Red River of the South

• Category: Inland Aquatic Biomes.
• Geographic Location: North America.
• Summary: The Red River of the South is an important watershed in North America, covering critical ecoregions, but it is seriously affected by human activities.

The Red River of the South is a major tributary of the Mississippi and Atchafalaya Rivers in the southern United States, and it drains the second largest river basin in the southern Great Plains. This Red River, previously known as the River Rouge, is 1,360 miles (2,189 kilometers) long, flowing generally in a west-to-east direction as it crosses the states of Texas, Oklahoma, Arkansas, and Louisiana. Its watershed covers approximately 65,598 square miles (169,900 square kilometers). The high, middle, and bottom drainages on the basin are located in the first two states, with a small portion of the bottom in the last two.

The climate of the watershed is arid; in the higher parts of the basin, there is a mean annual precipitation of 20 to 28 inches (508 to 711 millimeters), with minimum and maximum temperatures in January and July of 28 to 54 F (minus 2 to 12 C) and 72 to 95 F (22 to 35 C), respectively. The moister situation is quite different in bottomland areas, which receive 42 to 48 inches (1,066 to 1,219 millimeters) of mean annual precipitation, with minimum and maximum temperatures in January and July of 30 to 52 F (minus 1 to 11 C) and 72 to 91 F (22 to 33 C), respectively. The drainage basin includes different major ecoregions; among these, from west to east, are: Red Prairies, Broken Red Plains, and Red River Bottomlands.

Biodiversity

In the Red Prairies and Broken Red Plains ecoregions, the dominant vegetation includes the prairie midgrasses or shortgrasses, depending upon soil, moisture availability, and grazing pressure. Under less disturbing practices, the typical grasses include the little bluestem (Schizachyrium scoparium), Texas wintergrass (Stipa leucotricha or Nassella leucotricha), white tridens (Tridens albescens), Texas cupgrass (Eriochloa sericea), and sideoats grama (Bouteloua curtipendula).

Under heavier grazing conditions, the buffalograss (Bouteloua dactyloides), hairy tridens (Erioneuron pilosum), and purple threeawn (Aristida purpurea) become dominant.

Riparian zones in these ecoregions are usually dominated by pecan (Carya illinoinensis), mixed with American elm (Ulmus americana), black willow (Salix nigra), and little walnut (Juglans microcarpa).

The upper parts of the basin include conspicuous wildlife, of types mostly related to grassland habitats. Across most of the river, the black-tailed prairie dog (Cynomys ludovicianus) is one of the key species defining the entire landscape. Associated with this important rodent are other species—including several prairie-dog predators—such as the black-footed ferret (Mustela nigripes) and rattlesnakes (Crotalus spp.). Some prefer to take up residence in the extensive underground burrow systems the prairie dogs create. Among these are the kit fox (Vulpes macrotis), the burrowing owl (Athene cunicularia), and the horned lizard (Phrynosoma cornutum).

Some grassland birds benefit from the presence of prairie dogs, such as the mountain plover (Anarhynchus montanus), which mainly feeds on the shortgrass around prairie dog towns. With this seemingly one-directional fauna community, the large-scale extermination of prairie dogs, historically considered pests, substantially impacted the entire region. Poisoning, mechanical reduction, and systematic extermination have transformed most of the area, changing the entire aspect of some landscapes and significantly reducing other species populations related to and dependent on the prairie dogs or their burrows.

In the Red River Bottomlands, the river flows through a series of marshes and swamps, where its flow is dramatically moderated. The plain of the river is composed of fertile deposits with variations in permeability. The original vegetation in the lower region, despite being almost completely depleted, is mainly composed of hardwood forests in which a number of species are common. These include various oaks such as common water oak (Quercus nigra), willow oak (Q. phellos), blackjack oak (Q. marilandica), overcup oak (Q. lyrata), and southern red oak (Q. falcate). Other tree species include sweetgum (Liquidambar styraciflua), blackgum (Nyssa sylvatica), river birch (Betula nigra), red maple (Acer rubrum), green ash (Fraxinus pennsylvanica), and American elm (Ulmus americana).

Wildlife in this part of the basin includes white-tailed deer (Odocoileus virginianus), turkeys (Meleagris spp.), squirrels (Sciurus spp.), rabbits (Sylvilagus spp. and Lepus spp.), raccoon (Procyon lotor), and bobcat (Lynx rufus). Perhaps the most remarkable are the bald eagle (Haliaeetus leucocephalus) and black bear (Ursus americanus).

Environmental Issues

The Red Prairie ecoregion is mostly cultivated, in contrast to the Broken Red Plains ecoregion, which is predominately used as grazing land. In the western stretches of the watershed, grasslands are common, but so are dry lands and irrigated ranges for farming cotton, wheat, and grain sorghum. Additionally, the area is used for cattle, sheep, and goat grazing. Also, most of the bottomland natural woodland has been cleared for cropland and improved pastures, although some woodland still occurs in very poorly drained and flooded areas.

The economy of the region is largely influenced by water, both directly and indirectly, for water processing, drinking water, and irrigation related to farming. Dam operations and sand mining in the region have impacted the river’s water levels. Because of past problems, this resource is monitored for pollution and environmental damage. The potential effects of climate change related to rising temperatures and lower precipitation regimes in the southern Great Plains are complex. Droughts in the Red River basin will likely lead to reduced water flow in the western part of the basin.

Bibliography

Benke, A., and C. Cushing. Rivers of North America. Academic Press, 2005.

Delong, Michael D., et al. Rivers of North America. 2nd ed., Academic Press, an imprint of Elsevier, 2023.

Gill, Kenneth C. et. al. "Hotspots of Species Do Not Vary across Future Climate Scenarios in a Drought-Prone River Basin." Ecology and Evolution, vol. 10, no. 17, pp. 9200-38, Aug. 2020, doi.org/10.1002/ece3.6597. Accessed 15 Dec. 2024.

Griffith G. E., et al. “Ecoregions of Texas.” Texas Commission on Environmental Quality, 2004, gaftp.epa.gov/EPADataCommons/ORD/Ecoregions/tx/TXeco‗Jan08‗v8‗Cmprsd.pdf. Accessed 15 Dec. 2024.

Kleiner, Diana J. "Red River." Texas State Historical Association, 1 May 2019, www.tshaonline.org/handbook/entries/red-river. Accessed 10 Dec. 2024.

Pair, John C. “Stress-Tolerant Trees for the Southern Great Plains.” Journal of Arboriculture, vol. 20, no. 2, 1994.

"Red River." Encyclopedia of Arkansas, 1 Nov. 2024, encyclopediaofarkansas.net/entries/red-river-2650. Accessed 10 Dec. 2024.