prehistoric yet fragile system, one inclined to do so in perpetuity if uninterrupted. Restoring this system to its natural state has taken both compromise and ingenuity. TPWD's desire has been to mimic the resaca's natural cycles and revive it for future generations. But in order to do so they had to replicate its past.
Resaca de la Palma State Park is located along a primal delta, terra firma recovered from the nearby ocean by the handiwork of the Rio Grande. The river literally forged the land over centuries through flooding and silt deposition. The river would flood its banks each season in accordance with the snow melt far upriver and the gulf's tropical storms downstream. As the water receded it would leave behind layers of soil along with scoured arroyos or resacas that retained water for longer periods, thus transforming the habitat into wetlands as the moisture lingered, then slowly evaporated.
However, a culmination of human flood control measures over the last century succeeded in altering the delta's pattern of inundation, deposition and evaporation, thus ending the ancient cycle. The resacas were then divided and dammed and utilized for storing irrigation water. Irrigation districts and farmers used the natural canal structure to moderate the flow of water to townships and crops in a display of agrarian adroitness. But as urban development encroached and water delivery networks went underground, the resacas were no longer needed. Once abandoned, they dried up permanently, and crucial south Texas wetlands were lost.
Today, TPWD habitat restoration specialists are modifying the pre-existing water delivery system already in place along the resaca to recreate natural conditions. Through a series of irrigation pipelines, levees, open canals and water-control structures, TPWD will ultimately succeed in restoring four separate sections of the resaca, controlling and staggering the water depth of each section to achieve the broadest variation of resaca habitats in order to draw the greatest number of wetland birds. This system will also allow park staff to maintain these varied water levels all year long. Unlike much of the region's isolated, transitory wetlands, the park's resaca was once part of an open, persistent system that meandered across 30 miles of delta country. The evidence can still be seen in aerial photographs.
The presence of water year-round means habitat is made available to migrating as well as breeding and wintering birds such as waterfowl, cranes and hummingbirds. It also provides a safe haven for aquatic and semiaquatic organisms including the Rio Grande lesser siren and the black-spotted newt, both considered threatened species in Texas. The plants that thrive alongside the resaca will also benefit, including the regionally rare Bailey's ball moss and the largest concentration of Runyon's water-willow known. In essence, Resaca de la Palma provides a microcosm of the vast wetland diversity that once dominated the southern Rio Grande delta.
This is good news for Texans as well as for the World Birding Center, a partnership endeavor "dedicated to increasing the appreciation, understanding, and conservation of birds and other wildlife and their habitat." The center's lower Rio Grande Valley partners include Resaca de la Palma, Bentsen-Rio Grande Valley State Park (the center's headquarters), Estero Llano Grande State Park, nine tracts of national wildlife refuge property and six urban sites. Together their efforts represent approximately 9,735 acres of protected lower Rio Grande delta habitat.
It is a laudable start to an overwhelming conservation task. However, the state's lower delta environment encompasses a far greater tract of unprotected habitat, land that extends 150 miles from Falcon Dam to the Gulf of Mexico. Agriculture and urban development have increasingly dominated the region over the last century, and continue to do so today. Thus, South Texans have left little room for native species to survive and follow them into the future. Hope lies in efforts by TPWD and other conservation-minded organizations to reverse this course. Resaca de la Palma State Park represents more than just a stopgap in the collapse of our river delta wetlands. By employing the tools that were once meant to control and eliminate its namesake, the partners in Resaca de la Palma's creation have succeeded in bringing a small piece of Texas natural history back to life.
For more information, visit www.worldbirdingcenter.org.