Santa Ana National Wildlife Refuge

Santa Ana National Wildlife Refuge is a 2,088-acre (8.45 km²) National Wildlife Refuge situated along the banks of the Rio Grande, south of Alamo in the Lower Rio Grande Valley, in Hidalgo County, Texas. This sub-tropical sanctuary harbors one of the highest wildlife diversities of any single unit in the National Wildlife Refuge system and has been referred to as the “Gem of the National Wildlife Refuge System”. Many Mexican and tropical species reach the northern limit of their distributions in the Lower Rio Grande Valley, including several that occur nowhere else in the US. Santa Ana National Wildlife Refuge preserves one of the largest tracks of old growth habitat in the Lower Rio Grande, in a region where much of the land use has been dominated by, and shifted over the last century, from small farms, to commercial agro-industries, to significant population growth and urban development in recent decades.

The wildlife refuge was established in 1943 to protect one of the last remnants of subtropical Rio Grande riparian forest and migratory birds. In a unique location in the US, where diverse climates and habitats of south Texas merge (tropical, temperate, thorn forest, wetlands, Gulf Coastal grasslands), it has a reputation for diverse birding. In addition to birding, the refuge offers opportunities for nature photography, hiking (with over 12 miles of trails), and biking (on paved roads only) and nature tram rides (seasonal), with an observation tower, a canopy bridge, as well as a visitors’ center with nature and wildlife exhibits, an auditorium, nature shop, and restrooms.

The refuge is located within the Tamaulipan Biotic Province (Tamaulipan mezquital), a xeric region with thorn scrub vegetation. However, contrasting with much of the semi-arid ecosystems of the region, the refuge is situated in the riparian zone of the Rio Grande protecting resacas (sloughs and oxbow lakes formed by old channels of the river), mudflats, bottomland forest, riparian terraces, and some areas of upland thorn forest. The topography is relatively flat, with small hills and terraces descending to the river. Elevations in the refuge range from 22 to 34 meters. The refuge is largely bordered by agriculture and croplands to the north, east, and west, and the Rio Grande forms the southern boundary. The geology of the area consists of a Cretaceous base, covered by Cenozoic sedimentary marine depositions of limestone, sandstone, siltstone, claystone, topped with deep Quaternary alluvial soils of sand, clay, and loam.

Due to its location near the Mexico–United States border, the refuge was at risk of environmental damage during the construction of the Mexico–United States border wall. The administration exempted the construction in the refuge, but built on the border of it, leading to possible interference due to noise.