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Biomes and Ecosystems

Red River of the South

by José F. González-Maya, Marylin Bejarano

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 20–28 inches (508–711 millimeters), with minimum and maximum temperatures in January and July of 28–54 degrees F (minus 2 to 12 degrees C) and 72–95 degrees F (22–35 degrees C), respectively. The moister situation is quite different in bottomland areas, which receive 42–48 inches (1,066–1,219 millimeters) of mean annual precipitation, with minimum and maximum temperatures in January and July of 30–52 degrees F (minus 1 to 11 degrees C) and 72–91 degrees F (22–33 degrees 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 bluestern (Schizachyrium scoparium), Texas wintergrass (Stipa leuchotricha), white tridens (Tridens albescens), Texas cupgrass (Eriochloa sericea), and sideoats gramma (Boutelowa curtipendula).

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

Riparian zones in these ecoregions are usually dominated by pecan (Carya illinoensis), 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 grasslands 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 veloxmacrotis), the burrowing owl (Athene cunicularia), and the horned lizard (Phrynosoma cornutum).

Even some grassland birds can benefit from the presence of prairie dogs, such as the mountain plover (Charadrius 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 as pests, has had substantial impact on the entire region. The use of poisoning, mechanical reduction, and systematic extermination have transformed most of the area, not only changing the entire aspect of some landscapes, but also reducing significantly other species both 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 by fertile deposits with variations in permeability. The original vegetation in the lower region, despite being almost completely depleted, is mainly composed of hardwood forest 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 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 endangered bald eagle (Haliaeetus leucocephalus) and black bear (Ursus americanus).

Environmental Issues

The Red Prairie ecoregion is currently mostly cultivated, in contrast to the Broken Red Plains ecoregion that is predominately use as grazing land. In the western stretches of the watershed, grasslands are common, but so are dry lands and irrigated ranges for farming of 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. 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; their impact on the species of this biome, however, is sure to be deleterious.

Further Reading

1 

Benke, A. and C. Cushing. Rivers of North America. San Diego, CA: Academic Press, 2005.

2 

Griffith G. E., S. A. Bryce, J. M. Omernik, and A. C. Rogers. “Ecoregions of Texas.” Austin: Texas Commission on Environmental Quality, 2004.

3 

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

Citation Types

MLA 9th
González-Maya, José F., and Marylin Bejarano. "Red River Of The South." Biomes and Ecosystems, edited by Robert Warren Howarth, Salem Press, 2013. Salem Online, online.salempress.com/articleDetails.do?articleName=BIOMESECO_101536901435.
APA 7th
González-Maya, J. F., & Bejarano, M. (2013). Red River of the South. In R. W. Howarth (Ed.), Biomes and Ecosystems. Salem Press. online.salempress.com.
CMOS 17th
González-Maya, José F. and Bejarano, Marylin. "Red River Of The South." Edited by Robert Warren Howarth. Biomes and Ecosystems. Hackensack: Salem Press, 2013. Accessed September 24, 2026. online.salempress.com.