Ecological and Cultural
Characteristics
Habitat Type:
The U.S. Fish and Wildlife Service
identified eleven biotic communities in the Land
Protection Plan for Lower Rio Grande Valley National
Wildlife Refuge (1985): Chihuahuan Thorn Forest, Upper
Valley Flood Forest, Barretal, Upland Thornscrub,
Mid-Valley Riparian Woodland, Sabal Palm Forest, Clay
Loma/Wind Tidal Flats, Mid-Delta Thorn Forest, Ramaderos,
Wooded Potholes and Basins, and Coastal Brushland
Potholes.
Rare/Endangered Species:
The following species are
identified as endangered or threatened by the U.S. Dept.
of Interior:
Wood Stork, Bald Eagle, Aplomado
Falcon, Piping Plover, Least Tern, Jaguarundi, Ocelot,
American Alligator, Green Sea Turtle, Hawksbill Sea
Turtle, Loggerhead Sea Turtle, Kemp’s Ridley Sea Turtle,
Leatherback Sea Turtle. Tx. Parks and Wildlife Dept
identify numerous additional species as threatened or
endangered including: Reddish Egret, Hook-billed Kite,
American Swallow-tailed Kite, Common Black Hawk, Gray
Hawk, White-tailed Hawk, Zone-tailed Hawk, Ferruginous
Pygmy-owl, Northern Beardless Tyrannulet, Rose-throated
Becard, Black Capped Vireo, Golden-cheeked Warbler,
Botteri’s Sparrow, Coues’ rice rat, Coati, Texas
tortoise, reticulated colared lizard, Texas horned
lizard, speckled racer, Texas indigo snake,
black-striped snake, northern cat-eyed snake,
black-spotted newt, Rio Grande lesser siren, Mexican
burrowing toad, giant toad, Rio Grande chirping frog,
white-lipped frog, Mexican treefrog, sheep frog, river
goby, and blackfin goby
Breeding/Nursery Area:
The refuge provides breeding
habitat for numerous coastal wetland, inland wetland,
and upland migratory bird species; nesting sea turtles,
including Kemp’s ridley sea turtle; and numerous other
amphibians, reptiles, and mammal species.
Forage Area:
The refuge provides foraging
habitat for numerous coastal wetland, inland wetland,
and upland migratory bird species; nesting sea turtles,
including Kemp’s ridley sea turtle; and numerous other
amphibian, reptile, and mammal species.
Migratory Species:
The refuge provides habitat for
numerous coastal wetland, inland wetland, and upland
migratory bird species.
Geomorphic Features:
Portions of the Refuge are
juxtaposed at the mouth of the Rio Grande, adjacent to
South Bay. Features include: Beach dune systems; lomas;
and tidally influenced sand, mud, and algal flats. Lands
managed by the Refuge extend upstream to Falcon
Reservoir and include additional tracts surrounding the
La Sal del Rey, La Sal Vieja, and East Lake inland salt
lakes.
Ecosystem Function:
When this project began in 1979,
ninety-five percent of the Lower Rio Grande Valley’s
unique habitat had been eliminated or altered, primarily
for agriculture. Consequently, the Refuge protects much
of the remnant Lower Rio Grande riparian forest and
adjacent xeric ecotone. Much of the land purchased by
the Refuge has been, and continues to be, actively
cultivated. To address this, the Refuge has developed an
extensive cooperative farming and revegetation program
that restores between 750 and 1000 acres of farmland per
year to native habitat. The earliest restoration efforts
have matured to produce habitats that are harboring
native species of plants and animals that can not be
seen elsewhere in the United States.
Uniqueness of Natural Community:
The protected lands of the Refuge
support perhaps the richest and rarest biodiversity in
the continental United States. The Refuge manages
habitats supporting 13 federally threatened and
endangered species, two recently down listed species,
and 57 state protected species. In total, 485 species of
birds, 294 species of butterflies, 115 species of
reptiles and amphibians, and 83 species of mammals are
known to occur in the Lower Rio Grande Valley and
adjacent Gulf of Mexico coastal waters. Presently, 776
plant species are documented on the Lower Rio Grande
Valley National Wildlife Refuge, but an estimate of the
total number of plant species occurring in the Refuge’s
area of ecological concern is placed at 1,200 species.
Archaeological and Cultural
Significance:
Included as a National Historic
Landmark, the Palmito Ranch Battlefield is the site of
the last land engagement of the Civil War. Union and
Confederate soldiers fought here on May 12-13, 1865,
more than a month after Gen. Robert E. Lee surrendered
at Appomattox. The Union force under Col. T.H. Barrett
was defeated by the Confederate troops under Col. "Rip"
Ford.
Listed on the National Register of
Historic Places, El Sal Del Rey has been the site of
salt harvest for at least 3,000 years. Warring Native
American tribes set it aside as a truce area. In the
1500’s Spanish explorer’s claimed it for Spain. In the
1930’s it provided the legal precedent establishing
mineral rights in the State of Texas.
Current and Potential Use of
the Site
Existing or Potential Educational
Use:
The Refuge supports various
educational activities carried out by both individuals
and groups. Throughout the school year, area public and
private schools use the refuge by for field trips and
outdoor classroom activities. Students doing graduate or
post-graduate research conduct wildlife research under
Special Use Permits.
Recreational Use:
The refuge offers wildlife
observation and photography, and seasonal hunting and
fishing access.
Commercial Use:
Oil and Gas activities: All of the
subsurface mineral rights below the refuge are privately
held and exploration, and production activities are
ongoing.
Private Use:
The refuge is used by private
entities for public use related activities, for example
bird tours.
Management Status
Land Ownership:
LRGVNWR is owned and administered
by the National Wildlife Refuge System, Fish and
Wildlife Service, U.S. Department of the Interior.
Existing Designations:
The Refuge manages two nationally
significant historical sites: Palmito Ranch Battlefield
, a National Historic Landmark; and El Sal Del Rey,
listed on the National Register of Historic Places.
Management Status:
The refuge is managed by the U.S.
Fish and Wildlife Service as a unit of the National
Wildlife Refuge System, a network of lands and waters
for the conservation, management and restoration of the
fish, wildlife and plant resources and their habitats
for the present and future generations of Americans.
Existing Monitoring Activities:
The refuge conducts numerous
biological monitoring activities including: sea turtle
patrols, shorebird surveys (including Piping Plover),
ocelot surveys, and a variety of academic research is
permitted.
Site Viability
Threats to Ecological Integrity:
The most significant threats to
the refuge and the Lower Rio Grande Ecosystem are
primarily related to development: urban, suburban, and
industrial; including specific issues such as flood
control and water demand and competition (most notably
as water demand relates to instream flow and the health
of the river and associate estuary as a nursery for
numerous aquatic species). Additional significant
threats relate to illegal immigration, drug smuggling,
and border law enforcement activities.
Management Potential:
The most significant action
necessary to maintain the viability of the refuge and
the ecosystem is continuation of refuge land acquisition
program. All 77,000 acres of the refuge have been
purchased since 1979 and the refuge has authority to
purchase additional lands up to 132,500 acres total.
Additionally, continued enhancement and development of
the refuge law enforcement program will contribute to
diminished impacts to refuge resources.
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