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Habitat

Habitat2_512x219The refuge is a landscape of coastal prairie, thorn forest, sand and clay dunes, and tidal flats set within thousands of acres of wetlands bordering the lower Laguna Madre, one of five hypersaline lagoons in the world.

The refuge’s topography is typical of the Texas Coastal Plain, a flat landscape that gradually slopes down to the salty water’s edge of the lower Laguna Madre.

Laguna Atascosa Refuge’s wetlands and tidal flats make it a significant wintering and migratory stopover area, as well as a major shorebird and waterbird breeding area. From freshwater to brackish to salty, the wetlands of the refuge are affected by tides, rainfall, freshwater runoff, evaporation, wind and in some instances, all of the above. The Laguna Atascosa (muddy lagoon), for which the refuge is named, is a 5,000-acre impoundment that is especially important for redhead ducks when they first arrive to their winter home on the Lower Laguna Madre. The refuge’s other large ponds, impoundments, resacas (oxbows) and pothole wetlands are also important as they are often the only source of freshwater for wildlife. These freshwater sources are also havens for alligators, turtles, frogs and many other species.

Between land and water, moving toward the shoreline, the fresh and saltwater begin to mix. Brackish wetlands serve as nurseries for young fish and are teeming with blue crab and shellfish, food sources for reddish egrets, herons and other wildlife. Gradually, the influence of fresh water is completely diminished and the saltwater marshes and tidal flats emerge. The changing tides bring rich nutrients to the variety of worms, clams and other creatures living in the mud flats. They in turn feed the shorebirds, ducks and herons that depend on the rich nutrients provided.

In addition to the diversity of wetlands, the refuge has nearly 20,000 acres of coastal prairie and savannah habitat, both of which are affected by elevation and soil salinity. The saltprairie is at or near sea level and includes salt-tolerant plants such as leatherleaf, sea ox-eye daisy and sea lavender. On higher elevations, the diversity of grasslands contain species like cordgrass and blue stem and are occasionally interspersed with woody vegetation such as yucca and prickly pear cactus. The coastal prairie and savannah in South Texas provides important foraging and nesting habitat for many species, including the endangered northern aplomado falcon.

The brushlands of the refuge are a thorny entanglement of tree and shrub species and typically occur on the refuge’s lomas, natural silty-clay dunes. Lomas can reach heights of 36 feet and, because of the higher elevations and change in soil salinity, ensure an entirely different plant community. Considered vegetation “islands,” lomas often include plant species such as granjeño, coyotillo and Texas ebony. Beneath those is an understory of snake eyes, cenizo, and Texas lantana. The lomas provide much of the dense, impenetrable brushlands that are especially important to the ocelot, a small, wild cat that finds food, shelter and protection within the thorny environment.

The unique convergence of temperate, subtropical, coastal, and Chihuahuan desert habitats in this region supports the habitat diversity, which, to date, includes a documented 450 plant species -- and the list is still growing.
Page Photo Credits — Redhead Ridge / Dora Martinez ©
Last Updated: Mar 06, 2013
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